Aqueous Extracts of Organic Mulch Materials Have Nematicide and Repellent Effect on Infective Juveniles: A Laboratory Study.

While the nematicidal effectiveness of mulching against root-knot nematodes ( spp.) is calculated within organic crop protection, underlying mechanisms are not yet fully explored. Laboratory experiments were set up to determine whether mulch-derived substances cause mortality directly, or repel juveniles from crop rhizosphere. Mortality and area choice tests were conducted with mulch-derived extracts, supported by the measurements on tannic acid content and the pH values of extracts as supplementary examinations. In our study, leaf litter and straw extracts were generally found lethal to the juveniles, which is in line with the results from area preference tests. However, compost extract had no effect on juveniles. Tannic acid content showed positive correlation with mortality only in the case of straw and sycamore leaf litter extracts. Tannic acid and pH weakly correlated with repellent effect of the applied extracts generally. Our results have inspired further experiments to explore nematicidal components of leaf litters, contributing to the development of a new approach in crop protection based on the repellent effect of these materials.