Side-effects of 100 pesticides on the predatory mite Phytoseiulus persimilis, collected and evaluated according to the EPPO Guideline

Meta-Analysis of Herbicide Non-Target Effects on Pest Natural Enemies

A critical component of integrated pest management is minimizing disruption of biological control by reducing the use of pesticides with significant non-target effects on natural enemies. Insecticide non-target effects testing for natural enemies has become increasingly common, but research examining the non-target effects of herbicides on natural enemies is scarce, and recommendations regarding herbicide selectivity are non-existent. We used meta-analysis to summarize laboratory bioassays testing non-target effects of herbicides on arthropod natural enemies and identify patterns in taxon susceptibility and active ingredient toxicity. Data were extracted from 78 papers representing 801 total observations. Herbicides increased natural enemy mortality and decreased longevity, reproduction, and predation. Mesostigmatan mites and hemipterans were the most sensitive to herbicides, and spiders, neuropterans, and hymenopterans were the least sensitive. Mortality was higher in juvenile predators versus parasitoids but did not differ between adults; parasitoid juveniles are likely better protected within the host. In terms of acute mortality, metribuzin, glufosinate, and oxyfluorfen were the most harmful herbicides. Only nicosulfuron, rimsulfuron, pendimethalin, phenmedipham, atrazine, and urea did not increase natural enemy mortality. The large effect size of glufosinate is particularly concerning, as it is the most likely replacement herbicide for glyphosate in many crops. Many active ingredients remain under-studied. Our analysis indicates that herbicides have a strong potential to disrupt biological control in cropping systems.

Herbicides Harm Key Orchard Predatory Mites

The phytoseiid mites Galendromus occidentalis and Amblydromella caudiglans are critical for conservation biological control of pest mites in Washington State, U.S.A. apples. While the non-target effects of insecticides on phytoseiids are well described, research on herbicide effects is limited. Using laboratory bioassays, we examined lethal (female mortality) and sublethal (fecundity, egg hatch, larval survival) effects of seven herbicides and five adjuvants on A. caudiglans and G. occidentalis. The effects of mixing herbicides with recommended adjuvants were also tested to determine if the addition of an adjuvant increased herbicide toxicity. Glufosinate was the least selective herbicide tested, causing 100% mortality in both species. Paraquat caused 100% mortality in A. caudiglans and 56% mortality in G. occidentalis. Sublethal effects were significant for both species when exposed to oxyfluorfen. Adjuvants did not cause non-target effects in A. caudiglans. The non-ionic surfactant and methylated seed oil increased mortality and decreased reproduction in G. occidentalis. The high toxicity of glufosinate and paraquat for both predators is concerning; these are the primary "burn down" herbicide alternatives to glyphosate, which is decreasing in use due to consumer toxicity concerns. Field studies are needed to determine the extent to which herbicides disrupt orchard biological control, focusing on glufosinate, paraquat, and oxyfluorfen. Consumer preferences will need to be balanced with natural enemy conservation.

Nontarget Impacts of Herbicides on Spiders in Orchards

Spiders are key predators in many agroecosystems, including orchards. Despite the importance of spiders in biological control, pesticide nontarget effects on this group are poorly described. This is especially true for herbicides, which spiders frequently encounter as they move between the ground cover and tree canopy. We sought to determine the nontarget effects of seven herbicides used in orchards on three species of spiders that are commonly found in Washington state (USA) orchards: Pelegrina aeneola (Curtis) (Araneae: Salticidae), Philodromus cespitum (Walckenaer) (Araneae: Philodromidae), and Phanias watonus (Chamberlin & Ivie) (Araneae: Salticidae). Immature spiders were collected from orchards and used in laboratory assays. Single spiders were placed in vials with dried herbicide residues and mortality was evaluated after 1, 2, and 5 d. We also evaluated herbicide impacts on prey consumption rates and on spider movement using motion-tracking software. Only oxyfluorfen caused significant spider mortality. P. cespitum seemed to be less acutely sensitive to oxyfluorfen than the two salticid species. Several herbicide treatments significantly increased locomotion in P. cespitum, whereas rimsulfuron numerically decreased movement of P. aeneola. Sulfonylurea herbicides (rimsulfuron, halosulfuron) decreased prey consumption of P. aeneola. Our work indicates that although spiders may be less acutely sensitive to some pesticides than beneficial insects, they can be affected by sublethal effects of herbicides. Future work should determine if herbicide applications impact spider abundance in the field and reduce biological control services. In general, more work is needed on the impacts of herbicides on natural enemies.

Meta-analysis and review of pesticide non-target effects on phytoseiids, key biological control agents

Understanding pesticide non-target effects on natural enemies is a key element of successful conservation biological control. Due to their importance in agroecosystems worldwide, the phytoseiid mites are the most well-studied natural enemies in pesticide selectivity research. The wealth of literature associated with this topic allows for a thorough meta-analysis of pesticide non-target effects and may also indicate general trends relevant to many cropping systems. We conducted a meta-analysis using 2386 observations from 154 published papers examining the impact of pesticides on lethal (adult and juvenile mortality) and sublethal (fecundity, egg hatch) effects. Insecticides and herbicides did not statistically differ in toxicity to phytoseiids, but research on herbicide non-target effects is scarce. Specific insecticides, fungicides, and miticides were sorted into least and most harmful categories. Phytoseiid species also differed in sensitivity, with Galendromus occidentalis (Nesbitt), Neoseiulus californicus (McGregor), and Typhlodromus pyri Scheuten among the least sensitive species. Sensitivity variation may be partly due to pesticide resistance; the greatest differences between species were within older mode of action (MOA) groups, where resistance development has been documented. It has been speculated that specialist phytoseiids, which closely associate with Tetranychus spp. spider mites, have more opportunities for resistance development due to their necessary proximity to a pest that rapidly develops resistance. Effect sizes were higher for generalist phytoseiid species, supporting this hypothesis. This meta-analysis highlights pesticide types (herbicides) and MOA groups where more research is clearly needed. Our analysis also allows for more robust generalizations regarding which pesticides are harmful or selective to phytoseiids. © 2021 Society of Chemical Industry. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Not all predators are equal: miticide non-target effects and differential selectivity

BACKGROUND

Biological control in conventional agroecosystems involves the integration of chemical and conservation tactics, requiring knowledge of pesticide non-target effects on key natural enemies. Even for natural enemy groups such as predatory mites (Acari: Phytoseiidae), where pesticide non-target effects have been thoroughly examined, there may be significant differences in species susceptibility to specific active ingredients, including newer selective products. Using bioassays, we examined lethal (female mortality) and sublethal (fecundity, egg hatch, larval survival) effects of ten miticides on a spider mite pest (Tetranychus urticae) and three insectary-purchased predatory mites (Phytoseiulus persimilis, Neoseiulus californicus, and N. fallacis) commonly used for its management. Susceptibility of field-collected and insectary-reared populations of P. persimilis was also compared. Cumulative impacts on production of larvae by treated female spider mites and predators were compared to create a metric that simultaneously accounted for miticide efficacy and selectivity.

RESULTS

Bifenthrin was the least selective, as it caused acute toxicity to all predators and had little efficacy against T. urticae. Hexythiazox and cyflumetofen were the most selectively favorable. Phytoseiulus persimilis populations were similar in which miticides they were sensitive to, although the insectary-purchased population was generally more sensitive.

CONCLUSIONS

All products, including those considered selective (cyflumetofen, bifenazate, acequinocyl) had non-target effects on at least one species of predator tested. This work emphasizes that there is high variability in selectivity among species, highlighting the need to examine key natural enemies individually when creating management programs. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Non-target effects of herbicides on Tetranychus urticae and its predator, Phytoseiulus persimilis: implications for biological control

BACKGROUND

A key element of conservation biocontrol is identifying and limiting the use of pesticides that have substantial non-target effects on natural enemies to prevent biocontrol disruption. The Phytoseiidae (predatory mites) are one of the most studied natural enemy groups in the field of pesticide non-target effects. Although there is substantial research on the non-target effects of insecticides on arthropod natural enemies, research on herbicide impacts is limited. Natural enemies, including phytoseiids, associate with weeds due to the presence of alternative prey, shelter, or floral resources. Therefore, a whole-systems approach to integrated pest management should integrate weed management with biocontrol. We conducted a study to examine the non-target effects of vegetable herbicides on Phytoseiulus persimilis Athias-Henriot, and the primary pest that it controls, Tetranychus urticae Koch. Two assays were used to assess the effects of direct application and walking on residues.

RESULTS

In both assays, S-metolachlor was highly toxic to P. persimilis (80-90% mortality) and had minimal effect on T. urticae. Dicamba, oxyfluorfen, and napropamide also caused moderate levels of P. persimilis mortality (21-74%). Check mortality of P. persimilis was higher in the direct contact assay (19%) than the residue assay (3%).

CONCLUSIONS

Halosulfuron-methyl, flumioxazin, and mesotrione were the most compatible herbicides with biocontrol by P. persimilis, whereas S-metolachlor and napropamide were the least compatible. We also determined that the residue assay may be more useful than direct contact slide-dips for future assessment of herbicide non-target effects. Future efforts should continue to examine the impacts of weed management on natural enemies to better integrate pest management practices. © 2019 Society of Chemical Industry.

Compatibility of insecticides and fungicides with the zoophytophagous mirid predator Nesidiocoris tenuis

Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is an effective predator of multiple pests of vegetable crops, such as thrips, mites, aphids, whiteflies, leafminers. It is mass-reared and released for augmentative biocontrol programs mainly aimed at controlling whiteflies and Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in greenhouses and open field. We evaluated the lethal and sublethal toxicity upon N. tenuis adults of label doses of three insecticides (pyriproxyfen, spirotetramat, cypermethrin) and seven fungicides (benomyl, chlorothalonil, copper oxychloride, cyazofamid, fluopicolide + propamocarb hydrochloride (FPH), penconazol, trifloxystrobin) commonly used in various crops. Two exposure routes were tested: (i) contact with dry residues of insecticides or fungicides on tomato sprouts and (ii) multiple exposure to these chemicals via topical sprays on adults which foraged on treated sprouts; and fed on treated eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) simultaneously. Mortality and reproductive capacity were investigated as indicators of lethal and sublethal effects on N. tenius. The tested insecticides and fungicides were all classified as harmless when predator was exposed only to the dry residues of each. However, the multiple exposure to either cypermethrin, benomyl, chlorothalonil, copper oxychloride or trifloxystrobin caused significant mortality of N. tenuis adults. Cypermethrin also significantly reduced its reproductive capacity. Interestingly, N. tenuis produced a higher number of progeny when exposed to fungicides penconazol and FPH in both exposure scenarios. Overall, findings suggest that the two insecticides, pyriproxyfen and spirotetramat but not cypermethrin, and all tested fungicides can be considered compatible with N. tenuis.

Effects of Insecticides and Fungicides Commonly Used in Tomato Production on Phytoseiulus persimilis (Acari: Phtyoseiidae)

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important pest of tomatoes in North Carolina. Resident populations of the predatory mite Phytoseiulus persimilis have recently been detected on field-grown tomatoes in central North Carolina, and potentially can be a useful biological control agent against T. urticae Laboratory bioassays were used to assess lethal and reproductive effects of 10 insecticides and five fungicides commonly used in commercial tomato production (chlorantraniliprole, spinetoram, permethrin, imidacloprid, dimethoate, dinotefuran, thiamethoxam, bifenthrin, fenpropathrin, lambda-cyhalothrin, azoxystrobin, chlorothalonil, boscalid, cyazofamid, and mancozeb) on P. persimilis adult females and eggs. Insecticides were tested using concentrations equivalent to 1×, 0.5×, and 0.1× of the recommended field rates. Fungicides were tested at the 1× rate only. Dimethoate strongly impacted P. persimilis with high adult mortality, reduced fecundity, and reduced hatch of eggs laid by treated adults, particularly at high concentrations. The pyrethroids lambda-cyhalothrin, bifenthrin, and fenpropathrin were associated with repellency and reproductive effects at high concentrations. Bifenthrin additionally caused increased mortality at high concentrations. Chlorantraniliprole, dinotefuran, and permethrin did not significantly affect mortality or reproduction. Imidacloprid significantly reduced fecundity and egg viability, but was not lethal to adult P. persimilis Thiamethoxam negatively impacted fecundity at the 1× rate. There were no negative effects associated with fungicide exposure with the exception of mancozeb, which impacted fecundity. Field trials were conducted to explore the in vivo impacts of screened insecticides on P. persimilis populations in the field. Field trials supported the incompatibility of dimethoate with P. persimilis populations.

Regulation of female reproduction in mites: a unifying model for the Acari

It is well established in the literature that circulating high levels of juvenile hormone (JH) are responsible for the initiation of vitellogenesis and female reproduction in most insects studied so far. Exceptions include some Diptera, Lepidoptera and Hymenoptera. The current view is that JH also regulates yolk protein (vitellogenin, Vg) synthesis and female reproduction in mites. However, there is no published evidence that mites have the common insect JHs at any stage of their development. Also, research on the effects of exogenous applications of JH and JH analogs on the reproduction of mites is contradictory. Significant information is available on the life history of mite reproduction, and new information has become available on mite storage proteins including Vg. Although initial studies suggested that ticks may respond to exogenously applied juvenile hormone or anti-JHs, current research shows that ticks cannot synthesize the common insect JHs and have no detectable levels of these hormones in their hemolymph during female reproduction. In ticks, it appears that ecdysteroids, and not JH, regulate expression of the Vg gene and the synthesis and release of Vg protein into the hemolymph. In fact within the Arthropoda, JH has been found only in insects. Methyl farnesoate and not JH regulates Vg synthesis in the Crustacea, the sister group to the insects. Based on this evidence, a new working hypothesis is proposed, i.e., that ecdysteroids and not the JHs regulate vitellogenesis in the Acari including both ticks and mites. To the present, the role of neuropeptides in the regulation of female reproduction in mites is not known.

Testing for non-target effects of spinosad on twospotted spider mites and their predator Phytoseiulus persimilis under greenhouse conditions

The compatibility of the selective insecticide spinosad (Conserve SC), at rates recommended for thrips control in greenhouses, with release of the predatory mite Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) to control spider mites, was investigated in a crop of ivy geranium Pelargonium peltatum, cultivar 'Amethyst 96.' Plants were inoculated with twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), 2 weeks before treatments were applied. There were three treatment variables, each at two levels: predators (released or not), spray application (water or Conserve SC at 2 ml/3.79 l), and timing of spray (1 day before or after predators were released). Twospotted spider mite populations then were sampled twice each week over a three-week period. The application or timing of spinosad had no effect on the ability of the predator to reduce the population of spider mites. Spider mite populations in the no-predator treatment continued to expand over the course of the experiment, while those in the predator-release treatment declined. We conclude that P. persimilis can be used in conjunction with spinosad on ivy geraniums without causing obvious detrimental effects to this predator or leading to a reduction in biological control.

Seletividade de agroquímicos ao ácaro predador Iphiseiodes zuluagai Denmark & Muma (Acari: Phytoseiidae)

Testes de efeito adverso de agroquímicos sobre Iphiseiodes zuluagai Denmark & Muma (Acari: Phytoseiidae) foram conduzidos em laboratório, utilizando o método residual de contato com pulverização em superfície de vidro. Foram testados 42 produtos químicos, a maioria utilizada na citricultura brasileira. A mortalidade e o efeito dos produtos na reprodução do ácaro foram avaliados diariamente durante oito dias. Os produtos foram classificados quanto ao efeito total causado ao ácaro (combinação da mortalidade e efeito na reprodução) em quatro classes de toxicidade propostas pela IOBC/WPRS. Os resultados mostraram que cerca de 26% dos produtos testados foram inócuos (captan, clofentezine, fenbutatin oxide, fosetyl, hexythiazox, hidróxido de cobre, naled, oxicloreto de cobre, óxido cuproso e tetradifon), 14% levemente nocivos (abamectin, chlorothalonil, sulfato de cobre, thiophanate-methyl (PM) e ziram), 7% moderadamente nocivos (enxofre, parathion-methyl e thiophanate-methyl (SC)) e 52% nocivos ao ácaro (acrinathrin, amitraz, azinphos-ethyl, azocyclotin, benomyl, bifenthrin, bromopropylate, carbaryl, carbosulfan, chlorfenapyr, cyhexatin, dicofol, fenpropathrin, fenpyroximate, mancozeb, óleo mineral e vegetal, phosmet, propargite, quinomethionate, triazophos, e vamidothion).