Evening Republican, Volume 20, Number 284, Rensselaer, Jasper County, 27 November 1916 — HOW TO FIGHT THE HESSIAN FLY [ARTICLE+ILLUSTRATION]

HOW TO FIGHT THE HESSIAN FLY

by Leoinard Haseman

This destructive wheat pest can be controlled only by careful farming methods, and farmers of the whole .community must work together in order to protect their grain crops.

F ALL the insect pests of v wheat the Hessian fly is I most destructive. It was first Introduced into this country in straw brought from Europe by the Hessian soldiers in Itevolutionary days.

It is widely distributed nnd does more or less injury locally every year. Like most of our destructive pests, however, it appears as a general scourge more or less periodically following a series of favorable years. One or more dry summers followed by mild winters usually brings on Hessian fly troubles. The dry weather keeps the pest in the resting t'ffifdffton fii the stubble and also prevents the plowing under of stubble and then with the early fall rains wheat is sown early and the flies appear and lay their eggs on the young wheat. These are the Ideal conditions for an outbreak of the flyThe injury to wheat is due to the work of the maggot or larval stage of the fly. The small, dark, winged, mosquitolike fly does not attack the wheat. ■The maggot rasps on the tender plant •with a pair of sharp fangs, causing a flow of sap which it drinks. The young wheat, when attacked Ift the fall, stopfc growing and turns yellow. Usually this first, appears where the ground js poorest, but if the infestation is bad 1t will flnully show up over the whole field. If the weather is favorable tillers are usually produced and the crop is not completely destroyed, unless the infestations be very severe. In aV,.v i —o ~~n*T^r~ Tiitr spring Tire wncai inn*' strong and thrifty, but as soon as the rains cease nnd the spring brood of maggots begins to feed, the wheat stops growing and turns yellow. When the pest is not too abundant the wheat may head out and produce a partial crop, though the heads do not fill properly and the grain is light. The lodging or falling of wheat begins about the time of heading and continues until it is ripe. In case of severe infestations no heads form at all. Develops Like Other Fies. The development of the Hessian fly is similar to that of other flies. The adult winged fly lays eggs on the wheat leaves. These hatch into very small, whitish maggots which feed on the sap of the plant. When nearly full fed the maggot may appear green due to the green sap it contains. When full fed the maggot turns brown and takes on the shape of a flaxseed. The maggots in the ftxseed stage are often packed together in groups of from six to thirty in the base of a wheat plant. Within- this brown ease the small maggot changes to the resting or pupal stage and later the fly emerges. In Kansas and other states of about the same latitude, there is normally one fall brood, one full spring brood and a later partial spring brood of flies. From the last of August to the middle of October the small black mosqultolike flies continue to emerge and lay eggs on the leaves of wheat. Each fly lives but a few days. The females __]ay an average of 100 eggs. When the eggs hatch the small maggots pass down between the leaf and the small stalk to feed on the stalk. By the time cold weather comes, the maggots are full fed and change to the brown flaxseed stage. In this form they spend the winter below grounc} in the crown of the wheat plant. About the middle of April they hatch and the first brood of Hessian flies appears. These flies lay eggs which hatch during May, producing the spring brood of maggots. In cuse of a warm, damp spring these may mature and produce a second brood of flies which pass the summer in the wheat stubble in the flaxseed stage. It is the brood which is mainly responsible for the destructive fall swarms of flies. While this is the normal cycle, some years additional secondary broods may appear and during a dry spring the secondary spring brood may not appear at all. Cool, dry weather always retards the development of the flywhile warm, damp weather hastens it. If there is an excess of moisture during the summer the flies may come from the flaxseed stages in the stubble and deposit eggs on volunteer wheat producing a secondary summer ibrood. In the same way a small secondary fall brood may appear during November in case of excessive rainfall though such cases are rare. Late sown wheat is seldom attacked except by the spring brood which migrates in from infested fields. The Hessian fly is most effectively controlled by proper methods of farm practice. The destruction of all infested stubble very early and the sowing Of wheat late enough in the fall

to escape the fall brood of flies are the most practical** methods known for controlling this pest. Since the pest is found in the wheat stubble during the summer in the resting flaxseed stage it can be completely destroyed if all infested stubble be destroyed. Plowing under stubble early in July where it is not too dry, is the most logical and economical method of placing the stubble where the pest will be destroyed. Some farmers disk thoroughly and then in a week or two plow the stubble under. In case the pest be located in the stubble above ground, burning off stubble will destroy it though the stubble is also lost. The flaxseed stages are often located so low in the stubble that burning them inay not destroy all of them. By all means get rtd of ntt stubble in the Infested regions before August. Co-op-eration is necessary. One infested stubble field will furnish flies for a whole community. Farmers must work together in order to fully destroy the pest. After the stubble has been plowed under, work the ground so asp to pack it, and keep down all volunteer wheat. Sow Wheat Very Late. The second effective remedy for the fly is to sow wheat as late in the fall as possible so as to escape the heavy swarm of flies. If wheat is not yet up when the flies come they die without a place to lay their eggs and the crop escapes injury. It is folly to suppose that wheat sown after the swarm has come and gope, will be as badly infested as early sown wheat. As an example, in a normal fall the flies have largely come and gone In north Missouri by October 1, in central Missouri by October 7 nnd in south Missouri by October 15 and wheat sown aftero these dates is seldom attacked by the fly in the fall. Late sown wheat may suffer severe injury in the spring if the spring brood of flies migrates to it from neighboring fields which were sown sufficiently early in the fall to be attacked by the fall brood of flies. It shows poor judgment to sow wlveat in August or September for pasture, in a region where the fly is abundant. Look out for trouble in the crop of wheat"following a year in which the Hessian fly has been destructive. Avoid this by thoroughly destroying the infested* stubble and by sowing late enough in October to escape the fall swarm of flies. If these precautions are taken by all farmers there is no need of completely abandoning the growing of wheat in any community for a few years. Life History—The adult flies of the fall brood appear in the fields early in September, and the females scatter about to lay their eggs on the young wheat plants as soon as they are large enough. These eggs are laid in regu: lar rows of one to a dozen along the j veins on the upper side of the wheat I blades. The individual egg is very

small, about one-flftieth of an Inch long, of a glossy reddish eolor. In about three to five days these eggs hatch Into small reddish larvae scarcely larger than the egg from which they hatched, and these larvae migrate down the blade between the leafsheath and the stem until they reach a point near the root. Here they stop, begin to absorb the plant juices, and cause a gall-like enlargement or swelling at the point of attack. They grow rapidly, and three weeks later are thick, whitish maggots about oneeighth of an inch long. Become Lively in April. Once fully grown the larvae contract, leaving their outer skins to form hard, dark brown shells, commonly known as flaxseeds or pupuria, and remain in this condition and situation through the winter. Inside tlj,e§S flaxseeds the white larvae may be found until toward spring when they change to the pupa stage. Early in April the pupae push off the end of the flaxseeds and then force their way out from under the enveloping leaf-sheath. Having found a way out of the plant the thin pupal skin splits and the adult fly escapes. Eggs are laid back on the wheat during April and early May and the same development is gone through as in the fall, except that the migrating larvae locate in the first or second joints above the roots. They become full grown and enter the flaxseed stage before harvest, remaining in the stubble through the summer if it is ormaliy dry, to give forth the adult flies of the fall brood in September; but if the summer is rainy many will come forth soon after harvest and go through an additional summer brood on the volunteer wheat. The injury by the Hessian fly is done during the fall and spring by the growing larvae of the two broods. In the fall the first effect of attack is to cause the wheat to become abnormally dark green and to tiller freely, later turning yellowish and brownish and finally killing the affected blades. The field then appears dead in spots, or sometimes over the whole field. Badly attacked plants may later recover if there is plenty of moisture. In the spring the presence of the larvae"in the lower joints interferes with the sap flow and weakens the straw, so that the-heads fail to fill and toward harvest the straw Is apt to crinkle or break at the point of attack so that the grain becomes badly lodged and often not worth harvesting. Only wheat, rye and barley among our cultivated grains are attacked by the Hessian fly. crops is a practicable Hessian fly control pleasure, for not only does the bringing in of corn, oats, alfalfa, or clover tend to starve out the pest, but if the wheat field is changed the fall brood of ..flies must migrate to more or less distant fields to find wheat and this results in a large mortality among them.