Disease management strategies are very similar for both organic and conventional small fruit production systems in the Midwest. In both systems it is important to develop and use an integrated disease management program that integrates as many disease control methods as possible, the more the better. Major components of the disease management program include: use of specific cultural practices; developing knowledge of the pathogen and disease biology, use of disease resistant cultivars, and timely application of organically approved fungicides or biological control agents or products when needed. These guidelines have been written for caneberries (raspberry and blackberry), strawberry, blueberry and grape. Specific information is provided for each crop in its respective chapter. Most disease control methods or strategies are identical for both conventional and organic production systems. Perhaps the greatest difference between organic and conventional production systems is that organic growers are not permitted to use synthetic "conventional" fungicides. If disease control materials are required in the organic system, growers are limited to the use of "inorganic" fungicides such as sulfur (elemental sulfur and lime-sulfur) or copper fungicides (Bordeaux mixture and fixed copper products). In addition, there are several new "alternative" disease control materials and biological control products that are currently available and are cleared for use in organic production.

  There are several problems associated with the use of these inorganic fungicides and "alternative" products in small fruit disease control programs. Among the most important are 1) Phytoxicity, which is the potential to cause damage to foliage, fruit set and fruit finish (this is a concern primarily with copper and sulfur fungicides); and 2) their limited spectrum of fungicide activity, which means they may not be capable of providing simultaneous control of the wide range of fungal pathogens that can cause economic damage to the crop. For example, sulfur is highly effective for controlling powdery mildew on most fruit crops, but provides little or no control of most other diseases.

  In a climate like the Midwest, environmental conditions during the growing season are generally very conducive (warm and wet) to the development of several important diseases, insect pests and weeds. Limitations in relation to which pesticides may or may not be used, present the organic grower with some unique and very demanding challenges. Whereas the use of various cultural practices and disease resistance will be the "back bone" of the organic disease management program, the limited use of organically approved pesticides or biocontrol agents will probably be required at times.

In relation to disease control, blueberries have the greatest potential for organic production. The lack of wild relatives of blueberry in much of the Midwest provides a degree of isolation from some of the more damaging diseases. In addition, blueberry plantings in states like Ohio are often scattered and somewhat isolated. Several commercial plantings in Ohio that are 15 to 20 years old have never received a fungicide application, yet have been very productive. However, if diseases such as mummy berry and anthracnose are introduced into the planting, they can be very destructive. For the most destructive blueberry diseases, organic fungicides are of little value once the diseases are established in the planting. 

As with all crops, the development and use of an integrated disease management program will be essential to the organic production of blueberries. The objective of an integrated disease management program is to provide a commercially acceptable level of disease control on a consistent (year-to-year) basis. This is accomplished by developing a program that integrates all available control methods into one program. An effective disease management program for blueberries must emphasize the integrated use of specific cultural practices, knowledge of the pathogen and disease biology, disease resistant cultivars and timely applications of organically approved fungicides or biological control agents, when needed. In order to reduce the use of fungicides to an absolute minimum, the use of disease resistant cultivars and various cultural practices must be strongly emphasized.

Identifying and Understanding the Major Blueberry Diseases

It is important for growers to be able to recognize the major blueberry diseases. Proper disease identification is critical to making the correct disease management decisions. In addition, growers should develop a basic understanding of pathogen biology and disease cycles for the major blueberry diseases. The more you know about the disease, the better equipped you will be to make sound and effective management decisions.

The following literature contains color photographs of disease symptoms on blueberries, as well as information on pathogen biology and disease development.

Compendium of Blueberry and Cranberry Diseases - Published by the American Phytopathological Society, 3340 Pilot Knob Rd., St. Paul, Minnesota 55121. Phone: 612-454-7250 (1-800-328-7560). This is the most comprehensive book on blueberry diseases available. All commercial growers should have a copy. The following information gives a description of symptoms, causal organisms, and control of the most common blueberry diseases in the Midwest.

Highbush Blueberry Production Guide - This is a very comprehensive book covering most phases of blueberry production. It can be purchased from: Northeast Regional Agricultural Engineering Service, 152 Riley-Robb Hall, Cooperative Extension, Ithaca, NY 14853. Phone: 607-255-7654.