Microbial control of the fruit tree leafroller,Archips argyrospila [Lep.: Tortricidae] in California

Field populations of larvae of the fruit tree leafrollerArchips argyrospila (Wlk). were practically eliminated following spray application ofBacillus thuringiensis Berliner serotype III at 192 and 80×10⁶ I.U. per litre on the host trees,Cercis occidentalis. Spray applications of lower rates ofB. thurienginsis serotype III at 18.9 and 32.1×10⁶ I.U. per litre and mist application ofB. thuringiensis serotype 1 at 8.0 and 16.0×10⁶ I.U. per litre gave partial control of populations ofA. argyrospila larvae. A granulosis typeBaculovirus, applied by hand sprayer at 1.4×10⁹ granules/ml produced approximately 50% reduction of 5th instarA. argyrospila larvae onC. occidentalis trees. It was concluded thatB. thuringiensis and the granulosis typeBaculovirus are promising control agents forA. argyrospila larvae.