BIOLOGICAL CONTROL OF EARLY BLIGHT IN TOMATOES

Early blight is a limiting factor in production of organic tomato in semiarid climate regions. Control of this disease is crucial, because in the near future the treatment currently used, copper fungicide, wil be prohibited in organic cultivation, making it necessary to find an effective alternative.

Tomato plants inoculated in summer 1993 with A. solani were sprayed with 14-days old compost extract (CEX) prepared in a ratio of 1:5 compost to water (v/v). A significant reduction in desease index was observed in the CEX treated plants, as well as in the fungicide treatment, as compared with inoculated plants. The yield of CEX treated plants was significantly higher than in the inoculated ones. similarly to the fungicide treated plants.

In the summer of 1994, 7 and 14 day old were sprayed to tomato plants. Disease index in plants treated with either CEX or the fungicide was reduced as compared with the inoculated plants. Yield of these treatments was significantly improved: 20.9, 19.9 and 13.9% by fungicide treatment. 14-day old CEX and 7-day old CEX, respectively. Results of this study indicate that spraying the plants compost extracts similarly as to copper fungicide treatments reduced disease index and increased yield.