The European Corn Borer Situation in the United States at the Close of 1932

Abstract

New infestations of the com borer ( Pyrausta nubilalis ) discovered during 1932 were confined to a very few localities located chiefly along the margin of territory formerly known to be infested. The 1932 infestation survey revealed an increase in borer population amounting to approximately 6 per cent in the surveyed territory of the North Central States area, when compared to the borer abundance in the same counties during 1931. A similar survey in the Eastern States area disclosed a decrease of approximately 2 per cent in the borer population of the territory surveyed, when compared to the last survey conducted in the same counties in 1930. Distinct commercial loss from com borer attack occurred to field corn in eastern Michigan and northwestern Ohio, and to both field and sweet corn in the Lake Ontario district of NewYork, eastern Massachusetts, southern Rhode Island, and eastern Long Island. Experimental results obtained with the more efkctive insecticides tested have shown the feasibility of such applications to com and dahlias of high market value, as a protective control measure. Approximately 5,200,000 imported parasites have been liberated during the last 13 years. Several species are known to have become permanently established. Fieldrecovery records during 1932 indicate that the total parasitization by such species ranges from less than 1 per cent to 50 per cent in different localities. Preliminary experiments indicate that the commercial application of new facilities for refrigeration may be successfully and economically employed in the low-temperature sterilization of car corn infested by the com borer. Field tests have shown that certain varieties and strains of corn are more resistant and tolerant to corn borer attack than others. The plant characteristics associated with tolerance and resistance are being sought. Plat experimentation in damage tests have shown that for each additional borer in an infested plant there occurs, on an average, a corresponding, correlated reduction in yield.