EFFICACY OF DICYCLANIL IN THE PREVENTION OF SCREWWORM INFESTATION (COCHLIOMYIA-HOMINIVORAX) IN CATTLE CASTRATION WOUNDS

A field trial was carried out during summer 1996 in a commercial beef cattle farm located in the central area of Argentina (30 degrees 16'S, 60 degrees 30'W) to evaluate the efficacy of a new insect growth regu lator material (dicyclanil) in the prevention of myiosis caused by scr ewworm (Cochliomyia hominivorax) larvae. Forty bull calves (Bos indicu s X Bos taurus), 5 to 6 months old were allocated by ranked pairs to a control (G.1) and a treated group (G.2) of the same number of animals . On day 0, all experimental animals were surgically castrated and cal ves of group 2 were treated topically with 20 ml as a single dose of a ready-to-use formulation containing 5% w/v dicyclanil. Inspections fo r screwworm larva infestation were carried out on days 4, 8, 12, 16, 1 9, 23 and 25 after castration. The incidence of egg masses on the scro tal wounds evidenced a similar challenge for all groups (P > 0.05 chi( 2)). However, 16 animals of G.1 (80%) and only one of G.2 (5%) develop ed active myiosis, respectively. This difference was significant (P = 0.003 chi(2)). (C) 1998 Elsevier Science B.V.