MILKY DISEASE

In Japanese Beetle Grubs (Drawings greatly enlarged)

MILKY DISEASE

The milky disease of grubs of the Japanese beetle has caused marked reductions in the abundance of the pest in the older infested areas. The disease is caused by germs, which the grubs take in as they work their way through the soil and feed on plant roots. The germs multiply rapidly within the grubs and form tiny bodies known as spores. The spores are long-lived and can stand dryness, heat, cold, and other unfavorable conditions. Billions of spores are produced in the blood of the grubs, which is normally clear but then becomes milky in appearance hence the name "milky disease." Under favorable conditions the disease kills a high percentage of the grubs of the Japanese beetle and some of the grubs of closely related insects. It has no effect on other insects, warm-blooded animals, earthworms, plants, or human beings. Once established it protects treated areas indefinitely and spreads to new areas. Milky disease spores are processed with talc to make a spore-dust powder that is available commercially.

Milky disease usually works slowly, and its full effect may not be evident for several years. The first noticeable effect will be a reduction in the grub population in the treated area; adult beetles will not be affected by it nor prevented from flying in from an untreated area.

Application: The spore dust may be applied to lawns or other grass areas (comparatively small numbers of grubs are found in cultivated soil, unless sod or turf has recently been turned under for garden purposes) in spots spaced at regular intervals or broadcast. In the spot-treatment method, apply 1 level teaspoonful (about 2 grams) at intervals of 3 feet (at 3-foot intervals in rows 3 feet apart), 5 feet, or 10 feet, depending on the degree of infestation. A teaspoon or an ordinary hand corn planter with a rotary disk seeder, adjusted to deposit the desired amount of material each time it is tripped, may be used to apply the spore dust. The 3-foot intervals will require about 20 pounds of material to treat 1 acre; the 5-foot intervals about 7 1/2 pounds, and the 10-foot intervals about 1 3/4 pounds. The broadcast method of treatment is less effective. If it is used, apply at least 10 pounds of spore-dust material to treat 1 acre and spread it by hand or with a fertilizer distributor. In either case mix the spore dust with several times its volume of topsoil, fairly coarse sand, or commercial fertilizer before spreading the dust.