INFLUENCE OF PYRETHROID FORMULATIONS AND SPRAYER NOZZLE SIZE ON MORTALITY OF TOBACCO BUDWORM (LEPIDOPTERA, NOCTUIDAE) LARVAE ON COTTON

Encapsulated formulations of two synthetic pyrethroids, Baythroid (cyf luthrin) and Scout (tralomethrin), were compared with respective nonen capsulated formulations for efficacy against tobacco budworm (TBW), He liothis virescens (F.), larvae on greenhouse-grown cotton on a spray t able using 650033 and 8002E flat fan nozzles. The volume median diamet er (D-V0.5) of spray droplets in the selected plumes of the two nozzle s averaged 246.0 and 324.8 mu m, respectively; these values were signi ficantly different. Using a spray volume of 18.7 L per ha, Baythroid w as applied at 0.014 kg (AI)/ha and Scout was applied at 0.010 kg (AI)/ ha. Encapsulation of Baythroid and Scout neither increased mortality o f TBW larvae nor reduced fruit damage to cotton. Regardless of Baythro id formulations, smaller droplet sprays of the 650033 nozzle significa ntly increased mortality of TBW larvae compared to larger droplet spra ys of the 8002E nozzle. However, the nozzle size of sprayers did not s ignificantly influence TBW mortality for the Scout formulations.