. The book of wheat : an economic history and practical manual of the wheat industry. ars is doubtless theresult of a coincidenceof climatic conditions fa-vorable to their develop-ment and the absence toa great degree of Spring Grain Aphis {Toxoptera graminum Rond).—Thisspecies, popularly called the green bug, was first describedin 1852, and 30 years later it was discovered in America. It isfound most abundantly in the southwest. This pest can befound in the wheat fields duiing any year, throughout the in-fested region, but it is rather erratic in its outbreaks. In ordi-n
. The book of wheat : an economic history and practical manual of the wheat industry. ars is doubtless theresult of a coincidenceof climatic conditions fa-vorable to their develop-ment and the absence toa great degree of Spring Grain Aphis {Toxoptera graminum Rond).—Thisspecies, popularly called the green bug, was first describedin 1852, and 30 years later it was discovered in America. It isfound most abundantly in the southwest. This pest can befound in the wheat fields duiing any year, throughout the in-fested region, but it is rather erratic in its outbreaks. In ordi-nary seasons it is held in check by its natural enemies. It isextensively parasitized, and lady beetles devour both young andold. It can withstand a lower temperature than its enemies,however, and outbreaks occur after a mild, open winter fol-lowed by a late and wet spring. Such outbreaks occurred in1890, 1900 and 1907. In the soutli it may breed all winter, andit has an enormous rate of increase. The eggs are laid amongthe grain plants in the fields. AVheat and rye are the chief. SPRING GRAIN-APHIS OR GREENBUG. ENLARGED INSECT ENEMIES OF WHEAT 181 foods, but the insect thrives on the other cereals also, and onorchard grass. Late sowing is a preventive measure. Other Insect Enemies.—The most important of these are thewlieat straw-worms, the wheat bulb worm, the cut-wonns, thejoint worm, several species of sawflies, and the army damage caused is local and not great. Most of them canbe more or less controlled. The total loss from insect enemies of growing wheat is es-timated to average at least 20 per cent of the crop. That is,in the absence of attacks from these pests, the wheat cropwould have a value approximately $100,000,000 greater than itnow has. General Eiemedies.—Cultivation upsets the equilibrium es-tablished by nature. The resulting environment may be sofavorable for the development of an insect as to enable it tomultiply beyond all previous proportions.
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