What makes milky spore disease work?
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.
