Transactions of the Department of Agriculture of the State of Illinois with reports from county and district agricultural organizations for the year Volume 31 - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...corn root aphis serves to intensify the effect of drouth and other unfavorable influences, and it is often difficult to say how much is to be ascribed to the action of the insect pest and how much to other causes cooperating. There is some evidence to the effect that a too serious check to the growth of the corn results in the early evolution of a great number of winged plant lice of the second spring generation, whose escape from the fields in which they start so breaks the force of the attack that in a favorable season very badly damaged plants may rally and make good corn; but if the insect injury is followed or reinforced by drouth, the corn may grow sluggishly the whole season through, and either fail to ear, or bear small imperfect nubbins only. Sometimes a field not infested the year before is permanently damaged in June, or even late in May, as the result of an early accidental concentration of the winged lice originating in other fields. INJURY TO OTHER PLANTS. No other crop plants are especially liable to injury by this aphis, unless possibly we should except broom corn and sorghum. Although not at all uncommon on these plants, it does not commonly thrive on them, and so far as my observations have extended, can scarcely be called injurious to them. It has been observed in the field, however, or bred in the insectary, on the roots of a number of other species of plants, some of which are, in fact, important to its maintenance. Many of the first generation hatch from the egg in the field before the corn is ready to receive them, and at this time young smartweed plants and foxtail grass (Polygonum and Setaria) are their principal resource. These plants harden early and lose the succulence which makes them especially desirable to plant lice, a fact w...