Whitefly does not overwinter in the soil so putting anything down now will not be effective. The best strategy is to prevent a breakout by not planting species prone to attract them. Remove all plants that have served as a host and find alternatives. Come spring, be vigilant about removing any foliage that does become infected; hose down plants with water sprays (whitefly likes dusty conditions). Laying down a reflective mulch of silver polyethylene can help to reduce populations, as can yellow sticky traps and insecticidal soaps or oils. The main thing is to get ahead of those pesky flies—once they arrive, they are very tough to get rid of!
Whitefly does not overwinter in the soil so putting anything down now will not be effective. The best strategy is to prevent a breakout by not planting species prone to attract them. Remove all plants that have served as a host and find alternatives. Come spring, be vigilant about removing any foliage that does become infected; hose down plants with water sprays (whitefly likes dusty conditions). Laying down a reflective mulch of silver polyethylene can help to reduce populations, as can yellow sticky traps and insecticidal soaps or oils. The main thing is to get ahead of those pesky flies—once they arrive, they are very tough to get rid of!