Is Botrytis latent in cold-stored strawberry runners? Previous HDC work in 2008 (SF 84) showed that latent Botrytis was present in the crowns of cold-stored A+ Elsanta strawberry runners from five different propagators at levels ranging from six per cent to 38 per cent. This was the first report of Botrytis in the crowns. A+ plants are taken directly from mother plants, with runners growing at high densities, but waiting bed plants are grown at half the density to produce multi-crowned plants.
It is possible that the denser growing conditions of A+ runners compared with waiting bed runners might provide more favourable conditions for Botrytis pre-lifting. This may be because of higher humidity and/or increased volumes of dying leaves caused by shading. HDC project SF 111 was carried out to determine the occurrence of latent Botrytis in commercial strawberry plants after cold-storage, by testing samples of both A+ and medium-density waiting bed plants of the same variety (Elsanta).
Ten batches of 50 ex-cold store plants from propagators in the Netherlands (7 samples) Germany (2) and the UK (1) were examined for latent infection by Botrytis and also Colletotrichum. Combining the results of the three test methods, Botrytis was detected in all the samples at levels ranging from six to 84 per cent. Internal infection of crowns was found in nine of the samples. It was also detected in trimmed leaf stalks, roots and leaves. No Colletotrichum was found in any test.
In all the tests, the mean level of latent infection by Botrytis was greater in A+ runners than in waiting bed plants. Further work is needed to determine the importance of latent Botrytis on crop production and fruit Botrytis and if propagators could apply any treatments to reduce the problem.
- Horticultural Development Company
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