ISHS Acta Horticulturae 525: International Conference on Integrated Fruit Production
SCAB INFECTION RISKS IN RELATION TO BIOLOGICAL FACTORS AND THE OPTIMUM SPRAY-TIMING OF MODERN FUNGICIDE FAMILIES |
| Authors: | P. Creemers, A. Vanmechelen |
| Keywords: | Apple scab, Demethylation inhibitors, anilino-pyrimidines, strobilurines |
| Abstract:
In IPM, the control of fungal diseases is mainly based on the reduction of the inoculum in the orchard, the determination of the infection risks during the growing season and the use of selective fungicides which minimise damage to beneficial insects. Scab is the key parasite amongst the fungal diseases. From a calender spray scheme using more or less fixed spraying intervals, we moved to treatments based on warning devices. In recent years, these warning systems have became more and more electronic which has facilitated the transfer of the meteorological data to a central point for the calculation of the infection risk in different regions. The integration of biological factors, like orchard inoculum, ascospore release and leaf growth, can give a better estimation of the real scab risk in a favourable climatological period for scab. Simulation models are being developed as an alternative to the labourous work usually needed for the determination of these biological parameters. The use of several fungicide families, each with a different mode of action on the fungus, is the best guarantee for the durable control of diseases which demand several treatments per season. In general, anti-resistance strategies are based on a limitation of the number of applications per fungicide family. We strongly stressed in our research the the need to look for complementary effects between two different fungicide families and the best positioning of the different fungicidal groups during the season, in relation to climatological and biological circumstances. In this respect, the Demethylation Inhibitors (DMI's) and the Anilino-pyrimidines (ANP's) are recommended for curative scab control and are complementary with the classic protectants. They provide a direct activity on spore germination and give better protection of scab on the fruits. With this combination there is also a beneficial effect on minor diseases like Nectria canker and Blossom-end rot. The choice between both of these curative families in the spray program is based on their efficacy in relation to the prevailing temperatures. ANP's are used at lower and DMI's at higher temperatures. On the other hand, at higher temperatures the risk of powdery mildew is greater and with the DMI's both diseases are controlled together. The | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
-methoxyacrylates (MOA's) are applied in a block of 3 (maximum 4) treatments.
The interval between the treatments is related to the infection pressure and leaf growth and varies between 8 and 14 days.
The benefit of such successive treatments is to provide, besides the protective activity, curative and eradicative properties also by the deposits that are built up.
In the spray program, the MOA's are positioned after full bloom, to give good protection of the fruits, supplementary activity on powdery mildew and also good tolerance by the fruit tree.
If the block is starting curative, the addition of a DMI or ANP is recommended.
