The nematicide activity of aqueous extracts of Wedelia (Sphagneticola trilobata), tridax daisy (Tridax procumbens), marigold (Tagetes patula), Mexican sunflower (Tithonia diversifolia), "botão de ouro" (Unxia suffruticosa) and Peruvian zinnia (Zinnia peruviana) was studied in vitro and in vivo on Meloidogyne incognita. The extracts were prepared at a ratio of 1.0 g of dry and crushed material to 10 ml of distilled water, stored for 24 hours, and then used in the experiments. In in vitro tests, 4.0 mL of crude extract and 2.0 ml of an aqueous suspension containing 200 nematode eggs were deposited on Petri plates of 5cm diameter and, fifteen days later, the number of hatched juveniles and the remaining eggs were counted to calculate the percentages of hatching. In in vivo tests, the extracts were separately applied by leaf spraying, root treatment and pouring onto the soil, weekly for 60 days. As control, only water was used in both experiments. The in vitro test showed that all extracts were effective in reducing the hatching of juveniles of M. incognita when compared to the control; the reduction percentages were 89.96%, 91.13%, 92.48%, 92.72%, 93.2% and 97.48% for tridax daisy, marigold, Mexican sunflower, Wedelia, "botão de ouro" and Peruvian zinnia, respectively, while in the in vivo assay, treatments did not have any effect on the root system weight of tomato plants; however, results differed between the used species and the way of application of the extract in the evaluation of the fresh weight of shoots. As to the reproduction rate, none of the extracts showed a statistical difference, compared to control; however, comparing the different ways of application, there was statistical difference when the extracts of tridax daisy and Mexican sunflower were applied through leaf spraying and root treatment, but there was no difference when these extracts were applied as irrigation on the soil.
antagonistic plant; root-knot nematodes; plant extracts
