HPIPM:Wheat Stem Maggot
Author: Frank B. Peairs[1], Gary L. Hein & Michael J. Brewer
Identification (and life cycle/seasonal history)
Adult wheat stem maggots, Meromyza americana Fitch, are yellowish-white flies, about five millimeters (1/4 inch) long, with three conspicuous black stripes on the thorax and abdomen and bright green eyes. The maggots are white and legless and have a pair of hook-like mouthparts.
Wheat stem maggot passes the winter in the larval stage, in the lower parts of the stems of wheat and other hosts. They pupate in the spring and the adults emerge in June. Females lay eggs, about 30 per female, on the leaves and stems of wheat and other hosts. The newly hatched maggots of this generation enter the leaf sheaths and tunnel into the tender tissues of the stem. Maggots feed for about three weeks before pupating. Another generation of flies emerges in midsummer to lay eggs on volunteer and other grasses. The fall generation emerges in late August to early September and lays eggs in the new winter wheat crop.
Plant Response and Damage
Wheat stem maggots construct two or three inch long tunnels in wheat. Damage becomes evident during seed development when wheat heads and upper internodes turn white while the lower stem and leaves remain green. A single maggot will be found inside the straw just above the last node. The plant stem pulls out easily and if larvae are not found, the stem is usually cut off. This pest attacks cereal crops, including wheat, rye, barley, and oats. Other hosts include bluegrass, millet, timothy, and a range of other native and introduced grass species.
Management Approaches
Resistant Varieties
Currently, resistant wheat varieties are not available.
Biological Control
Parasites which attack wheat stem maggot include Bracon meromyzae Gahan and Coelinidea meromyzae (Forbes). These parasites are important in maintaining pest populations at low densities.
Cultural Control
The use of delayed planting, following the dates recommended to escape Hessian fly infestation, is an effective management practice for wheat stem maggot. Destruction of volunteer plants is also recommended. Incorporation of non-susceptible crops such as corn, sunflower, flax, soybeans, safflower, oats, and legumes into rotation systems will reduce the numbers of this pest.
Chemical Control
The effectiveness of chemical control is unknown. Planting time applications of systemic insecticides should be effective against the fall generation. Control of the spring generation would have to be directed against adults and newly hatched larvae before they enter the leaf sheaths and stems, but we do not currently have the knowledge to time such applications properly.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
