ISHS Acta Horticulturae 595: International Symposium on Apple Breeding for Scab Resistance
REDUCTION OF FUNGICIDES TO CONTROL APPLE SCAB ON A PARTIAL RESISTANT CULTIVAR, BASED ON TYPE OF CHEMICAL, BIOLOGICAL AND CLIMATOLOGICAL CONDITIONS |
| Authors: | A. Duponcheel, J. Keulemans, P. Creemers, I. Millet |
| Keywords: | Venturia inaequalis, infection risk, protectant activity, curative fungicides, polygenic resistance, ascospore release |
| Abstract:
On Merlijn, a cultivar with polygenic resistance developed at the Fruitteeltcentrum-KULeuven, the effectiveness of four different spraying schemes was tested: one protectant scheme and three curative schemes. Within the curative schemes one was based on biological parameters (ascospore release and infectable tissue area), one on climatological parameters and the last one on a combination of both. The mean percentage of infected leaves on one-year-old shoots of untreated Merlijn, was 29.5 % in June 1999 and 13.3 % in June 2000. In September 1999 every tree had scab symptoms on fruit, with an average of 33.8 % of infected fruit per tree. In the protectant program or in a scab control program based on climatological conditions, all the trees showed scab symptoms on the leaves in June 1999. Fruit infections could be controlled due to regular chemical treatments in May, June, July and August. The number of treatments and thus the cost of scab control were much higher than in a program based on biological parameters where four treatments were sufficient during the 1999 season to keep the orchard (leaves and fruits) free of scab. The first treatment in this program was two weeks earlier than for the other programs and could control the important infection at the end of March. These results show that it is very important to avoid primary scab infections in the orchard to control scab with minimum spraying, a conclusion that was confirmed by the observations in 2000. | |
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