Effect of Naled, Trichlorfon, and Bacillus thuringiensis on Three Species of Lepidopterous Larvae Attacking Alfalfa in California1

Abstract

In 1967 there was an outbreak of the western yellow-striped armyworm, Prodnia praefica Grote, and the alfalfa caterpillar, Colias eurytheme Boisduval, in thousands of acres of alfalfa in the central valley of California. The beet armyworm, Spodoptera exigua (Hubner), also was present but was not sufficiently abundant to cause damage by itself. Bacillus thuringiensis Berliner (Thuricide® “SS” ) (Batch no. D05712; label claim minimum of 15X109 viable spores per gram) was applied at 1 pint and 2 quarts per acre, while naled and trichlorfon were applied at 7.2 and 8 oz actual, respectively, per acre on alfalfa to test their effectiveness on these 3 species. Both dosages of Thuricide gave excellent control of the alfalfa caterpillar as did naled and trichlorfon. The data indicate that slightly higher dosages of naled and trichlorfon are required to give satisfactory control of the beet armyworm and the western yellow, striped armyworm. Thuricide had no effect on these 2 species. Ecological comments on these 3 species are presented.