5.6.4
FUNGICIDE FOR CONTROLLING GAEUMANNOMYCES GRAMINIS VAR. TRITICI, THE MOST IMPORTANT CROP ROTATION DISEASE IN WHEAT

CW HEPPNER1, JM HEADRICK1 and JM GRIFFIN2

1Monsanto Services International S.A., European Crop Research Center, Rue Laid Burniat 5, B-1348 Louvain-La-Neuve, Belgium; 2 Monsanto Crop Protection, Lane End Road, High Wycombe, HP 12 4NL, UK

Background and objectives
More than 140 years after take-all (Gaeumannomyces graminis var. tritici) was first recognised, it is still a major problem for cereal growers. The disease is very widespread and can cause up to 50% yield loss [1]. The impact of the disease can be reduced using crop rotation and its integration with triazole fungicides such as triadimenol, but these are only palliative and the development of host resistance or effective chemical control methods has not been previously achieved. This paper presents growth room tests for the control of take-all in wheat, using a novel chemical discovered by Monsanto.

Materials and methods
A test assay was carried out in growth cabinets at 15-18C. Artificial inoculum of G. graminis var. tritici, produced on oat grains, was applied to a soil and vermiculite mixture at a rate of 4% (v/v). Winter wheat seeds (cvs Soissons and Forby) were treated with the novel fungicide, MON 65500, at a range of dose rates. It was compared with a triadimenol-based fungicide which is considered to have some limited activity against take-all. The treated seeds were placed 2 cm below the soil surface and the containers were regularly watered. The plants were assessed for disease 3 weeks after inoculation by estimating the severity of root rot.

Results and conclusions
High levels of take-all were observed in the untreated inoculated plants. MON 65500 significantly reduced root rot (P<0.05), while the triadimenol-based treatment had no significant effect. In addition, MON 65500 did not show any adverse effect on emergence or vigour of the wheat seedlings, even when it was applied at high application rates.

The data show the potential value of the compound for take-all control and as a tool to provide a more flexible approach to crop rotation.

References
1. Hornby D, Bateman GL, 1991. Home Grown Cereals Authority Research Review 20, pp. 9-18.