Ovo-Larvicidal Activity of Selected Insecticides, 1989

Abstract

Abstract A small plot insecticide trial was conducted on the Northeast Research Station near St. Joseph, LA, to compare the ovicidal activity and residual toxicity of selected insecticides against Heliothis spp. on cotton. Cotton was planted on 15 Jun in plots 4 rows (40 inch centers) by 50 ft. Treatments were arranged in a randomized complete block design and replicated 4 times. Insecticides were applied on 23 Aug with a CO2 charged application system mounted on a John Deere high clearance plot sprayer. A total volume of 5 gal/acre was applied through Teejet X-6 hollow cone nozzles (2/row) at 44 psi. No insecticides had been applied on those plots prior to the initiation of this trial. Eggs were collected 4 and 48 h posttreatment from the center 2 rows of each plot. Samples of freshly laid white eggs (10/plot) and a small piece of foliage to which the eggs were attached were removed from the plants and transported to the laboratory. Eggs were individually placed into 1 oz plastic cups partially filled with artificial diet for rearing Heliothis spp. Mortality to eggs and larvae were determined 96 h after each field collection. The surviving cohort of larvae in the control treatments were reared to adults and the species composition was found to be 100% tobacco budworm. A trace amount of rainfall (0.41 cm) was recorded 24 h after treatment, which did wet the adaxial surface of the plant leaves and could have reduced residual efficacy of some treatments.