Effectiveness of compost extracts as disease suppressants in fresh market crops in BC

One of the major challenges facing organic producers is disease management. The losses in vegetable production due to disease can be significant and in some, cases, can devastate entire crops. Cultural methods of disease  control are commonly used on organic farms. The application of organic chemicals for disease control is often a
last resort and regulated while biological control is still not readily available. The use of compost extracts, then, presents a simple, inexpensive and potentially effective method to supplement the on-farm disease management program.
The effectiveness of using composts for disease control, particularly against fungal pathogens, has been studied extensively (Weltzein, 1991;Grobe, 1997; reviewed in Hoitink et al., 1997). Composts of various kinds have been used to reduce the incidence of Pythium and Rhizoctonia in a variety of vegetables and fruits
(Gottschall et al., 1987; Weltzien and Ketterer, 1986). These results have led to further work using filtered extracts of composts. In some cases, the compost extracts were even more effective in controlling disease than conventional pesticides (Weltzien et al., 1987). Stindt and Weltzien (1988) at the University of Bonn achieved effective control of Botrytis cinerea in strawberries as well as blight in potatoes. Similarly, powdery mildew and root rot were significantly reduced in peas and beets in other trials in Germany (Thom and Moller, 1988). The results of studies on compost extracts have been variable and seem to be crop and region specific, amongst other
factors. Therefore, a study was undertaken to look at the effectiveness of disease control with compost extracts on some cash crops in the Southern Interior of British Columbia.
Project Objectives:
1. To determine which compost extract is more effective in reducing disease in strawberries, lettuce, broccoli
and leeks
2. To identify the point at which application of the compost extracts are more effective