Insect chewing damage to wheat reported in western Montana
News from MSU Lake County Extension Agent
MISSION VALLEY — Unusual chewing damage to both winter and spring wheat has been reported from Ravalli and Lake Counties. Samples have been sent to MSU and the source of the damage is currently unknown. The chewing damage appears as multiple parallel rows, the result of damage that has occurred to new leaves before they have unfurled.
Billbugs are one insect that can cause this type of damage. Other possible sources are early-stage army cutworm larvae, young grasshoppers, or perhaps flea beetles. So far damage has not been economic, but because it has been reported from several areas, and it is unusual, MSU extension entomology recommends scouting. Concerned growers should scout foliage and soil carefully. If damage is observed, collect about ten plants with intact roots. Check the soil and lower stem and crown (splitting it with a knife) for grubs. Sweep samples (about 50) can be collected into a zip-lock bag and inspected for potential foliar pests including adult billbugs. Samples can be submitted to MSU for inspection.
Billbugs are a group of weevils in the family Sphenophorus (=Calendra). Several species occur in Montana. While billbugs are most commonly a pest of turf grass, some species also damage small grains, corn, orchard grass, and other plantings.
Billbugs lay their eggs in unfurled leaf sheaths early in May. The adult females chew into the tissue to create cavities for their eggs. The holes pierce several layers of folded leaf tissue so that later, when the leaves expand, the punctures appear as transverse rows near the base of the leaf blade. Some species of billbugs also tunnel within the lower stems and crown of their hosts as larvae, or may be found in the soil below.