Efficacy of two phytonematicides as influenced by container type and positioning on growth of tomato plants and suppression of meloidogyne incognita

Thesis(M.Sc.(Plant Protection))-- University of Limpopo,2019

Previously, cucurbitacin-containing phytonematicides that were drench-applied in black plastic containers filled with pasteurised loam soil when placed on the soil surface had no effect on suppression of population densities of root-knot (Meloidogyne species) nematodes. The active ingredients of cucurbitacin-containing phytonematicides, namely, the cucurbitacins, had been shown to be thermophilic, with the failure of the products explained from the view of the variability induced by container-type and aboveground positioning. The view was investigated further using Nemarioc-AL and Nemafric-BL phytonematicides as influenced by container-type and positioning on growth of tomato (Solanum lycopersicum L.) plants and suppression of M. incognita population densities. Tomato cv. ′Floradade′ seedlings were transplanted into 30-cm-diameter brown pot belowground, brown pot aboveground, black pot belowground, black pot aboveground, 5 L polyethylene plastic bag belowground and 5 L polyethylene plastic bag aboveground, each containing 5-dm3 steam-pasteurised sandy loam soil amended with Hygromix at 3:1 (v/v) ratio. Seedlings were inoculated with 2000 eggs and second-stage juveniles (J2) of M. incognita race 2, with Nemarioc-AL and Nemafric-BL phytonematicides applied once 17 days after inoculation in both Experiment 1 and Experiment 2. Also, standard cultural practices were applied throughout the trial. At 56 days after inoculation, container-type and positioning had significant effects on various plant growth and essential nutrient element variables in Experiment 1 and Experiment 2, except that the six treatments did not have significant effects on nutrient elements and nematode population densities in Experiment 2. Relative to brown plastic pot belowground, treatments either increased or decreased plant growth, essential nutrient elements and nematode densities in Experiment 1, with selective similaritiesin Experiment 2. Specifically, nematode variables except for J2 in soil and total nematode population densities were significantly affected by the treatments in Experiment 2. Relative to the standard, plastic bag belowground increased J2 in soil and total population in soil by 18%. In conclusion, both container-type and positioning had effects on the efficacy of phytonematicides on plant growth, accumulation of essential nutrient elements and suppression of nematode population densities. Consequently, in trials where cucurbitacin-containing phytonematicides are conducted in microplots, brown plastic pots with the belowground positioning should be used to enhance the efficacy of the phytonematicides in stimulating plant growth and suppression of nematode population densities.