Nutrition management for apple scab
Some apple varieties are quite susceptible to apple scab, while others are resistant.
Plant sap analysis indicates the resistant varieties are much better at absorbing cobalt than the susceptible varieties in the same soil conditions. They will often show 2-3x higher cobalt levels.
When we balance all the other nutrients and apply foliar applications of cobalt to susceptible varieties, apple scab is not present. We have implemented this treatment successfully on enough different apple varieties on enough different orchard blocks to be confident of its success.
Many other diseases have similar correlations to nutritional imbalances and can be managed effectively by managing nutrition.
Preventing and reversing scab infections can occur very quickly. We expect to see reduced pressure within weeks of the first application. In several cases, we have been able to eliminate all the later scab treatments after cobalt was applied in the spring, within several weeks of beginning to work with a block for the first time. This reduced the pesticide budget requirements by $500.00-$600.00 in the first year.
Like any trace mineral, cobalt can easily be overdone. Don’t attempt treatments without using sap analysis to evaluate progress and nutritional balance.
Not all diseases respond this quickly to nutrition management, but many do. When we begin managing nutrition differently, we can dramatically reduce fungicide and insecticide applications on most crops.
These Gala apples had severe scab pressure in a mild scab year in the year before treatment. In the current year, they had no scab, in spite of heavy scab pressure.