Contact Toxicity of Az1Nphosmethyl and Monocrotophos To 3Rd Stage F] Progeny Of Field-Collected Scb Populations: Insecticide Resistance Screening, 1978

Colonies of the SCB initially collected in the Fall (1978) from 2 South LA Sugarcane fields near Lockport and St. James (after seasonal insecticide applications had ceased) were maintained on a meredic diet in the laboratory. Responses of the 3rd stage F] larval progeny to topical application of two insecticides labeled for SCB Control in LA (azinphosmethyl and monocrotophos) were compared to (1) toxicity baseline data acquired previously from the 3rd stage F] progeny of a field collected SCB colony that had not been exposed to organophosphorous insecticides and (2) LD50 and LD90 values for 3rd stage F] larval progeny of comparable SCB colonies collected near St. James and Lockport during the fall of 1977. Six concentrations of azinphosmethyl and 5 of monocrotophos were evaluated by applying the required scalar dosage in acetone to individual groups of larvae. One ul of acetone and toxicant was applied to the thoracic surface of each larva with a shardlow micrometer equipped with a 1 ml alga syringe. All larvae were maintained individually in diet cups except during the time when toxicant was applied. Mortality counts were recorded 24 and 72 hr after treatment, however only the 72 hr counts were used for probit analyses and calculation of Ld-p lines (Daum R.J. ESA Bull. 16:10-15).