• Pest Type: Insect
• Crops Affected: Wheat, Triticale, Rye, Barley, Cereals
• Scientific Name: Cephus cinctus
• Pest Order: Hymenoptera

Damage
The larvae of wheat stem sawflies bore within the straws, filling them with sawdust-like cuttings and causing the straws to break. They bore through the joints of the straw, girdling the stem, and resulting in straw breakage similar to that caused by the Hessian fly.

Life Cycle
Larvae: Larvae, the damaging stage, hatch in only 5 to 8 days; are wrinkled and nearly legless; measure about 0.5 inch long; and are pale yellow or dull white with brown heads. The tail end is covered with stiff bristles. When extracted from the stem, the larvae are S-shape.

Adult: Adults of the wheat stem sawfly are small, slender black wasps about 0.375 to 0.5 inch long. The wasp’s body is shiny black, with 3 yellow bands on the abdomen. These wasps fly from plant to plant and spend most of their time resting on grass stems. Female wasps lay eggs in elongating wheat stems.

Control Measures
Rotate crops that are not hosts to this pest. Several wheat varieties have been developed that are resistant. Delayed planting, tillage and early harvest tend to minimize damage. If a susceptible variety is planted and the population of adult sawflies is large, there is a very short time (1 to 2 weeks) when insecticide treatment may be effective. Once the female wasps have laid their eggs in the stem, insecticides are no longer as effective. Contact local advisers regarding economic thresholds and effective management techniques for your area.

Geography
This pest can be found across most of the US wheat-growing areas, but is most serious in the northern Great Plains and into Canada, particularly in Alberta.