Insect identification on collards and tomatoes
District of Columbia County District of Columbia
Hi- the flies are fungus gnats, flies that lay their eggs in organic matter. Larvae feed on fungi and plant roots. They are common in high humidity, high-temperature environments where the grow mix stays overly moist. You can look for the larvae in the top inch of your growing media. Let the top of your media dry a bit before watering. They are not considered a big problem and no controls are required. Fungus gnats can be brought into the home on infested plants but they are fairly ubiquitous in homes in our region.
The white insect is probably whitefly. (there are white aphids but usually only the females fly during mating. If they are aphids you will see two short "tail pipes" emerging from their backsides). Whitefly immatures sit on the plants, they don't fly. Adults fly off when disturbed. Whitefly can survive indoors year-year on housplants, herbs, and transplants. With climate change, they are probably overwintering outside in urban areas.
Yes, insecticidal soap will control whitefly. For a full description, prevention and control: