International Journal of Tropical Insect Science

Aedes aegypti is of utmost public health concern transmitting various diseases of human health concern. Employment of chemical-based control interventions has induced immunity in mosquitoes, harmed environment, and adversely affected human health and non-targets diverting the research focus on alternate measures. Current study investigates the efficacy of an Insect Growth Regulator, lufenuron, against early fourth instars of Ae. aegypti. The larvae exposed to lufenuron for 24 h were assessed for the effects on the development and adult emergence. The impact of sub-lethal and median-lethal dose of lufenuron was determined on the nutrients and detoxification enzymes of Ae. aegypti. The larvae exposed to lufenuron showed reduced adult emergence exhibiting the respective IE30 and IE50 as 0.13 μg/L and 0.96 μg/L. Larval treatment with IE30 and IE50 lufenuron reduced the carbohydrate and lipid content in Ae. aegypti. However, the protein levels in the larvae decreased only on exposure to IE30 lufenuron while increased with IE50 lufenuron. Besides, IE30 and IE50 lufenuron treatment elevated α-esterases (1.05-fold; 1.15-fold); β-esterases (1.29-fold;1.62-fold), and Glutathione-S-transferases (1.19-fold; 3.1-fold) expression in the Ae. aegypti larvae. The % acetylcholinesterase inhibition also reduced by 3.75-fold and 2.07-fold, correspondingly, while the cytochrome P450 monooxygenase expression rose (1.15-fold) only with IE50 dosage of lufenuron. It is suggested that lufenuron stress probably ampliflied the catabolism of nutrients and expression of metabolic detoxifying enzymes in Ae. aegypti larvae in order to meet higher energy requirements and counteract the adverse effects of lufenuron. This is the first ever report unravelling the effect of lufenuron on the biochemical parameters of Ae. aegypti larvae.

One tactic of importation of natural enemies for biological control of stemborers and other pests is the use of parasite species that have had no previous association with the pest. This ’novel association’ approach offers the possibility of using parasites that have proven effective against a stemborer species other than the target stemborer pest. Nevertheless, creation of a novel host-parasite association requires that the novel host be ecologically and physiologically equivalent to the ancestral host. Selecting natural enemies based on ecological and physiological equivalence offers the best possibility of temporal, behavioural, nutritional and immunological compatibility in the host-parasite interaction, and reduces the chances of failure with the imported parasite species.

This study aimed to investigate antifungal activity of hemolymph of American cockroaches (Periplaneta americana) against three human invasive fungal species, including Aspergillus niger, Candida albicans, and Penicillium oxalicum. To stimulate the immunity of cockroaches, the strains of fungal species were injected into the coelom of cockroaches. The amphotericin B, non-induced and induced hemolymphs of cockroaches, and phosphate buffer were added to the cultured plates of fungal species strains. Phosphate buffer was used as negative control. Formation of the inhibitory zone represents the antifungal activity of hemolymph of P. americana cockroaches in the cultured plates of fungal species. Diameter of inhibitory zone of the growth of each fungal strain was measured by a calliper. Phosphate buffer does not have to inhibit the ability of growth of fungal species. The non-induced hemolymph of cockroaches exhibits a very low antifungal activity against the growth of fungal species. The induced hemolymph of cockroaches inhibits the growth of fungal species approximately as strong as amphotericin B. The impact of the induced hemolymph of cockroaches as inhibition of the growth of fungal species were: Penicillium oxalicum > Candida albicans > Aspergillus niger. This study indicates that with stimulation of the immunity of P. americana cockroaches using the strains of A. niger, C. albicans, and P. oxalicum, it is possible to acquire the antifungal activity by induced hemolymph of cockroaches approximately as the strong of amphotericin B.

Stem borer Stromatium barbatum has recently emerged as a serious pest problem of grapevines in India. Hidden biology and lack of effective chemical control of stem borer warranted finding out weak links in its life cycle which aids in formulating effective management strategies. Being a monovoltine pest with annual life cycle, the systematic studies on developmental biology and stage specific mortality of stem borer in grapes are limited. In present study, a cohort life table was constructed for S. barbatum by rearing it on grapevine wood logs in the laboratory at 27 ± 1 ℃ temperature and 65 ± 5% RH. The life cycle of S. barbatum was tracked from egg hatching through larval and pupal stages till adult emergence and observations were recorded on stage specific developmental durations and mortality of immature stages, and longevity and fecundity of adult stages. The results revealed that the mean durations of egg, larvae and pupae were 6.60 ± 0.28 days, 296.10 ± 1.06 days and 19.70 ± 1.17 days, respectively. The adults after emerging from pupae could survive up to 36.40 ± 0.81 days. The egg hatching and adult emergence from pupae were 42.51% and 83.02%, respectively. S. barbatum population attained a net reproductive rate of 64.96 females/female/generation and a gross reproductive rate of 72.93 females/female/generation in her mean oviposition period of 9.80 ± 0.13 days. The data indicated that, S. barbatum population potentially might increase with an intrinsic rate (rm) of 0.087 females/female/day and a finite rate $$(\lambda )$$ of 1.09 females/ female/ day with a doubling time of 9.98 days and a mean generation time of 324.30 days. The mortality was relatively higher during the egg and larval stages, which was then gradually decreased for rest of the life span when S. babatum was reared on grapevine wood logs under laboratory conditions. Generation mortality for S. barbatum was 90.72%. The present study has generated detailed information on critical life events such as days to egg hatch, adult longevity and fecundity, time required for adults to oviposit after mating, and age-stage specific mortality. This could facilitate formulation and implementation of effective management strategies for S. barbatum in grape vineyards.

The black been aphid, Aphis fabae Scopoli (Homoptera: Aphididae), is an important pest of many garden, vegetable and ornamental plants in the world. To evaluate Orius albidipennis potential for biological control of the aphid, prey stage preference of the predator to different life stages of the aphid and functional responses of it to different densities of the most preferred life stage were studied under laboratory conditions. Free choice experiment was conducted for evaluation of the bug prey preference between different instar nymphs and wingless female adults of A. fabae. In functional response trials, densities of 5, 10, 15, 20, 25 and 30 s instar nymphs, as the most preferred life stage, per arena were exposed to male and female of the predatory bug for 24-h period. The logistic regression analysis and Roger’s model were used for determinate the type and the parameters of predator’s functional response, respectively. The results showed that O. albidipennis preferred first and second instar nymphs of the aphid in comparison with other life stages. Both sexes of O. albidipennis showed the type II functional response to different densities of the nymphs. The handling times (Th) of O. albidipennis female and male were 1.344 and 1.584 h, respectively. The attack rate value (a) of the female and male bugs were 0.0839 and 1.4814 h−1, respectively. No significant differences were observed between the calculated Th and a for the female and male bugs. From the findings of this study, O. albidipennis can be used in biological control program of A. fabae.

The fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), is a new invasive species in India. This pest is occurring in serious proportions, causing significant damage to the maize crop in several states of India. Insecticides are sprayed regularly for the control of fall armyworm that could lead to the development of resistance. Hence, we measured the levels of susceptibility to insecticides among different populations of fall armyworm in India. The median lethal concentrations (LC50 value) were estimated through leaf dip bioassays using third instar larvae for various conventional and newer insecticide molecules. The lowest LC50 values were recorded on emamectin benzoate(0.11-0.12 ppm) and highest LC50 values was recorded on chlorpyrifos (99.73-106.32 ppm). This study suggested that emamectin benzoate was relatively more toxic and chlorpyrifos was less toxic to the fall armyworm. Differences in LC50 values for a given insecticide across populations was non-significant, suggesting the occurrence of similar populations in South India. Results of this study throw light on current levels of susceptibility prevailing in S. frugiperda for various insecticides and may form a basis for monitoring the development of resistance in S. frugiperda in India.

The penetration of adult Sitophilus zeamais Motschulsky through maize grain bulks (0.75 m deep), treated with Protect-It®, a diatomaceous earth (DE) at 0, 0.05, 0.1 and 0.2% (w/w), was determined 12 weeks after weevils were released at the upper surface of the grain. Maize was stored in columns in polyvinyl chloride (PVC) pipes, under controlled conditions of 26 ± 2°C and 70 ± 10% RH. Grain samples were collected from various pre-determined depths and the numbers of S. zeamais adults counted. Differences in insect numbers between treatments and at different depths from which samples were collected were highly significant (P < 0.001). The bottom 2–3 layers (0.65–0.75 m deep) had significantly more insects than the upper layers for all the DE concentrations. No significant differences in total insect numbers (live + dead) were found between the DE concentrations. Dead S. zeamais weevils were found at the bottom of grain treated with Protect-It®, indicating that insects can penetrate through DE-treated grain 0.75 m deep but then subsequently die. There was no strong evidence that DEs admixed with bulk grain restrict S. zeamais movement within the grain.