Response of Spodoptera litura Fab. (Lepidoptera: Noctuidae) larvae to Citrullus colocynthis L. (Cucurbitales: Cucurbitaceae) chemical constituents: Larval tolerance, food utilization and detoxifying enzyme activities

Authors: PONSANKAR, A - St Francis Xavier University; VASANTHA-SRINIVASAN, P - St Petersburg State University; THANIGAIVEL, A - Manonmaniam Sundaranar University (MSU); EDWIN, E - Manonmaniam Sundaranar University (MSU); SELIN-RANI, S - Manonmaniam Sundaranar University (MSU); CHELLAPPANDIAN, M - Manonmaniam Sundaranar University (MSU); SENTHIL-NATHAN, S - Manonmaniam Sundaranar University (MSU); KALAIVANI, K - Sri Jayachamarajendra College Of Engineering; MAHENDIRAN, A - Sri Jayachamarajendra College Of Engineering; Hunter, Wayne; ALESSANDRO, R - Former ARS Employee; DURALPANDIYAN, V - King Saud University; AL-DHABI, V - King Saud University

Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2016
Publication Date: 12/19/2016
Citation: Ponsankar, A., Vasantha-Srinivasan, P., Thanigaivel, A., Edwin, E., Selin-Rani, S., Chellappandian, M., Senthil-Nathan, S., Kalaivani, K., Mahendiran, A., Hunter, W.B., Alessandro, R., Duralpandiyan, V., Al-Dhabi, V. 2016. Response of Spodoptera litura Fab. (Lepidoptera: Noctuidae) larvae to Citrullus colocynthis L. (Cucurbitales: Cucurbitaceae) chemical constituents: Larval tolerance, food utilization and detoxifying enzyme activities. Physiological and Molecular Plant Pathology. 101:16-28. https://doi.org/10.1016/j.pmpp.2016.12.006.
DOI: https://doi.org/10.1016/j.pmpp.2016.12.006

Interpretive Summary: Insects rapidly develop chemical insecticide resistance. Many caterpillar species are major pests of citrus, grapevine, and other fruit crops. To develop new treatments, fruit extract from Citrullus colocynthis, called bitter apple from the family: Cucurbitaceae were analyzed for toxicity to Spodoptera litera, a caterpillar related to the Orange dog caterpillar that is a pest of citrus trees. Ethyl acetate was used to produce extracts. Nine major chemical groups were identified. The greatest activity was from fraction-5, which produced 90% mortality on treated third instar larvae. The activity appeared to disrupt production of enzymes needed to digest the caterpillar's food. Gas-Chromatography-Mass-Spectrometry analyses of fraction-5, identified a subfraction A3, that produced significant mortality of 84% at 100 ppm concentration on larvae. When characterized, the phytochemical stigmasterol was identified. Stigmasterol – is a natural plant sterol– and among the most abundant of plant sterols, having a major function to maintain the structure and physiology of cell membranes. Treating plants with increased concentration of Stigmasterol may provide new treatments to protect fruit tree crops and vegetables from caterpillar pests. Further analyses will determine if these compounds are active against other citrus pests like the Asian citrus psyllid.

Technical Abstract: Insects rapidly develop chemical insecticide resistance. Many caterpillar species are major pests of citrus, grapevine, and other fruit crops. To develop new treatments, fruit extract from Citrullus colocynthis, called bitter apple from the family: Cucurbitaceae were analyzed for toxicity to Spodoptera litera, a caterpillar related to the Orange dog caterpillar that is a pest of citrus trees. Ethyl acetate was used to produce extracts. Nine major chemical groups were identified. The greatest activity was from fraction-5, which produced 90% mortality on treated third instar larvae. The activity appeared to disrupt production of enzymes needed to digest the caterpillar's food. Gas-Chromatography-Mass-Spectrometry analyses of fraction-5, identified a subfraction A3, that produced significant mortality of 84% at 100 ppm concentration on larvae. When characterized, the phytochemical stigmasterol was identified. Stigmasterol – is a natural plant sterol– and among the most abundant of plant sterols, having a major function to maintain the structure and physiology of cell membranes. Treating plants with increased concentration of Stigmasterol may provide new treatments to protect fruit tree crops and vegetables from caterpillar pests. Further analyses will deter other citrus pests like the Asian citrus psyllid.