A field-release device and protocol for dispensing cocoons of Cotesia flavipes against sugarcane borers

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. Non-parametric 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 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.