Efficacy of wood vinegars for the control of Sclerotium rolfsii affecting tomato (Solanum lycopersicum L.)

Wood vinegar is claimed to be pesticidal by several researchers but its bioefficacy data on specific pests are lacking. This study evaluated 17 wood vinegars against S. rolfsii causing sclerotium wilt in tomato in vitro and in vivo. Eleven out of 17 wood vinegars showed direct inhibition to S. rolfsii at 2% concentration. These include wood vinegars from bamboo, banaba, cacao, caimito, ipil-ipil, lumboy, madre de cacao, malunggay, mango, panyawan and rice hull. These wood vinegars varied in their effectiveness in inhibiting the colony growth of S. rolfsii in vitro, with wood vinegar from ipil-pil showing the highest inhibition to the fungal growth followed by wood vinegar from lumboy. Wood vinegar from ipil-ipil however was the most phyto-toxic to tomato. The wood vinegar from lumboy, is promising since it was one of the most effective in reducing the disease severity in inoculated seedlings and was one of the least phyto-toxic. The wood vinegars from malunggay and panyawan, although not very effective in vitro were the most effective in reducing the disease severity in inoculated tomato plants and retained their effectiveness longer. Lower concentrations of the wood vinegars as a whole (0.2%) was the most effective in reducing sclerotium wilt severity over time, even though this concentration showed no direct inhibition to the fungus in vitro. This finding implies that wood vinegar may possess another mode of action in controlling the disease aside from the direct antifungal activity, which could be induction of resistance in plants to specific diseases.