Effects of lime sulfur on Neoseiulus californicus and Phytoseiulus macropilis, two naturally occurring enemies of the two-spotted spider mite Tetranychus urticae.

BACKGROUND: The application of lime sulfur is a common practice used to control arthropod pests in organic production of fruits. However, the unintended effects of this insecticide preparation on non-targeted organisms have not received the adequate attention. Here, we evaluated the lime sulfur toxicity on the phytophagous mites Tetranychus urticae Koch (Acari: Tetranychidae) and on two predatory mite species [i.e., Neoseiulus californicus (McGregor) and Phytoseiulus macropilis (Banks)] (Acari: Phytoseiidae) of natural occurrence in strawberry plants. We also assessed the repellency and potential effects on the oviposition rates and the egg viability of mites that were exposed to field-used lime sulfur concentrations (i.e., 2%). RESULTS: The lime sulfur exhibited higher toxicity to the predators N. californicus (LC50 = 5.4 [4.5%-6.8%]) and P. macropilis (LC50 = 5.0 [4.0%-6.5%]) than to the phytophagous T. urticae (LC50 = 12.4 [9.0%-17.1%]). However, the exposure to field-applied concentrations resulted in higher reductions on the oviposition rate of T. urticae (36%) than on the predatory mites (N. californicus = 18%. P. macropilis = 19%). Interestingly, although the egg viability of P. macropilis was less affected (i.e., reduction of 50%) by such lime sulfur exposures, these mites were unable to avoid lime sulfur-treated areas. Egg viability of N. californicus was only 18.6%. CONCLUSION: Lime sulfur at field-applied concentrations harmed T. urticae fecundity and fertility and it showed selectivity against naturally occurring predatory mites, which reinforces its potential as a tool for integrated mite pest management. © 2019 Society of Chemical Industry.

Supplementary food for Neoseiulus californicus boosts biological control of Tetranychus urticae on strawberry.

BACKGROUND: A wide range of supplementary food resources can be offered to generalist predatory mites to improve their survival and reproduction and enhance their persistence in the environment. We investigated the relative suitability of different pollen types for the survival and reproduction of Neoseiulus californicus and its life history on a mixed diet of pollen and prey. We also evaluated the population dynamics of Tetranychus urticae in the presence of N. californicus with or without pollen, and in comparison to Phytoseiulus macropilis. RESULTS: Survival and reproduction of N. californicus adults were satisfactory on exclusive diets of T. urticae, cattail pollen, palm pollen and bee pollen. However, mites did not reproduce when fed only pollen during both immature and adult stages. Both predatory mites successfully controlled T. urticae. Although the specialist P. macropilis was more efficient in suppressing the pest population in the short term, it abandoned plants at low prey densities, whereas N. californicus performed better and persisted longer under prey scarcity. CONCLUSION: N. californicus is an efficient biological control agent of T. urticae and the provision of supplementary food could retain them in the crop prior to the arrival of the pest or in periods of prey scarcity. © 2019 Society of Chemical Industry.

Ricoseius loxocheles (Acari: Phytoseiidae) is not a predator of false spider mite on coffee crops: What does it eat?

Ricoseius loxocheles (De Leon) (Acari: Phytoseiidae) is often found in coffee crops and is known to feed on coffee leaf rust, Hemileia vastatrix Berkeley and Broome (Uredinales). As the occurrence of coffee leaf rust is limited primarily to the rainy season, the mite may use other food sources to survive during the periods of low pathogen prevalence. It is well known that phytoseiid mites can survive on a variety of food sources, such as herbivorous mites, fungi and pollen. We evaluated the ability of R. loxocheles to survive and reproduce on a diet of Brevipalpus phoenicis Geijskes (Acari: Tenuipalpidae), cattail pollen (Typha spp.), clover rust (Puccinia oxalidis), bee pollen (Santa Bárbara® dehydrated pollen, Santa Bárbara, MG, Brazil) and coffee leaf rust. Ricoseius loxocheles did not survive or reproduce on any B. phoenicis stages tested (egg, larva, adult). The survival and oviposition of R. loxocheles were directly affected by the presence of coffee rust urediniospores, but not by the presence of the prey. Survival and oviposition of the phytoseiid were similar when fed cattail pollen, clover rust and coffee leaf rust but was lower when fed bee pollen. Our results show that R. loxocheles is not a predator of B. phoenicis but it is able to utilize other resources besides coffee leaf rust.

Toxicity to and egg-laying avoidance of Drosophila suzukii (Diptera: Drosophilidae) caused by an old alternative inorganic insecticide preparation.

BACKGROUND: The application of synthetic insecticides remains the most used tool for the management of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). However, management of this pest in the organic production of soft-skinned fruits is a complex task due to the restricted number of registered products. Here, we assess the toxicity of lime sulfur and evaluate whether lime sulfur-treated strawberry plants affected the oviposition and development of D. suzukii. RESULTS: Lime sulfur exhibited adequate toxicity to D. suzukii (LC50 = 26.6 mL L-1 ) without phytotoxicity to strawberry plants. When D. suzukii females were exposed to lime sulfur-treated plants in no-choice bioassays, oviposition was significantly (t-test, P < 0.05) reduced compared with that on untreated plants. In free-choice bioassays, D. suzukii females laid significantly (paired t-test, P < 0.05) more eggs on untreated plants. Furthermore, in the free-choice bioassays, immature development was slower for adults that originated from eggs laid on lime sulfur-treated plants than from those laid on untreated plants. CONCLUSIONS: Lime sulfur showed adequate control and, therefore, has potential for use as a management tool against D. suzukii infestations in organic production systems. This old, alternative insecticide preparation not only caused adult fly mortality, but also reduced the number of eggs laid on lime sulfur-treated plants. © 2017 Society of Chemical Industry.

Relative Toxicity of Two Aphicides to Hippodamia convergens (Coleoptera: Coccinellidae): Implications for Integrated Management of Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae).

Flupyradifurone and sulfoxaflor present novel insecticide chemistries with particular efficacy against aphids, and the recent emergence of sugarcane aphid, Melanaphis sacchari (Zehntner), as a pest of sorghum in the United States has resulted in their widespread use. We examined their toxicity to Hippodamia convergens Guerin-Meneville, an important aphid biocontrol agent. We exposed beetles to topical applications of the field rate (FR) of these insecticides, fed them contaminated food (eggs of Ephestia kuehniella Zeller), and gave first-instar larvae 24-h exposures to leaf residues. More than half of fourth-instar larvae receiving topical applications of sulfoxaflor at FR survived, whereas flupyradifurone at 0.1× FR caused 90% mortality. Adults survived topical treatments better than larvae and without measurable mortality, except flupyradifurone at FR, which killed more than 80% of beetles. Survivors of all treatments had fertility similar to controls, whether treated as larvae or adults. Ingestion of contaminated food caused significant mortality in all treatments (15-40% for adults and 55-85% for larvae), with no significant differences between insecticides at FR. Leaf residues of sulfoxaflor at 1.0 and 2.0× FR caused approximately 60 and 80% mortality of first instars, respectively, whereas flupyradifurone at 0.1 and 1.0× FR caused > 90% mortality. Although sulfoxaflor was less toxic to H. convergens than flupyradifurone, the tested FR of flupyradifurone has now been reduced by half. We conclude that neither insecticide appears as toxic as other nicotinic acetylcholine receptor agonists, and that both materials are compatible with integrated pest management programs for M. sacchari.

Indigenous Aphid Predators Show High Levels of Preadaptation to a Novel Prey, Melanaphis sacchari (Hemiptera: Aphididae).

The performance of four aphid predators, Hippodamia convergens Guerin-Meneville, Coleomegilla maculata DeGeer, Chrysoperla carnea Stephens and Orius insidiosus Say was compared on three prey species: Schizaphis graminum Rondani, Melanaphis sacchari (Zehntner), and Ephestia kuehniella Zeller eggs. Species predatory in both life stages (all except Ch. carnea) were reared on E. kuehniella eggs and switched to aphid prey for assessment of reproduction. Differences were greater between the E. kuehniella and aphid diets than between the two aphid species. Juvenile survival was high for all predators on all prey, except for O. insidiosus, which had survival on E. kuehniella > S. graminum > M. sacchari. The fastest development of Ch. carnea and O. insidiosus was obtained on E. kuehniella, whereas H. convergens developed fastest on S. graminum, and C. maculata did not differ among diets. S. graminum also yielded the largest H. convergens adults, whereas the largest adults of other predators were obtained on E. kuehniella. Female fecundity and egg viability were similarly high on both aphid diets for H. convergens and C. maculata, whereas, on E. kuehniella, 50% of the former entered reproductive diapause and the latter species had reduced fecundity. Reproductive success of Ch. carnea was S. graminum = M. sacchari > E. kuehniella, but it was similar among treatments for O. insidiosus, although female infertility ranged from 25 to 37.5%. We concluded that all the predators studied are preadapted to utilize sugarcane aphid as prey and have excellent potential to provide sustainable biological control of this newly invasive pest.

Rational Practices to Manage Boll Weevils Colonization and Population Growth on Family Farms in the Semiárido Region of Brazil.

Because boll weevil, Anthonomus grandis Boh. develops partially protected inside cotton fruiting structures, once they become established in a field, they are difficult to control, even with nearly continuous insecticide spray. During two cotton-growing seasons in the Semiárido region of Pernambuco State, Brazil, we tested the use of kaolin sprays to disrupt plant colonization through visual cue interference, combined with removal of fallen fruiting bodies to restrain boll weevil population growth after colonization. Kaolin spray under non-choice trials resulted in 2.2×, 4.4×, and 8.6× fewer weevils, oviposition and feeding punctures on kaolin-treated plants, respectively, despite demonstrating no statistical differences for colonization and population growth. Early season sprays in 2010 occurred during a period of rainfall, and hence, under our fixed spraying schedule no significant differences in boll weevil colonization were detected. In 2011, when kaolin sprays were not washed out by rain, delayed boll weevil colonization and reduction on attacked fruiting bodies were observed in eight out of 12 evaluations, and kaolin-treated plots had 2.7× fewer damaged fruiting bodies compared to untreated plots. Adoption of simple measures such as removal of fallen fruiting bodies and prompt reapplication of kaolin sprays after rainfall show promise in reducing boll weevil infestation.

Response of different populations of seven lady beetle species to lambda-cyhalothrin with record of resistance.

Simultaneous use of biological and chemical controls is a valued and historic goal of integrated pest management, but has rarely been achieved. One explanation for this failure may be the inadequate documentation of field populations of natural enemies for insecticide tolerance or resistance because natural enemies surviving insecticide application do not create problems like resistant pest species. Therefore, this study investigated 31 populations of lady beetles (Coleoptera: Coccinellidae) regarding their susceptibility to lambda-cyhalothrin, a pyrethroid insecticide that is widely used in cotton and other crops to control lepidopteran and coleopteran pests that are not targeted as prey by lady beetles. The study focused on seven coccinellid species common in cotton fields Coleomegilla maculata De Geer, Cycloneda sanguinea (L.), Eriopis connexa Germar, Harmonia axyridis (Pallas), Hippodamia convergens Guérin-Méneville, Olla v-nigrum (Mulsant), and Brumoides foudrasi (Mulsant) and one lady beetle species [Curinus coeruleus Mulsant] from a non-cotton ecosystem for comparisons. Dose-mortality curves were estimated after topical treatment of adult lady beetles with lambda-cyhalothrin. Statistically significant variations in lady beetle susceptibility were observed between species and between populations of a given species. Seven and eighteen populations of lady beetles exhibited greater values of LD50 and LD90, respectively, than the highest recommended field rate of lambda-cyhalothrin (20g a.i./hectare≈0.2g a.i./L) for cotton fields in Brazil. Furthermore, based on LD50 values, 29 out of 30 tested populations of lady beetles exhibited ratios of relative tolerance varying from 2- to 215-fold compared to the toxicity of lambda-cyhalothrin to the boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae). Four populations of E. connexa were 10.5-37.7 times more tolerant than the most susceptible population and thus were considered to be resistant to lambda-cyhalothrin, the first record of resistance for this species. These findings demonstrate that field selection for resistance to lambda-cyhalothrin in common lady beetles is occurring, opening up possibilities to effectively integrate biological control where the popular insecticide lambda-cyhalothrin is used.

Parasitoid increases survival of its pupae by inducing hosts to fight predators.

Many true parasites and parasitoids modify the behaviour of their host, and these changes are thought to be to the benefit of the parasites. However, field tests of this hypothesis are scarce, and it is often unclear whether the host or the parasite profits from the behavioural changes, or even if parasitism is a cause or consequence of the behaviour. We show that braconid parasitoids (Glyptapanteles sp.) induce their caterpillar host (Thyrinteina leucocerae) to behave as a bodyguard of the parasitoid pupae. After parasitoid larvae exit from the host to pupate, the host stops feeding, remains close to the pupae, knocks off predators with violent head-swings, and dies before reaching adulthood. Unparasitized caterpillars do not show these behaviours. In the field, the presence of bodyguard hosts resulted in a two-fold reduction in mortality of parasitoid pupae. Hence, the behaviour appears to be parasitoid-induced and confers benefits exclusively to the parasitoid.