Every year, Cape wine farmers spend millions of rands on fungicides to prevent diseases such Botrytis and powdery and downy mildews; blights that have affected our winelands for hundreds of years. These fungal infections occur in wine-growing regions all over the world, and their impact can be catastrophic, so controls are necessary. However, fungicides are not necessarily a failsafe as, from time to time, the fungi do develop resistance to specific toxins used.
With our commitment to organic and Biodynamic farming, and to preserve our healthy vineyard ecosystem, we’ve turned to biological controls in order to avoid fungicides. Nature provides alternatives in the form of various strains of beneficial bacteria, such as Bacillus amyloliquifaciens and Bacillus subtilis, which are highly effective at preventing common, threatening fungal infections.
Botrytis, which is also known as grey rot or black rot is caused by the fungus Botrytis cinera. It usually infects bunches of grapes close to harvest time and it can cause serious losses in yields. In wetter, humid years, the risks are greater. To avoid Botrytis, we firstly ensure that there is good airflow around the bunches of grapes. While they want to ripen in the shade of the vines leaves, we mechanically remove leaves where this cover is very dense. We then spray when the berries are pea-sized and before the clusters close up. The beneficial bacteria strains are applied directly in the bunch zone, outcompeting fungi for nutrients, even feeding parasitically on them and all the while, emitting anti-microbial excretions that make the grapes a hostile environment for Botrytis cinera. We find that one application during the growing season is sufficient.
Similarly, Bacillus amyloliquifaciens and Bacillus subtilis will also keep downy and powdery mildews at bay if applied to the grapes and leaves. Bacillus subtilis is specifically known for activating the vines’ immune systems and boosting the plants’ overall health.
Going the biocontrol route means that you have to remember that you are dealing with living organisms, not an inorganic poison. Spraying should be done during the cooler, moist times of day, morning or evening, in order to give the bacteria optimal conditions to establish themselves on the vines. It’s also important to be aware of any possible sulphur or copper residues as these can compromise the bacteria’s capacity to get a hold on life, thrive and do their job of protecting the grapes. When used correctly they can add a great tool within the total disease strategy.