Field efficacy of the NRD-12 strain of Bacillus thuringiensis against gypsy moth (Lepidoptera: Lymantriidae)

Single and double aerial application treatments at 30 billion international units (BIU)/ha of an aqueous formulation (SAN 415 SC 32LV) of the NRD-12 strain of Bacillus thuringiensis Berliner were evaluated against a moderately dense population of gypsy moth, Lymantria dispar L. Egg mass densities before spray averaged 5,055 egg masses per ha; egg mass density after spray increased to over 19,500 egg masses per ha in the control woodlots but decreased to 2,600 and 4,500 egg masses per ha in the single and double application treatments. No significant defoliation occurred in the woodlots treated with NRD-12, but control woodlots suffered a significant (33%) defoliation.