Q. I am building a compost heap for the first time this fall. How hot does it have to get in order to kill fungi, insect eggs or other pests that may be on the garden debris?
A. Most fungi, molds and bacteria will be killed off at 145 degrees. Soil insects cannot survive temperatures over 160 degrees, and weed seeds will be killed at 180 degrees. To generate temperatures this high, compost heaps must have a good ratio of grassy material to dried leaves and twigs. Compost heaps must be turned regularly and kept evenly moist. Some gardeners leave out diseased material just to be on the safe side.