Milky spore disease is a bacterium that attacks grubs that live in your lawn. In large numbers, the grub can cause severe damage to a lawn.
Once the grub transforms into a beetle (typically a Japanese beetle) it goes on a feeding rampage that can devastate many succulent landscape plants. Once the transformation into a beetle takes place, it is an insect that is very difficult to control.
Adult grub (Japanese beetle)
Japanese beetle traps don't normally work unless used properly. While they do trap hundreds of the Japanese beetles in that smelly bag, thousands more are attracted to the area making things even worse for years to come.
For beetle traps to work, they need to be used throughout the neighborhood in a coordinated effort. Ideally, several traps should be placed around the perimeter of your property and away from any plants that are likely targets of the beetles.
A better way to really control Japanese beetle infestations, is to control the grubs. Grubs are the larval stage in the beetle's life cycle. Eggs are deposited about 3" into the ground in mid summer by the female beetle. Once the eggs hatch, they quickly grow into grubs which then move to just below the surface. There they feed on the tender roots of your favorite turf grass, that soon dies out and you see large dead patches in your lawn (usually in early fall).
Applying an insecticide to all the plants in the landscape would mean killing all the insects in the yard. This can have devastating results that far outweigh the damage caused by the Japanese Beetle. To control the Japanese Beetle, it needs to be attacked when it is most vulnerable— during the early larval stages.
The grub is considered the weakest link in the life cycle of the Japanese beetle. It is in the larval or grub phase that the beetle is most vulnerable. This is where milky spore becomes effective.
One way of attacking the grub is with Milky Spore. Milky Spore is harmless to food crops. It is not a chemical pesticide. It may be used in gardens, around pools and wells. You can think of it as a deadly flue that attacks only larva.
Once applied to the turf according to the directions, resident spores in treated turf are swallowed by grubs during their normal pattern of feeding; this starts the demise of healthy grubs.
Milky Spore then begins to cripple the grub, and within the next 7 — 21 days will eventually die. As the grub decomposes, it releases billions of new spores into the soil which will remain for several years.
Milky Spore is not harmful to beneficial insects, birds, bees, pets or man. The product is approved and registered with EPA.
The ideal way to combat area infestation is through organized community efforts. Large areas treated with Milky Spore can result in long term control.
Milky spore comes in two versions: granulated where you apply it with a fertilizer spreader, and a concentrated powder that is put out using a tube dispenser.
Milky Spore Powder in cans is a one time application put down in spots in measuring teaspoon amounts every four feet apart creating a checkerboard pattern of spots throughout your yard. Each spot contains 100 million spores.
Left: healthy grub; Right: diseased grub
Milky spore disease is caused by the bacteria B. popilliae. This bacteria causes the disease in the beetle larvae when they ingest spores in the soil. The spores germinate in the gut within 2 days and the vegetative cells proliferate, attaining maximum numbers within 3 — 5 days. By this time some of the cells have penetrated the gut wall and begun to grow in the haemolymph (blood system of the grub), where large numbers of cells develop by day 5 — 10. After 14 — 21 days the grub develops the typical milky appearance (hence the name, milky spore disease).
The cause of insect death is not fully known. Physiological starvation caused by the growth of bacterial cells in the haemolymph seems the most likely explanation, and fat reserves of diseased larvae are greatly reduced compared with those of healthy larvae.
Milky spore was first introduced as a grub control in the 1940s. Since then, there has been some significant re-infestations of the grubs and the adult Japanese beetles in areas that had be completely eradicated. This might indicate that either the bacteria may lose it's effectiveness over a long period of time or the grubs may have developed a certain immunity to the disease.
This being said, milky spore disease is an effective long-term solution for controlling a devastating insect without resorting to highly toxic chemicals.