Kairomone activity of okra, Abelmoschus esculentus (L.) Moench, genotypes on lepidopteran pests and their entomophages

Authors: MURALI-BASKARAN, R - Indian Council Of Agricultural Research (ICAR); SENTHIL, NATHAN - Manomaniam Sundaranar University; Mankin, Richard; SURESH, K - College Of Agriculture

Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2017
Publication Date: 1/1/2018
Citation: Murali-Baskaran, R.K., Senthil, N.S., Mankin, R.W., Suresh, K. 2018. Kairomone activity of okra, Abelmoschus esculentus (L.) Moench, genotypes on lepidopteran pests and their entomophages. Physiological and Molecular Plant Pathology. 101:29-37.
DOI: https://doi.org/10.1016/j.pmpp.2017.10.004

Interpretive Summary: There is increasing use of natural enemies against insect crop pests because many insect pests are developing resistance to commonly used insecticides and pesticides are causing increased environmental and water supply damage. Kairomones are volatile organic chemicals attractive to natural enemies of crop pests. To develop improved methods for use of kairomones in pest management, scientists at agricultural Universities in India and at the USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida, studied how a parasitoid and a predator responded to different odors of 26 different varieties of okra. It was found that extracts of various parts of a highly susceptible type of okra increased the efficiency of the parasitoid and predator for finding and controlling pest insects. The findings suggest that a systematic isolation, identification and the synthesis of these chemical cues may lead to the development of formulations that enhance the feeding activities of natural enemies. This will be of value to farmers and managers attempting to reduce pesticide usage by making the use of biocontrol agents more efficient in managing crop pests.

Technical Abstract: The infestation level of two destructive lepidopteran pests, [Earias vittella (Fab.) and Helicoverpa armigera (Hübner)] and the abundance of entomophages, Trichogramma chilonis Ishii and Chrysoperla zastrowi sillemi (Esben-Peterson) were studied on 10 germplasm and 16 cultivars/hybrids of Abelmoschus esculentus (L.) under field conditions. High population of the host insects on susceptible genotypes of A. esculentus increased the foraging activities of natural enemies. Among 26 genotypes, the hybrid No. 55 was noted as highly susceptible to E. vittella and H. armigera, with mean counts per 10 plants of 16.66 and 15.40 larvae, respectively. In addition 3.00 eggs/grub of C. zastrowi sillemi were recorded and 9.33% field recovery of T. chilonis. The resistant germplasm, AE 9 was less hospitable to host insects and their entomophages. Choice test experiments were conducted in the laboratory to consider kairomonic activity of acetone extracts of various parts of highly susceptible (No. 55), susceptible (Arka Anamika) and resistant (AE 9) genotypes of A. esculentus. The tests indicated that No. 55 contained kairomone substances which enhanced the parasitic activity of T. chilonis from 6.67 to 55.33% (1% of flower extract of No. 55) and predatory activity of C. zastrowi sillemi from 10.67 to 58.22% on eggs of E. vittella. Similarly, on eggs of H. armigera, the parasitic and predatory activity of T. chilonis and C. zastrowi sillemi were enhanced from 10.67 to 65.33 and 10.67 to 68.67%, respectively. Maximum abundance of herbivoures and their entomophages in susceptible genotype (No. 55) of A. esculentus might be due to the abundance of secondary metabolites which are favourable to the enhanced foraging activities of entomophages. A systematic isolation, identification and the synthesis of these chemical cues may lead to the development of kairomone formulations that enhance the foraging efficiency of the entomophages in A. esculentus for the successful bio-suppression of E. vittella and H. armigera.