Observations on Commercial Application of Insecticides for Control of Sap Beetles on Sweet Corn1

Abstract

Seven fields of canning sweet corn ranging from 3.0 to 40 acres were treated by airplane with phosphate insecticides in oil. Two per acre 1 pint of parathion emulsifiable in 1 gallon of oil per acre, 1 field 1 pint of parathion in 2 gallons of oil, 2 fields were treated with 1 quart of Diazinon® ( O,O -diethyl O -(2-isopropyl-4- methol-6-pyrimidinyl) phosphorothioate) in 2 gallons of oil and 2 fields received 1 quart of malathion in 2 gallons of oil per acre. All insecticides reduced the initial sap beetle populations. The greatest reduction and the lowest rate of reinfestations occurred in malathion-treated fields. The percentage of ears free of sap beetle at harvest time was reasonably well associated with reduction of the initial infestation. Residues of parathion and Diazinon were more persistent than malathion residues when applied in oil. In these results higher reduction of sap beetle infestations was associated with the higher rate of oil used. It was evident that treatment should he wade when the adult population is highest before invasion of the ears has taken place. Observations indicated that this occurred when about 50% of the plants were in silk, although the uniformity of plant development, the susceptibility of varieties (NK199, Illinois 13, and Iowa Chief are considered very susceptible to sap beetle invasion) and the seasonal f1uetuation in sap beetle populations should influence the most favorable time of treatment.