Ask an Expert: Fall ornamental pest management
Q: What are best practices for tackling ornamental pests such as fungus gnats, thrips and whiteflies?
A: Fungus gnat control begins with cultural activities to prevent the potential for larvae. Greenhouse sanitation, watering practices and media selection are critical, and should this fail, use chemical treatments that target fungus gnats in their two vulnerable stages: immature and adult. Control is made simple by drench or spray application to the media.
Thrips control is more difficult due to their ability to grow from egg to adult within one week and remain an active adult for more than one month. No known insecticide is effective on the pupal stage, so if you missed the larva by not using a translaminar insecticide as a spray, you’ll have to try to control the winged adult.
Regarding whiteflies, cultural activities and sanitation are also critical. Inspect all plant materials from propagators, and monitor each pest using sticky cards at plant level on benches. Remember that the egg stage and non-feeding pupae stages will not be controlled with pesticides—only the feeding larval stage and adult stage are controllable.