THE INFLUENCE OF THE NEMATODE MELOIDOGYNE-INCOGNITA ON COMPETITION BETWEEN SOLANUM-NIGRUM AND TOMATO

The effect of Meloidogyne incognita (Kofoid & White) Chitwood, 1949, o n the competitive relationship between tomato (Lycopersicon esculentum Mill.) and black nightshade (Solanum nigrum L.) was investigated unde r glasshouse conditions. Two intraspecific competition treatments were set up for the crop and the weed, and five interspecific treatments w here the emergence of S. nigrum plants was progressively delayed in re lation to tomato. Nematodes reproduced in all inoculated plants, their multiplication rates being much higher in tomato than in S. nigrum pl ants. Under nematode-free conditions, intraspecific competition of tom ato was more severe than the interspecific competition shown by the we ed S. nigrum. Tomato was a stronger competitor with S. nigrum than the weed was with itself. However, when infested by M. incognita, both sp ecies displayed a similar competitive ability. Tomato yield losses inc reased with prolonged weed competition but were greater under nematode -infested conditions.