PURDUE UNIVERSITY
Agricultural Experiment Station
Circular No. 82 LaFayette, Ind., August, 1918
THE CONTROL OF THREE IMPORTANT WHEAT PESTS IN INDIANA
J. J. Davis 1
The two important insect pests of wheat in Indiana are the joint-worm and Hessian fly. They occur throughout the State, but are most evident in the wheat belt of southern Indiana, and both are similarly controlled by certain farming methods. A third wheat enemy which usually occurs in northern Indiana and which was unusually severe and com mon the past year is the wheat-midge, erroneously spoken of as the “red weevilj’ an insect closely related to the Hessian fly but affecting the plant quite differently.
The jointworm has but one brood annually and affects the wheat plant in the spring of the year only, producing a hardening of the stem at the point where the egg is deposited. The yellowish worm subsequently developing in the stem weakens the stalk, often causing it to bend just above the point of infestation and to fall. The point of infestation and subsequent hardening varies from three to 20 inches above ground according to the size of the wheat at the time the adult jointworms are active, and is usually just above a joint of the wheat stalk. The adult insect, a small, shining black wasp, issues in late April or early May in southern Indiana, about the middle of May in the central part of the State and towards the end of May in the northern section, and the characteristic falling of the straws is not usually apparent until shortly before harvest, that is, about the first or second week in June in central Indiana. The life history is briefly illustrated in the accompanying chart, Fig. 1.
The Hessian fly has at least two generations each year. The fall brood larva kills the plants outright as a rule, and the spring brood larva causes the stalks to fall, resembling the jointworm injury in this respect but can be distinguished from it by the absence of the hardening of the stalk and by the whitish green larva or resulting brown ‘‘flax seed” to be found beneath the leaf sheath, just above a joint and not within the stem as is the jointworm. Fall infested plants have broader leaves of a dark-
1 The work reported in this publication is a result of cooperation between the Bureau of Entomology of the United States Department of Agriculture. Washington, D. C., and the Purdue University Agricultural Experiment Station