Contact Toxicity of Insecticides and Biopesticides to Trichogramma Chilonis Ishii. (Hymenoptera: Trichogrammatidae) under Laboratory Condition

Integration of insecticides and biological controls is an important tactic of Integrated Pest Management (IPM). Trichogramma chilonis is a promising natural enemy of many lepidopteran insect pests. However, this hymenopteran egg parasitoid is adversely affected by most insecticides. Contact toxicity of nineteen insecticides and three biopesticides on adults of T. chilonis was investigated by using dry film residue bioassays under laboratory conditions. Profenofos and chlorpyrifos were highly lethal to the adults even at sublethal doses followed by dimethoate, spinosad, indoxacarb and acephate + imidacloprid. Diafenthiuron, nimbecidine and flubendiamide were categorised as less toxic. The biopesticides viz., Metarhizium anisopliae, Beauveria bassiana and Metarhizium rileyi were found innocuous to T. chilonis. The studysuggests that the insecticides with less toxicity and biopesticides with apparently no harmful effects on the parasitoid can be used in conjunction with parasitoids in IPM programmes. This will also advice the plant protectionists in avoiding the one with detrimental effects on this hymenopteran wasp with appropriate timing of application that controls the pests without adversely affecting their natural enemies

A Novel Reference for Bt-Resistance Mechanism in Plutella xylostella Based on Analysis of the Midgut Transcriptomes

The diamondback moth, Plutella xylostella, is a lepidopteran insect that mainly harms cruciferous vegetables, with strong resistance to a variety of agrochemicals, including Bacillus thuringiensis (Bt) toxins. This study intended to screen genes associated with Bt resistance in P. xylostella by comparing the midgut transcriptome of Cry1Ac-susceptible and -resistant strains together with two toxin-treated strains 24 h before sampling. A total of 12 samples were analyzed by BGISEQ-500, and each sample obtained an average of 6.35 Gb data. Additionally, 3284 differentially expressed genes (DEGs) were identified in susceptible and resistant strains. Among them, five DEGs for cadherin, 14 for aminopeptidase, zero for alkaline phosphatase, 14 for ATP binding cassette transport, and five heat shock proteins were potentially involved in resistance to Cry1Ac in P. xylostella. Furthermore, DEGs associated with “binding”, “catalytic activity”, “cellular process”, “metabolic process”, and “cellular anatomical entity” were more likely to be responsible for resistance to Bt toxin. Thus, together with other omics data, our results will offer prospective genes for the development of Bt resistance, thereby providing a brand new reference for revealing the resistance mechanism to Bt of P. xylostella.

CRISPR/Cas9 mutagenesis against sex pheromone biosynthesis leads to loss of female attractiveness in Spodoptera exigua, an insect pestt

Virgin female moths are known to release sex pheromones to attract conspecific males. Accurate sex pheromones are required for their chemical communication. Sex pheromones of Spodoptera exigua, a lepidopteran insect, contain unsaturated fatty acid derivatives having a double bond at the 12th carbon position. A desaturase of S. exigua (SexiDES5) was proposed to have dual functions by forming double bonds at the 11th and 12th carbons to synthesize Z9,E12-tetradecedienoic acid, which could be acetylated to be a main sex pheromone component Z9,E12-tetradecenoic acetate (Z9E12-14:Ac). A deletion of SexiDES5 using CRISPR/Cas9 was generated and inbred to obtain homozygotes. Mutant females could not produce Z9E12-14:Ac along with Z9-14:Ac and Z11-14:Ac. Subsequently, pheromone extract of mutant females did not induce a sensory signal in male antennae. They failed to induce male mating behavior including hair pencil erection and orientation. In the field, these mutant females did not attract any males while control females attracted males. These results indicate that SexiDES5 can catalyze the desaturation at the 11th and 12th positions to produce sex pheromone components in S. exigua. This study also suggests an application of the genome editing technology to insect pest control by generating non-attractive female moths.

Ontogenetic description of Proctolaelaps bickleyi (Bram) (Acari: Melicharidae), newly recorded from lepidopteran insect cultures in Japan

Proctolaelaps bickleyi (Bram) (Acari: Melicharidae) is an edaphic predatory mite commonly associates with insects. Although P. bickleyi has been reported from many countries worldwide, it is reported herein for the first time in Japan from laboratory cultures of Chilo suppressalis (Walker) and Cossus insularis (Staudinger) (Lepidoptera: Crambidae, Cossidae). Proctolaelaps bickleyi is redescribed and illustrated from females, males, deutonymphs, protonymphs and larvae. The morphological ontogeny of idiosomal and leg chaetotaxy is discussed and a key to the Japanese species of Proctolaelaps is provided.

Population dynamics of stem fly and defoliator pests of soybean and their natural enemies in relation to weather parameters

The field experiment was carried out at Polasa Farm, Regional agricultural research station Jagtial during the Kharif, 2014-15 and 2015-16. Study about pre dominant lepidopteran insect –pests in soybean crop noticed that the tobacco cut worm, (Spodptera exigua Hubner), green semi looper(Crysodexis acuta Walker), and tobacco caterpillar (Spodoptera litura Fab) along with stemfly, (Melanagromyza obtusa Zehnter) as non lepidopteran pest were noticed at various growth stages of cropgrowth. The peak activity of stem fly (37.84%) was observed during 37th standard week per meter row) for the year 2014 and for the year 2015 to a maximum infestation of 35.70 per cent during 30th std.week. The peak activity of caterpillar pests i.e., S. litura (7.6 larvae per meter row) for the year 2014 was observed during 34th std.week and for the year 2015 (12.4 per meter row during 36th std.week and C. acuta (0.7 larvae per meter row) during 36th std. week for the year 2014 and for the year 2015 (2.20 larvae/mrl on 37th std week. S. exigua (1.6 larvae per meter row) for both the years 2014 and 2015 was observed during 32th std.week Among the natural enemies, one predators namely, spiders (Oxyopes sp. was observed to prey on the insect pests.The biocontrol agent’s one species, lynx spider, Oxyopes sp. population recorded on the crop during Kharif , 2014 ranged from 0.15 to 0.40 /mrl and 0.15 to 0.60/ mrl during Kharif, 2015.

A New Species of Sympiesis Förster, 1856 (Hymenoptera: Eulophinae) Parasitizing Lepidopteran Pest Feeding on Dioscorea bulbifera in Almora, Uttarakhand, India

In the present study, a new species of eulophid parasitoid i.e. Sympiesis almorensis (Hymenoptera: Eulophidae: Eulophinae) is described which was parasitizing to a larval host, most probably larval stage of a Lepidopteran insect.

Studies on Genetic Diversity and Population Structure of Tasar Silkworm, Antheraeamylitta.Drury

The populations of Indian tropical Tasar silkworm, Antheraeamylitta Drury, the semi-wild, sericigenous, lepidopteran insect are distributed in eco pockets of various States. These ecoraces vary in geography, topography, ecology, food plant flora and frequency of life cycle in latitudinal and altitudinal gradients. They exhibit diversity in phenotypic, behavioural, physiogenetic and commercial characters. In the present study, the SSR amplification of 7 silkworm strains/ecoraces (16 individuals in each, with seven primers which generated polymorphism) yielded a total of 887 bands, out of which 420 were (47.3 %) polymorphic. Most of the bands were observed within the range 130 to 500 base pairs which is in accordance with the allelic size of the primers taken for studies. The subsequent analysis of its population structure using these alleles revealed the formation of population clusters. The study suggests that these markers could be effectively utilized for identifying the genetic variability among tasar ecoraces.

Coevolutionary transitions from antagonism to mutualism explained by the Co-Opted Antagonist Hypothesis

There is now good evidence that many mutualisms evolved from antagonism; why or how, however, remains unclear. We advance the Co-Opted Antagonist (COA) Hypothesis as a general mechanism explaining evolutionary transitions from antagonism to mutualism. COA involves an eco-coevolutionary process whereby natural selection favors co-option of an antagonist to perform a beneficial function and the interacting species coevolve a suite of phenotypic traits that drive the interaction from antagonism to mutualism. To evaluate the COA hypothesis, we present a generalized eco-coevolutionary framework of evolutionary transitions from antagonism to mutualism and develop a data-based, fully ecologically-parameterized model of a small community in which a lepidopteran insect pollinates some of its larval host plant species. More generally, our theory helps to reconcile several major challenges concerning the mechanisms of mutualism evolution, such as how mutualisms evolve without extremely tight host fidelity (vertical transmission) and how ecological context influences evolutionary outcomes, and vice-versa.

Repat33 Acts as a Downstream Component of Eicosanoid Signaling Pathway Mediating Immune Responses of Spodoptera exigua, a Lepidopteran Insect

Repat (=response to pathogen) is proposed for an immune-associated gene family from Spodoptera exigua, a lepidopteran insect. In this gene family, 46 members (Repat1–Repat46) have been identified. They show marked variations in their inducible expression patterns in response to infections by different microbial pathogens. However, their physiological functions in specific immune responses and their interactions with other immune signaling pathways remain unclear. Repat33 is a gene highly inducible by bacterial infections. The objective of this study was to analyze the physiological functions of Repat33 in mediating cellular and humoral immune responses. Results showed that Repat33 was expressed in all developmental stages and induced in immune-associated tissues such as hemocytes and the fat body. RNA interference (RNAi) of Repat33 expression inhibited the hemocyte-spreading behavior which impaired nodule formation of hemocytes against bacterial infections. Such RNAi treatment also down-regulated expression levels of some antimicrobial genes. Interestingly, Repat33 expression was controlled by eicosanoids. Inhibition of eicosanoid biosynthesis by RNAi against a phospholipase A2 (PLA2) gene suppressed Repat33 expression while an addition of arachidonic acid (a catalytic product of PLA2) to RNAi treatment recovered such suppression of Repat33 expression. These results suggest that Repat33 is a downstream component of eicosanoids in mediating immune responses of S. exigua.