Fitness Cost Associated with Diamide-Resistant Population of Brinjal Shoot and Fruit Borer <i>Leucinodes orbonalis</i> Guenee

Abstract

Brinjal shoot and fruit borer, Leucinodes orbonalis is a serious pest of brinjal and has evolved resistance to commonly used diamide insecticides such as flubendiamide and chlorantraniliprole. Lifetable parameters of the field populations of L. orbonalis, collected from brinjal fields of Kullarayanpalayam (Palakkad) (PKD) and Anchal (Kollam) (KLM), Kerala, reported resistance to diamides was studied and compared with that of laboratory-reared susceptible population of L. orbonalis (Lo-S) procured from ICAR- NBAIR, Bengaluru to determine the fitness cost associated with diamide resistance. The results revealed that the PKD population was found to have a significantly longer larval period with 12.7± 0.82 days as compared to the Lo-S population (10.6± 2.71 days), while the KLM population showed a larval period of 11.1± 0.87 days. The pupal duration was significantly longer in both KLM and PKD populations with 10.3± 0.48 and 11.8± 0.63 days respectively; whereas, the Lo-S population showed only 9.6± 0.69 days. The longevity of female adults of PKD population was (3.80± 0.63 days), while KLM and Lo-S populations showed 4.20± 0.63 and 4.40± 0.51 days respectively. The fecundity of KLM (178.9± 6.08 eggs/ female) and PKD (171.40± 5.64 eggs/ female) populations were significantly lower when compared with the Lo-S population (194.1± 4.38 eggs/ female). Only 89.11% eggs hatched in the PKD population while 89.34± 2.73and 91.87± 4.01% of eggs hatched in KLM and Lo-S populations, respectively. However, the fitness parameters like the incubation period, pupation rate, adult emergence rate, female ratio, and male longevity were not significantly different. The PKD and KLM populations showed both negative and positive biological trade-offs exhibiting a relative fitness of 0.74 and 0.82 respectively compared to the Lo-S population (1).