EFFECT OF COLORED MULCHES ON ROOT-KNOT OF TOMATO

The effect of different colored polyethylene mulches on quantity and spectra of reflected light, plant morphology, and root-knot disease was studied in field grown staked tomato (Lycopersicon esculentum). Spring versus fall experiments were conducted in 1987 and 1988 near Florence, South Carolina. Tomato plants were inoculated with Meloidogyne incognita at initial populations (Pi) of 0, 10, 50, 100, and 200 (X 10(3)) eggs per plant, and grown for 60 days over white, red, and black polyethylene mulch. White reflected more total light, more blue and a lower far-red to red ratio than red, whereas black reflected less than 5% of any color. Soil temperatures were warmer under black and red mulch than under white. Plants grown with white mulch had greater shoot, stem, and leaf weights, and leaf area than plants grown over black mulch (P less than or equal to 0.004). Plants grown with red mulch also had greater shoot, leaf, and stem weights, and leaf area, than plants grown over black mulch (P less than or equal to 0.068). Treatment interactions were observed for root weight (mulch color X Pi, P less than or equal to 0.001) and root-gall indices (season X mulch color X Pi, P less than or equal to 0.001). Reductions in shoot weights with increasing Pi coincided with increases in root weight. Linear and quadratic coefficients (absolute values) of the regressions (shoot and root weights on Pi), based on standardized data, were not different (P = 0.05) within each color. Although shoot and leaf biomass and leaf area varied among mulch colors, the relationship between biomass or area and Pi was described by quadratic equations for plants grown over white mulch and black mulch but not red mulch (P less than or equal to 0.057). The linear and quadratic coefficients of the equations (leaf area, leaf weight or stem weight on Pi) did not differ among tissues (P = 0.05) within a mulch color when calculations were based on stanadard values.