Pest Profile

Take-all got its name over 100 years ago in Australia when a severe seedling blight emerged killing entire fields, destroying entire stands of wheat, and "taking-all" seed­ lings it infected. The disease affects the root, crown, and stem base of wheat and inter­rupts plant development. Cool, damp conditions and alkaline soils promote infection, and irrigation increases damage.

Take-all is caused by a soilborne fungus that survives year-to-year in wheat residues and on volunteer wheat and grassy weeds such as bromegrass, quack grass, and bent grass. Wheat becomes infected when plant roots come in contact with infested resi­dues or infected plants. The fungus moves to its new host via the growth of runner hyphae through the soil. Spores are produced, but are not important in spreading the disease.

Soil conditions affect the severity of the disease. Sandy, light, poorly drained soils promote take-all severity as do soils with low fertility and a high pH and heavy, poor­ly drained soils. Wet weather, particularly in the second half of the growing season, promotes take-all fungal growth. Increased damage occurs when soil temperatures are between 54 and 68°F (12-20°C). Usually, damage is worse the earlier plants are infected.
Nutritional stress also plays a part in determining the severity of take-all in wheat plants. Take-all incidence is decreased with adequate soil fertility, particularly with nitrogen. Spring nitrogen application in a deficient wheat crops can reduce take-all development.

Wheat plants can endure mild to moderate infection with no apparent symptoms and minimal yield loss. However, when weather and soil conditions favor the disease, symptoms may be severe and yield losses as high as 50 percent may occur. Symptoms of take-all are most noticeable near heading and include plant stunting and early maturation. Circular patches of stunted, yellow plants may appear during the early growth stages, commonly occurring in wetter areas of the field. Infected plants tend to be yellow in color and produce fewer tillers. Because plants are killed prematurely, bleached and sterile heads are produced (“white heads”). The white heads may be void of grain or produce only a few shriveled kernels. Wet weather promotes fungal growth that blackens the dead, white heads.

Rotation with crops not affected by take-all, e.g., corn or sunflower, is an effective management strategy. Eliminate volunteer wheat and grassy weeds, such as downy brome, for these may serve as take-all hosts and allow the fungus to persist from year to year. If tillage is used, till as late in the year as possible. Early planting promotes take- all, so plant wheat after the Hessian fly-safe date for your area.