Their products may be bought at many of the seed and hardware stores throughout the - beetle-infested area. Samples of the spore dust made by the companies are tested by the Moorestown laboratory several times each year to see that a proper standard is maintained. Such samples have always been found to be satisfactory. Spore dust made by the companies has been used to treat small yards, estates, golf courses, parks, and similar areas. In some places garden clubs or other civic organizations have stimulated the purchase and distribution of spore dust. At times State and municipal agencies have purchased spore dust and used it to supplement that supplied by the Moorestown laboratory in cooperative programs.

In some counties the county agents and boards of supervisors have bought quantities of spore dust for sale to farmers at a fraction of the usual retail price. Sometimes the county agents have arranged to have the dust distributed on fields.

INEXPERIENCED OBSERVERS would probably see little difference in the appearance of healthy grubs and those which have milky disease, especially in the early stages. The hollow body cavity of a beetle grub is filled with blood, which is kept in circulation by the pulsations of the dorsal blood vessel, a tube-like organ that serves as a heart. It runs lengthwise just beneath the semitransparent upper body wall and may readily be seen in a healthy grub. Because of the spores in the blood, it becomes increasingly difficult to see the dorsal blood vessel as the milky disease develops. In the final stage of the disease, the entire grub ( even the legs, through which the blood circulates as it does through other parts of the body) has a milky white appearance. If one of the legs is snipped off by pressing it with a fingernail, a drop of blood will be formed on the remaining stump. The drop will be clear and watery in a healthy grub and opaque and white in a milky one. The final test for milkiness is to examine a drop of blood with a compound microscope for the presence of disease organisms.

THE FEMALE Japanese beetle lays eggs in the ground in summer. The grubs that hatch from the eggs are one-sixteenth inch long at first, but they feed and grow until they are about an inch long. As they grow, they pass through three stages, or instars. The change from one instar to the next is brought about by shedding the outer skin. The grub stage starts in midsummer and continues through the fall and winter and until the change to pupa late the following spring or early summer. During the pupal stage, the insect is inactive and goes through the changes that produce the beetle. The cycle from egg to adult beetle requires nearly a year and is spoken of as one generation or brood of the insect. For example, the eggs laid in the summer Of 1951 gave rise to the beetles of 1952, and this constituted the 1951-52 brood.

Grubs of the Japanese beetle may become infected by milky disease at any time during the long span of grub life. In experimental feeding tests, more than one-half of all milky grubs found became diseased in the first and second instars. If a grub becomes diseased in one instar, it seldom lives to change to the following instar, but continues on for some time in a fully milky state before it finally dies. Grubs that become Infected in late summer or fall frequently live through the winter with the disease in a dormant state. As the temperature rises in spring, the disease again becomes active. Milky disease has been produced experimentally in prepupae, pupae, and adults of the Beetle, but natural infection in these stages is probably not common.

Since grubs contract milky disease Ind die over such a long period, an inspection of the grubs in the soil will how only those that are milky at that )articular time. You will find no trace )f the ones that have become infected Ind died, because their bodies will have decomposed in the soil. The time that must elapse after the grub first takes in he spores until it is fully milky varies with the temperature. At 86 F., grubs vill show the first symptoms of milky disease in 6 to 9 days. At lower temperatures it will take longer. Milky disease organisms will not develop at temperatures above 97 or so; there-ore they cannot infect man, domestic animals, or wild game, whose body temperatures are higher than that. It also will not develop when temperatures fall below about 62 . The milky disease will not show up in spring-infected grubs until the soil tempera-ire has been above this point for about 2 weeks. You would have to make soil examinations nearly every week during the time grubs are present to get a complete picture of the action of milky disease. You can estimate the mortality due to milky disease by making soil examinations in August, when the soil population is the highest for a brood, and then making later examinations to determine the drop in numbers.

A grub count made in the fall will show the number present just before hibernation. A count in May or June of the following year will show the number present as the time nears for the change to beetles. The number of grubs that are milky is usually highest at that time. The change in the number of grubs per square foot found in examinations in August of one year and June of the next year will give some idea of the number killed by milky disease in any brood. Of course grubs die from causes other than milky disease, and due credit should be given to any other known agent causing death.

Ralph T. White of the Moorestown laboratory has been in charge of investigations of the milky disease under field conditions for many years. I give a few examples of the action of the disease as he found them.

BEETLES were so abundant at the Glen Brook Country Club in Stroudsburg, Pa., in 1941 that the grubs caused serious damage to the turf. White uncovered no evidence of milky disease at that time. Using the spot method, plots were treated at 5- by 5-, 5- by 10, and 10- by 10-foot intervals with the milky disease in October 1941. Soil surveys made all over the course on May 26, 1942, showed an average grub population of 66 per square foot. On the more heavily treated plots the count was 81 per square foot. If there had not been an abundance of rain the turf on the course would have been severely damaged by grub feeding.

When the new brood was in the ground in August 1942 the grub population on the course averaged 88 per square foot. By early June 1943, there had been a drop from 130 grubs per square foot to 31 in the 10- by 10-foot Plot, from 53 to 11 in the 5- by 10-foot plot, and from 82 to 11 per square foot in the 5- by 5-foot plot. In two untreated areas, grubs averaged respectively 62 and 66 per square foot in June and there was turf damage there but not in the treated plots. The disease incidence ranged from 30 to 62 percent in treated areas in late June and a few milky grubs were found in untreated areas, showing that the disease had begun to spread. By the fall of 1943, 2 years after the treatment with spore dust, milky disease had spread all over the course and there was no evidence of turf injury. The entire course was examined in June 1949 and the grub population averaged only 1.7 per square foot; 69 percent of all grubs found were milky. In 1952 so many spores were in the soil that turf damage by beetles is unlikely in the future.

On the extensive grounds of the Perry Point Veterans' Administration and Facility at Perryville, Md., the grubs in the soil averaged 37 per square foot in August 1939, and there was marked browning of the grass due to their feeding. A low incidence of milky disease occurred at that time. Soil surveys were made at Perryville several times each year from 1939 through 1949, except during some war years.

In surveys covering six broods, White found reductions of 86.1 to 94.4 percent in the grub populations, due largely to milky disease. At the time of the June examinations, the number of milky grubs varied from 27.7 to 67.0 percent. In computing the figures, all milky grubs were counted as dead, since milky grubs almost always die. The question has often been raised how, with grub mortality approaching go percent in each brood as it did at Perryville, it is possible to have enough beetles emerge from the disease-laden soil to produce such high grub counts by August each year. One reason for this is that a female beetle deposits from 40 to 60 eggs in the ground, and if conditions are favorable a few beetles can concentrate many eggs in a small area. Another reason is that so many favored food plants grow at Perryville that beetles move into the area to feed from other places and, as they lay their eggs in the well-cared-for turf, grub populations are high in August each year.