Note:  Do not rely on this information. It is very old.


Blight (plant) is the name applied to a number of plant diseases. The term is best restricted to those due to the attacks of large numbers of minute animals or fungi. Of the animal blights the most important in England are aphidae, or plant lice, which, owing to their enormous powers of reproduction, can do serious damage to any crops they attack; this group includes the Phylloxera, which lives on the vine. Most of the orders of insects supply cases of blight: thus among the Diptera there is the genus Cecidomya (the corn midge and Hessian fly); among the Coleoptera, Haltica, the turnip fly; among the Hymenoptera, besides the Aphidae, there are the Cynipidae or gall flies; amongst the Lepidoptera various caterpillars swarm in such number as to be included in this category. Amongst other classes of animals that act as blights, there are the Phytoptidai, a family of Acarina, which cause galls on plants; and some species of worms as Anguillula tritici which causes the "ear cockle" of wheat. Sultry weather is favourable to the development of insect pests, and thus the belief has arisen that the haziness of the air overladen with moisture is itself a blighting substance. The name points to a common effect of fungus growth, viz. the bleaching or yellowing of leaves by the destruction of their chlorophyll.