Take-all decline and cereal disease management

Take-all is an important soilborne disease in UK cereals. As pathogen levels increase in the soil, so do antagonistic microbial organisms – these help stabilise disease pressure and, eventually, contribute to its decline.

Take-all decline occurs because microbial organisms antagonistic to the take-all fungus build up in soil, reducing the rate of secondary spread.

If successive cereal crops are grown (wheat, barley or triticale), take-all generally builds up during the second or third years but can decline during subsequent years, until it reaches a stable position when yields are acceptable.

Take-all is most important in UK winter wheat. This is how take-all and take-all decline develops in successive wheat crops.

Break from cereals

Take-all inoculum: Rapidly declining

Antagonistic organisms: Declining

Crop debris, which contains inoculum, starts to decay soon after harvest. The rate of decay is an important determinant of amounts of disease in second and subsequent crops. 

Relatively long or frequently repeated breaks also result in the complete loss of take-all decline.

Wheat 1 (first wheat)

Take-all inoculum: Low

Antagonistic organisms: Low

The low levels of take-all inoculum after a break from cereals leads to few primary infections to initiate secondary infection. Thus, there is likely to be little disease during grain filling. 

Wheat 2 (second wheat)

Take-all inoculum: High levels of take-all inoculum may present in the soil

Antagonistic organisms: Starting to increase (but still too low to provide effective take-all decline)

The residual inoculum leads to more primary and, hence, secondary infection. Second wheats are more severely diseased that first wheats and yields decline.

Wheat 3 (third wheat)

Take-all inoculum: Very high levels of take-all inoculum may present in the soil

Antagonistic organisms: Continuing to increase (but still too low to provide effective take-all decline)

After two susceptible wheat crops, amounts of soil inoculum are higher than in wheat 2. This ensures more primary infection, secondary infection and inoculum. Yields continue to decline.

Wheat 4 (continuous wheat)

Take-all inoculum: Very high levels of take-all inoculum may present in the soil (similar levels to a third wheat)

Antagonistic organisms: High levels 

The disease becomes less severe because take-all decline reduces the rate of secondary infection. The timing of decline is variable and may not appear until the fifth crop. When effective take-all decline kicks in, yields increase (compared to the previous crop).

The yields of long-term cereals, where take-all decline is established, are never as high as those of first wheats but may allow the crop to continue to be grown economically.

Effective take-all decline, established after a long run of susceptible crops, will not be completely lost after a one-year break or fallow.