EFFICACY OF 6 GRAIN PROTECTANTS APPLIED ALONE OR IN COMBINATION AGAINST 3 SPECIES OF COLEOPTERA

Laboratory experiments were carried out to establish whether there wer e synergistic or antagonistic interactions in combination treatments o f certain grain protectants, Six protectants were applied alone, or in combination, against Rhyzopertha dominica (F.) in stored maize and wh eat, and Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) in st ored wheat. There were four organophosphorus (OP) insecticides (fenitr othion, chlorpyrifos-methyl, pirimiphos-methyl and methacrifos), one j uvenile hormone analogue (methoprene) and one synergised pyrethroid (d eltamethrin + piperonyl butoxide); and combination treatments consiste d of either methoprene or synergised deltamethrin plus an OP insectici de. Based on the levels of control of adult progeny and periods of pro tection, there were no interactions between protectants. The results s how that there is no need to alter field application rates to compensa te for antagonism or to take advantage of synergism, They also support the view that application rates for combination treatments can be est imated from experiments on individual protectants using target species or strains. (C) 1998 Published by Elsevier Science Ltd. All rights re served.