Efficacy of garlic straw application against root-knot nematodes on tomato

Highlight
• Garlic straw significantly decreased the immobility, mortality and hatching of M. incognita in vitro.
• Application of garlic straw could reduce the infection of M. incognita in tomato.
• Garlic straw pre-application combined with manure and plastic film mulch was a feasible method for nematode control in tomato production.
• Nematicidal activity of garlic straw might be due to sulfur-containing substances.

Toxicity of garlic straw to Meloidogyne incognita under lab conditions and pots of tomato was studied. Results indicated that the immobility and mortality of M. incognita juveniles were significantly increased with increasing water extract concentrations of 1%, 2% and 4% (w/v) raw garlic straw, and hatchability was significantly inhibited by application of the extract. 2% fermenting garlic straw increased mortality of M. incognita rate from 9.8% to 36.6% when compared with 2% raw garlic straw in different treatment time. While the effect of fermented garlic straw was greatly lower in toxic activity, about 11.4–49.4% lower in mortality of M. incognita in different treatment time. Pot trials also showed that M. incognita infestation of tomato roots was dramatically reduced with increasing volume of raw garlic straw application, however, higher concentration also inhibited the tomato plant growth, this might be due to the allelopathy compounds from garlic straw. Based on the analysis of above results, 2% raw garlic straw was chosen to combine with plastic film covering and rabbit manure, and it was obtained that the combinations of 2% raw garlic straw application before planting, animal manures and plastic film covering are an effective method in both inhibiting M. incognita incidence and increasing yield of tomato, which could decrease 72.39% in galling index (GI) and increase 72.64% in tomato yield when compared with control treatment. To make clear possible mechanism of garlic straw protecting tomato from M. incognita infestation, GC–MS were used to investigate the compounds constituents, and sulfur-containing compounds mainly accounted for the constituents and they might be responsible for the inhibition of M. incognita.