Optimizing control of lettuce aphid, Nasonovia ribis-nigris, through improved insecticide placement

The lettuce aphid, Nasonovia ribisnigri, is a major pest for lettuce growers throughout the western United States.  A field study on head lettuce was undertaken to investigate the impact on efficacy of four chemical pesticides (spirotetramat, tolfenpyrad, pyrifluquirazon, and acetamiprid), and utilizing three different application modes: tray drench before transplanting, soil drench (band/drench) before transplanting, and foliar after transplanting.  All pesticides had high efficacy against nymph stages of the aphid, up to 20 days after planting.  Tray drench of spirotetramat and pyrifluquirazon before transplanting showed the greatest efficacy compared to other pesticides and application modes.  A weighted average count of insects per day indicated that a foliar application of spirotetramat, and tray drench application of either spirotetramat or pyrifluquirazon had high significant efficacy against nymphal aphids.  These results indicate that tray drench application shows better control of N. ribisnigri in lettuce compared to a foliar or soil drench application.