This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The Shot-hole Borer is a small beetle about 1/8 in. long, of a dark-brown to black colour, with reddish-brown wing cases. The female commences her attack by boring into the main stem of fruit trees, but also into the branches. The beetles hatch out in May and June, and lay their eggs in tunnels in the wood. The small white maggots partly fill up the tunnels, being packed close together in a line. The maggots feed on a grey-and-black substance lining the galleries, called "ambrosia". One female will lay as many as forty ova at different times in June. They pupate in the galleries close together, and when the beetles hatch out they are found packed together like shot. The beetles are found in January, February, May, September, on to December in the galleries, but flight time occurs mainly in May and June and in August and September. All badly attacked trees should be cut down and burnt in winter.