News Update on insect pests April-21

[1] Control of coleopteran insect pests through RNA interference

Commercial biotechnology solutions for controlling lepidopteran and coleopteran insect pests on crops depend on the expression of Bacillus thuringiensis insecticidal proteins1,2, most of which permeabilize the membranes of gut epithelial cells of susceptible insects3. However, insect control strategies involving a different mode of action would be valuable for managing the emergence of insect resistance. Toward this end, we demonstrate that ingestion of double-stranded (ds)RNAs supplied in an artificial diet triggers RNA interference in several coleopteran species, most notably the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte. This may result in larval stunting and mortality. Transgenic corn plants engineered to express WCR dsRNAs show a significant reduction in WCR feeding damage in a growth chamber assay, suggesting that the RNAi pathway can be exploited to control insect pests via in planta expression of a dsRNA.

[2] The potential effects of climatic change on agricultural insect pests

Climate and weather can substantially influence the development and distribution of insects. Anthropogenically induced climatic change arising from increasing levels of atmospheric greenhouse gases would, therefore, be likely to have a significant effect on agricultural insect pests. Current best estimates of changes in climate indicate an increase in global mean annual temperatures of 1°C by 2025 and 3°C by the end of the next century. Such increases in temperature have a number of implications for temperature-dependent insect pests in mid-latitude regions. Changes in climate may result in changes in geographical distribution, increased overwintering, changes in population growth rates, increases in the number of generations, extension of the development season, changes in crop-pest synchrony, changes in interspecific interactions and increased risk of invasion by migrant pests. To illustrate some of these effects, results of a study investigating the impact of climatic change on the European corn borer (Ostrinia nubilalis) in Europe are shown. Under the climatic changes projected by the Goddard Institute for Space Studies general circulation model, northward shifts in the potential distribution of the European corn borer of up to 1220 km are estimated to occur, with an additional generation found in nearly all regions where it is currently known to occur.

[3]  On the possibility of a new method for the control of insect pests

This publication contains a summary of the meetings and recommendations of a Panel on the application of the sterile-male technique [cf. also RAE B 58 104-121, 439] held in Vienna in May 1968. The summary of the Panel includes notes on insects on which research information is available and which are ready for field testing, a list of insects on which basic and applied research is needed, notes on various aspects of research and a request for a scientific manual describing methods for and approaches to successful application of the sterile-male release techniques, together with a shorter one for non-specialists. The papers read include the following [cf. also A 58 1465-1477], which are noticed mainly from the authors’ abstracts:

A version in English (pp. 123-237, 4 figs.) of a paper [752] On the possibility of a new method for the control of insect pests by A. S. SEREBROVSKY that was originally published in Russian in 1940 has been included in this publication on account of its historic significance and the basic information it contains on genetic methods of insect control. The following is virtually the author’s original English summary. The new principle of insect control consists of disrupting the reproduction of the pest population by means of translocations. It is well known that individuals heterozygous for some translocations usually form a portion of aneuploid gametes and give more or less non-viable progeny. Therefore, if a sufficient number of individuals with a chromosome set altered by translocations is released into a wild population (with allogamous reproduction), there will arise hétérozygotes for translocations yielding a certain percentage of non-viable offspring. Crosses within this population will be similar to those between species, resulting in sterile hybrids. Theoretical analysis reveals that if a wild population is mixed in the proportion 1: 1 with some race containing only one translocation that produces viable progeny in the homozygous condition and 50% aneuploid gametes in hétérozygotes, the reproduction of the population will be reduced by 43%. If several races with different allelic translocations are released, the reduction in progeny can reach 75%, and if races with 4-5 independent translocations are used, the reduction can attain 95-99% or even more. A population consisting of races with different translocations cannot remain in balance.

[4] Potential of Azadirachtin and Neem (Azadirachta indica) Based Saponins as Biopesticides for In vitro Insect Pests Cellulase (Beta-1,4-Endoglucanase) Enzyme Inhibition and In vivo Repellency on Tribolium castaneum

Aims: The work was undertaken to identify the role of Neem derived compounds (saponins and azadirachtin) on the digestive cellulose hydrolyzing enzyme activity of red flour beetle   (T. castaneum), rice grasshopper (Oxya chinensis) and red pumpkin beetle (Aulacophora foveicolis).

Place and Duration of Study: The work was carried out at the Institute of Biochemistry and Biotechnology University of the Punjab Lahore Pakistan.

Methodology: Total cellular proteins were isolated from the insect’s gut and salivary glands and were tested for cellulose hydrolyzing activity on substrate agar plates. Saponins and Azadirachtin were isolated from Azadirachta indica tissues and used for enzyme inhibition studies. Repellancy test was performed for T. Castaneum, using saponins and Azadirachtin. For computational studies sequence of endoglucanase gene was identified from T. castaneum genome and protein structure was deduced.

Results: Saponins were able to inhibit beta-1,4-endoglucanase  enzyme activity, present in all the three insect pests. A computational dissection of T. castaneum endoglucanase enzyme, deduced from T. castaneum genome, showed that there were five cys involved in the formation of disulphide bridges in the molecule. The disulfide bridges did not provide any protection to endoglucanase active site. Azadirachtin had no effect on cellulase activity of Oxya chinensis and Aulacophora foveicolis, while beta-1,4-endoglucanase activity of T. castaneum was inhibited. Repellency test for T. castaneum revealed that each group of compounds (Saponins and Azadirachtin) was able to repel the insect.

Conclusion: Neem derived compounds had a considerable inhibitory effect on the digestive cellulose hydrolyzing enzyme of T. castaneum.

[5] Field Evaluation of Levo Botanical Insecticide for the Management of Insect Pests of Eggplant (Solanum melongena L.)

Renewed interest in the use of botanical insecticides for the management of insect pests necessitated field experiments to be carried out during the major and minor cropping seasons in 2013 at the plantation crops section of the Department of Crop and Soil Sciences of the Kwame Nkrumah University of Science and Technology (KNUST), Ghana to evaluate the insecticidal potency of Levo botanical insecticide for the management of insect pests of eggplant (Solanum melongena L.). The study comprised the following treatments: (i) Levo (a.i. Oxymatrine) at 1.68 ml /0.5 litre water and (ii) Lambda-super (a.i. Lambda-cyhalothrin) (a check) at 1.5 ml /0.5 litre water; an untreated control (water only) was also maintained. Leuninodes orbonalis (Guen), Bemisia tabaci (Gennadius), Aphis gossypii (Glover), and Eublemma olivacea (Walker) were collected on eggplant in the study area. Significant differences (PË‚0.5) were observed among the treatments with respect to the abundance of A. gosspyii, L. orbonalis, B. tabaci and E. olivacea on eggplant during the major season. Similar results were obtained in the minor season. Significantly higher yields were obtained from the insecticide-treated eggplant plots. The study showed that Levo was as effective as Lambda super and can be a substitute in the management of insect pests of eggplant.

Reference

[1] Baum, J.A., Bogaert, T., Clinton, W., Heck, G.R., Feldmann, P., Ilagan, O., Johnson, S., Plaetinck, G., Munyikwa, T., Pleau, M. and Vaughn, T., 2007. Control of coleopteran insect pests through RNA interference. Nature biotechnology, 25(11), pp.1322-1326.

[2] Porter, J.H., Parry, M.L. and Carter, T.R., 1991. The potential effects of climatic change on agricultural insect pests. Agricultural and Forest Meteorology, 57(1-3), pp.221-240.

[3] Serebrovsky, A.S., 1969. On the possibility of a new method for the control of insect pests. Sterile-male technique for eradication or control of harmful insects. Proceedings of a panel on application of the sterile-male technique for the eradication or control of harmful species of insects, organised by the Joint FAO/IAEA Division of Atomic Energy in Food and Agriculture and held in Vienna, 27-31 May 1968., pp.123-237.

[4] Sami, A.J. and Shakoori, A.R., 2014. Potential of Azadirachtin and neem (Azadirachta indica) based saponins as biopesticides for in vitro insect pests cellulase (Beta-1, 4-Endoglucanase) enzyme inhibition and in vivo repellency on Tribolium castaneum. Biotechnology Journal International, pp.904-917.

[5] Aetiba, J.P.N. and Osekre, E.A., 2015. Field evaluation of levo botanical insecticide for the management of insect pests of eggplant (Solanum melongena L.). Journal of Experimental Agriculture International, pp.61-67.