Hot Water as Insecticide? Research conducted by Dr. Robert McMahon (ATI, Wooster, OH), Milley Casey and Dr. Robin Taylor (OARDC, Wooster, OH) has shown that hot water drenches of 130F will effectively kill fungus gnat larvae infesting the soil of 'Riviera Red' New Guinea impatiens and 'Bright Freedom Red' poinsettias potted in 4.5" pots without harming the plants. Experiments were conducted with these two crops whereby there were replicates of five plants per treatment, including a tap water (60F) control, with hot water treatments ranging from 130F to 160F in five degree increments. Each pot received a 12 oz drench of hot water (or tap water for the control), followed by a 24 oz tap water drench 1 minute after treatment. The pots were then caged and emerging fungus gnat adults were counted (caught on sticky traps placed in the pots) for 30 to 45 days after treatment. Results showed that there was over 80% mortality of fungus gnat larvae for all hot water treatments, and there was no significant difference between treatments, as opposed to 0% mortality with the tap water control. New Guinea impatiens showed no hot water damage until the 150F treatment, whereas the poinsettias were damaged starting at the 135F treatment. Thus, 130F hot water drenches (heating media to 110F) killed fungus gnat larvae in root media, and was not harmful to plants. Such a pest control treatment shows great potential for an IPM program. For more information, contact Dr. Robert McMahon at: mcmahon.2@osu.edu