Takeall

Takeall is less severe when crops are fertilised with ammonium N rather than nitrate N and the use of nitrification inhibitors can also reduce Take all

Fungus has growth optimum at pH7 and is sensitive to low pHLiming therefore increases the incidence.

Factors which decrease availability of Mn also increase Take all eg liming and nitrate fertilisers.

The capacity of the roots to resist infection is decreased in areas where Mn and Cu are deficient.

G.graminis is a powerful oxidiser of Mn although isolates vary in their oxidation power and thus capacity to reduce Mn availability.

Soil applications of Mn⁺² fertilizers helps to suppress wheat take-all on non-calcareous soils. In high pH soils, Mn⁺² is rapidly oxidized and made unavailable for plant uptake. Supplying N fertilizers in the ammonium form helps to lower soil pH and increase Mn⁺² availability (Thompson et. al., 1995). Foliar sprays are less effective because of poor phloem mobility.

Chloride is an anion like nitrate and sulphate and is therefore very mobile in soil. Although much of our potassium is applied in the chloride form it is usually applied in autumn and often ploughed in thus the chloride applied may have leached by spring.

Chloride has been shown to inhibit nitrification in acid soils and stimulate mineralisation. If plants absorb more ammonium N and less nitrate N they become less susceptible to Take-all. Chloride fertilisers have been shown to reduce Take-all in Germany as well as the US.

Liming appears to increase nitrification and hence Take-all, and disease reductions from chloride use are less on limed soil than unlimed soil.

Nitrogen and phosphorus deficiency also increase Take-all, possibly because plants are less vigorous.

Copper deficiency increases Take-all because of decreased lignification- soil applied Cu reducing infection level more than foliar application. The addition of Cu and calcium together to the soil reduced Take-all levels more than either element alone.

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