MSc

ABSTRACT

An investigation entitled “Behavioural response of cucumber moth Diaphania indica (Saunders) (Lepidoptera: Pyralidae) towards select host plant extracts” was conducted at the Department of Entomology, College of Agriculture, Vellayani during 2021-2023 with an objective to evaluate plant extracts and synthetic volatiles for the behavioural and electrophysiological responses of D. indica and identify the components of the plant extract. The plants evaluated in the study were Momordica charantia L, Trichosanthus anguina L., Cucumis sativus L., Coccinia grandis (L.) Voigt (wild and cultivated type), Cucumis melo var. acidulus Naudin., Solanum melongena L. and Amaranthus tricolor L.
The behavioural bioassay of adult D. indica in Y-tube and modified olfactometer using plant extracts did not give any reliable response. The olfactory response of D. indica larvae was highest to C. grandis (wild) with a mean attraction of 23.33% followed by M. charantia, C. grandis and C. sativus with 10.83%, 9.17% and 8.33% attraction, respectively.
In the GC-MS analysis of fresh leaf extracts, fatty acid, (Z,Z,Z)- 9,12,15-Octadecatrienoic acid (α-linolenic acid) and n-hexadecanoic acid (palmitic acid) was detected in all plant extracts except C. grandis (wild) and M. charantia, respectively. The alkane, dotriacontane was found in M. charantia, T. anguina, C. grandis (wild), A. tricolor and C. melo var. acidulus. The volatile compound benzaldehyde was identified in all samples except C. grandis (wild) and C. melo var. acidulus in headspace GCMS analysis of dried leaves.
Electroantennographic studies showed gravid females are more responsive to plant extracts followed by unmated females. Gravid females showed highest response to extracts of M. charantia (0.25mV) and unmated females to C. sativus extract (0.14 mV). The synthetic volatile compounds, benzaldehyde and benzyl, alcohol when tested alone elicited the highest responses in the crude state. Among different combinations of these compounds, a mixture of 10µL of crude benzaldehyde and 30 µL of crude benzyl alcohol had the highest response (0.210 mV). This was on par with the response values of M. charantia and C. sativus extracts. While evaluating synthetic compounds for behavioural responses, a mixture of plateiiiiiii that D. indica shows a considerable electrophysiological, oviposition and feeding preference for M. charantia and C. sativus compared to other host plants. Linolenic acid, palmitic acid, dotriacontane and benzaldehyde were identified as common components in these plants which have reported kairomonal properties. The kairomonal property of benzaldehyde in combination with benzyl alcohol was proved in this study.