Agriculture Reference
In-Depth Information
veloped by W. O. Mills of Cornell University and modified by A. L. Jones.
The infection period starts with the beginning of rain.
Tests have shown that compost has the ability to help manage apple scab.
Consider making fall applications of compost within tree rows to help break
down infected leaves and destroy the overwintering fungus. Applying com-
post tea to the foliage, flowers, and fruit may help establish populations of in-
nocuous or beneficial microorganisms that can help reduce apple scab infec-
tions by competing for space with the pathogen. Be sure when using compost
tea that you have met the National Organic Program standards for compost-
if animal manures are used in the compost.
By far the most important apple scab management practice for organic
growers is to use scab-resistant varieties such as 'Freedom', 'Goldrush', 'Jona-
resistance for popular apple varieties. For commercial growers, there is often
a trade-off when it comes to selecting apple varieties. Many varieties that are
highly resistant to apple scab presently are not popular with sellers. Some
organic growers, particularly those in arid regions where apple scab is less
serious, choose varieties that have some scab resistance but that are also
profitable to market.
Fungicides serve as the last defense against apple scab. Sulfur, lime sulfur,
and Bordeaux mix are the standard organic choices. All can be phytotoxic,
so follow label directions carefully. Use as needed, but do not use excessively
because sulfur can damage or repel predatory mites and other beneficial or-
ganisms. These fungicides have little or no eradicant activity, and you must
apply them before infection takes place. This means you need to apply the
