ACTION OF BIOLOGICAL AND CHEMICAL AGENTS IN THE REDUCTION OF THE EGG POPULATIONS OF Heliothis spp, IN COTTON

Abstract

High parasitism of Heliothis spp eggs by Trichogramma pretiosum Riley has observed in field evaluations realized during the cotton season of 1980 at Centro Nacional de Investigaciones Agropecuarias "Palmira" (Valle del Cauca). The parasitism varied from 47 to 840/0, emerging an average of 2,44 parasite adults per egg. Besides, the infertile egg was observed. The effectiveness of three chemicals in the control of H. virescens eggs was studied. The chemicals were sprayed over eggs previously incubated for 8 - 32 hours. Chlordimeform (1,0 kg i.a./ha) decreased hatching up to 60.69%; methomyl at two rates (0,225 and 0,315 kg i.a./ha) controlled 31,4 and 44,2% of hatching, respectively and cartop al three rates (0,25; 0,50 and 1,0 kg i.a./ha) decreased egg populations of H. virescens in 8,61, 40,72, and 35,600, respectively. Information is also included on the selectivity shown by ovicides such as chlordimeform and cartops toward Tricho-gramma and on the morphological and coloration changes use to differentiate under field conditions fertile from infertile eggs and those that have been parasitized of affected by the ovicide.