INTEGRATED CONTROL OF FUNGAL DISEASES IN APPLE PRODUCTION

E. Bosshard, U. Hilber, J. Rüegg, H. Schüepp, W. Siegfried
The control of apple scab by SBI (sterol biosynthesis inhibitors) fungicides applied according to infection periods is now well established in Switzerland. However, the presence of scab conidia overwintering on the shoots, as an additional inoculum source, and the increasing number of orchards where SBI fungicides failed to control scab sufficiently make it necessary to adapt treatment strategies continously.

Considering the fact that scab control by treatments according to infection periods depends entirely on the curative activity of SBI fungicides, more efforts should be put on the monitoring of scab populations for SBI resistance, to get information on the level of resistance in Swiss orchards.

Since 1985 attacks by powdery mildew have been less severe in most apple growing areas. Examining the weather data of this period it can be assumed that the cold winters of 1985/86 and 1986/87 reduced the mildew populations considerably. Also frequent rainfall in spring and early summer were unfavourable for mildew development, but might have favoured the spread of the mildew hyperparasite, Ampelomyces quisqualis. Studies are under way on the influence of scab control strategies, including late summer sprays with captan, on the development of storage diseases in cold and controlled atmosphere (CA) storage. An extended survey of fungicide residues at harvest in 179 apple orchards showed that values were well below the maximum permitted residue level. In trials on the control of storage diseases by SBI fungicides it was found that the incidence of Pezicula species (Gloeosporium) was significantly reduced.

The distribution of spray drift within the orchard and the decomposition of the active ingredients in decaying leaves, grass sward and soil are being investigated. In the same survey the presence and activity of VA mycorrhizal fungi in differently treated plots are also being studied.

Bosshard, E., Hilber, U., Rüegg, J., Schüepp, H. and Siegfried, W. (1993). INTEGRATED CONTROL OF FUNGAL DISEASES IN APPLE PRODUCTION. Acta Hortic. 347, 97-106
DOI: 10.17660/ActaHortic.1993.347.10
https://doi.org/10.17660/ActaHortic.1993.347.10

Acta Horticulturae