Voorkom botrytis GB

Avoid botrytis in plants that are too dry

When one has botrytis in the greenhouse, the fuchsia enthusiast knows that he must be careful not to give the fuchsias too much water. It is generally known that this fungal disease easily develops in an environment with high humidity. Regularly removing fallen leaves and the like and properly ventilating the greenhouse prevents the formation of botrytis. Less known will be that botrytis can also occur if the plants are too dry.

Botrytis in a flared Fuchsia

Foto: S. van Schaik.

After pruning in the fall of 1994 I put my plants in the greenhouse at the end of October. And as usual I had too many plants at the time, so that they only fit tightly together in the small greenhouse. A problem that almost every fuchsia enthusiast has in the fall, because it is difficult to discard plants. As a result, the occurrence of botrytis in the closely spaced plants. You know that the greenhouse needs to be better ventilated.

But with an autumn like in 1994, which was cold and damp for a long time, ventilation of the greenhouse is not that easy. With the help of a fan you can keep good air flow in the greenhouse, but you cannot stop the growth of the plants.

And that happened to me too.

Due to the strong growth, the whole had become even denser. "Watering as little as possible would slow growth," I thought. However, the humidity did not fall below 90% and that is much too high in a small greenhouse with many plants. If you do not have a hygrometer in the greenhouse, you can also see this by the many condensed water on the windows. I therefore dared to give the plants almost no more water, with the result that they went limp.

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At such a moment it goes wrong. Because the limp leaves hang against each other, botrytis is formed on those leaves, while the potting soil is then completely dry. You will then really have to give water, although the humidity can still be around 85%. Watering is best done in nice sunny weather if the greenhouse can be well ventilated.

The water must not be colder than 15 ° C. Because otherwise the following happens: the plants drop their leaves and they get stuck between the branches. These spots are then also infected by the fungus, causing the fungus to spread throughout the entire plant and to the adjacent plants. You can of course spray against the fungus. But it is better to first clean all plants and to cut off all affected branches, regardless of the amount of work.

Also remove the many fallen leaves on the ground, otherwise the base of the plant will be affected again. When all plants are clean and in their place, it is advisable to spray with an antifungal (for example Eupareen). Young plants with branches that are not yet wooded are more likely to be affected by botrytis than old plants.

Auteur: Hans van Aspert.