If you're in a warmer climate, beneficial nematodes are most effective in the summer. In any case, if you're unsure of when to apply beneficial nematodes, call your Extension service. Find out when and for how long the soil-dwelling stage of the target insect will be present and plan your nematode application for that time. Moisture Beneficial nematodes move in water-filled spaces between particles of soil. If the soil is too dry or too tight, they are not able to move and search out host insects.
Commercial suppliers recommend watering the insect-infested area before applying nematodes.
An additional sprinkling after releasing the nematodes will help rinse them off plants and grass into the soil. Ultraviolet Light Exposure to ultraviolet light or extreme temperatures can kill nematodes. During the warmer summer months, apply nematodes in the early evening, when the intensity of light is reduced and soil temperature is lower. Remember, watering your lawn before application will lower the soil temperature. For the typical garden, nematodes will take about two to three weeks to show results.