Efficacy and Residual Toxicity of Insecticides on Plutella xylostella and Their Selectivity to the Predator Solenopsis saevissima

We evaluated the efficacy and residual toxicity of nine commercial insecticides on Plutella xylostella and their selectivity to the predator ant Solenopsis saevissima under laboratory and field conditions. First, to test the insecticides' effectiveness and selectivity, we conducted concentration-response bioassays on both species and the mortalities were recorded 48 h after exposure. Next, rapeseed plants were sprayed following label rate recommendations in the field. Finally, insecticide-treated leaves were removed from the field up to 20 days after application and both organisms were exposed to them as in the first experiment. Our concentration-response bioassay indicated that seven insecticides caused mortality ≥80% of P. xylostella: bifenthrin, chlorfenapyr, chlorantraniliprole, cyantraniliprole, indoxacarb, spinetoram, and spinosad. However, only chlorantraniliprole and cyantraniliprole caused mortality ≤30% of S. saevissima. The residual bioassay indicated that four insecticides had a long-lasting effect, causing mortality of 100% to P. xylostella 20 days after application: chlorantraniliprole, cyantraniliprole, spinetoram, and spinosad. For S. saevissima, bifenthrin caused mortality of 100% during the evaluated period. Additionally, mortality rates below 30% occurred four days after the application of spinetoram and spinosad. Thus, chlorantraniliprole and cyantraniliprole are safe options for P. xylostella management since their efficacy favor S. saevissima.

Spatial Distribution of Frankliniella schultzei (Thysanoptera: Thripidae) in Open-Field Yellow Melon, With Emphasis on the Role of Surrounding Vegetation as a Source of Initial Infestation

Frankliniella schultzei (Trybom) is a serious pest of melon crops and is commonly found in the main producing areas of melon in Brazil (North and Northeast regions). This pest causes significant losses, damaging plants through feeding and tospovirus vectoring. Thus, the proper management of F. schultzei is crucial to prevent economic losses, and knowledge of the within-field distribution patterns of F. schultzei can be used to improve this pest management. This study aimed to determine the within-field distribution (through semivariogram modeling and kriging interpolation) and the factors associated with F. schultzei abundance in open-field yellow melon crops. We surveyed four yellow melon fields located in Formoso do Araguaia (Tocantins state, North Brazil) for thrips abundance in various crop stages (vegetative, flowering, and fruiting) in 2015 and 2016. Twelve models were fitted and it was determined that F. schultzei counts were strongly aggregated. The median spatial dependence was 4.79 m (range 3.55 to 8.02 m). The surface maps generated by kriging depicted an edge effect in fields 3 and 4. In addition, correlation analyses indicated that air temperature and presence of surrounding cucurbits are positively associated with F. schultzei abundance in yellow melon fields. Altogether, these insights can be combined for spatially based pest management, especially when the conditions (cucurbits in the surroundings and warmer periods) are favorable to F. schultzei.

Chemical composition and in vitro inhibitory effects of essential oils from fruit peel of three Citrus species and limonene on mycelial growth of Sclerotinia sclerotiorum

Essential oils (EO) from aromatic and medicinal plants generally perform a diverse range of biological activities because they have several active constituents that work in different mechanisms of action. EO from Citrus peel have an impressive range of food and medicinal uses, besides other applications. EO from Citrus reticulata, C. sinensis and C. deliciosa were extracted from fruit peel and analyzed by GC-MS. The major constituent of EO under evaluation was limonene, whose concentrations were 98.54%, 91.65% and 91.27% for C. sinensis, C. reticulata and C. deliciosa, respectively. The highest potential of inhibition of mycelial growth was observed when the oil dose was 300 μL. Citrus oils inhibited fungus growth in 82.91% (C. deliciosa), 65.82% (C. sinensis) and 63.46% (C. reticulata). Anti-Sclerotinia sclerotiorum activity of 90% pure limonene and at different doses (20, 50, 100, 200 and 300 μL) was also investigated. This monoterpene showed to be highly active by inhibiting 100% fungus growth even at 200 and 300 μL doses. This is the first report of the in vitro inhibitory effect of natural products from these three Citrus species and its results show that there is good prospect of using them experimentally to control S. sclerotiorum, in both greenhouse and field conditions.

Economic injury levels and sequential sampling plans for control decision-making systems of Bemisia tabaci biotype B adults in watermelon crops

BACKGROUND

Decision-making systems are essential parts of integrated pest management programs. The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a major pest of many crops, including watermelon (Citrullus lanatus), the second most consumed fruit worldwide. However, there are still no studies on decision-making systems for B. tabaci on this crop. Thus, we aim to determine a decision-making system to control B. tabaci biotype B on watermelon crops.

RESULTS

The highest densities of B. tabaci biotype B reduced the yield of watermelon crops by up to 56%. Watermelon plants were more susceptible to the pest at the vegetative stage than at the reproductive stage. The economic injury levels of B. tabaci biotype B when watermelon prices were low, average, and high were respectively, 0.52, 0.21 and 0.13 adults leaf^-1 at the vegetative stage, and 1.69, 0.69 and 0.44 adults leaf^-1 at the reproductive stage. The sequential plans reached the same decisions as the conventional plan, and reduced the time and cost of sampling by up to 92.68%.

CONCLUSION

The decision-making systems determined in this study enable an expedited and proper decision to be made for controlling B. tabaci, biotype B and can be used in different price situations for watermelon and in crops at different phenological stages. © 2018 Society of Chemical Industry.

Spatiotemporal Dynamics of Whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) in Commercial Watermelon Crops

Spatiotemporal dynamics studies of crop pests enable the determination of the colonization pattern and dispersion of these insects in the landscape. Geostatistics is an efficient tool for these studies: to determine the spatial distribution pattern of the pest in the crops and to make maps that represent this situation. Analysis of these maps across the development of plants can be used as a tool in precision agriculture programs. Watermelon, Citrullus lanatus (Thunb.) Matsum. and Nakai (Cucurbitales: Cucurbitaceae), is the second most consumed fruit in the world, and the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the most important pests of this crop. Thus, the objective of this work was to determine the spatiotemporal distribution of B. tabaci in commercial watermelon crops using geostatistics. For 2 yr, we monitored adult whitefly densities in eight watermelon crops in a tropical climate region. The location of the samples and other crops in the landscape was georeferenced. Experimental data were submitted to geostatistical analysis. The colonization of B. tabaci had two patterns. In the first, the colonization started at the outermost parts of the crop. In the second, the insects occupied the whole area of the crop since the beginning of cultivation. The maximum distance between sites of watermelon crops in which spatial dependence of B. tabaci densities was observed was 19.69 m. The adult B. tabaci densities in the eight watermelon fields were positively correlated with rainfall and relative humidity, whereas wind speed negatively affected whiteflies population.

Sampling Plans for the Thrips Frankliniella schultzei (Thysanoptera: Thripidae) in Three Lettuce Varieties

The common blossom thrips, Frankliniella schultzei Trybom (Thysanoptera: Thripidae), is an important lettuce pest worldwide. Conventional sampling plans are the first step in implementing decision-making systems into integrated pest management programs. However, this tool is not available for F. schultzei infesting lettuce crops. Thus, the objective of this work was to develop a conventional sampling plan for F. schultzei in lettuce crops. Two sampling techniques (direct counting and leaf beating on a white plastic tray) were compared in crisphead, looseleaf, and Boston lettuce varieties before and during head formation. The frequency distributions of F. schultzei densities in lettuce crops were assessed, and the number of samples required to compose the sampling plan was determined. Leaf beating on a white plastic tray was the best sampling technique. F. schultzei densities obtained with this technique were fitted to the negative binomial distribution with a common aggregation parameter (common K = 0.3143). The developed sampling plan is composed of 91 samples per field and presents low errors in its estimates (up to 20%), fast execution time (up to 47 min), and low cost (up to US $1.67 per sampling area). This sampling plan can be used as a tool for integrated pest management in lettuce crops, assisting with reliable decision making in different lettuce varieties before and during head formation.

Feasible sampling plan for Bemisia tabaci control decision-making in watermelon fields

BACKGROUND

The silverleaf whitefly Bemisia tabaci is one of the most important pests of watermelon fields worldwide. Conventional sampling plans are the starting point for the generation of decision-making systems of integrated pest management programs. The aim of this study was to determine a conventional sampling plan for B. tabaci in watermelon fields.

RESULTS

The optimal leaf for B. tabaci adult sampling was the 6^th most apical leaf. Direct counting was the best pest sampling technique. Crop pest densities fitted the negative binomial distribution and had a common aggregation parameter (K_common ). The sampling plan consisted of evaluating 103 samples per plot. This sampling plan was conducted for 56 min, costing US$ 2.22 per sampling and with a 10% maximum evaluation error.

CONCLUSIONS

The sampling plan determined in this study can be adopted by farmers because it enables the adequate evaluation of B. tabaci populations in watermelon fields (10% maximum evaluation error) and is a low-cost (US$ 2.22 per sampling), fast (56 min per sampling) and feasible (because it may be used in a standardized way throughout the crop cycle) technique. © 2017 Society of Chemical Industry.

Economic injury levels and sequential sampling plans for Frankliniella schultzei in watermelon crops

BACKGROUND

The thrips Frankliniella schultzei is an important watermelon pest. Nevertheless, economic injury levels and sampling plans for this pest have not yet been determined for this crop. Thus, the objective of the present study was to determine the economic injury levels and develop sequential sampling plans for F. schultzei in conditions of low, medium and high fruit prices.

RESULTS

The attack of F. schultzei on watermelon plants at the vegetative stage reduced the crop's productivity, which did not happen at the flowering and fruiting stage. The economic injury levels were 0.09, 0.04 and 0.02 thrips leaf^-1 when the watermelon price was low ($US 62.5 t^-1 ), medium ($US 140.63 t^-1 ) and high ($US 218.75 t^-1 ) respectively. The three sequential sampling plans for F. schultzei generated for the economic injury levels resulted in similar and more rapid decisions compared with the conventional plan, especially when the pest density was high.

CONCLUSIONS

The three economic injury levels and the sequential sampling plans generated in the present study can be incorporated into integrated pest management programmes for watermelon crops because these plans provide a rapid and adequate control decision for F. schultzei. © 2016 Society of Chemical Industry.

Anti-inflammatory and anti-nociceptive effects of Zeyheria montana (Bignoniaceae) ethanol extract

In this work, the analgesic and anti-inflammatory activities of Zeyheria montana Mart. ethanol leaf extract were investigated at doses of 75, 150 and 300 mg/kg body weight. In the analgesic assay, against a chemical stimulus in mice, acetic acid-induced writhes were significantly inhibited by the extract at doses of 75 mg/kg (67.27%), 150 mg/kg (49.38%) and 300 mg/kg (82.87%). Also, a vigorous decrease in hyperalgesia was observed when measured after 2 h and 6 h of lipopolysaccharide stimulation of rats for all doses of extract tested. Z. montana extract, at doses of 75 and 300 mg/kg, caused very slight central analgesia in rats submitted to thermal stimulus, particularly noticeable at 30 min following treatment. The anti-inflammatory activity of Z. montana extract on carrageenan-induced oedema in rats was evaluated. The oedema development, measured at 180 min following carrageenan intraplantar injection, was significantly reduced by all tested doses: 75 mg/kg (33.30%), 150 mg/kg (45.80%) and 300 mg/kg (75.00%). The LD50 value was greater than 2000 mg/kg. These results demonstrated that the ethanol extract from Z. montana leaf possesses anti-nociceptive and anti-inflammatory activities, which could be of relevance for the pharmacological control of pain and inflammatory processes.

In vitro evaluation of the cytotoxic and trypanocidal activities of Ampelozizyphus amazonicus (Rhamnaceae)

Ampelozizyphus amazonicus Ducke is a tree commonly found in the Amazon region and an extract of its stem bark is popularly used as an antimalarial and anti-inflammatory agent and as an antidote to snake venom. Ursolic acid; five lupane type triterpenes: betulin, betulinic acid, lupenone, 3beta-hydroxylup-20(29)-ene-27,28-dioic acid, and 2alpha,3beta-dihydroxylup-20(29)-ene-27,28-dioic acid, and three phytosteroids: stigmasterol, sitosterol and campesterol, have been isolated from stem extracts of A. amazonicus Ducke. Their structures were characterized by spectral data including COSY and HMQC. In an in vitro biological screening of the isolated compounds, 3beta-hydroxylup-20(29)-ene-27,28-dioic acid was cytotoxic against the SKBR-3 human adenocarcinoma cell line (1 to 10 mg/mL), while 2alpha,3beta-dihydroxylup-20(29)-ene-27,28-dioic acid exhibited cytotoxicity against both SKBR-3 human adenocarcinoma and C-8161 human melanoma tumor cell lines (>0.1 mg/mL). In the present study, different extracts and some fractions of this plant were also investigated for trypanocidal activity due to the presence of pentacyclic triterpenes. The triterpene classes are potent against Trypanosoma cruzi. The bioassays were carried out using blood collected from Swiss albino mice by cardiac puncture during the parasitemic peak (7th day) after infection with the Y strain of T. cruzi. The results obtained showed that A. amazonicus is a potential source of bioactive compounds since its extracts and fractions isolated from it exhibited in vitro parasite lysis against trypomastigote forms of T. cruzi at concentrations >100 microg/mL. Fractions containing mainly betulin, lupenone, 3beta-hydroxylup-20(29)-ene-27,28-dioic acid, and 2alpha,3beta-dihydroxylup-20(29)-ene-27,28-dioic acid showed more activity than crude extracts.

A 3' cis-regulatory region controls wingless expression in the Drosophila eye and leg primordia

The precise regulation of wingless (wg) expression in the Drosophila eye disc is key to control the anteroposterior and dorsoventral patterning of this disc. Here, we identify an eye disc-specific wg cis-regulatory element that functions as a regulatory rheostat. Pannier (Pnr), a transcription factor previously proposed to act as an upstream activator of wg, is sufficient to activate the eye disc enhancer but required for wg expression only in the peripodial epithelium of the disc. We propose that this regulation of wg by Pnr appeared associated to the development of the peripodial epithelium in higher dipterans and was added to an existing mechanism regulating the deployment of wingless in the dorsal region of the eye primordium. In addition, our analysis identifies a separate ventral disc enhancer that lies adjacent to the eye-specific one, and thus altogether, they define a 1-kb genomic region where disc-specific enhancers of the wg gene are located.

Dynamics and function of intron sequences of the wingless gene during the evolution of the Drosophila genus

To understand the function and evolution of genes with complex patterns of expression, such as the Drosophila wingless gene, it is essential to know how their transcription is regulated. However, extracting the relevant regulatory information from a genome is still a complex task. We used a combination of comparative genomics and functional approaches to identify putative regulatory sequences in two introns (1 and 3) of the wingless gene and to infer their evolution. Comparison of the sequences obtained from several Drosophila species revealed colinear and well-conserved sequence blocks in both introns. Drosophila willistoni showed a rate of evolution, in both introns, faster than expected from its phylogenetic position. Intron 3 appeared to be composed of two separate modules, one of them lost in the willistoni group. We tested whether sequence conservation in noncoding regions is a reliable indicator of regulatory function and, if this function is conserved, by analyzing D. melanogaster transgenic reporter lines harboring intron 3 sequences from D. melanogaster (Sophophora subgenus) and the species from the Drosophila subgenus presenting the most divergent sequence, D. americana. The analysis indicated that intron 3 contains pupal enhancers conserved during the evolution of the genus, despite the fact that only 30% of the D. melanogaster intron 3 sequences lie in conserved blocks. Additional analysis of D. melanogaster transgenic reporter lines harboring intron 3 sequences from D. willistoni revealed the absence of an abdomen-specific expression pattern, probably due to the above-mentioned loss of a regulatory module in this species.

The RGS domain-containing fission yeast protein, Rgs1p, regulates pheromone signalling and is required for mating

BACKGROUND

When nutritionally starved, the fission yeast Schizosaccharomyces pombe enters a cell differentiation process which leads to mating and meiosis. The Ste11 protein is a key regulator of this differentiation pathway, activating the transcription of mating and meiotic genes upon starvation.

RESULTS

Here, we describe rgs1, a member of the Regulator of G-protein Signalling (RGS) family, as a novel Ste11 target gene. rgs1 expression requires both an Ste11-mediated nitrogen starvation signal and the pheromone-induced activation of the Byr2/Byr1/Spk1 MAPK pathway. We show that rgs1 deletion results in a sensitivity to pheromone and in a mating defect. Deltargs1 cells initiate the mating pathway normally, undergoing sexual agglutination and G1 arrest, while inducing pheromone-dependent transcription, but then fail to fuse with a mating partner while elongating abnormal conjugation tubes. Endogenous Rgs1 tagged with GFP localizes to the nucleus and cytoplasm, and this localization pattern is not altered during pheromone treatment. Importantly, Rgs1 function requires its C-terminal RGS domain, as well as a central DEP domain and a novel homology domain present in its N-terminal region (Fungal-DR domain).

CONCLUSIONS

These results demonstrate that rgs1 expression requires nutritional starvation and pheromone signalling. Rgs1 negatively regulates pheromone signalling during mating, acting in a negative feedback loop that is essential for the mating process.

Inhibition of the lethal and myotoxic activities of Crotalus durissus terrificus venom by Tabernaemontana catharinensis: identification of one of the active components

In Brazilian folk medicine, victims of bites by poisonous animals are usually treated with plant extracts derived from the diverse national flora. The chemical and pharmacological properties of most extracts were yet not investigated. In the rural community of Assis-SP, the root bark of Tabernaemontana catharinensis ("leiteiro", "cow milk") is applied to the site of the snake bite and believed to neutralize the effect of the venom. We report here the ability of the lyophilized aqueous extract (AE) and of a pure compound obtained from the ethanolic extract of T. catharinensis to inhibit the lethal and myotoxic activities of C. d. terrificus (South American rattlesnake) venom. Doses of 10 mg AE/100 g, injected (i.m., rat) 20 s after injecting (i.m.) the venom and that of 2.5 mg AE/100 g, incubated for 1 h at 25 degrees C with the venom before injection (i.m.) were able to neutralize the lethal activity of 2LD50. These data indicate that T. catharinensis could be used as a source of a model molecule able to neutralize the lethality and myotoxicity induced by C. d. terrificus venom. Its ethanolic extract was then fractionated on a silica gel 60 chromatography column affording fractions A to F. Fraction A consisted basically of non-polar compounds, terpenes and sterols. Fraction D showed a pronounced antiophidian activity which was later correlated with the presence of the quaternary alkaloid 12-methoxy-4-methylvoachalotine in this fraction. This alkaloid was isolated and inhibited 100% lethality when injected 20 s after 2 LD50 at 1.7 mg/100 g.

A case of mosaic trisomy 21 with Down's syndrome signs and normal intellectual development

The present case study describes an adult male with clinical signs of mild Down's syndrome (DS), who performed well at school and reached university level. A karyotype was done on a lymphocyte culture and mosaic trisomy 21 was found in 3% of the 437 cells analysed. Eleven signs from Jackson's checklist were found in the clinical evaluation, which along with the analysis of the subject's dermatoglyphic traits, confirmed the DS diagnosis. Cognitive evaluation was done with several psychological tests and the results were within the average range. This rare phenotypic association shows that normal intellectual development may be possible in DS. This finding could be explained by the low trisomic cell frequency, which may have little effect on the critical tissues for intellectual development, and it might also reflect the wide phenotypic variation in mosaic trisomy 21. Other factors, such as strong family support, early and continued intervention programmes for both physical and speech therapy, and a thorough educational process, also provided opportunities for the development of the cognitive potential of the subject.