Reduced-risk insecticides in Neotropical stingless bee species: impact on survival and activity

Background: As honeybees are the main pollinator species subject to an intense research regarding effects of pesticides, other ecologically important native bee pollinators have received little attention in ecotoxicology and risk assessment of pesticides in general, and insecticides in particular, some of which are perceived as reduced-risk compounds. Here the impact of three reduced-risk insecticides – azadirachtin, spinosad, and chlorantraniliprole – was assessed in two species of stingless bees, Partamona helleri and Scaptotrigona xanthotrica, which are important native pollinators in Neotropical America. The neonicotinoid imidacloprid was used as a positive control.Results: Spinosad exhibited high oral and contact toxicities in adult workers of both species at the recommended label rates, with median survival times (LT50s) ranging from 1 to 4 h, whereas these estimates were below 15 min for imidacloprid. Azadirachtin and chlorantraniliprole exhibited low toxicity at the recommended label rates, with negligible mortality that did not allow LT50 estimation. Sublethal behavioral assessments of these two insecticides indicated that neither one of them affected the overall group activity of workers of the two species. However, both azadirachtin and chlorantraniliprole impaired individual flight take-off of P. helleri and S. xanthotrica worker bees, which may compromise foraging activity, potentially leading to reduced colony survival.Conclusion: These findings challenge the common perception of non-target safety of reduced-risk insecticides and bioinsecticides, particularly regarding native pollinator species.Keywords: behavioral impact; biopesticides; colony and individual level effects; native bee pollinators; sublethal effect

Bioinsecticide-Predator interactions: Azadirachtin behavioral and reproductive impairment of the coconut mite predator Neoseiulus baraki

Synthetic pesticide use has been the dominant form of pest control since the 1940s. However, biopesticides are emerging as sustainable pest control alternatives, with prevailing use in organic agricultural production systems. Foremost among botanical biopesticides is the limonoid azadirachtin, whose perceived environmental safety has come under debate and scrutiny in recent years. Coconut production, particularly organic coconut production, is one of the agricultural systems in which azadirachtin is used as a primary method of pest control for the management of the invasive coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae). The management of this mite species also greatly benefits from predation by Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae). Here, we assessed the potential behavioral impacts of azadirachtin on the coconut mite predator, N. baraki. We explored the effects of this biopesticide on overall predator activity, female searching time, and mating behavior and fecundity. Azadirachtin impairs the overall activity of the predator, reducing it to nearly half; however, female searching was not affected. In contrast, mating behavior was compromised by azadirachtin exposure particularly when male predators were exposed to the biopesticide. Consequently, predator fecundity was also compromised by azadirachtin, furthering doubts about its environmental safety and selectivity towards biological control agents

Female beetles facilitate leaf feeding for males on toxic plants

1. Milkweed plants produce latex, which works as a defence against some herbivorous insects. The cerambycid beetles Tetraopes femoratus (LeConte) puncture the leaf midrib vein to extravasate the latex, and thus render the leaf edible. Nonetheless, it has not yet been investigated whether there is any further implication beyond food acquisition regarding this behaviour. 2. The present study examined the hypothesis that leaf latex drainage is done mainly by females of T. femoratus, and that the males opportunistically prefer to feed on those ‘disarmed’ leaves. 3. The experiments revealed that puncturing the leaf midrib vein to extravasate latex is done mainly by females of T. femoratus and not only serves their purpose of food acquisition, but also mediates an opportunistic feeding behaviour among males. 4. Males of T. femoratus preferred to feed on milkweed leaves that had previously been fed upon by females. In addition, field observations showed that mating occurred more frequently on recently ‘disarmed’ leaves, suggesting increased copulation opportunities for females during leaf feeding. 5. In sum, the results reveal that the feeding defence strategy of T. femoratusfemales to toxic milkweed foliage has created an opportunity for males to feed on milkweed leaves with a reduced risk of latex exposure and entanglement. Thus, this research provides empirical evidence of plant–insect interactions contributing to the appearance of an opportunistic adaptive feeding behaviour, which has broader implications for eco-evolutionary systems

Plant architecture and prey distribution influence foraging behavior of the predatory mite Phytoseiulus persimilis (Acari: Phytoseiidae)

Citation: Gontijo, L. M., Nechols, J. R., Margolies, D. C., & Cloyd, R. A. (2012). Plant architecture and prey distribution influence foraging behavior of the predatory mite Phytoseiulus persimilis (Acari: Phytoseiidae). Retrieved from http://krex.ksu.eduThe arrangement, number, and size of plant parts may influence predator foraging behavior, either directly, by altering the rate or pattern of predator movement, or, indirectly, by affecting the distribution and abundance of prey. We report on the effects of both plant architecture and prey distribution on foraging by the predatory mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae), on cucumber (Cucumis sativus L.). Plants differed in leaf number (2- or 6-leafed), and there were associated differences in leaf size, plant height, and relative proportions of plant parts; but all had the same total surface area. The prey, the twospotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae), were distributed either on the basal leaf or on all leaves. The effect of plant architecture on predator foraging behavior varied depending on prey distribution. The dimensions of individual plant parts affected time allocated to moving and feeding, but they did not appear to influence the frequency with which predators moved among different plant parts. Overall, P. persimilis moved less, and fed upon prey longer, on 6-leafed plants with prey on all leaves than on plants representing other treatment combinations. Our findings suggest that both plant architecture and pattern of prey distribution should be considered, along with other factors such as herbivore-induced plant volatiles, in augmentative biological control programs

Alyssum flowers promote biological control of collard pests

Collard greens Brassica oleracea (L.) are often attacked by various pests including whiteflies, aphids and diamondback moth. Hitherto, the main method used to manage these pests in Brazil has been the application of a limited number of registered insecticides. The search for more sustainable pest management strategies is therefore warranted. In this context, the conservation biological control stands out as an appealing alternative. Conservation biological control is achieved, at least in part, by strip-cultivating and/or conserving flowering plants within the agroecosystem. The present study investigates how alyssum flowers Lobularia maritima (L.) could contribute to the attraction of natural enemies and to the management of collard pests. Two field experiments were conducted in different years. Each experiment consisted of two treatments and three replicates, which were set up in a completely randomized design. The treatments were (1) collards alone, and (2) collards + alyssum. We evaluated weekly the population density of natural enemies and pests on both treatments. The results show that the alyssum flowers attractiveness contributed to increase the abundance of generalist predators during both experiments, which in turn translated into a significant reduction of collards pests, especially aphids. Some of the main predators attracted/harbored by alyssum flowers were spiders, coccinellids, syrphids and Orius sp. Finally, strip intercropping alyssum with collards can be an important strategy to manage brassica pests and cope with the limited availability of insecticides registered for this vegetable crop

Natural enemies of woolly apple aphid (Hemiptera: Aphididae) in Washington State

Woolly apple aphid, Eriosoma lanigerum (Hausmann), has become a pest of increasing importance in Washington apple orchards in the past decade. The increase in aphid outbreaks appears to be associated with changes in pesticide programs and disruption of biological control. We sampled woolly apple aphid colonies in central Washington apple orchards for natural enemies of this pest from 2006 to 2008. The most common predators encountered were Syrphidae (Syrphus opinator Osten Sacken, Eupeodes fumipennis Thomson, and Eupeodes americanus Wiedemann); Chrysopidae (Chrysopa nigricornis Burmeister); and Coccinellidae (Coccinella transversoguttata Brown and Hippodamia convergens Guérin-Méneville). The specialist syrphid Heringia calcarata Loew was recorded for the first time occurring in Washington apple orchards. The only parasitoid found in aerial colonies of woolly apple aphid was Aphelinus mali Haldeman; root colonies, however, were not parasitized. Identification of important natural enemies provides a better basis for conservation biological control of this pest

Seasonal phenology of woolly apple aphid (Hemiptera: Aphididae) in Central Washington

The seasonal abundance of woolly apple aphid (Eriosoma lanigerum Hausmann) was studied from 2005 to 2008 in commercial orchards in central Washington State. There was a single period of crawler migration on the tree trunks each year lasting from 7 to 16 wk. The peak period of crawler activity ranged from early June to late July, although peaks in June were more common. In one orchard, peak densities occurred 7 wk later in 2006 than in 2005. In all orchards where large numbers of crawlers were caught (up to 1,420 per band per week), more crawlers were caught in the lower band (migrating up from root colonies) than in the upper bands (migrating down from the aerial colonies). However, the peak period of crawler migration was similar for root and aerial colonies. In contrast, peaks in population densities of aerial colonies were sometimes bimodal, usually spanning the period from late May through mid-October; however, colonies were detected in mid-April in one orchard. There was no consistent relationship between the crawler density and aerial colony density within an orchard; this raises challenging questions regarding annual reinfestation of the aerial portions of the tree. Nymphs and adults formed 66 and 15%, respectively, of all stages found throughout the season. Alates were only found in September and October in orchards with fall populations, comprising up to 43% of individuals in aerial colonies. Overwintering survival was higher on the root colonies than in the aerial colonies in both years this was studied. Fruit infestation by aphids was relatively rare, and occurred only when aerial colonies were numerous

Impacts of azadirachtin and chlorantraniliprole on the developmental stages of pirate bug predators (Hemiptera: Anthocoridae) of the tomato pinworm Tuta absoluta (Lepidoptera: Gelechiidae)

Conservation of natural enemies is an important approach for enhancing biological control. Selective insecticides have become important for managing arthropod pests, and the prospects for their use in combination with biological control agents are increasing. In addition, progress has been made in recent decades to develop reduced-risk insecticides that have novel modes of action and, therefore, likely to have a minimum non-target effect. In this study, we use a series of laboratory bioassays to investigate the impact of two reduced-risk insecticides, azadirachtin and chlorantraniliprole, on the egg, nymph and adult stages of two predatory pirate bugs, Amphiareus constrictus (Stal) and Blaptostethus pallescens Poppius (Hemiptera: Anthocoridae), important predators of the tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). All three stages were exposed to the label recommended field rate of these two insecticides, which is indicated for the control of T. absoluta. Neither azadirachtin nor chlorantraniliprole affected the mortality of adult predators or their egg hatchability, suggesting a safe acute toxicity for these stages. However, azadirachtin and chlorantraniliprole negatively decreased the capacity of predator nymphs to reach the adult stage. This decrease can directly affect the size of the predator population in the next generation, and may undermine the biological control of pests such as T. absoluta. In general, our results call for caution when using these reduced-risk insecticides in integrated programs of chemical and biological control of this pest.A conservação de inimigos naturais é urna estratégia importante para o controle biológico de insetos-praga. O uso de inseticidas seletivos também tem sido importante para o manejo de insetos-praga, e a prospectiva de ter seu uso combinado com agentes de controle biológico tem ganhado espaço últimamente. Além disso, tem ocorrido um grande progresso nas ultimas décadas com relação ao desenvolvimento de inseticidas de risco reduzido que apresentam novos modos de ação, e possívelmente uma menor chance de causar efeitos nao-alvo. No presente trabalho, nós conduzimos uma série de bioensaios em laboratorio para investigar o impacto de dois inseticidas de risco reduzido, azadiractina e clorantraniliprole, sobre os estádios de ovo, ninfa e adulto de dois predadores hemípteras, Amphiareus constrictus (Stal) and Blaptostethus pallescens Poppius (Heteroptera: Anthocoridae), que são importantes inimigos naturais da traça do tomate Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). Todos os três estádios foram expostos à dose de campo destes dois inseticidas, a quai é recomendada para o controle de T. absoluta. Tanto azadiractina como clorantraniliprole nao afetaram a mortalidade dos predadores adultos ou a eclosão de seus ovos para qualquer espécie, sugerindo a ausencia de uma toxicidade aguda para estes estádios de desenvolvimento. Porém, azadiractina e clorantraniliprole afetaram negativamente a capacidade de ninfas dos predadores alcançarem o estádio adulto. Essa redução na capacidade das ninfas alcançarem o estádio adulto pode afetar diretamente o tamanho da população de predadores na próxima geração, um impacto que poderia reduzir o controle biológico de pragas como T. absoluta. Em géral, nossos resultados sugerem a necessidade de cautela quando usar inseticidas de risco reduzido em programas que visam integrar o controle químico e biológico desta praga

Azadirachtin-mediated reproductive response of the predatory pirate bug Blaptostethus pallescens

The little-known pirate bug Blaptostethus pallescens Poppius is a biocontrol agent observed in tropical tomato fields in Brazil regulating fruit borer populations. In this study, the lethal response of B. pallescens to the bioinsecticide azadirachtin and to two synthetic insecticides, chlorpyrifos and deltamethrin, was assessed. The mild effect of the azadirachtin label rate (0.006 mg a.i. ml−1) on the predator (median lethal time (LT50) of 27 days), relative to label rates of deltamethrin (0.02 mg a.i. ml−1) and chlorpyrifos (1.44 mg a.i. ml−1) (with LT50 of 25 and 60 min, respectively) led to the assessment of its potential sublethal effects. Azadirachtin did not cause behavioral avoidance in the pirate bug, but the daily fecundity, adult progeny production and sex ratio were impaired when both male and female parents were exposed. These effects reduced the population growth of the predator in subsequent generations. Therefore, although safer than the conventional synthetic insecticides tested, the bioinsecticide azadirachtin does impair predator reproduction requiring attention when used in fields with this biological control agent

Ontogenic behavioral consistency, individual variation and fitness consequences among lady beetles

The potential relevance of complete metamorphosis for the individual variation in sets of behavioral traits and their fitness consequences in predatory species led to the present study. A set of nine behavioral traits were assessed for the larvae and adults of a pyrethroid-resistant and a susceptible population of the lady beetle Eriopis connexa. The aim was to assess: 1) the average individual behavioral (pheno)types and their within-population variation, 2) their ontogenic behavioral consistency from larva to adult, and 3) whether the observed correlated sets of behavioral traits can impact fitness. The average behavioral type differed between populations. The pyrethroid-resistant population consistently exhibited lower aggressiveness (as larvae) and exploration, but showed higher activity, as well as larva sociality, and sometimes boldness than the susceptible population. Behavioral trait variation was higher among pyrethroid-resistant individuals, particularly during the larval stage, but there was significant behavior correlation between larvae and adults, regardless of the insect population. Reduced aggressiveness, and to a lesser extent intermediate levels of boldness against heterospecific individuals were associated with higher population growth. Besides shedding light on the ontogenic consistency of behavioral traits and their fitness impact, our results also suggest that reduced aggressiveness is associated with predator population increase, but may compromise its effectiveness as a biocontrol agent