APPLICATION OF ULTRA-LOW-VOLUME MALATHION BY AIR-ASSISTED GROUND SPRAYER FOR BOLL-WEEVIL (COLEOPTERA, CURCULIONIDAE) CONTROL

During 1994 and 1995, test of ultra-low-volume applications of insecti cides conducted on cotton, Gossypium hirsutum L., at Stonealle, MS, ev aluated the effectiveness of malathion applied with a new technology i n ground application, the air-assisted ultra-low-volume ground sprayer . Two tests conducted in 1994 determined the effectiveness of ultralow -volume applications of malathion (91%) with and without cottonseed oi l and established effective malathion rates against boil weevils, Anth onomus grandis grandis Boheman. An emulsifiable concentrate (EC) formu lation of azinphosmethyl was used as a standard. In 1995, ultra-low-vo lume malathion (95%) was applied at 1.36 and 1.02 kg (AI)/ha plus cott onseed oil in a total volume of 1.17 liter/ha. These treatments were c ompared with a 1.12 kg (AI)/ha rate of an EC formulation of malathion applied with water in a total volume of 46.8 liter/ha. In the 1994 ins ecticide comparison test, ultra-low-volume malathion treatments result ed in 70% mortality throughout the 48-h test period whereas mortality from the azinphosmethyl standard steadily decreased from 71% at 4 h af ter treatment to 12% at 48 h after treatment. In the 1994 malathion ra te test, 1.30 and 0.98 kg (AI)/ha produced mortalities comparable to t hose of azinphosmethyl at 0.28 kg (AI)/ha. In 1995, 48-h mortalities a t 24 and 48 h after treatment were highest for the rate at 1.36 kg (AI )/ha (99 and 90%, respectively), followed by the rate at 1.02 kg (AI)/ ha (78 and 54%, respectively), and lowest in the EC formulation treatm ent (28 and 21%, respectively). There were no differences in mortality at 72 h after treatment. The air-assisted ground sprayer permitted ap plication of insecticides at considerably lower volumes than a convent ional hydraulic ground sprayer and also permitted a reduction in the c urrent rate of ultra-low-volume malathion required for effective boil weevil control.