Effect of Green Brassica Manure and Brassica Defatted Seed Meals in Combination with Grafting and Soil Solarization against Verticillium Wilt of Eggplant and Fusarium Wilt of Lettuce and Basil

The biocidal activity of Brassica green manure is linked to the presence of the glucosinolate-myrosinase system in the plant and to its capacity after incorporation to release in soil a number of biologically active compounds, including isothiocyanates, nitriles, epithionitriles and thiocyanates. In recent years, several tests have shown a potentially wide biocidal effect against soilborne pests and diseases such as nematodes and fungi. This paper reports data collected from a first set of trials carried out in Liguria (northern Italy) to test the efficacy of a biofumigant green manure of Brassica juncea selection ISCI20 (Cerealtoscana-Italy) in combination with grafting and soil mulching. The same experimental design was adopted during three years in a naturally infested soil with Verticillium dahliae. In May 2004, 2005 and 2006, B. juncea at blooming time was chopped and incorporated into the soil. Some plots were then mulched with a clear plastic film. After 25-30 days of mulching, mulched plots were uncovered and grafted eggplants ('Prosperosa') were transplanted at 2 plants m(-2). Severe infections of V. dahliae were recorded in control plots, and in plots without plastic mulch. Soil mulching alone and biofumigation alone provided only partial results. In contrast, treated and mulched plots showed a significant reduction of disease incidence, particularly in 2005 and 2006. The combination of biofumigation and grafting on resistant rootstocks provided the best results. A second set of trials was carried out during the years 2005 and 2006 in plots in order to evaluate the effectiveness of soil application of biofumigant pellets based on a patented formulation of Brassica carinata defatted seed meals, combined or not with a simulation of soil solarization (carried out by heating the soil at 45 +/- 2 degrees C for 7, 14, 21 days) against Fusarium wilt of lettuce and basil. Biofumigant defatted seed meals alone, applied at 2 or 4 g L-1 of soil, partially reduced the disease incidence. Simulated solarization carried out for 3 weeks confirmed a very good efficacy. The combination of Brassica defatted seed meals and 1-2 weeks of solarization provided very good results against both Fusarium oxysporum f. sp. lactucae and Fusarium oxysporum f. sp. basilici.