Shot-holes are perforations in leaves presenting the appearance, from their more or less rounded shape, of gunshot wounds. They may be due to insects which bore through the young leaves while still folded in the bud - e.g. Willow Beetle - or which gnaw out the tissue - e.g. the Beech Miner. Similar but usually more torn and irregular holes are eaten out by many caterpillars - e.g. the Cabbage Moth.
Shot-holes on Peas may be the work of Thrips.
Leaf perforations are commonly caused by severe hail-storms, the hail-stones beating right through the thin mesophyll. Certain chemicals used for spraying have also been known to cause shot-holes by killing the tissue beneath the standing drops.
There is, however, a class of shot-holes in thin leaves which are due to the action of minute fungi, the mycelium of which so rots the tissues in a more or less circular area round the point of infection, that, in wet weather, the decomposing mass falls out and leaves a round hole - e.g. certain Chytridiaceae, Peronosporeae, Gloeosporium, Exoascus, etc. If dry weather supervenes these holes frequently dry at the edges, and the leaves appear as if eaten out.
Shot-holes in Cherry, Walnut, Tobacco, and Plum leaves are due to Phyllosticta, in Cherry leaves also to Clasterosporium, and in Potato leaves to Haltica.