Greenhouse Tests with Nematocides for Control of Nematodes Attacking Tomato (Lycopersicon esculentum var. Rutgers) in Puerto Rico

Abstract

It has been found that, in Puerto Rico, tomatoes are severely attacked by several species of plant parasitic nematodes and particularly by Meloidogyne incognita (the root-knot nematode) and Rotylenchulus reniformis, the reniform or kidney-shaped nematode. Several experiments were conducted to determine the efficacy of different nematocides against these pests. The last experiment conducted in the greenhouse using eight different nematocides and one of the most susceptible tomato varieties, Rutgers, is discussed. Evidence presented in the form of graphs and tables demonstrates that at least the four fumigants D-D, Dorlone, EDB, and Nemagon are effective in the control of both species of nematodes mentioned. Two compounds, Telone and Fumazone, although not completely effective against root knot, gave a perfect control of the reniform nematodes. Dorlone was superior to all other nematocides, giving the best results in relation to growth, weight of stem, yield, and general appearance of the plants. It also gave perfect control of the reniform and root-knot nematodes. The difference in height of plants over the control was statistically significant at the 5-percent level with EDB and at the 1-percent level with Dorlone and Nemagon. There was no significant statistical difference among the chemicals tested nor between the rest of the chemicals and the control. The severity of root-knot infection varied from degree 0, no infection, to degree 5, very high infection. Root knot was outstanding in the control plants, which showed a very high infection average of degree 5 for galling. At time of harvesting the plants were smaller than those under all the other treatments, but exhibited very little chlorosis and yellowing. In previous trials symptoms developed to a maximum only after blooming or the first picking of fruits. Blooming was retarded, which was shown by the small amount and weight of fruits. A very heavy gall and secondary root-formation was observed. Dorlone gave the best results and showed no phytotoxic effects. Similar observations have been made in field experiments. Phytotoxicity was shown by treatments with Nemagon, EDB, and DCB-60. This condition can be avoided using a lower dosage of the first two nematocides. DCB-60 proved to be ineffective.