Take-all life cycle and disease symptoms in cereals
Take-all is an important soilborne disease in UK cereals. Learn about the pathogen, its life cycle and the symptoms commonly seen on infected cereal crops.
Classic take-all symptoms
Take-all attacks the roots of plants. However, it can infect plants at a low level without causing obvious symptoms. Moderate or severe infections cause roots to become blackened, rotten and have a ‘rat-tail’ appearance. In severe outbreaks, the base of plants may also blacken. The reduction in root activity restricts water and nutrient uptake. This slows canopy growth and causes yellowing and stunting in severe cases. Patches of stunted plants and whiteheads (bleached ears) form, which are usually first seen during grain filling. Generally, whiteheads contain small and shrivelled grains or, occasionally, no grain at all.
Life cycle of the take-all pathogen
- Gaeumannomyces tritici attacks wheat, barley, rye and may attack some grass species, particularly couch grass. Oats are immune.
- Gaeumannomyces avenae attacks oats, wheat, barley, rye and many grass species. This strain is rare.
The take-all fungus is soilborne, with primary infection occurring in the autumn from inoculum in the soil, and from mycelium on infected roots and cereal debris.
Secondary infection, where the disease spreads directly from root to root, usually occurs in the spring and summer.
The disease then spreads from infected seedling roots to developing crown roots (where the roots and stem meet).
As the disease progresses during the season, the root area lost to the disease increases and the ability of the plant to absorb water and nutrients from the soil declines.
When root rotting is severe, plants are unable to absorb water and nutrients. As a result, the plants ripen prematurely, resulting in whiteheads and poor grain filling.
The disease survives the winter primarily as mycelium on infected roots or stubble debris, and can then spread to volunteer cereals, early autumn-sown crops and some grass weeds.
More secondary infection occurs when soils are warm and moist.
Take-all development is encouraged by a warm winter followed by a wet spring/early summer.
The pathogen is active in the soil when temperatures are above 10–12˚C.