The Effect of Bacillus thuringiensis Berliner on Some Lepidopterous Larval Pests, Apple Aphid and Predators, and on Phytophagous and Predaceous Mites on Young Apple Trees1

Abstract

The effect of Bacillus thuringiensis Berliner on the arthropod fauna of young apple trees when used as a fullseason spray program during 1961 and 1962 is discussed. Mortality of overwintering larvae of the eye-spotted bud moth, Spilonota ocellana (Denis & Schiffermuller), was approximately 50% higher in the Bacillus plot; spring larval growth was retarded, pupation delayed, and mortality increased; and the summer larval infestation was less than half that occurring in the check. Casebearer populations were adversely affected; the apple aphid, Aphis pomi De Geer, population was increased; and aphid predators apparently were unaffected by the Bacillus sprays. Fruit injury was reduced by approximately 50% in the Bacillus plot owing primarily to its adverse effect on codling moth, Carpocapsa pomonella (L.) ; redbanded leaf roller, Argyrotaenia velutinana (Walker); and eye-spotted bud moth larval populations. The European red mite, Panonychus ulmi (Koch), population increased and phytoseiid mites decreased on Red Delicious trees in the Bacillus plot, with the former reaching numbers twice as high as those attained in the check. The potential role of B. thuringiensis in apple insect control programs is discussed.