Determination of Residual Control and Concentration of Chlorantraniliprole in Soybean

Studies were conducted in 2020 and 2021 at the Delta Research and Extension Center in Stoneville, MS to determine concentrations of chlorantraniliprole (Prevathon, FMC Corporation, Philadelphia, PA) in soybean (Glycine max L.) leaves and florets. Chlorantraniliprole was applied as a foliar spray at four rates (0.028, 0.053, 0.078, 0.103 kg ai ha-1) for leaves and two rates (0.053, 0.078 kg ai ha-1) for florets. Leaf bioassays with corn earworm, Helicoverpa zea (Boddie), were conducted concurrently to determine mortality within three plant zones to evaluate chlorantraniliprole distribution throughout the canopy. For the leaf study, plants were partitioned into three zones consisting of a top (18th node), middle (13th node), and bottom (9th node) zone. Leaf samples from each zone were analyzed for chemical concentrations and bioassays were conducted at 1, 7, 14, 21, and 28 days after treatment (DAT). Floret samples were analyzed at 4, 7, 10, and 14 DAT. Concentrations of chlorantraniliprole, though variable, provided >71% control through all sampling dates, application rates, and canopy zones tested. Chlorantraniliprole was viable up to 28 DAT. Results from the soybean floret study suggested chlorantraniliprole was detected in florets up to 14 DAT. An additional leaf bioassay was conducted using concentrations detected in the floret study. Concentrations in florets provided mortality of corn earworm up to 48% out to 14 DAT. With a long residual expected, chlorantraniliprole applications should continue to be used to control corn earworm infestations in soybean and some additional control could be expected in florets.

CD200 ectodomain shedding into the tumor microenvironment leads to NK cell dysfunction and apoptosis

The basis of immune evasion, a hallmark of cancer, can differ even when cancers arise from one cell type such as in the human skin keratinocyte carcinomas: basal and squamous cell carcinoma. Here we showed that the basal cell carcinoma tumor-initiating cell surface protein CD200, through ectodomain shedding, was responsible for the near absence of NK cells within the basal cell carcinoma tumor microenvironment. In situ, CD200 underwent ectodomain shedding by metalloproteinases MMP3 and MMP11, which released biologically active soluble CD200 into the basal cell carcinoma microenvironment. CD200 bound its cognate receptor on NK cells to suppress MAPK pathway signaling that in turn blocked indirect (IFN-γ release) and direct cell killing. In addition, reduced ERK phosphorylation relinquished negative regulation of PPARγ-regulated gene transcription and led to membrane accumulation of the Fas/FADD death receptor and its ligand, FasL, which resulted in activation-induced apoptosis. Blocking CD200 inhibition of MAPK or PPARγ signaling restored NK cell survival and tumor cell killing, with relevance to many cancer types. Our results thus uncover a paradigm for CD200 as a potentially novel and targetable NK cell-specific immune checkpoint, which is responsible for NK cell-associated poor outcomes in many cancers.

Impacts of Winter Annual Cover Crops and Neonicotinoid Seed Treatments on Arthropod Diversity in Mississippi Soybean

Winter annual cover crops can be planted before soybean in Mississippi for many agronomic reasons. Incorporating winter annual cover crops into soybean production changes the seasonal hosts within fields. Some studies suggest that reducing tillage and using diverse species of cover crops can increase arthropod diversity and predator activity. Neonicotinoid seed treatments are often implemented to combat early season insect pests in soybean that follow cover crops, but negative effects on the environment such as reductions in biodiversity are often attributed to these compounds. We conducted an experiment to measure the effects on the diversity of the soybean epigeal and foliar communities when incorporating cover crops as well as insecticidal seed treatments into Mississippi soybean growing systems. Our results showed that legume cover crops had significant impacts on the epigeal community diversity of soybean planted behind them. These cover crops, especially hairy vetch, supported a more diverse foliar community before termination. To prevent increases in herbivorous arthropods, neonicotinoid seed treatments can be used without affecting epigeal predators such as beetles, ants, and spiders. The neonicotinoid seed treatments affected arthropod diversity, but the reductions were mainly caused by decreases in herbivorous pest insects that fed on treated soybean plants.

The use of a transient transfected expression system to deliver high quality bispecific T-cell engager drug product, NVG-111, to the clinic for a fraction of the cost and time associated with the development and use of a producer cell line

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Background: Bispecific antibodies provide an opportunity to treat a diverse range of disorders because of their ability to simultaneously attenuate several different pathways precisely and effectively, thus overcoming many of the limitations of monoclonal antibodies. The adaptability of bispecifics has facilitated the generation of compelling preclinical data covering a range of malignant and non-malignant disorders. Proof-of-concept early phase clinical trials with bispecific antibodies, including bispecific T-cell engagers (TCE) have been hindered by manufacturing challenges, including a heavy burden in terms of time, quality and costs associated with generating a stable producer cell line. We took a more agile approach, using transient transfection to manufacture a ROR1×CD3 bispecific TCE drug product (DP [NVG-111]) for a first in human, Phase I/II clinical trial. Methods: A HEK293T cell line was expanded into 10-layer cell factories. The cells were transfected with a ROR1xCD3 scFv bispecific antibody (NVG-111) plasmid and incubated. Post incubation, the supernatant containing NVG-111 was clarified by filtration and subjected to solvent/detergent viral inactivation. This was followed by a concentration/buffer exchange step and subsequent DNA reduction using an endonuclease. NVG-111 was captured using a bind/elute Protein A column and the eluate polished on a multimodal anion exchange column in flow through mode to remove residual impurities. The eluate was formulated and concentrated to the target protein concentration, viral and sterile filtered and QC tested. The bulk drug substance was 0.2 µm filtered into Din 2R vials and the DP stored at ≤-65°C pending release. Results: The transient transfection approach resulted in the rapid tech transfer and GMP manufacture of clinical NVG-111 DP. Two batches of DP were manufactured producing 1,971 vials of NVG-111, sufficient to support the Phase I/II clinical trial in patients with advanced Chronic Lymphocytic Leukaemia and Mantle Cell Lymphoma (Clinical Trial.gov NCT04763083). Both batches met the approved specifications for identity, potency, purity/impurities, strength and safety. The exercise took less than 7 months from contract signature to DP in the freezer and cost ̃50% of the more traditional producer cell line approach. Conclusions: We established a novel GMP process in 7 months, using transient transfection to manufacture NVG-111 for Phase I/II trials. The process costed less than the more conventional manufacturing approach of using a producer cell line. The strategy offers a rapid, and very efficient way of reaching a first in human study without a trade-off between time, quality and cost.

A sensitive and robust bioanalytical assay for pharmacokinetic analysis of ROR1xCD3 bispecific T cell engager (NVG-111) in a first-in-human study

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Background: Receptor tyrosine kinase-like Orphan Receptor-1 (ROR1) is widely expressed on hematological and solid tumors. NVG-111, a first in class humanized tandem scFv ROR1xCD3 bispecific antibody elicits potent killing of ROR1+ tumor cells in vitro and in vivo. This bispecific T-cell engager (TCE) is being evaluated in a first in human, Phase I trial in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). The predicted therapeutic dose and steady state serum concentrations of NVG-111 were estimated by allometric scaling using relevant doses from a murine PK study. To assess free drug levels in patients following 21 days of continuous infusion of NVG-111, a bespoke, sensitive pharmacokinetics (PK) assay with high levels of specificity and sensitivity was developed. Methods: Anti-idiotype (anti-ID) antibodies directed to anti-ROR1 (αROR1-ID) and anti-CD3 (αCD3-ID) were generated by mouse immunization or by phage display from customized libraries. A proof-of-concept sandwich ELISA assay was developed using αCD3-ID to capture NVG-111 and detection by biotinylated hROR1-streptavidin-HRP. Gyrolab and Quanterix Simoa high sensitivity ELISA platforms were used to detect NVG-111 by αCD3-ID capture and αROR1-ID detection. The mesoscale discovery electrochemiluminescence assay (MSD-ECLA) was developed using a reversed format; NVG-111 capture with αROR1-ID and detection with αCD3-ID. Results: Allometric scaling predicted a theoretically relevant therapeutic dose and steady state serum concentration of 1ng/mL NVG-111 in humans, which was just at the level of sensitivity of a conventional ELISA under non-matrix conditions. Transferring the format to Quanterix Simoa had limited success due to high background levels in all configurations evaluated. The Gyrolab platform increased sensitivity to 75pg/mL, but suboptimal individual human sera matrix selectivity limited assay validity. Assessment of MSD-ECLA provided the best signal/noise, enhanced human disease and healthy sera selectivity, and a dynamic sensitivity range of 250pg/mL to 32ng/mL, which enabled the development of a GCLP qualified PK assay. The MSD-ECLA assay was employed to measure NVG-111 concentrations in CLL or MCL subjects dosed with 0.3-30µg/day NVG-111. MSD-ECLA detected drug in patients receiving NVG-111, with a range of steady-state serum concentrations (Cavg.ss) of 168-610pg/mL. This was in-line with the predicted drug levels from the single species allometric scaling, albeit with observed levels being marginally lower than expected. Conclusions: Development, custom optimization and validation of a highly sensitive MSD-ECLA PK assay has enabled GCLP-compliant measurement of circulating NVG-111 in CLL or MCL patients treated with at least 10µg/day cIV NVG-111.

Activity and biophysical properties related to clinical evaluation of a first-in-class EHL ROR1xCD3 T Cell Engager

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Background: NVG-111, a T cell engager (TCE) targeting ROR1 and CD3, is in clinical development for the treatment of Chronic Lymphocytic Leukemia (CLL) and Mantle Cell Leukemia (MCL). This 55KDa molecule consisting of humanised tandem scFvs is administered into patients as a continuous intravenous infusion. The intrinsically short half-life of NVG-111 has its advantages, such as rapid management of CRS by cessation of infusion. Early safety and efficacy clinical data supports the development of an extended half-life (EHL) ROR1xCD3 TCE for ease of administration and convenience for patients, building on the favorable activity and biophysical attributes of NVG-111. A next generation therapy possessing such an EHL has potential to improve patient experience by offering a different drug administration paradigm. Methods: Several formats were designed and evaluated, incorporating different EHL technology solutions by increasing the size and enabling FcRn-mediated recycling. EHL TCEs and non-EHL TCEs were cloned in-format with Fc, HSA, or an HSA binding moiety into a suitable expression vector. The resultant clones were expressed using Expi293 cells and the potency of TCEs were evaluated by co-culture assays using MCL derived JeKo-1 target cells and T cells from healthy donor PBMCs. Cytotoxic responses and T cell activation as determined by CD69 expression were measured by flow cytometry. T cell activation was also assessed by measuring CD3 signalling in a reporter gene assay. Biophysical properties were evaluated by determining the post-purification expression titer, the aggregation profile using analytical SEC, and the impact of stability challenge in formulation buffer and serum on target cell binding and activity. Results: Reformatting NVG-111 into an IgG-like heterodimeric bispecific scFv-Fc resulted in loss of potency, which may be due to a change in geometry of binding and/or poorer target engagement. Activity and expression titer were also deleteriously affected by directly fusing NVG-111 to human serum albumin (HSA), or to an HSA binding moiety. Fusing NVG-111 directly to Fc resulted in maintained potency in cytotoxicity and T cell activation assays, the expression titer of parental NVG-111, and exhibited very low levels of aggregation. Stability studies performed in formulation buffer and in human serum showed that NVG-111-Fc was at least as stable as parent. Furthermore, other studies with this molecular format indicate that the half-life in mice is comparable to a heterodimeric bispecific scFv-Fc. Conclusions: NVG-111 has been successfully engineered into an EHL format that increased the molecular size and has the potential to engage in FcRn-mediated recycling. This format maintains functional activity, is stable, and expresses well with a favorable aggregation profile. Further molecular refinements are being actively evaluated in readiness for IND enabling studies.

Feeding Behavior and Fruiting Form Damage by Bollworm (Lepidoptera: Noctuidae) in Bt Cotton

Bt technologies have played a major role in the control of bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), in cotton. Variation in expression levels among varieties and plant parts, along with selection pressure on bollworm populations, has led to the development of resistance to some Bt proteins. Trials were conducted to evaluate how cotton varieties expressing different Bt proteins affect bollworm larval behavior and their damage in flowering cotton. Differences in larval recovery were observed among cotton varieties at 3 d with 3-gene Bt cotton having the lowest recovery and non-Bt cotton having the greatest recovery. Loss of bloom tags and abscission of small bolls at the site of infestation affected bollworm larval recovery among varieties. Day after infestation was the main factor that affected bollworm movement across all varieties. Number of total damaged fruiting forms by an individual bollworm larva was different among all varieties. Overall, flower bud (square) and fruit (boll) damage by an individual larva was lower on 3-gene cotton than 2-gene cotton and non-Bt cotton. An individual larva damaged fewer squares on 2-gene cotton than non-Bt cotton, but boll damage from bollworm was similar among 2-gene cotton and non-Bt cotton. The level of square and boll damage in 2-gene cotton has increased compared to previous research further supporting the occurrence of bollworm resistance to Cry proteins. The 3-gene cotton containing the Vip3A gene experienced low levels of damage and survival. These results will be important for improving management recommendations of bollworm in Bt cotton technologies.

Quantifying the Contribution of Seed Blended Refugia in Field Corn to Helicoverpa zea (Lepidoptera: Noctuidae) Populations

Helicoverpa zea (Boddie), a pest of cotton that also occurs in field corn, is commonly controlled through the use of foliar-applied insecticides or transgenic crops expressing Bacillus thuringiensis (Berliner) (Bt) genes. To minimize the risk of Bt resistance in pest populations, refuge systems have been implemented for sustainable agroecosystem management. Historically, structured refuge compliance among growers has been low, leading to the commercialization of seed blended refugia. To test the viability of seed blended refugia in southern U.S. field corn, field studies were conducted in Mississippi and Georgia during 2016, 2017, and 2018 growing seasons. To quantify adult H. zea emergence from structured (non-Bt corn) and seed blended refuge options, emergence traps were utilized. Kernel damage among seed blended refuge and structured refuge corn ears were recorded and compared. The timing of moth emergence was recorded. When compared to a structured refuge, H. zea adult moth emergence from seed blended refugia did not significantly differ. Kernel damage of non-Bt plants in the seed blended treatments was not significantly different than non-Bt plants in the structured refuge treatments. Moth emergence timing was not significantly delayed between the structured refuge and seed blended refuge treatments. Results of this study suggest that a seed blended refuge may provide an effective insecticide resistance management alternative for H. zea in areas where structured refuge compliance is low.

Influence of Soil Moisture Zones on Rice Water Weevil (Coleoptera: Curculionidae) Populations in Furrow Irrigated Rice

Water conservation is an important factor for production of rice in the United States because of declining aquifer levels, but little research has been done to evaluate insect management in rice systems integrating water conservation practices. Rice water weevil, Lissorhoptrus oryzophilus Kuschel, is an important insect pest of rice in the U.S. Rice water weevil is a semiaquatic species that relies on flooded conditions to complete larval development, so water conservation practices are likely to impact their pest status. The study was conducted across the Mississippi River alluvial floodplain to compare rice water weevil population densities in different zones of a furrow irrigated rice field to a conventionally flooded rice field. All locations were sampled at 3, 4, and 5 wk after the initial irrigation. Larval densities were greatest in the lower end of furrow irrigated fields and in the adjacent flooded rice field compared with the upper and middle sections that did not hold standing water when averaged across three sample dates. Also, rice water weevil densities were greater during week five than week three. In terms of rice yields, the top third of furrow irrigated rice fields, the section that remained mostly dry, produced lower rough rice yields than all other sections and the flooded field. These results suggest that rice water weevil populations can be lower in a furrow irrigated rice system. As a result, more research is needed to determine whether a spatial management plan can be developed based on soil moisture zones in furrow irrigated rice.

Sublethal Impacts of Novaluron on Tarnished Plant Bug (Hemiptera: Miridae) Adults

Tarnished plant bug, Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae), has become a primary pest of cotton in the Midsouthern United States. Insect growth regulators such as novaluron are an important part of L. lineolaris management. While novaluron is lethal to nymphs, it does not kill adults, so it has been used when nymphs are the primary stage present. However, cotton yield protection was observed from an application of novaluron when adults were the predominant stage present. To explain this, a series of studies were conducted to examine sublethal impacts of novaluron to L. lineolaris adults. Novaluron ingestion by adults reduced hatch rate and sometimes reduced oviposition rate. Ingestion by either males or females reduced hatch rates, but the reduction was greater from female exposure. Contact exposure of adults with novaluron residues within 1 d of application reduced hatch rate by about 50%, but the impact on oviposition was inconsistent. A field study showed reduced hatch rate from contact exposure to mixed-age natural populations, but the overall net reproductive rate was not reduced. Surface exposure of eggs to novaluron did not reduce hatch rate. Overall, exposure of tarnished plant bug adults to novaluron, regardless of adult age or exposure route, reduced egg viability. However, the impact on oviposition rate and net reproductive rate varied with adult age and exposure route. This understanding of sublethal impacts of novaluron, in addition to lethal impacts on nymphs, should be considered when choosing application times to maximize effects on L. lineolaris populations.

Evaluation of Flood Removal in Combination with Insecticide Seed Treatment for Rice Water Weevil (Coleoptera: Curculionidae) Larval Management in Rice

An experiment was conducted at the Delta Research and Extension Center in Stoneville, MS during 2017 and 2018 to determine whether removal of the flood is an economical method of control for rice water weevil, Lissorhoptrus oryzophilus Kuschel. This experiment compared a continuous flood production system to draining a rice field completely and reestablishing a flood for the remainder of the growing season. In addition, two insecticide seed treatments, thiamethoxam and chlorantraniliprole, were compared with an untreated control within each system. Rice water weevil densities were measured prior to draining at 3 wk after flood and again after the flood was reestablished in drained plots. Rice water weevil densities were greater in 2017 than 2018. Chlorantraniliprole at the predrainage and postdrainage sample timing reduced larval numbers compared with the untreated control. The plots where water was removed until soil cracking then re-flooded had significantly lower weevil populations than plots that were continuously flooded during 2018 only. Draining of plots resulted in lower yields in 2018, but not in 2017. Additionally, both of the insecticide seed treatments resulted in greater yields and economic returns than the untreated control. Draining of flooded rice when rice water weevil larvae were present did not provide a consistent benefit, and may result in yield and economic penalties. Insecticide seed treatments consistently provided greater yield benefits in flooded rice. Based on these results, draining of flooded rice is not recommended to manage rice water weevil and insecticide seed treatments should be used to minimize economic losses.

Evaluation of Current Tarnished Plant Bug (Hemiptera: Miridae) Thresholds in Transgenic MON 88702 Cotton Expressing the Bt Cry51Aa2.834_16 Trait

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is an important pest of cotton in many areas of the southern United States. An experiment was conducted at two locations in Mississippi during 2016 and 2017 to evaluate action thresholds for tarnished plant bug on a novel Bacillus thuringiensis cotton that expresses the Cry51Aa2.834_16 toxin. Treatments included the current action threshold, a 2× threshold, and treatments where insecticides were only applied during the early season (preflower) or only during late season (during flowering) based on the current action thresholds. These were compared to an untreated control and a weekly insecticide use regime that received weekly insecticide sprays. All treatments were imposed on both Bt Cry1Aa2.834_16 cotton and a nontraited cotton. The Bt Cry1Aa2.834_16 trait reduced the number of tarnished plant bugs and injury, and improved yields compared to nontraited cotton. For all spray treatments except the weekly insecticide use regime, yields were greater for the Bt Cry51Aa2.834_16 cotton than the nontraited cotton. In terms of thresholds, Bt Cry1Aa2.834_16 cotton sprayed based on current action thresholds resulted in similar yields to the weekly insecticide use regime of both cotton types. In contrast, the 2× threshold resulted in lower yields than the current threshold for both cotton types. Though thresholds intermediate to the currently recommended action threshold and the 2× threshold were not tested, these data suggest that currently recommended action thresholds appear appropriate for Bt Cry51Aa2.834_16 cotton. These results suggest that this trait will be an important component of current IPM programs in cotton where tarnished plant bug is an important pest.

Susceptibility of Rice to Oebalus pugnax (F.) (Hemiptera: Pentatomidae) Feeding at Different Levels of Grain Maturity and Impacts on Insecticide Termination

The stages of rice, Oryza sativa L. (Poales: Poaceae), grain maturity that are most susceptible to rice stink bug, Oebalus pugnax (F.), damage have been identified; however, the stage at which they are no longer capable of causing appreciable damage during grain maturity is unclear. The objective of this study was to determine the susceptibility of rice to rice stink bug feeding at different levels of grain maturity and determine an insecticide termination timing. Rice stink bug damage was examined using five levels of grain maturity described as percent of kernels reaching mature straw coloration referred to as hard dough (20, 40, 60, 80, and 100%) across a range of infestation levels using single panicle sleeve cages and large cages. Hybrid and conventional cultivar rice panicles at 20, 40, and 60% hard dough were found to be susceptible to indirect yield loss, as two rice stink bugs per panicle resulted in over 7% peck. In large cage trials, 25 rice stink bugs caused 0.7-1% peck to hybrid and conventional rice plots at 20% hard dough. Much less damage was observed once rice reached 60% hard dough, where peck averages only reached 0.4%. Decreased damage at 60% hard dough was validated using uncaged trials where 0.4% additional peck was observed in unsprayed plots. These data indicate that rice in the early stages of hard dough is susceptible to large levels of indirect yield loss, but unless significant densities of rice stink bug are present at 60% hard dough, no more sampling or applications are necessary.

Impact of Simulated Corn Earworm (Lepidoptera: Noctuidae) Kernel Feeding on Field Corn Yield

Corn earworm, Helicoverpa zea (Boddie) Lepidoptera: Noctuidae, has not been considered an economic pest of field corn. Historical losses estimates ranged from 1.5 to 2.5%, and a large number of foliar insecticide applications would be needed to minimize infestations. In recent years, Bt, Bacillus thuringiensis (Berliner) field corn, Zea mays (L.) Poales: Poaceae, technologies that exhibit activity against corn earworm have been introduced. However, it is unclear how much damage to corn ears (number of damaged kernels) is required to reduce yield. In this study manual damage methods were utilized to inflict defined levels of kernel damage and to impose damage at levels greater than observed with natural corn earworm infestations. Bt corn hybrids expressing the Agrisure Viptera (Vip 3A) trait were used to minimize injury from natural infestations of corn earworm. Manual kernel damage was imposed at R3 stage to mimic corn earworm feeding while avoiding interference with pollination. These methods were used in experiments where treatments were applied to individual ears and hand-harvested and in experiments where treatments were applied to all primary ears in the plot and machine-harvested. Damage of ≥60 kernels per ear was required to significantly reduce yield regardless of harvest method. Kernel damage from natural corn earworm infestations reported in other studies was much lower than 60 kernels per ear. Timely planting is a key component of all integrated pest management programs. Field corn planted during the recommended planting window for optimum yield is unlikely to experience corn earworm damage great enough to reduce yield.

Establishing Defoliation Thresholds for Insect Pest of Peanut in Mississippi

Defoliation of peanut by foliage-feeding insects reduces photosynthetic capacity, and in turn, may reduce pod yield, particularly when canopy loss occurs at critical growth stages, i.e., 40 or 80 d after full plant emergence (DAE). The objective of this research was to determine the impact of peanut defoliation levels of 0, 20, 40, 60, 80, and 100%, at 40 or 80 DAE on canopy height and width, plant biomass, pod grade and yield, and economic injury level. Research was conducted in Stoneville and Starkville MS in 2015 and 2016. The experimental design was a six (defoliation level) by two (defoliation timing) factorial arranged in a randomized complete block. Up to four wk after defoliation, canopy height, canopy width, and plant biomass were negatively correlated with defoliation level regardless of defoliation timing (40 and 80 DAE). Neither defoliation level nor timing had an effect on peanut grade or maturity. Similarly, defoliation at 40 DAE did not affect pod yield but when damage occurred 80 DAE, pod yield was reduced 18.6 kg/ha for every 1% increase in defoliation. Considering average crop value and insect control costs, the economic injury for peanut defoliation at 80 DAE is 5% defoliation. These data indicate that control of canopy-feeding insects is only economically viable when defoliation exceeds 5% defoliation at 80 DAE.

Value of Neonicotinoid Insecticide Seed Treatments in Mid-South Corn (Zea mays) Production Systems

Neonicotinoid seed treatments are one of several effective control options used in corn, Zea mays L., production in the Mid-South for early season insect pests. An analysis was performed on 91 insecticide seed treatment trials from Arkansas, Louisiana, Mississippi, and Tennessee to determine the value of neonicotinoids in corn production systems. The analysis compared neonicotinoid insecticide treated seed plus a fungicide to seed only with the same fungicide. When analyzed by state, corn yields were significantly higher when neonicotinoid seed treatments were used compared to fungicide only treated seed in Louisiana and Mississippi. Corn seed treated with neonicotinoid seed treatments yielded 111, 1,093, 416, and 140 kg/ha, higher than fungicide only treatments for Arkansas, Louisiana, Mississippi, and Tennessee, respectively. Across all states, neonicotinoid seed treatments resulted in a 700 kg/ha advantage compared to fungicide only treated corn seed. Net returns for corn treated with neonicotinoid seed treatment were $1,446/ha compared with $1,390/ha for fungicide only treated corn seed across the Mid-South. Economic returns for neonicotinoid seed treated corn were significantly greater than fungicide-only-treated corn seed in 8 out of 14 yr. When analyzed by state, economic returns for neonicotinoid seed treatments were significantly greater than fungicide-only-treated seed in Louisiana. In some areas, dependent on year, neonicotinoid seed treatments provide significant yield and economic benefits in Mid-South corn.

Value of Neonicotinoid Insecticide Seed Treatments in Mid-South Cotton (Gossypium hirsutum [Malvales: Malvaceae]) Production Systems

Neonicotinoid insecticides are currently one of two classes of chemicals available as a seed treatment for growers to manage early season insect pests of cotton, Gossypium hirsutum L. (Malvales: Malvaceae), and they are used on nearly 100% of cotton hectares in the midsouthern states. An analysis was performed on 100 seed-treatment trials from Arkansas, Louisiana, Mississippi, and Tennessee to determine the value of neonicotinoid seed treatments in cotton production systems. The analysis compared seed treated with neonicotinoid insecticides seed treatments plus a fungicide with seed only treated with fungicide. When analyzed by state, cotton yields were significantly greater when neonicotinoid seed treatments were used compared with fungicide-only treatments. Cotton treated with neonicotinoid seed treatments yielded 123, 142, 95, and 104 kg ha-1, higher than fungicide only treatments for Arkansas, Louisiana, Mississippi, and Tennessee, respectively. Across all states, neonicotinoid seed treatments provided an additional 115 kg lint ha-1 comparedwith fungicide only treated seed. Average net returns from cotton with a neonicotinoid seed treatment were $1,801 per ha-1 compared with $1,660 per ha-1 for cottonseed treated with fungicide only. Economic returns for cotton with neonicotinoid seed treatments were significantly greater than cottonseed treated with fungicide only in 8 out of 15 yr representing every state. These data show that neonicotinoid seed treatments provide significant yield and economic benefits in Mid-South cotton compared with fungicide only treated seed.

microRNA-10b enhances pancreatic cancer cell invasion by suppressing TIP30 expression and promoting EGF and TGF-β actions

This corrects the article DOI: 10.1038/onc.2013.405.

Residual and Systemic Efficacy of Chlorantraniliprole and Flubendiamide Against Corn Earworm (Lepidoptera: Noctuidae) in Soybean

Experiments were conducted in Mississippi from 2013 to 2015 to determine the systemic and residual efficacy of chlorantraniliprole and flubendiamide against corn earworm, Helicoverpa zea (Boddie), in soybean. Both insecticides were applied at V4 and R3. Ten leaves that were present at the time of application and 10 newly emerged leaves that were not present at the time of application were collected to measure residual and systemic efficacy, respectively. Ten pods were removed from each plot at R5.5. For all assays, corn earworm larvae were placed on plant material. Chlorantraniliprole appeared to provide systemic control of H. zea, but was dependent on soybean growth stage at the time of application. In the V4 experiment, chlorantraniliprole resulted in greater mortality than the control on new leaves at 7 d after treatment, but not at 14 d. In the R3 experiment, chlorantraniliprole resulted in greater than 90% mortality on new leaves at all evaluation intervals. Mortality of H. zea on new leaves was <17% for flubendiamide and was not different than the control. Both insecticides resulted in significant mortality of H. zea on leaves that were present at the time of application for at least 31 d after application. Chlorantraniliprole resulted in greater mortality than flubendiamide at 24 and 31 d. Neither insecticide resulted in mortality of H. zea feeding on reproductive structures. These results suggest that chlorantraniliprole moves to new vegetative structures but not to reproductive structures of soybean, and that flubendiamide does not move systemically.

Susceptibility of Helicoverpa zea (Lepidoptera: Noctuidae) Neonates to Diamide Insecticides in the Midsouthern and Southeastern United States

Corn earworm, Helicoverpa zea (Boddie), is a significant pest of agroecosystems in the midsouthern and southeastern regions of the United States. These insects have developed resistance to, or inconsistent control has occurred with, most insecticide classes. With their unique mode of action, insecticides in the diamide class have become a key component in management of agriculturally important lepidopteran pests. In this study, field populations of H. zea were collected in the southern United States and compared to susceptible laboratory colonies to generate baseline concentration-mortality data. LC50 and LC90 values were generated for flubendiamide and chlorantraniliprole using neonates. To achieve equivalent levels of mortality, a higher concentration of flubendiamide was required compared to chlorantraniliprole. Flubendiamide LC50 values for H. zea ranged from 16.45 to 30.74 ng/ml, with a mean of 23.53 ng/ml. Chlorantraniliprole LC50 values for H. zea ranged from 2.94 to 4.22 ng/ml, with a mean of 3.66 ng/ml. Significant differences were observed for some field populations relative to the laboratory colony. For flubendiamide, five populations had greater LC50 values and two populations had lower LC50 values compared to the laboratory colony. For chlorantraniliprole, three populations had greater LC50 values and three populations had lower LC50 values compared to the laboratory colony. The response of these populations most likely represents natural variability among populations and does not indicate a significant shift in susceptibility of this species.

Susceptibility of Flowering Cotton to Damage and Yield Loss from Tarnished Plant Bug (Hemiptera: Miridae)

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is a major pest of cotton in the midsouthern United States, including the states of Arkansas, Mississippi, Louisiana, western Tennessee, and southeastern Missouri. Insecticides provide the primary form of control for this pest, and numerous applications are required annually to control the tarnished plant bug. Little information exists regarding when to terminate insecticide applications targeting tarnished plant bugs in cotton. Numerous sprays are made late in the season to protect a small percentage of the overall yield. Experiments were conducted at the Mississippi State University Delta Research and Extension Center to determine the impact of tarnished plant bug infestation timings on cotton yield. Two separate planting dates were utilized to determine the weeks of flowering that tarnished plant bugs can cause significant yield losses. There was a significant planting date by treatment interaction. Overall, yields were greater in the first planting date than the second planting date. In both planting dates, the first 4 wk of flowering were the most critical for tarnished plant bug control, and this is when the greatest yield losses occurred. Also, when no insecticide applications were made after the fourth week of flowering, no significant yield loss was observed. These data demonstrate the importance of scouting and adhering to treatment thresholds during the early flowering period. These data also suggest that thresholds may be able to be modified or eliminated after the fourth week of flowering, but more research is needed to confirm this.

Value of Neonicotinoid Insecticide Seed Treatments in Mid-South Soybean ( Glycine max ) Production Systems

Early-season insect management is complex in the Mid-South region of the United States. A complex of multiple pest species generally occurs simultaneously at subthreshold levels in most fields. Neonicotinoids are the only insecticide seed treatment widely used in soybean, Glycine max L., production. An analysis was performed on 170 trials conducted in Arkansas, Louisiana, Mississippi, and Tennessee from 2005 to 2014 to determine the impact of neonicotinoid seed treatments in soybean. The analysis compared soybean seed treated with a neonicotinoid insecticide and a fungicide with soybean seed only treated with the same fungicide. When analyzed by state, soybean yields were significantly greater in all states when neonicotinoid seed treatments were used compared with fungicide-only treatments. Soybean treated with neonicotinoid treatments yielded 112.0 kg ha -1 , 203.0 kg ha -1 , 165.0 kg ha -1 , and 70.0 kg ha -1 , higher than fungicide-only treatments for Arkansas, Louisiana, Mississippi, and Tennessee, respectively. Across all states, neonicotinoid seed treatments yielded 132.0 kg ha -1 more than with fungicide-only treated seed. Net returns from neonicotinoid seed treatment usage were US$1,203 per ha -1 compared with US$1,172 per ha -1 for fungicide-only treated seed across the Mid-South. However, economic returns for neonicotinoid seed treatments were significantly greater than fungicide-only treated seed in 4 out of the 10 yr. When analyzed by state economic returns the neonicotinoid seed treatments were significantly greater than fungicide-only treated seed in Louisiana and Mississippi. These data show that in some areas and years, neonicotinoid seed treatments provide significant economic benefits in Mid-South soybean.

Evaluation of Corn Earworm, Helicoverpa zea (Lepidoptera: Noctuidae) , Economic Injury Levels in Mid-South Reproductive Stage Soybean

Field experiments were conducted in Starkville and Stoneville, MS; Marianna, AR; Winnsboro, LA; and Jackson, TN, during 2012 and 2014 to evaluate the relationship of corn earworm, Helicoverpa zea (Boddie), larval density and yield and the relationship between the percentage of damaged pods and yield in Mid-South soybean systems. Corn earworm moths were infested into field cages at R2 for 5-11 d to achieve a range of larval densities within each plot. Larval density was estimated at 14 d after infestation. Total pods and damaged pods were determined at 19 days after infestation to obtain the percentage of damaged pods. Plots were harvested at the end of each growing season and yield recorded. Data were subjected to regression analysis, and the relationship between larval density and yield and the relationship between the percentage of damaged pods and yield both can be described by a linear relationship. Each increase of one larvae per row-m resulted in a yield loss of 45.4 kg/ha. Similarly, each increase of 1% damaged pods resulted in a yield loss of 29.4 kg/ha. From these data, economic injury levels were developed for a range of crop values and control costs. These data suggest that current corn earworm threshold use in the Mid-South should be reduced.

Influence of Dual-Bt Protein Corn on Bollworm, Helicoverpa zea (Boddie), Survivorship on Bollgard II Cotton

Similar Cry proteins are expressed in both Bt corn, Zea mays L., and cotton, Gossypium hirsutum (L.), commercial production systems. At least one generation of corn earworm, Helicoverpa zea (Boddie), completes development on field corn in the Mid-South before dispersing across the landscape into other crop hosts like cotton. A concern is that Bt corn hybrids may result in selection for H. zea populations with a higher probability of causing damage to Bt cotton. The objective of this study was to determine the susceptibility of H. zea offspring from moths that developed on non-Bt and VT Triple Pro (VT3 PRO) field corn to lyophilized Bollgard II cotton tissue expressing Cry1Ac and Cry2Ab. Offspring of individuals reared on VT3 PRO expressing Cry1A.105 and Cry2Ab had a significantly higher LC50 two out of the three years this study was conducted. Excess larvae were placed on artificial diet and allowed to pupate to determine if there were any inheritable fitness costs associated with parental development on VT3 PRO corn. Offspring resulting from males collected from VT3 PRO had significantly lower pupal weight and longer pupal duration compared with offspring of individuals collected from non-Bt corn. However, offspring from females collected from VT3 PRO were not different from non-Bt offspring. Paternal influence on offspring in insects is not commonly observed, but illustrates the side effects of development on a transgenic plant expressing less than a high dose, 25 times the concentration needed to kill susceptible larvae.

Efficacy of Selected Insecticides Applied to Hybrid Rice Seed

Hybrid rice and insecticide seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel, have altered the landscape of rice production. The effect of reduced seeding rates on seed treatment efficacy in hybrid rice has not been studied. During 2011 and 2012, an experiment was conducted at seven locations to determine the relationship between low seeding rates used in hybrid rice and efficacy of selected insecticidal seed treatments as measured by rice water weevil densities and yield. Labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin were compared with higher rates of these products to determine if labeled rates provide an acceptable level of control of the rice water weevil. Study locations were divided into low, moderate, and high groups based on rice water weevil larval densities. All seed treatments and seed treatment rates reduced rice water weevil densities. However, there was no observed yield or economic benefit from the use of an insecticidal seed treatment in areas of low pressure. Differences in yield were observed among seed treatments and seed treatment rates in moderate and high pressure locations, and all seed treatments yielded better than the untreated plots, but these differences were not always economical. All seed treatments showed an economic advantage in areas of high weevil pressure, and there were no differences among seed treatment products or rates, suggesting that currently labeled seed treatment rates in hybrid rice are effective for rice water weevil management.

Seasonal Abundance and Phenology of Oebalus pugnax (Hemiptera: Pentatomidae) on Graminaceous Hosts in the Delta Region of Mississippi

The rice stink bug, Oebalus pugnax (F.), is a graminaceous feeder, and the most injurious insect pest of heading rice, Oryza sativa L., in the United States. Rice growers are aware of the economic importance of host grasses in O. pugnax abundance. However, the need for increased knowledge of host sequence relative to O. pugnax abundance is vital. Densities of O. pugnax on 15 graminaceous hosts were evaluated in the central Mississippi Delta from April through August in 2011 and 2012. Two cultivated and 13 wild host grasses were sampled using a sweep net. Overall, populations of O. pugnax were lower in 2012 than in 2011. Italian ryegrass, Lolium perenne L. ssp. multiflorum (Lambert), was the main host that supported O. pugnax survival and reproduction from overwintering to early summer. Echinochloa spp., Digitaria spp., and Eriochloa spp. maintained greater populations of O. pugnax in the summer. Browntop millet, Urochloa ramosa (L.) Nguyen, and broadleaf signalgrass, U. platyphylla (Munro ex C. Wright) R. D. Webster, were important for populations of O. pugnax populations immediately prior to overwintering. Host switching was also an important factor that contributed to O. pugnax abundance. The evolution of Italian ryegrass resistance to the broad spectrum herbicide glyphosate in the central Mississippi delta has become an important component of O. pugnax population dynamics because of its increased abundance in and around agricultural areas. Cultural control measures on host grasses before flowering could result in less use of insecticides, thereby reducing cost of rice production.

Impact of Oebalus pugnax (Hemiptera: Pentatomidae) Infestation Timing on Rice Yields and Quality

Sleeve and large field cage experiments were conducted in Stoneville, MS, in 2010 and 2011 to assess adult rice stink bug, Oebalus pugnax (F.), injury in rice. 'Cocodrie' and 'Wells' were infested at bloom, milk, and soft dough stages of panicle development. Twenty rice panicles were infested individually in the sleeve cage experiment as replicates with 0, 1, or 2 O. pugnax in a split-plot, completely randomized design. The large cage experiment had four replications infested with 9 or 18 O. pugnax per square meter over multiple rice panicles in a split-plot, randomized complete block design per cultivar. Caged uninfested controls were included in each experiment. Rough rice yield and percentage of clean, damaged, and blank kernels were evaluated. In both experiments, stage of panicle development impacted grain yield and quality. Yield loss was greatest during the bloom stage, while kernel damage was greatest during the milk and soft dough stages. Rice yield decreased with increased infestation density. Kernel damage increased with increased infestation density. Blank kernels affect yield, while kernel damage affects grain quality. While grain yield is the bottom line, grain quality affects marketability, which directly affects yield profitability. Based on these results, this study considers O. pugnax injury significant in all three stages of panicle development and concludes that a more aggressive threshold is recommended from panicle emergence through soft dough. More research is needed to determine the specific threshold, but it appears to be lower than the current threshold of 5 per 10 sweeps.

Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice

Two experiments were conducted at the Delta Research and Extension Center in Stoneville, MS, during 2011 and 2012 to determine the impact of water management practices on the efficacy of insecticidal seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel. Larval densities and yield were compared for plots treated with labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin and an untreated control. In the first experiment, plots were subjected to flood initiated at 6 and 8 wk after planting. Seed treatments significantly reduced larval densities with the 8-wk flood timing, but not the 6-wk flood timing. Overall, the treated plots yielded higher than the control plots. In the second experiment, the impact of multiple flushes on the efficacy of insecticidal seed treatments was evaluated. Plots were subjected to zero, one, or two flushes with water. All seed treatments reduced larval densities compared with the untreated control. Significantly fewer larvae were observed in plots that received one or two flushes compared with plots that did not receive a flush. All seed treatments resulted in higher yields compared to the untreated control in the zero and one flush treatments. When two flushes were applied, yield from the thiamethoxam and clothianidin treated plots was not significantly different from those of the control plots, while the chlorantraniliprole treated plots yielded significantly higher than the control. These data suggest that time from planting to flood did not impact the efficacy of seed treatments, but multiple flushes reduced the efficacy of thiamethoxam and clothianidin.

The Impact of Simulated Corn Earworm (Lepidoptera: Noctuidae) Damage in Indeterminate Soybean

Field experiments were conducted in Starkville and Stoneville, MS, during 2012 and 2013 to evaluate fruit removal level and timing on soybean growth, crop maturity, and yield. Fruit removal treatments consisted of 0, 50, and 100% of all fruit removed at specified growth stages (R2, R3, R4, and R5.5). Plant heights were determined at least biweekly from the time damage was imposed until R7. The impact of fruit removal level and timing on crop maturity was determined by estimating the percentage of naturally abscised leaves at 137 days after planting (DAP) when control plots were ∼10-15 d from harvest and the percentage of nonsenesced main stems at 139 DAP. There was no significant impact of fruit removal timing or fruit removal level on plant height or canopy width. Significant delays in crop maturity were observed when fruit removal was imposed at the R5.5 growth stage. Significant reductions in yield and crop value were observed as early as R3 and R4 when 100% of fruit was removed. Both fruit removal levels at R5.5 resulted in a significant reduction in yield and crop value compared with the nontreated control. Indeterminate soybeans appear to have the ability to compensate for some fruit loss during the early to middle reproductive growth stages without delaying maturity. However, severe fruit loss causes increasingly more yield loss as the plant approached maturity. Thresholds and economic injury levels therefore need to be adjusted accordingly to account for the dynamic nature of yield losses and crop maturity delays.

Decomposition of S-nitroso species

Not an ordinary day for Mario and Luigi; this work explores the decomposition pathways of RSNO⁺ species.

Host preference and suitability of grasses for Oebalus pugnax

The rice stink bug, Oebalus pugnax (Fabricius) (Hemiptera: Pentatomidae: Carpocorini), though graminaceous, discriminates among its numerous host grass species. This could represent a feeding preference, it could be related to host suitability for growth and development. To clarify the role of host grass discrimination, two laboratory studies were conducted: (1) free-choice tests to evaluate preferences of O. pugnax among 11 wild host grass species found in three rice-producing counties of the central Mississippi Delta (MS, USA), and (2) no-choice tests to evaluate the impact of rice (Oryza sativa L.), junglerice [Echinochloa colona (L.) Link], and dallisgrass (Paspalum dilatatum Poir.) (all Poaceae), on the development of O. pugnax from second instar to adult. In the free-choice test, four experiments were conducted, each with four sets of host grass species and observed 1, 2, 4, 8, and 16 h after release in cages. Approximately 4 h was necessary for O. pugnax to settle on preferred host grasses. Oebalus pugnax showed a feeding preference for junglerice over all 10 other grass species. Bahiagrass, Paspalum notatum Flueggé, was the least preferred. The no-choice tests showed significant effect of host grass species on O. pugnax mean development time of nymphal survival to adults. Survival of nymphs was lower and mean development time was longer on dallisgrass compared to rice and junglerice. Knowledge of O. pugnax rate of growth and development on host grasses could be useful in the future development of rice integrated pest management strategies.

A biological comparison of tarnished plant bug (Hemiptera: Miridae) populations from Mississippi's major agricultural regions

A laboratory experiment was performed to compare fitness parameters of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), populations collected from the Hills and Delta regions of Mississippi. Each population was split into two cohorts to be reared on cotton or artificial diet to make comparisons of food source and region of collection. Each population was maintained separately and allowed to mate. Nymphal survivorship from the F1 generation of each population from each region and food source was compared. Parameters measured included development times to fourth instar, fifth instar and adult, total nymphal survivorship, fecundity, and fertility. Populations collected from the Delta region and reared on cotton developed significantly faster at all life stages than other populations. Tarnished plant bugs from the Hills reared on cotton developed significantly slower than other populations, except those from the Hills reared on artificial diet. Populations reared on diet had significantly higher survivorship than those reared on cotton. Tarnished plant bug populations from the Delta region laid significantly more eggs per female per day than those from the Hills region. Populations reared on cotton also laid significantly more eggs per female per day than those reared on diet. Populations collected in the Delta region laid significantly more viable eggs per female per day than those from the Hills region. Tarnished plant bugs reared on cotton produced significantly more nymphs per female per day than those reared on diet. These data indicate there are differences in several fitness parameters between tarnished plant bug populations from the Hills and Delta regions of Mississippi.

Impact of planting date and varietal maturity on tarnished plant bug (Hemiptera: Miridae) in cotton

A field experiment was conducted in Stoneville, MS, during 2010 and 2011 to investigate the impact of varietal maturity, planting date, and insecticide application on tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), populations and damage in cotton. Four planting dates were selected to encompass the cotton-planting period in Mississippi. An early and late maturing variety were planted at each planting date, and each variety and planting date combination was either sprayed or unsprayed for tarnished plant bugs. Plots were sampled weekly from first square until physiological maturity. Plots were harvested at the end of the season. Early planting dates had lower densities of tarnished plant bug and required fewer insecticide applications than the later planting dates. Mid-April to early May planting dates sustained less yield loss from tarnished plant bug than mid-May to late-May planting dates. Tarnished plant bug had less impact on yield of the early maturing variety than on the late maturing variety. The sprayed plots yielded more than unsprayed plots. These data demonstrate that later plantings of cotton in the Mississippi Delta are likely to experience yield losses from tarnished plant bug and need to be sprayed more compared with early cotton plantings. As a result, growers should manage their crop for earliness through planting date and varietal selection.

Cotton aphid (Heteroptera: Aphididae) susceptibility to commercial and experimental insecticides in the southern United States

Cotton aphid, Aphis gossypii Glover, has a history of developing resistance to novel insecticides. A program is needed to monitor cotton aphid susceptibility to new insecticides. Concentration-mortality bioassays were conducted from 2008 to 2011 to monitor the susceptibility of cotton aphids from fields across the midsouthern United States to thiamethoxam and sulfoxaflor. Flonicamid was included in 2010 and 2011. Bioassays followed the procedures described by the Insecticide Resistance Action Committee for testing neonicotinoids against cotton aphid. Mortality was rated at 48 and 72 h. These bioassays suggest that high levels of resistance to thiamethoxam occur in cotton aphid throughout the midsouthern United States. Resistance ratios ranged from 0.9 to 562.6 at 48 h, and from 0.9 to 29.1 at 72 h. Aphid colonies tested were considered susceptible to flonicamid and sulfoxaflor. The LC50 values ranged from 1.43 to 6.60 ppm for flonicamid. The LC50 values for sulfoxaflor ranged from 1.01 to 5.85 ppm and 0.92-4.13 ppm at 48 and 72 h, respectively. These values represent the baseline variability of the susceptibility of cotton aphid to flonicamid and sulfoxaflor. The moderate level of variability observed combined with the high level of efficacy at low rates and the high reproductive rate of cotton aphid suggests that an effective resistance management plan needs to be devised for these insecticides. Flonicamid and sulfoxaflor should provide effective control of cotton aphid in areas where thiamethoxam resistance occurs. However, these insecticides need to be incorporated into a rotation strategy to preserve their efficacy against cotton aphid.

Impact of twospotted spider mite (Acari: Tetranychidae) duration of infestation on cotton seedlings

The yield response of cotton, Gossypium hirsutum L., to twospotted spider mite, Tetranychus urticae Koch, duration of infestation during the seedling stage was measured at Starkville and Stoneville, MS, during 2010 and 2011. The treatments included a noninfested control, infestations lasting for 7, 14, 21, or 28 d, and a season long infested control. Twospotted spider mites from a greenhouse colony were inoculated on all of the infested cotton plots during the three-leaf stage. Applications of miticides were made to terminate infestations at the desired timings for each treatment. Twospotted spider mite densities and injury ratings were determined for each treatment at the end of the infestation period and yield was measured at the end of the season. Twospotted spider mite densities and injury rating significantly increased as duration of infestation increased. Significant differences in yield were observed between treatments. These data suggest infestations initiated at the three-leaf cotton growth stage with population densities at a minimum of 0.39 mites/cm2 existing > 14 d could result in reduction of cotton yields.

Effects of aldicarb and neonicotinoid seed treatments on twospotted spider mite on cotton

Twelve field experiments and one laboratory experiment were conducted to determine the effects of furrow applied aldicarb and seed treatments of thiamethoxam, imidacloprid, Avicta (thiamethoxam + abamectin), Aeris (imidacloprid + thiodicarb), and acephate on twospotted spider mite, Tetranychus urticae Koch, on cotton, Cossypium hirsutum L. For the field experiments, data were pooled across all experiments for analysis. Aeris, thiamethoxam, and imidacloprid treatments resulted in twospotted spider mite densities greater than those in the untreated check, aldicarb, and acephate treatments. However, cotton treated with Avicta (thiamethoxam + abamectin) had 34% fewer mites than other neonicotinoid seed treatments when infestations occurred near cotyledon stage. Untreated check and aldicarb treatments had the lowest mite densities. Only aldicarb reduced mite densities below that in the untreated check. In a laboratory trial, the fecundity of twospotted spider mite was measured. While neonicotinoid seed treatments increased mite densities in the field, they did not increase fecundity in the laboratory experiment. Foliar applied thiamethoxam slightly elevated average fecundity in the laboratory experiment. Increased use of neonicotinoid seed treatments instead of furrow applied aldicarb is likely at least partly responsible for recent increased twospotted spider mite infestations in seedling cotton across the mid-south.

Development of a plant-based threshold for tarnished plant bug (Hemiptera: Miridae) in cotton

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is an important pest of cotton, Gossypium hirsutum L., in the mid-southern United States. It is exclusively controlled with foliar insecticide applications, and sampling methods and thresholds need to be revisited. The current experiment was designed to establish a plant-based threshold during the flowering period of cotton development. Experiments were conducted in MisSissippi in 2005 and 2006, Arkansas in 2005, and Louisiana in 2005 through 2008. Treatments consisted of various combinations of thresholds based on the percentage of dirty squares that were compared with the current threshold with a drop cloth or automatic weekly applications. Dirty squares were characterized as those with yellow staining on the developing bud resulting from tarnished plant bug excrement. Treatments consisted of 5, 10, 20, and 30% dirty squares. Each plot was sampled weekly, and insecticides were applied when the mean of all replications of a particular treatment reached the designated threshold. At the end of the season, plots were harvested and lint yields were recorded. Differences were observed in the number of applications and yields among the different treatments. The 10% dirty squares threshold resulted in a similar economic return compared with the drop cloth. A threshold of 10% dirty squares resulted in a similar number of insecticide applications, yields, and economic returns compared with that observed with the drop cloth. These results suggest that a threshold of 10% dirty squares could be used to trigger insecticide applications targeting tarnished plant bugs in flowering cotton.

Acephate resistance in populations of the tarnished plant bug (Heteroptera: Miridae) from the Mississippi River Delta

A monitoring program that used a glass-vial bioassay to detect acephate resistance in populations of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Heteroptera: Miridae), was carried out with weed-collected populations from 20 sites in the delta of Arkansas, Louisiana, and Mississippi. Additional results from field tests using recommended rates of formulated acephate in cotton showed that plant bug populations with resistance ratio (RR50) values > 3.0 for acephate (from the glass-vial bioassay) would be difficult to control in the field. Over a 4-yr-period from 2001 through 2004, only one population tested with the glass-vial bioassay was found with an RR50 value > 3.0 for acephate, but six populations having RR50 values > 3.0 were found in the delta in 2005. In fall 2005, an additional 10 populations from the hill region (the cotton growing areas outside the delta) were tested and four of these populations had RR50 values > 3.0. The number of populations with RR50 values > 3.0 increased to five of 10 and 18 of 20 in the hills and delta, respectively, in fall 2006. Laboratory tests using resistant populations found that resistance to acephate was not sex-linked and the alleles controlling the resistance were semidominant in nature. Because of the large increase in resistant populations and the nature of the resistance found in this study, along with control problems experienced by growers in 2006, entomologists in the mid-South strongly recommended that alternation of insecticide classes in field treatments for plant bug control be used by growers in 2007. This control strategy probably helped control plant bugs in the hills of MS where plant bug pressure was low in 2007, and only one population was found in the fall with an RR50 value > 3.0. Plant bug pressure was very high in many parts of the delta in 2007, and 15 of the 20 populations tested in the fall had RR50 values > 3.0. In one field test in cotton, a population with multiple resistance was tested and not effectively controlled in treatments using recommended rates of carbamate, organophosphate, and pyrethroid insecticides. Alternation of insecticide classes may not work very well when populations are present that are resistant to three of the four main classes of cotton insecticides. New insecticides in different classes are badly needed for control of tarnished plant bugs in cotton in the mid-South.

Yield response of dual-toxin Bt cotton to Helicoverpa zea infestations

Field cage experiments were conducted to determine the impact of bollworms, Helicoverpa zea (Boddie), on yields of Bollgard II and Widestrike cotton, Gossypium hirsutum L. One-day-old bollworm larvae were infested in white flowers of Bollgard II and in white flowers and terminals of Widestrike cotton. The infestation levels included 0, 50, and 100% of white flowers for each type of cotton. Terminal infestations included one or two larvae per terminal on Widestrike cotton. Larvae were placed in flowers of Bollgard II cotton each day for 1 to 4 wk during the first 4 wk of flowering during 2003, 2004, and 2005 seasons and in the flowers or terminals of Widestrike cotton each day for 1 to 3 wk. Averaged across years and durations of infestation, yields of Bollgard II cotton were significantly reduced compared with noninfested Bollgard II cotton when 100% of white flowers were infested. For Widestrike cotton, there was a reduction in yield when 100% of white flowers were infested in 2005, but not in 2006. There was a significant relationship for cumulative numbers of white flowers infested on seedcotton yield of Bollgard II during one of the 3 yr of the experiment. The regression equation during that year had a slope of -0.77. No significant relationships were observed for cumulative numbers of white flowers infested on yields of Widestrike cotton. Results of the current experiment suggest bollworms will rarely cause yield losses of Bollgard II and Widestrike cotton. Future research will need to focus on developing specific thresholds for bollworms on Bollgard II and Widestrike cotton.