Conservation of natural enemies in cotton: comparative selectivity of acetamiprid in the management of Bemisia tabaci

Toxicity of Insecticides and Miticides to Natural Enemies in Australian Grains: A Review

Continued prophylactic chemical control to reduce pest populations in Australian grain farming systems has limited the effectiveness of biological control via natural enemies in crops within an integrated pest management (IPM) framework. While a variety of data is available to infer potential non-target effects of chemicals on arthropod natural enemies, much of it may be irrelevant or difficult to access. Here, we synthesise the literature relevant to Australian grain crops and highlight current knowledge gaps for potential future investment. A range of testing methodologies have been utilised, often deviating from standardised International Organization for Biological Control (IOBC) protocols. Consistent with findings from over 30 years ago, research has continued to occur predominantly at laboratory scales and on natural enemy families that are easily reared or commercially available. There is a paucity of data for many generalist predators, in particular for spiders, hoverflies, and rove and carabid beetles. Furthermore, very few studies have tested the effects of seed treatments on natural enemies, presenting a significant gap given the widespread global use of neonicotinoid seed treatments. There is a need to validate results obtained under laboratory conditions at industry-relevant scales and also prioritise testing on several key natural enemy species we have identified, which should assist with the adoption of IPM practices and decrease the reliance on broad-spectrum chemicals.

Can Generalist Predators Control Bemisia tabaci?

Simple Summary

Whiteflies are major insect pests on a global scale. The use of insecticides is the primary tool for controlling them, but there are many problems relying on this strategy. However, natural enemies like predators and parasitic insects that attack whiteflies can help provide a sustainable pest management approach. This paper focuses on predators that feed on whiteflies as well as other insect pests and are called generalist predators. We provide a comprehensive view of generalist predator contributions and review the currently recognized generalist predators of whiteflies. There are many generalist predators in agricultural cropping systems that help control whiteflies. We highlight the need for conservation biological control programs through habitat management strategies and the use of selective insecticides, with an aim for more sustainable management of whiteflies in crops.

Abstract

The whitefly, Bemisia tabaci, has developed resistance to many insecticides, renewing interest in the biological control of this global pest. Generalist predators might contribute to whitefly suppression if they commonly occur in infested fields and generally complement rather than interfere with specialized natural enemies. Here, we review literature from the last 20 years, across US cropping systems, which considers the impacts of generalist predators on B. tabaci. Laboratory feeding trials and molecular gut content analysis suggest that at least 30 different generalist predator species willingly and/or regularly feed on these whiteflies. Nine of these predators appear to be particularly impactful, and a higher abundance of a few of these predator species has been shown to correlate with greater B. tabaci predation in the field. Predator species often occupy complementary feeding niches, which would be expected to strengthen biocontrol, although intraguild predation is also common and might be disruptive. Overall, our review suggests that a bio-diverse community of generalist predators commonly attacks B. tabaci, with the potential to exert substantial control in the field. The key challenge will be to develop reduced-spray plans so that generalist predators, and other more specialized natural enemies, are abundant enough that their biocontrol potential is realized.

Comparative ecotoxicity of neonicotinoid insecticides to three species of Trichogramma parasitoid wasps (Hymenoptera: Trichogrammatidae)

Compatibility of neonicotinoid insecticides with the natural enemies has been concerned for decades. This study aims to evaluate and compare the acute and sublethal toxicity effects of neonicotinoid insecticides on three species of Trichogramma parasitoid wasps (i.e. Trichogramma dendrolimi, T. ostriniae and T. confusum) with broad distribution and great relevance to integrated pest management (IPM) strategies. A residual contact bioassay demonstrated that nitenpyram had the greatest intrinsic toxicity to T. dendrolimi and T. ostriniae with LC₅₀ values of 0.060 (0.056-0.065) and 0.066 (0.050-0.087) mg a.i. L^-1, respectively. But for T. confusum, the most toxic neonicotinoid insecticide is dinotefuran with a LC₅₀ value of 0.065 (0.055-0.078) mg a.i. L^-1. Furthermore, based on the risk quotient estimation, acetamiprid was considered to be the only safe neonicotinoid insecticide (Class 1, RQ＜50). A dipped egg contact bioassay showed that neonicotinoid insecticides induced significant toxic effects on the parasitism of three Trichogramma spp. at low-lethal concentrations. Additionally, emergence probability of the unexposed offspring was also significantly reduced by neonicotinoids. According to the estimated EC₅₀ values, acetamiprid possessed the least toxicity to the parasitism and emergence of T. dendrolimi and T. ostriniae, and for T. confusum, the least toxic neonicotinoid insecticide was thiacloprid. Overall, among the test neonicotinoid insecticides, acetamiprid and thiacloprid may exhibit the less ecotoxicity to the test Trichogramma species.

Lethal and Sub-Lethal Effects of Insecticides on the Pink Hibiscus Mealybug, Maconellicoccus hirsutus (Hemiptera: Pseudococcidae)

The pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) is a pest of many plants, and a new problem on dates in California. The effects of seven insecticides and water on different life stages of this mealybug were studied to identify the best material for control. Water did not have any significant effect on mealybugs, but the insecticide treatments significantly affected all life stages tested. The egg hatch rate ranged from 28.5% to 17.2% for spirotetramat, bifenthrin, flupyradifurone, fenpropathrin, and buprofezin treatments, and was lower for sulfoxaflor (2.8%) and acetamiprid (0.1%). Despite high survival of neonate crawlers in the non-treated control and water treatments, 53.1% and 34.6% survived in the spirotetramat and buprofezin treatments, respectively; survival was zero in the other treatments. Spirotetramat and buprofezin caused very low mortality of nymphs in the first day post-treatment, but mortality significantly increased over time and reached 42.8% and 50.6% by day 6, respectively. The other treatments were highly toxic to the nymphs (79.4⁻99.4% on day 6). Insecticides also had a significant effect on the feeding ability of nymphs. By day 6 after treatment, 73.9% to 100% of nymphs treated with different insecticides stopped feeding although they were still alive. Insecticides showed no effect on the mortality of adult females, but the percentages of ovipositing females were significantly reduced (51.1% to 10.6%) in all insecticide treatments, except buprofezin, which was not statistically different from water and the non-treated control. In the process of our studies, we identified abnormalities in the appearance of eggs from females treated with various insecticides, and these aberrant eggs are described.

Comparative susceptibility of two Neotropical predators, Eriopis connexa and Chrysoperla externa, to acetamiprid and pyriproxyfen: Short and long-term effects after egg exposure

Compatibility assessments between selective insecticides and the natural enemies of pests are essential for integrated-pest-management programs. Chrysoperla externa and Eriopis connexa are two principal Neotropical predators of agricultural pests whose conservation in agroecosystems requires a toxicity evaluation of pesticides to minimize the impact on those beneficial insects on the environment. The objective of this work was to evaluate the toxicity of the insecticides pyriproxyfen and acetamiprid on C. externa and E. connexa eggs exposed to the maximum recommended field concentrations of each along with three successive dilutions. The survival and the immature developmental time were assessed daily until adulthood and the mean survival time calculated over a 10-day period. The cumulative survival of E. connexa was reduced at all concentrations of both insecticides, while that of C. externa was significantly decreased by ≥50 mg L^-1 of acetamiprid and ≥37.6 mg L^-1 of pyriproxyfen. In both species, the reductions occurred principally on the eggs and first larval instar. Survival curves, in general, differed from those of the controls, with the mean survival time of E. connexa being significantly shorter in insecticides treatments than that of the controls. Certain concentrations of each of the insecticide lengthened the egg and first-larval-instar developmental periods of E. connexa and C. externa, respectively. Also, pyriproxyfen reduced the first-larval-instar period and lengthened the fourth of E. connexa. Acetamiprid was more toxic to E. connexa than to C. externa at the two highest concentrations. Conversely, at those same concentrations of pyriproxyfen, the relative toxicity to the two species was reversed. The present work represents the first investigation on the comparative susceptibility of two relevant Neotropical biological control agents to acetamiprid and pyriproxyfen. Also, it highlights the necessity of assessing long-term effects in the compatibility studies between natural enemies of agricultural pests and insecticides.

Impact of neonicotinoid insecticides on natural enemies in greenhouse and interiorscape environments

The neonicotinoid insecticides imidacloprid, acetamiprid, dinotefuran, thiamethoxam and clothianidin are commonly used in greenhouses and/or interiorscapes (plant interiorscapes and conservatories) to manage a wide range of plant-feeding insects such as aphids, mealybugs and whiteflies. However, these systemic insecticides may also be harmful to natural enemies, including predators and parasitoids. Predatory insects and mites may be adversely affected by neonicotinoid systemic insecticides when they: (1) feed on pollen, nectar or plant tissue contaminated with the active ingredient; (2) consume the active ingredient of neonicotinoid insecticides while ingesting plant fluids; (3) feed on hosts (prey) that have consumed leaves contaminated with the active ingredient. Parasitoids may be affected negatively by neonicotinoid insecticides because foliar, drench or granular applications may decrease host population levels so that there are not enough hosts to attack and thus sustain parasitoid populations. Furthermore, host quality may be unacceptable for egg laying by parasitoid females. In addition, female parasitoids that host feed may inadvertently ingest a lethal concentration of the active ingredient or a sublethal dose that inhibits foraging or egg laying. There are, however, issues that require further consideration, such as: the types of plant and flower that accumulate active ingredients, and the concentrations in which they are accumulated; the influence of flower age on the level of exposure of natural enemies to the active ingredient; the effect of neonicotinoid metabolites produced within the plant. As such, the application of neonicotinoid insecticides in conjunction with natural enemies in protected culture and interiorscape environments needs further investigation.

Identifying signature of chemical applications on indigenous and invasive nontarget arthropod communities in vineyards

Communities of arthropods providing ecosystem services (e.g., pest control, pollination, and soil nutrient cycling) to agricultural production systems are influenced by pesticide inputs, yet the impact of pesticide applications on nontarget organisms is normally evaluated through standardized sets of laboratory tests involving individual pesticides applied to a few representative species. By combining season-long pesticide applications of various insecticides and fungicides into a metric based on the International Organization for Biological and Integrated Control (IOBC) toxicity ratings, we evaluate season-long pesticide impacts on communities of indigenous and exotic arthropods across 61 vineyards assessed for an entire growing season. The composition of arthropod communities, identified mostly at the family level, but in some cases at the species level, was altered depending on season-long pesticide use. Numbers of mostly indigenous parasitoids, predatory mites, and coccinellids in the canopy, as well as carabid/tenebrionid beetles and some spider families on the ground, were decreased at higher cumulative pesticide metric scores. In contrast, numbers of one invasive millipede species (Ommatoiulus moreletti Lucas, Julida: Julidae) increased under higher cumulative pesticide metric scores. These changing community patterns were detected despite the absence of broad-spectrum insecticide applications in the vineyards. Pesticide effects were mostly due to indoxacarb and sulphur, applied as a fungicide. The reduction of beneficial arthropods and increase in an invasive herbivorous millipede under high cumulative pesticide metric scores highlights the need to manage nontarget season-long pesticide impacts in vineyards. A cumulative pesticide metric, based on IOBC toxicity ratings, provides a way of assessing overall toxicity effects, giving managers a means to estimate and consider potential negative season-long pesticide impacts on ecosystem services provided through arthropod communities.

Residual efficacy of pyriproxyfen and hydroprene applied to wood, metal and concrete for control of stored-product insects

BACKGROUND

Pyriproxyfen and hydroprene are insect growth regulators (IGRs) that have been evaluated to control insect pests of field crops, but there are limited reports of efficacy against stored-product insects. A laboratory study was conducted to determine residual efficacy of pyriproxyfen and hydroprene on wood, metal and concrete surfaces. Pyriproxyfen was applied to the surfaces at 1.15 and 2.3 mg active ingredient [AI] m(-2), while hydroprene was applied at the label rate of 19 mg AI m(-2). Late-instar larvae of Tribolium confusum Jacqueline DuVal, T. castaneum (Herbst), Oryzaephilus surinamenis L., Lasioderma serricorne (F.) and Plodia interpunctella (Hübner) were exposed with a food source on the treated surfaces. Residual testing was conducted at 1, 28 and 56 days post-treatment.

RESULTS

Hydroprene was least persistent on concrete and generally most persistent on metal. Pyriproxyfen gave greater residual persistence than hydroprene, and there was no consistent difference in efficacy among the three surfaces. Efficacy varied among the five insect species, but generally P. interpunctella was the most tolerant species to both IGRs.

CONCLUSIONS

Pyriproxyfen gave effective residual control of primary stored-product insect species by inhibiting adult emergence of exposed larvae. Results show that pyriproxyfen can be a useful addition for pest management programs in mills, warehouses and food storage facilities.

COMUNIDADE DE INIMIGOS NATURAIS E CONTROLE BIOLÓGICO NATURAL DO PULGÃO, APHIS GOSSYPII GLOVER (HEMIPTERA: APHIDIDAE) E DO CURUQUERÊ, ALABAMA ARGILLACEA HÜBNER (LEPIDOPTERA: NOCTUIDAE) NA CULTURA DO ALGODOEIRO NO DISTRITO FEDERAL

RESUMO O uso intensivo de inseticidas químicos é uma prática comum que pode causar o aumento na abundância de pragas devido ao desequilíbrio resultante da destruição de inimigos naturais e redução do controle biológico natural. Visando avaliar o controle biológico natural em algodoeiros no Distrito Federal na safra 2004/2005, predadores do pulgão, Aphis gossypii (Hemiptera: Aphididae) e parasitóides da lagarta curuquerê, Alabama argillacea (Lepidoptera: Noctuidae), foram identificados e avaliados/5. As avaliações foram realizadas em diferentes áreas de plantio e sob diferentes métodos de controle de pragas (inseticidas químicos, microbianos e controle). Cinco espécies de joaninhas, Cycloneda sanguinea, Scymnus sp., Hippodamia convergens, Eriopis conexa e Olla v-nigrum, a tesourinha, Doru cf. luteipes, a mosca Condylostylus sp. (Dolichopodidae) e várias espécies de aranhas foram os predadores mais abundantes de pulgões. Não houve diferença na riqueza de espécies nas áreas estudadas. Foi observada correlação positiva e significativa entre as populações de pulgões e alguns grupos de predadores apenas no tratamento com inseticidas biológicos, indicando possível resposta numérica do predador na ausência de inseticidas químicos de largo espectro. O uso de inseticidas químicos controlou satisfatoriamente a população de lagartas apenas na primeira geração, o que pode estar relacionado à menor incidência de parasitismo neste tratamento (2,20 ± 1,40%) quando comparado com a testemunha (23,90 ± 9,50%). Não foram observados efeitos deletérios de inseticidas biológicos nas taxas de parasitismo (5,80