Adaptive strategies of Rice Leaf Roller, Cnaphalocrocis medinalis in Response to Different Rearing Temperatures

Understanding how species that follow different life-history strategies respond to stressful temperature can be essential to efficient treatments against agricultural pests. Here we focus on how the development and reproduction of C. medinalis is influenced by exposure to different rearing temperatures in the immature stage. We found that low (18 or 22 °C) or high (30 and 34 °C) rearing temperatures negatively affected the immature development and flight performance compared to the normal temperature 26 °C, with higher larval and pupal mortality, lower pupation and eclosion rates and shorter flight duration and distance. Low rearing temperatures significantly slowed down the immature process, but accelerated adult reproduction. However, high rearing temperatures had the opposite impacts. Interestingly, the flight of adults with un-mature rearing low temperatures (18 and 22 °C) significantly decreased their lifetime fecundity and mating frequency, but increased pre-oviposition period of females compared to the control; On contrast, high rearing temperatures (30 and 34 °C) significantly accelerated onset of oviposition and enhanced synchrony of spawning. These results indicate high rearing temperatures in the immature stage are more likely to trigger the onset of migration, but low rearing temperatures induces adults to have a greater resident propensity with stronger reproductive ability.

Seasonal fitness parameters and selection indices in the natural population of Drosophila melanogaster Meig.

Aim. The purpose of investigation was to study the seasonal selection indices and its components in the natural population of Drosophila melanogaster Meig. Methods. The material for the study was the Gaidary-spring and Gaidary-autumn lines, obtained from the natural population of Gaidary in different seasons of the year. Fecundity and mortality/survival rates in the pre-reproductive period of development were studied. Based on these indicators, the selection indices were calculated according to the Crow`s formula. Results. In terms of individual components of fitness, such as egg production of females, the number of adult offspring, embryonic and pupal mortality, the spring and autumn populations of Gaidary did not show significant differences. Selection indices (Itot) in the autumn population of Gaidary were higher than in the spring population: in the embryonic period of development – by 50.4%, in the postembryonic period – by 67.5%. Differences in the intensity of selection are due to the variance of fertility, which was higher in the autumn population. Conclusions. Seasonal changes in the intensity of selection in different periods of ontogenesis are cumulative, which leads to increased selection pressure in the population of Gaidary in the autumn compared to spring. Keywords: Drosophila melanogaster Meig., natural population, fecundity, embryonic mortality, pupal mortality, Crow’s indices.

Biological activity of entomopathogenic nematodes on Anastrepha fraterculus (Diptera: Tephritidae)

Anastrepha fraterculus (Wiedemann) is one of the main pests of fruit farming, and entomopathogenic nematodes (EPNs) represent an important control tool of this species. Thus, the objective of this study was to evaluate the biological activity of different isolate against A. fraterculus larvae and adults. Bioassays were performed using a suspension of three isolates of Heterorhabditis amazonensis IBCB 24, Steinernema carpocapsae IBCB 02 and Steinernema feltiae IBCB 47 at six concentrations (control - without nematodes), 50, 150, 300, 500, 1000 and 1500 infective juveniles (IJs)/mL of water per 3º instar larvae. It was verified the susceptibility of larvae of A. fraterculus to isolates of EPNs and a significant increase of the pupal mortality in the function of the concentration of IJs inoculated by larva (above 75%). After the dissection of pupae and adults of A. fraterculus from infected larvae, the concentration of 1500 IJs/mL of EPNs provided the highest rate of multiplication of IJs by insect, equating to maximum concentration tested 1500 IJs/mL. Adults of A. fraterculus from larvae infected with EPNs longevity of five days, being less than adults from uninfected larvae by IJs (135 days). H. amazonensis IBCB 24, S. carpocapsae IBCB 02, and S. feltiae IBCB 47 proved to be promising as agents of biological control of A. fraterculus.

Heterodissemination: precision insecticide delivery to mosquito larval habitats by cohabiting vertebrates

Conventional larvicide delivery strategies originally developed for permanent and floodwater mosquitoes have proved suboptimal in the small, scattered, and cryptic larval habitats preferred by container-inhabiting Aedes mosquitoes. New methods such as autodissemination, wherein adult mosquitoes spread insecticides to their own larval habitats, have been under study. Another novel delivery method termed heterodissemination, i.e. larvicide delivery by other species sharing the same habitats, has also been proposed. We conducted a proof-of-concept study with four independent experiments using American bullfrogs (Lithobates catesbeianus) and green frogs Lithobates clamitans as carriers of pyriproxyfen, an insect growth regulator, under semi-field conditions in three different locations, two in New Jersey, and one in Utah. Frogs with attached slow-release pyriproxyfen tablets were introduced into outdoor enclosures with water containers. Water samples from the containers were periodically tested using larval Aedes albopictus and Culex pipiens mosquitoes to assess mortality and percent eclosure inhibition. Overall pupal mortality [95% credible intervals] estimated by Bayesian analysis for the treatment group was 73.4% [71.3–75.2] compared to 4.1% [2.9–5.5] for the control group. Mortality within treatment groups in four different experiments ranged from 41 to 100%, whereas control mortalities ranged from 0.5% to 11%. We conclude that heterodissemination is a promising and effective approach deserving of further study.

Ovicidal, larvicidal and pupicidal activity of Nelumbo nucifera Gaertn against the filarial vector Culex quinquefasciatus Say (Diptera: Culicidae)

In the current investigation, different solvent leaf extracts of Nelumbo nucifera were tested for their mosquitocidal potential against the filarial vector Culex quinquefasciatus. Further, bioactive compounds of the crude leaf extracts of N. nucifera were identified using GC-MS analysis. The benzene leaf extracts of N. nucifera showed significant egg, larval and pupal mortality at concentrations of 62.5, 125, 250 and 500 ppm, respectively. Mortality of ovicidal, larvicidal and pupicidal effect at 500 ppm at 48 h period were 89, 38 and 67 per cent with LC50 values 4.247, 6.694 and 4.975 and LC90 values 5.881, 9.628, 6.565 ppm, respectively. GC-MS profile of the leaf showed seven peaks and the major components identified as nuciferine, steporphine and mecambroline (29.40%). The study confirms N. nucifera has significant mosquitocidal effects.

Enhancement of Photocatalytic And Biological Activities of Chitosan/Activated Carbon Incorporated With TiO2 Nanoparticles

A Novel and sustainable chitosan (CS)/ activated charcoal (AC) composites were prepared by cross linking with epichlorohydrine (ECH) to form a porous structure. Different titanium dioxide nanoparticles (TiO2 NPs) concentrations (0, 0.2, 0.4, and 0.8% w/w) were added to enhance the photocatalytic, antibacterial, larvicidal, and pupicidal activities efficiency toward rose bengal (RB) dye and the Culex Pipiens. The composites were characterized by FT-IR, XRD and SEM. The SEM images revealed the porous structure of CS/AC and TiO2 nanoparticles were uniformly distributed in the CS/AC matrix. The degradation of RB dye was used to test the photocatalytic behavior of the composites. Supporting TiO2 on a CS/AC matrix resulted in a significant increase in photocatalytic performance. The antibacterial activities supported by CS/AC/TiO2 NPs were evaluated by bacterial growth inhibition against B. subtilis, S. aureus, E. coli and P. aeruginosa. The results showed that CS/AC/TiO2 NPs composite has an inhibitory effect and therefore considered as antibacterial agents. CS/AC/0.4%TiO2NPs showed maximum efficacy against larvicidal activity and pupicidal of mosquito vector which recorded 99.00 ± 1.14, 95.00 ± 1.43, 92.20 ± 2.64 for first, second and third larval instars and 66.00 ± 2.39 for pupal mortality, while the repellent activity reported high protection at 82.95 ± 2.99 with 3.24 mg/cm2 dose compared to control DEET.

Infection effects of the new microsporidian species Tubulinosema suzukii on its host Drosophila suzukii

Microsporidian infections of insects are important natural constraints of population growth, often reducing lifespan, fecundity and fertility of the infected host. The recently discovered Tubulinosema suzukii infects Drosophila suzukii (spotted wing drosophila, SWD), an invasive pest of many fruit crops in North America and Europe. In laboratory tests, fitness effects on larval and adult stages were explored. High level infection after larval treatment caused up to 70% pupal mortality, a decreased lifespan and a 70% reduced oviposition of emerging adults in biparental infection clusters. A shift to higher proportion of female offspring compared to controls suggested a potential parthenogenetic effect after microsporidian infection. A clear sex-linkage of effects was noted; females were specifically impaired, as concluded from fecundity tests with only infected female parents. Additive effects were noted when both parental sexes were infected, whereas least effects were found with only infected male parents, though survival of males was most negatively affected if they were fed with T. suzukii spores in the adult stage. Although most negative effects on fitness parameters were revealed after larval treatment, infection of offspring was never higher than 4%, suggesting limited vertical transmission. For that reason, a self-reliant spread in natural SWD populations would probably only occur by spore release from cadavers or frass.

Exposure to Inactivated Deformed Wing Virus Leads to Trans-Generational Costs but Not Immune Priming in Honeybees (Apis mellifera)

Pathogens are identified as one of the major drivers behind the honeybee colony losses, as well as one of the reasons for the reported declines in terrestrial insect abundances in recent decades. To fight infections, animals rely on their immune system. The immune system of many invertebrates can be primed by exposure to a pathogen, so that upon further exposure the animal is better protected. The protective priming effect can even extend to the next generation, but the species capable of priming the immune system of their offspring are still being investigated. Here we studied whether honeybees could prime their offspring against a viral pathogen, by challenging honeybee queens orally with an inactivated deformed wing virus (DWV), one of the most devastating honeybee viruses. The offspring were then infected by viral injection. The effects of immune priming were assayed by measuring viral loads and two typical symptoms of the virus, pupal mortality, and abnormal wing phenotype. We saw a low amount of wing deformities and low pupal mortality. While no clear priming effect against the virus was seen, we found that the maternal immune challenge, when combined with the stress caused by an injection during development, manifested in costs in the offspring, leading to an increased number of deformed wings.

Effectiveness of Entomopathogenic Nematodes Against Ceratitis capitata (Diptera: Tephritidae) Pupae and Nematode Compatibility with Chemical Insecticides

The Mediterranean fruit fly Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is among the main pests of fruit crops worldwide. Biological control using entomopathogenic nematodes (EPNs) may be an alternative to suppress populations of this pest. Thus, the aim of this study was to evaluate the pathogenicity and virulence of six EPN isolates (Heterorhabditis bacteriophora HB, H. amazonensis IBCB-n24, Steinernema carpocapsae IBCB-n02, S. rarum PAM-25, S. glaseri IBCB-n47, and S. brazilense IBCB-n06) against C. capitata pupae. The compatibility of EPNs with different chemical insecticides that are registered for management of C. capitata was also assessed. Isolates of H. bacteriophora HB and S. brazilense IBCB-n06 at a concentration of 1,000 infective juveniles (IJ)/ml proved to be most pathogenic to C. capitata (70 and 80% mortality, respectively). In contrast, the isolates H. amazonensis IBCB-n24, Steinernema carpocapsae IBCB-n02, S. rarum PAM-25, S. glaseri IBCB-n47 provided pupal mortality of less than 60%. Bioassays to determine lethal concentrations indicated that concentrations of 600 IJ/ml (H. bacteriophora HB) and 1,000 IJ/ml (S. brazilense IBCB-n06) showed the highest virulence against C. capitata pupae. In contrast, the highest numbers of IJs emerged at concentrations of 1,200 and 200 IJ/ml. In compatibility bioassays, malathion, spinetoram, phosmet, acetamiprid, and novaluron were considered compatible with and harmless (Class 1) to H. bacteriophora HB and S. brazilense IBCB-n06, according to IOBC/WPRS. This information is important for implementing integrated management programs for C. capitata, using biological control with EPNs, whether alone or in combination with chemical insecticides.