The harmful organisms that appear during the growing season—including pathogenic fungi, bacteria and, of course, animal pests—remain present in our orchards during winter. To prevent subsequent damage, their numbers should be reduced as much as possible in early spring. If this is successful, we can begin the growing season with a clean slate and have a better chance of preventing diseases and pests from spreading later.

Although this general principle is valid, it does not work against every pathogen and pest. Late-winter dormant spraying can only destroy or reduce harmful organisms that overwinter on the branches and shoots of trees and shrubs. It has no effect on those that overwinter in the soil or among fallen leaves.

The timing of dormant spraying is crucial to achieving good efficacy. As a general rule, the treatment should be carried out after the winter frosts but before bud break. The best results can be expected if treatment is delayed until vegetation is about to become active, as pests and pathogens also begin their more active life processes at this time. In certain cases, such as apple powdery mildew, the pathogenic fungus overwinters between the bud scales. Spraying should therefore be postponed until the buds begin to open, allowing the spray solution to reach their interior.

The answer depends on the problem being addressed. If large numbers of animal pests—such as mites, aphids or scale insects—are present on the woody parts of dormant plants, a product with a high oil content should be selected. If the objective is to prevent fungal or bacterial diseases, a dormant-spray fungicide containing copper and sulphur should be used. Drawing on several decades of professional experience, BVN’s development team has created solutions for controlling overwintering pests and pathogens in late winter.

A fungicidal dormant-spray product should contain multiple active ingredients to provide effective control against a wide range of pathogens. As a result of BVN’s development work, Vegesol® eReS combines copper hydroxide and sulphur in a ready-to-use commercial formulation containing vegetable oil, which provides outstanding adhesion for both fungicidal active ingredients. Copper and sulphur give the product a broad spectrum of activity against various pathogenic fungi. Thanks to its added formulation components, the oil-based formula creates a slowly degrading film on the surface, ensuring the prolonged biological efficacy of the active ingredients.

This patented technology makes BVN products unique. It explains why Vegesol® eReS provides excellent biological efficacy against downy mildew-type pathogens despite its lower copper load. The same efficacy-enhancing property also applies to the sulphur active ingredient. It is also worth noting that sulphur is effective not only against powdery mildew fungi but also has a considerable secondary effect in reducing mite populations. Both products are freely available and authorised for use in organic farming.

The table below shows the fruit species for which late-winter dormant spraying with the Vegesol® eReS fungicide is particularly important, together with the recommended treatment timing.

This article was originally published in the agricultural trade journal Értékálló Aranykorona.