Influence of Light and Temperature on Metribuzin Phytotoxicity to Tomato

Growth-chamber studies were conducted to identify the light and temperature factors associated with metribuzin (4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)one) injury to tomatoes (Lycopersicon esculentum Mill.). Plants exposed to 4 days of low light (6,500 lx) were more susceptible to metribuzin injury than those grown in high light (22,000 lx). Injury to tomatoes was greatest under conditions of low light prior to and high light after application of metribuzin to the foliage. Every increase in temperature from 21 C days and 13 C nights, to 25 C days and 18 C nights, to 27 C days and 18 C nights resulted in increased metribuzin injury to tomato.