Selectivity of avermectin-B1 (MK-936) to Trichogramma demoraesi Nagaraja, 1983 (Hym. Trochogrammatidae), under laboratory conditions

B. de Souza J.C. Matioli L.V.C. Santa-Cecília About the authors

This study was carried out under laboratory conditions to determine some parameters related to the selectivity of avermectin-B1 (MK-936) to Trichogramma demoraesi, parasite of eggs of several especies of agricultural pests. This compound at 1.8% EC formulation and rates of 0.1; 0.2; 0.4 and 0.8 ml/l have not affected the pre-imaginal development of the parasite before its emergence from the parasited eggs. The same situation have occured when high rates of the insecticides such as 8.0 ml/l was applied. No significant mortality was observed when the adult parasites oviposited in insecticide previously treated eggs of Anagasta kuehniella (Zeller, 1879) (Lep., Pyralidae). Contact action of avermectin-B1 applied inside the rearing vials was not evident due to the difficulty to discriminate the effects of the insecticide from the action of acetone, which was used as solvent. This chemical, even applied alone, caused significant mortality of insects and it could be associated to the 0.001% non-volatile residues presented in the product Therefore, more detailed studies are necessary to confirm this theory. Malathion 50 EC at 1,5 ml/l was highly toxic to T. demoraesi in all tests. It was concluded that avermectin-B1 shows selectivity to this parasite and could be recommended in integrated pest management programs at places where natural or introduced populations of this specie occur.

insecticide; integrated control; pest management; parasitism

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