Yellow and red tipped flag leaves in wheat
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
There have been a couple of reports in Michigan of wheat with a red or yellow discoloration beginning at the flag leaf tip and progressing toward the base of the leaf. There is no stunting of the heads and minimal stunting of the plants. These leaf discoloration symptoms, along with stunted heads, stunted plants and flag leaves remaining in an upright position, are classic symptoms of barley yellow dwarf virus, an aphid transmitted virus. Greg Shaner, professor of plant pathology at Purdue University, reported that barley yellow dwarf virus was the most significant disease problem of wheat in Indiana this year. Most of the reports of suspected barley yellow dwarf virus in Michigan have come from counties located along the Indiana border, however, one of our research sites in East Lansing shows the same symptoms (see photos). Barley yellow dwarf virus has not yet been confirmed from these suspect fields, but samples are being collected for virus testing, and we’ll report the results in the Field Crop CAT Alert. Environmental stresses and nutritional disorders can cause similar symptoms.
Barley yellow dwarf virus is transmitted by several different species of aphids, including oat bird-cherry, corn leaf and English grain aphids. The virus persists in volunteer grains or wild grasses. It is reintroduced to crops each year, sometimes from aphids that have migrated from great distances away on storms. The disease usually occurs in small patches or portions of rows, sometimes along field margins. Symptoms are most severe when infection takes place in the fall, less so when infection occurs in the spring. When temperatures are around 68°F, virus symptoms are visible in about two weeks. As temperatures warm, symptom expression takes longer, for example, four weeks at 77°F. No symptom expression occurs at 86°F. Yield losses to barley yellow dwarf virus depend on the growth stage at the time of infection, cool weather conditions that favor disease development and the susceptibility of the variety.
There is little that can be done to save diseased plants and management should focus on preventing the disease. There are resistant oat varieties, but wheat has limited resistance to barley yellow dwarf virus. Check with your seed dealer for recommendations about resistant varieties. Avoid early planting to avoid exposure to aphids during early crop growth stages. Control volunteer wheat barley, oats and wild grasses. Although foliar insecticides are available to control aphids, their short residual life gives them limited usefulness in barley yellow dwarf virus management.