Atividade de derivados de Nim aplicados por pulverização e via sistema radicular sobre a mosca-branca em meloeiro e o pulgão-preto em feijão-de-corda

Abstract

The effects of azadirachtin (Neemazal ), neem (Azadirachta indica) seed and leaf aqueous extracts were studied in the greenhouse conditions at Universidade Federal do Ceará, Ceará State (Brazil) applied as foliar sprays and through root system as a drench application, against the whitefly, Bemisia tabaci biotype B, on melon and against cowpea black aphid, Aphis craccivora, on cowpea. Extracts were prepared by adding the leaf or seed powders to destiled water, and filtrated it 24 hours later. Against whitefly, Neemazal was sprayed or applied as a drench at 12.0; 24.0; 48.0; 96.0 and 192.0ppm of azadirachtin and leaf or seed extract at 1.0; 2.0; 4.0; 8.0 and 16 grams per 100mI of water, including an absolute control and synthetic insecticide as a standard in six independant experiments. By spraying, both azadirachtin and seeds extracts reduced whitefly nymphs average, with efficiency ranging from 71.1 to 98.81%, but in contrast leaf extracts did not affect nymphs. When applied to soil as a drench from 24ppm on and seed extracts from 16g/100m1 showed good efficiency to nymph control. Leaf extracts showed no deleterious effect. In these method, no treatment showed the same efficacy as the standard insecticide as observed when sprays were used. When used against cowpea black aphid, all azadirachtin and seed extract above 2g/100m1 treatments used as spray affected the aphid population. Only azadirachtin at 96 and 192ppm caused the same efficacy as the synthetic insecticide. Azadirachtin at 12.0; 192.0; 384.0; 768.0 and 1539.0 ppm and neem seed extracts at 1.0; 16.0; 32.0; 64.0 e 128.0 g/200m1 were applied to soil as a drench. In this case, both azadirachtin and seed extracts reduced the aphid population with a maximum efficiency of 83.81% for azadirachtin at 1536ppm. The aphid reproduction capacity were studied for all soil treatment. Azadirachtin and seed extracts affected the aphid reproduction when applied above 192ppm and 16g/200m1. Maximum reduction were observed at 1536ppm and 128g/200m1, when the efficacy of 81.87 and 83.43% was detected respectively.