Rate of Development of Milky Disease in Japanese Beetle Populations1

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Abstract
The use of Bacillus popilliae against larvae of Popillia japonica in New York State, 1940-1945, is described. Where milky disease spore dust (100 million spores per g.) was applied at the rate of one 2-g. "spot" in each area of 10 X 10 ft. (equal to 2 lb. to 1.04 acre), the observed interval between soil inoculation and satisfactory grub control was 3-4 yrs. To determine whether heavier dosages would shorten the interval, spore dust was applied broadcast on duplicated 10 X 10-ft. plots at 5 rates ranging from 0.1 g. to 20 g. per sq. ft. (equal to 10 to 2000 lb. per 1.04 acre). Square-ft. diggings were made at intervals of 1 to 3 wks. In 18 mos. following the application, among 5000 forms dug on the untreated areas 10-20 ft. from the plots only a few cases of milky disease were found. On the plots, after 18 mos., reduction to only a few larvae to the sq. ft. was achieved only at the highest dosage. The not yet completed data indicate that, in New York, raising the spore dust dosage from 2 lb. to the acre to as much as 2000 lb. does not shorten the waiting interval for control by more than half. The results support the use of milky disease inoculum at low or inoculative dosages on areas where immediate grub control is not imperative.