3. Hot temperatures also influence performance for some common insecticides. Even though some insects thrive in the heat, products to control them may not. Pyrethroids (including deltamethrin and permethrin) perform better at temperatures below 25°C. Some companies specify this in product recommendations. Research (Harris and Kinoshita, 1977) showed that permethrin on flea beetles was ________ potent at 15°C than it was at 32°C. (Fill in the blank.)