For Japanese Beetles Milky Spore Disease attacks and kills Japanese Beetle grubs in the soil, requiring only an application every 10-15 years. Spores multiply inside the grubs and when the grub infestation subsides, the spores lie dormant in the soil, waiting for subsequent populations. Milky Spore Disease takes 2 to 3 years to achieve complete control and should be supplemented during this time with Japanese Beetle traps, which trap out adult beetles or parasitic nematodes. Best control occurs on non-tilled soil. Apply it at 10 oz/2,500 sq ft and 40 oz/10,000 sq ft or .25 acre