Jawala Jindal

Toxicity of some essential oil constituents and their binary mixtures against Chilo partellus (Lepidoptera: Pyralidae)

Allelochemicals from essential oil-bearing plants have been categorized as green pesticides because they are biodegradable and predominantly non-toxic to vertebrates. With an aim to reduce the use of synthetic insecticides, they represent one of the most promising approaches for eco-chemical control of insects. Eight compounds were evaluated via topical application against third instar Chilo partellus Swinhoe larvae. Thymol was the most active (lethal dose (LD)50 = 189.7 μg/larva) and methyl eugenol the least (LD50 = 1069.4 μg/larva). The compounds were also tested at sublethal levels, i.e. LD10 and LD30, and there was approximately 15–43% of reduction in growth, which was transitory, and some recovery was observed 6 days post-treatment. Compounds were also used as binary mixtures and tested for synergy, using toxicity and feeding inhibition parameters. The data showed that thymol and α-terpineol synergized the effects of both linalool and 1,8-cineole, but linalool with 1,8-cineole exhibited only an additive effect against C. partellus. Although there is no specific generalization that could be drawn relating to efficacy of binary mixtures, the present findings resulted in several complex mixtures that couid be developed and tested as leads for effective control of C. partellus.

Resistance of Cry1Ab maize to spotted stemborer Chilo partellus (Lepidoptera: Crambidae) in India

Three transgenic maize hybrids, viz. Prabal YG, Hishell YG and Double YG, producing Bacillus thuringiensis (Bt) CrylAb protein (event Mon 810), were evaluated under field and laboratory conditions for their resistance to spotted stemborer Chilo partellus (Swinhoe). The Bt maize hybrids suffered less damage than their non-Bt iso-hybrids with respect to per cent plant infestation (0.0-0.6), leaf injury rating (1.0-1.1) and per cent stem tunnelling. These hybrids also resulted in significantly higher larval mortality (79.4-100.0%) in laboratory bioassays. The toxin protein produced in leaves was equally effective against neonates and 15-day-old larvae. Neonate larvae consumed less leaf area (5.0-13.8%) in case of Bt hybrids than their non-Bt iso-hybrids.

Oviposition and feeding behavior of the maize borer, Chilo partellus , in response to eight essential oil allelochemicals

Eight essential oil compounds were evaluated against the maize borer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), to determine their influence on oviposition and feeding behavior. Thymol was the most active compound against C. partellus when evaluated as an oviposition deterrent (ODI50 = 1.36 mg ml−1), an ovicide (LC50 = 2.06 mg ml−1), or a feeding deterrent (FI50 = 141.8 μg cm−2) in laboratory experiments. The results corroborated with greenhouse experiments, in which egg laying on maize plants was inhibited significantly when the treatment was 15 times the concentration used in the laboratory experiments. However, there was neither any correlation between oviposition deterrence and feeding inhibition, nor between oviposition deterrence and ovicidal action. Apparently, toxicity per se or ovicidal action does not play any role in choice of oviposition in C. partellus. This was more obvious when the efficacy of compounds was compared in greenhouse experiments where ODI values and number of eggs laid on the treated leaves did not differ significantly in choice and no‐choice situations. Apparently, toxicity plays an important role in predicting host plant choice, but behavioral response in terms of oviposition preference is independent of toxic action, particularly for non‐host toxins. Thus, the same compounds affecting oviposition behavior on the one hand and having ovicidal or feeding deterrent properties on the other could be useful in field situations in any area‐wide integrated pest management model.

Potential of Napier millet, Pennisetum purpureum × P. glaucum, as a trap crop for managing Chilo partellus populations on maize

As a part of a habitat management strategy aimed at controlling Chilo partellus Swinhoe, Napier millet (Pennisetum purpureum × P. glaucum) was evaluated as a trap crop surrounding maize during 2008 and 2009 at Ludhiana, North India. Napier millet borders surrounding maize were compared to chemically protected maize and control maize plots for their effects on C. partellus oviposition, plant infestation and grain yield. Further experiments were carried out to determine whether adult experience could affect subsequent oviposition on test plants. Maize plots surrounded by Napier millet had fewer plants with borer eggs than control maize plots, although the results were significant only for the 2009 season. Percentage plant infestation and percentage dead hearts were less in Napier millet surrounded maize plots than in control maize plots during both seasons. Different treatments did not vary in terms of grain yield during the 2008 season, whereas maize plots surrounded by Napier millet had higher grain yield than control maize plots during the 2009 season. The preference of C. partellus females for Napier millet did not alter following experience with maize.