A field-release device and protocol for dispensing cocoons of Cotesia flavipes against sugarcane borers
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A field-release device and protocol for dispensing cocoons of Cotesia flavipes against sugarcane borers J. Srikanth & K. P. Salin & M. Punithavalli & P. Mahesh & R. Jayanthi & K. Subadra Bai
Received: 13 March 2020 / Accepted: 29 June 2020 # Springer Nature B.V. 2020
Abstract A field-liberation technique for cocoons of the parasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) against sugarcane borers was developed in two stages: (i) laboratory standardization of a gravimetric method to enumerate cocoons for field release and (ii) design and evaluation of a field-release device to dispense cocoons of the parasitoid. Field-collected and laboratory-reared cocoon masses of C. flavipes from two larval hosts were characterized for cocoon mass weight, cocoon number per mass (cocoon mass size), percent of adult emergence and percent of females. Nonparametric ANOVA of cocoon characteristics showed no significant differences among field-collected and laboratory-reared larvae of the two species. Cocoon mass size vs. cocoon mass weight correlation was significant for field-collected and laboratory-reared larvae of both species. Coincidence analysis of the four regression lines indicated adequacy of a single line to describe cocoon mass size vs. cocoon mass weight relationship and predict the former from the latter. Laboratory and field tests with a prototype field-release device established egress of the parasitoid from the device with minimum risk of predation. The protocol developed for dispensing C. flavipes cocoons in the field includes three steps: (i) determination of gross dosage from net dosage using proportions of females and adult J. Srikanth (*) : K. P. Salin : M. Punithavalli : P. Mahesh : R. Jayanthi : K. Subadra Bai Section of Entomology, ICAR-Sugarcane Breeding Institute, Coimbatore, Tamil Nadu State 641007, India e-mail: [email protected]
emergence as correction factors; (ii) estimation of cocoon number in individual cocoon masses from cocoon mass weight using the regression equation and (iii) dispensation of gross dosage of cocoon masses using the field-release device. Keywords Cotesia flavipes . Cocoon mass . Field dosage . Field-release device . Sugarcane borers
Introduction Cotesia flavipes Cameron (Hymenoptera: Braconidae) is a major larval parasitoid of stem borers of sugarcane, sorghum and maize in India. Among the sugarcane borers in the wild, the parasitoid preferred internode borer Chilo sacchariphagus indicus (Kapur) over shoot borer Chilo infuscatellus Snellen (both Lepidoptera: Crambidae) in the tropics (Srikanth et al. 1999). Higher levels of parasitism were reported in the subtropical Plassey borer Chilo tumidicostalis Hampson (Gupta and Avasthy 1959) and Gurdaspur borer Acigona steniellus (Hampson) (both Lepidoptera: Crambidae), the parasitoid occurring throughout the year even in diapausing larvae of the latter (Varma et al. 1981). Techniques had been standardized to multiply the parasitoid on the more suitable sorghum borer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae)
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