Milky spore is an interesting solution for an aggravating problem--beetles and grubs. Just about the time of spring and early summer when you are so proud of your plants and how well they are growing, you notice the holes in your leaves and brown patches in your lawn. The beetles have emerged and are eating your favorite roses and fruit trees, among other plants, and their larval stage, the grubs, are eating your grass roots. Milky spore is a bacterium that is spread on the soil for the grubs to eat. It multiplies in their gut, causing them to die and then spreading millions more spores through the soil. There are several criteria for effective treatment.
Check the soil for a grub count. The only way the milky spore nematodes will spread is if they are ingested by the grubs. If you don't have enough grubs, the nematodes will not spread. Cut a square foot section in your lawn and lift the turf. Turn it over and count the number of grubs you can find. If there are less than twelve, you do not need to apply the milky spore.
Measure the temperature of the soil. You can do this with a regular meat thermometer. The milky spore nematodes are sensitive to cold and heat. The idea temperature for effective treatment is right around 70 degrees, which is usually reached around May, or earlier in southern states. Apply the powder or granules first thing in the morning.
Water the soil before and after application. The nematodes will actually swim through the soil, so make sure it is well moistened before you apply the spore, and then add another 1/4 inch of water after you apply it. Try to apply the milky spore in a dry spell so there is not too much rain washing the milky spore nematodes to another area. Water the area every day for a week.
Allow time for the cycle of growth to occur with the beetles. If you live in an area where you can expect more than four months in which the soil will stay at 70 degrees, then the control will be almost complete in one growing season. However, in areas where cool weather sets in after three or four months of growing time, you can expect to have to wait two or three years for the nematodes to spread through the soil.