Take-all Control in Winter Wheat: I Planning (HGCA Topic Sheet No.49)

Take-all Control in Winter Wheat: I Planning

TS No.49
Summer
2001



Action:

  • Manage rotations to reduce frequency of second and subsequent wheat crops.
  • Assess the risk of take-all before sowing the next winter wheat crop based on previous disease incidence and rotational position.
  • Consider using a take-all seed treatment where risk is high.
  • This may be in second or subsequent wheats and early-drilled first wheats after set-aside or spring barley.
  • Avoid, where practicable, sowing second and third wheats in September. Delayed drilling until mid-October substantially reduces the risks of a severe attack.
  • Follow cultural guidelines in Topic Sheet 50 to minimise disease impact in growing crops.

Disease incidence

Take-all is a serious soil-borne disease. Half of UK wheat crops suffer 5-20% yield losses, costing farmers up to 60 million yearly.

Gaeumannomyces graminis var. tritici, the take-all fungus, infects winter wheat roots (also barley, rye and triticale, but not oats) in the autumn. Symptoms are coal-black lesions on roots. Early and severe infections can lead to uneven growth, reduced tillering and occasionally plant death in spring or early summer. Later infections and premature ripening (whiteheads) usually occur in patches, reducing yield and grain quality. Another strain of take-all, which affects oats as well as other cereals, occurs in some western areas of Britain. This is currently very rare.

Effects of rotation

Rotation plays a major part in reducing take-all. First wheat crops following a good break are generally highest yielding, partly because they are free of significant take-all, which is usually worst on second, third or fourth wheats. Suitable break crops include oats (except where the oat strain is present) and non-cereals. Couch and other perennial grass weeds must be controlled as they can carry take-all through a break. However, a two-year ryegrass ley can provide an effective break crop in a sequence of cereals.

Take-all can sometimes be more severe in second wheats after some break crops, eg oilseed rape, due to very early drilling of the first wheat which can increase disease build-up in the second wheat. Cereal volunteers may also carry the disease over between cereal crops.

When long runs of wheat are grown, yields may recover somewhat after a take-all peak, usually from about the fourth crop (Figure 1). This phenomenon take-all decline occurs because fungi antagonistic to take-all build up in soil and on roots.

New seed treatments

Two new seed treatments are now available for take-all:

  • Latitude (silthiofam)
  • Jockey (fluquinconazole + prochloraz)

Recent HGCA-funded research has shown that yield response to seed treatment depends on disease severity during the growing season. Yield benefit can be maximised by targeting use of a seed treatment where there is a significant risk.

In trials to date, both seed treatments have reduced epidemic development. Neither has any effect on antagonists. Ongoing work at IACR-Rothamsted and ADAS Rosemaund aims to understand indirect effects on the onset of take-all decline.

Drilling date and weather

Take-all does not survive well in the soil in the absence of a host plant. Increasing the interval between harvesting one crop and planting the next reduces disease severity (Figure 2).

Generally warm and wet conditions in autumn and spring encourage higher take-all levels. Summer drought further reduces yields, as the damaged root systems of infected plants cannot absorb sufficient moisture. This was verified in trials using irrigation and crop shelters to alter soil moisture (Figure 3).

Summary

A great deal of experimental work has been carried out on take-all over many years but, until recently, control depended principally upon rotation. Ongoing research funded by HGCA and carried out by ADAS, The University of Nottingham and IACR-Rothamsted is providing new insights into disease incidence and its likely impact on yield.

This Topic Sheet covers effects of rotation and seasonal weather on take-all risk and yield loss, as well as preliminary results on effects of seed treatment on these factors. Topic Sheet No. 50 considers agronomic factors and the use of the new fungicides in greater detail.

Further information:

John Spink, ADAS
Tel: 01432 820444

Projects 1301, 2443

Dr Geoff Bateman, IACR-Rothamsted
Tel: 01582 763133

Project 1308


Topic sheets are free

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The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted the research or written this report.While the authors have worked on the best information available to them, neither the HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered directly or indirectly in relation to the report or the research on which it is based.

Reference herein to trade names and proprietary products without stating that they are protected does not imply they may be regarded as unprotected and thus free for general use. No endorsement of named products is intended, nor is any criticism implied of other alternative, but unnamed products.

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