Predator-Prey Interaction Between Xylocoris sordidus (Hemiptera: Anthocoridae) and Enneothrips enigmaticus (Thysanoptera: Thripidae).

The peanut thrips, Enneothrips enigmaticus (Thysanoptera: Thrypidae), is an important pest of the peanut (Arachis hypogaea) in South America. Due to concerns about the environment and human health induced by the extensive use of pesticides in the management control of pests, environmentally and friendlier tactics must be targeted. Thus, this study investigates, for the first time, the behavior of Xylocoris sordidus (Hemiptera: Anthocoridae) as a biological control agent for E. enigmaticus. The methodology included no-choice tests to assess whether the predation rate varies according to the developmental stage of the prey, as well as the predator's developmental stage with the highest predation capacity. Additionally, an analysis of the functional response of adult and 5th instar nymphs of X. sordidus exposed to different densities of E. enigmaticus nymphs (1, 2, 4, 8, 16, and 32) was conducted. The results confirm the predation of peanut thrips by X. sordidus, with a higher predation rate in the nymphal stages of the prey. There was no difference in predation capacity between predator nymphs and adults, and exhibiting a type II functional response. Therefore, the potential of X. sordidus as a biological control agent for E. enigmaticus is confirmed, showing the importance of adopting measures to preserve this predator in peanut crops.

Bacillus thuringiensis-based bioinsecticides affect predation of Euborellia annulipes on diamondback moth larvae.

Interactions between earwigs and entomopathogens, such as Bacillus thuringiensis (Bt), are still poorly understood. This study tested whether Bt-based bioinsecticides have any effect on the predation of Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae) on Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the pests with the largest number of cases of use and resistance to Bt. Fourth instar larvae were Bt infected by feeding on collard green leaves treated with Dipel®WG and XenTari®WG at the manufacturer-recommended doses. We used one no-choice condition, in which the predator had access to uninfected or Bt-infected larvae separately, and four free-choice conditions: uninfected vs Dipel®-infected larvae, uninfected vs XenTari®-infected larvae, Dipel®-infected vs XenTari®-infected larvae, and uninfected vs Bt-infected larvae with both bioinsecticides. Uninfected larvae were less consumed than those infected by both Bt-bioinsecticides in the no-choice condition. There was a higher consumption of uninfected over Dipel®-infected larvae in the free-choice condition. Overall, uninfected larvae were preferred over both Bt-based bioinsecticides infected larvae. We also used six different prey densities. The ringlegged earwig's predation rate enhanced as the prey population density increased, but the functional response was not affected by Bt-infection, being type II. The predator invested a low amount of handling time on Bt-fed prey and increased the maximum predation rate. Bt-based bioinsecticides cause effects on E. annulipes predation by altering their feeding preference and some aspects of its predatory behavior. The results of our study provide an important background for understanding interactions between earwigs and Bt. In addition, they can be used for decision making during approaches to integrated P. xylostella management.

Silicon and boron on cauliflower induce attractiveness and mortality in Plutella xylostella.

BACKGROUND: Boron (B) and silicon (Si) are fundamental for brassica nutrition, and in some cases, they have potential as an insecticide. Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the most economically important agricultural pests, is difficult to control due to the resistance to insecticides and the absence of alternative control methods. RESULTS: Cauliflower leaves sprayed with Si and B showed a higher concentration of the beneficial element and micronutrient, respectively. When evaluating the firmness of the cauliflower leaves, it was found that the plants with leaf sprayings of Si and B did not differ statistically from each other. However, they showed an increase in firmness, in relation to the plants of the control treatment. Leaf spraying of Si and B on cauliflower did not influence the number of eggs/female. The attractiveness index showed that both Si and B applications stimulated the presence of second instar larvae, being more stimulating in relation to the control treatment. However, the use of Si and B in isolation showed a positive result, since it caused high mortality in diamondback moth larvae compared to the control treatment. CONCLUSION: The application of both foliar fertilizers positively affects the attractiveness index of the larvae, being attractive; however, both Si and B caused high mortality (~80%). The results showed that Si and B have the potential to control P. xylostella and serve as a basis for alternative pest management in brassica crops. © 2022 Society of Chemical Industry.

Artificial Diets With Different Protein Levels for Rearing Spodoptera frugiperda (Lepidoptera: Noctuidae).

Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is a pest of great economic importance which can feed on more than 300 plant species. As it is polyphagous, its host plants may have variable physical and chemical constitutions. This may influence larval development, as protein and carbohydrate levels are important factors for adequate biological development. The aim of this study was to evaluate insect developmental parameters as well as to compare the food consumption of S. frugiperda larvae reared using diets with different protein levels under laboratory conditions. Three artificial diet formulations were used: one typically used for routine laboratory rearing, based on bean, wheat germ and brewer's yeast (D1); one containing half the original amount of protein (D2), and the other with twice the original amount of protein (D3). The relative consumption rate (RCR), relative growth rate (RGR), and efficiency of conversion of ingested food (ECI) for S. frugiperda fourth instar larvae varied among diets. The protein present in the diet influenced the duration of larval and pupal periods and pupal weight, but did not affect larval survival, fecundity and longevity of adults. The different protein levels in the diets did not negatively influence population growth, so these three diet variations can be used for mass rearing in the laboratory. However, the influence of these diets on successive generations of the insect remains untested.

Temperature-dependent functional response of Euborellia annulipes (Dermaptera: Anisolabididae) preying on Plutella xylostella (Lepidoptera: Plutellidae) larvae.

Temperature mediates trophic interactions, including relationships between insect pests and predators, and functional response studies are often used to determine the suitability of predators as biocontrol agents. We investigated the effects of temperature on the functional response of Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae) preying on Plutella xylostella (L.) (Lepidoptera: Plutellidae) larvae. Predation rate, type of functional response, attack rate (a'), handling time (Th), and maximum predation rate (T/Th) of the predator were estimated using seven prey densities and three thermal conditions. The functional response of E. annulipes to P. xylostella was temperature-dependent, type III under the lower temperatur (18°C and 25 °C) , and type II at 32 °C. We observed increasing values of a' in 25 °C and 32 °C, decreasing values of Th and highest T/Th as the thermal condition increased. Our findings suggest that E. annulipes could be effective to control P. xylostella under different thermal conditions, however its predation behavior changes according to temperature variation.

Effects of a Bt-based insecticide on the functional response of Ceraeochrysa cincta preying on Plutella xylostella.

Plutella xylostella, is the main pest infesting Brassica crops, and products based on Bacillus thuringiensis (Bt) are frequently used in strategies for its biocontrol. The present study aimed to evaluate whether a Bt-based bioinsecticide affects the predation behavior of Ceraeochrysa cincta when preying on P. xylostella. Three larval instars of the predator and the eggs and second-instar larvae of the moth were used, with the prey either untreated or treated with a Bt-based product (Xentari®). Results showed that, the first larval instar of C. cincta presented a type II functional response when preying upon untreated eggs, and a type III response when preying upon Bt-treated eggs, while the second and third instars presented type II and III responses, respectively, in both situations. The predator's first and third larval instars presented a type II functional response when preying upon untreated larvae and a type III response when preying upon Bt-treated larvae. However, the predator's second-instar larvae showed a type II response in both treatments. The results obtained allowed us to conclude that the Bt-based insecticide tested affects the predation behavior of the first-instar larvae of C. cincta on eggs and of both the first- and third-instar larvae of this predator on P. xylostella larvae.

Interactions of Bacillus thuringiensis strains for Plutella xylostella (L.) (Lepidoptera: Plutellidae) susceptibility.

Bacillus thuringiensis (Bt) biopesticides are an environmentally safe alternative to the management of Plutella xylostella pesticide resistance evolution. We evaluated P. xylostella susceptibility to six Bt strains cultivated and applied individually, and 15 combinations of Bt strains mixed after cultivation. Three combinations resulted in synergism and one in antagonism. Promising results of larval mortality with synergistic effects were obtained with the combinations Bt var. thuringiensis strain HD-2 + Bt finitimus strain HD-3, Bt var. thuringiensis strain HD-2 + Bt dendrolimus strain HD-7 and Bt var. thuringiensis strain HD-2 + Bt var. aizawai strain HD-11.

Artificial Corn-Based Diet for Rearing Spodoptera frugiperda (Lepidoptera: Noctuidae).

Spodoptera frugiperda (J.E. Smith, 1797) is considered a key pest of maize. However, the artificial diets used for rearing this insect in the laboratory do not contain corn. The aim of this study was to evaluate the biology and to compare the food consumption by S. frugiperda, as well as the food preference of the larvae in the standard diet and the corn-based diet. Three of the following diets were evaluated: a standard diet based on beans (D1), a diet with corn flour as substitute for wheat germ (D2), and a diet replacing beans with green corn (D3). The biological parameters evaluated were period and survival of larvae and pupae; weight of male and female pupae; sex ratio; fecundity; egg incubation period; and adult longevity. The nutritional indices were determined and the biological data obtained were used to determine the parameters of fertility life tables; we also performed a multiple-choice test (feeding test). Larval development of S. frugiperda occurred in all three diets, although without oviposition by females developed from larval fed on D2. There was no difference among the diets in relation to the fertility life table parameters. The diet D2 resulted in better ingestion, digestion, assimilation, and conversion of food, but was associated with a metabolic cost to assimilate the food. Using a multiple-choice test, we observed that the larvae preferred diet D2. Based on our results, the most adequate diets for rearing S. frugiperda in the laboratory are D1 and D3.

Performance of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on eggs of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae).

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a polyphagous pest with a wide geographic distribution. This pest first arrived in Brazil in 2013, and since then studies on possible control methods for it have been necessary. A possible method for the control of H. armigera is using the egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). Therefore, the objective of this study was to evaluate the performance of T. pretiosum on H. armigera eggs, which are known to represent suitable hosts for the development of this parasitoid species in the laboratory. Parasitism and emergence rates and the duration of the egg-to-adult period of T. pretiosum were investigated following 24- and 48-h exposures of this parasitoid to H. armigera and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs. The longevity of offspring after the 24-h exposure was studied, as well as the frequency of parasitism and emergence, host preference, and the emergence of offspring from eggs of different ages or oviposited by lepidopterans on different days. Parasitism was 14.4 and 34.9% more frequent on C. cephalonica than on H. armigera after 24 and 48 h of exposure, respectively. In C. cephalonica, parasitism was 27.2% higher after 48 h. Parasitism was more frequent on C. cephalonica eggs collected on the second day of oviposition (76.2%), and on H. armigera on the third day of oviposition (71.1%). Parasitism frequency was lower on 2-day-old C. cephalonica eggs (63.3%) and on 3-day-old H. armigera eggs (41.3%). When tested with a chance of choice between hosts, T. pretiosum preferred H. armigera, while in the test with no chance of choice there was no difference in preference. Thus, T. pretiosum may be considered a tool for the Integrated Pest Management (IPM) of H. armigera.

Food Consumption Utilization, and Life History Parameters of Helicoverpa armigera (Lepidoptera: Noctuidae) Reared on Diets of Varying Protein Level.

Helicoverpa armigera (Hübner) is an important pest of crops worldwide, and several studies have focused on the development of this species on different artificial diets. However, studies evaluating the insect's food consumption and utilization using nutritionally different diets are scarce. The aim of this study was to evaluate the biology and to compare the consumption and use of food by H. armigera larvae on diets with different protein levels provided by several dietary ingredients used in the diets. The nutritional index, the relative consumption rate, the relative metabolic rate, the relative growth rate, and the apparent digestibility were higher in the diet with higher than the optimum level of protein. On the other hand, the conversion efficiency of digested food was lower, resulting in a higher metabolic cost. In terms of biological aspects, larval survival was higher for the diet with optimal protein content and lower for the diet with a higher protein level. The pupal period was longer for the diet with a higher protein content, while pupal survival was lower. Among the evaluated diets, the diet with an optimal protein containing white bean 75 g, wheat germ 60 g, soy bran 30 g, milk powder 30 g, brewer's yeast 37.5 g as the protein sources resulted in a higher net reproductive rate, a shorter time for the population to double in number, and the highest rates of population growth. The results suggest that lower or higher protein contents in the diets of H. armigera negatively affect the biological aspects of this species.

Consumo foliar da traça-das-crucíferas em couve e brócolis tratados com sinigrina / Leaf area consumed by diamondback moth feeding on kale and brocolis treated with sinigrin

A estimativa da área foliar, em função da sua redução causada pelo consumo por insetos filófagos, é uma metodologia básica em várias áreas da Entomologia, como, por exemplo, em estudos sobre resistência de plantas, entomologia econômica e ecologia nutricional. Um dos fatores que pode interferir na quantidade de área foliar consumida pelo fitófago é a presença de certos químicos nas folhas, como a sinigrina em brassicáceas. Dessa forma, foram aplicadas em folhas de couve e brócolis diversas concentrações de sinigrina (0,2, 0,4, 0,8, 1,6, e 3,2 mg/mL em solução a 5% de Tween20(r)), medindo-se o consumo da área foliar por lagartas de P. xylostella, o qual foi aferido pela porcentagem de redução da área, diferença de peso e escala visual de notas. Os resultados mostraram que as concentrações 0,2, 0,4 e 3,2 mg/mL de sinigrina aumentam o consumo em folhas de couve e diminuem em folhas de brócolis por lagartas de P. xylostella. As metodologias utilizadas proporcionam resultados similares, sendo as estimativas de peso fresco e nota visual mais práticas.(AU)

Leaf area estimation, based on their reduction due to consumption by phytophagous insects, is a basic methodology in several areas of Entomology, for instance, in studies about plant resistance, economic entomology and nutritional ecology. One of the factors that can affect the amount of leaf area consumed by insects is the presence of certain chemicals in the leaves, such as sinigrin in Brassicaceae. Thus, several concentrations of sinigrin were applied on the leaves of cabbage and broccoli (0.2, 0.4, 0.8, 1.6, and 3.2 mg/mL in 5% Tween20(r) solution) in order to measure leaf area consumption by larvae of P. xylostella, estimated by the percentage of area reduction, weight loss and visual scale of notes. The results show that the concentrations of 0.2, 0.4 and 3.2 mg/mL of sinigrin increase larvae consumption of P. xylostella on kale leaves and decrease it on broccoli leaves. The methodologies used provide similar results, and fresh weight measurements and visual grades are more practical.(AU)

Efeito de vitaminas e esterol como aditivos foliares no desenvolvimento de Bombyx mori L. e influência do modo de aplicação / Effect of vitamins and sterol as foliar additives in the development of Bombyx mori L. and influence of the application mode

O objetivo deste estudo foi avaliar os efeitos e os métodos de aplicação dos aditivos foliares decanoato de nandrolona (esteroide anabolizante) a 0,5%, ácido ascórbico (vitamina C) a 0,5%, palmitato de retinol (vitamina A) a 0,5% e acetato de retinol (vitamina A) a 1,0% em alguns parâmetros biológicos do bicho-da-seda. No experimento do modo de aplicação (pulverização foliar antes do fornecimento, depois do fornecimento e por imersão antes do fornecimento) foram utilizados: decanoato de nandrolona 0,5%; ácido ascórbico 0,5%; e palmitato de retinol 0,5%. No ensaio de desenvolvimento do inseto foram avaliados: duração e viabilidade larval; peso de casulo; taxa de encasulamento; teor líquido de seda; longevidade de adultos; número de ovos por fêmea; e duração do período de subida ao bosque. Para o modo de aplicação determinaram-se: ganho de peso, comprimento, diâmetro do tórax e diâmetro do abdome de lagartas de 5º ínstar, assim como comprimento, diâmetro e peso de glândula sericígena. Os resultados mostraram que, apesar de o ácido ascórbico proporcionar os melhores valores para o desenvolvimento corpóreo das lagartas, este não corresponde a incrementos significativos na produção; o palmitato de retinol não melhora o desenvolvimento das lagartas; o acetato de retinol e o palmitato de retinol prolongam o período larval, sem, no entanto, alterar significativamente os parâmetros de produção; a imersão de folhas antes do fornecimento às lagartas é mais viável para a aplicação dos aditivos.(AU)

The present study was aimed to evaluate the effects of different methods of foliar application of the additives nandrolone decanoate (anabolic steroid) 0,5%; ascorbic acid (vitamin C) 0,5%; retinol palmitate (vitamin A) 0,5%; and retinol acetate (vitamin A) 1,0% on some biological parameters of the silkworm. The experiment of application method (foliar spray prior to delivery, after delivery and soaking before feeding) used: nandrolone decanoate 0.5%, ascorbic acid 0.5%, and retinol palmitate 0.5%. The test of insect development evaluated: duration and larval viability, weight of cocoon, cocooning rate, liquid silk content, adult longevity, number of eggs per female and rising up time. For the application of foliar additives, the following were determined: weight gain, length, diameter and abdomen diameter of fifth instar larvae, and length, diameter and weight of silk gland. The results showed that although ascorbic acid provided the best value for the development of the caterpillars body, it did not correspond to significant increase in production; retinol palmitate did not affect the larvae body development; retinol acetate and retinol palmitate prolong the larval period, without, however, significantly altering the production parameters. The immersion method of leaves before being delivered to the caterpillars is the most feasible for the foliar application of additives.(AU)