Do Aphids Overwinter?
Q: I grow kale in a raised bed. Last year it got covered (smothered) in aphids. After using Neem oil spray on it for a month, I decided to just pull the darn things completely out (sad face). Will the aphids be in the soil again this year? If I plant anything in the area where kale was will it get aphids too? Thanks in advance.
A: Cabbage aphid feeds happily on kale, cabbage, broccoli, cauliflower, kohlrabi, and any other plants in the cabbage family. You may not be able to eradicate them completely but you can keep them to a tolerable minimum. The aphid makes the vegetables very unappealing to eat.
Cabbage aphid does seem to gain momentum from year to year. This is often a factor of the number of eggs and/or nymphs that are overwintering in or near the garden. The eggs or nymphs can survive on leaves or stems of leftover kale, broccoli, cabbage, or other members of the brassica family. Mustard weeds and other weeds can be overwintering hosts. Eliminate all crop residue and weeds carefully in the fall. The aphid eggs hatch in April so you should be sure that any crop residue is turned under, composted, or disposed of before the hatching stage. Oils, soaps, and organic pesticides may all work to control cabbage aphid but I've found that neem oil combined WITH insecticidal soap works better than either alone. Monitor and spray regularly from the beginning of the crop. Monitor weekly to keep ahead of the aphid population. Another effective way to minimize both cabbage aphid and cabbageworm is to grow your crops under row-cover cloth from the very beginning. Monitor and spray transplants if necessary (or prophylactically) before setting them in the ground and using the row cover material. Seeds germinating from the ground will naturally be aphid-free. Leave the row cover on all season. Cabbage aphid infestation is generally worse in the fall. Row cover cloth and support systems may be available from local garden suppliers or from online vendors. It's also quite useful in preventing psyllids, aphids, whiteflies, caterpillars, and most other invading insects on most vegetables. Lastly, applying predatory insects such as ladybugs (beetles), aphid wasps, or lacewing larvae can be very useful. These insects can predate hundreds of aphids per day. Try using them in combination with row cover cloth to keep the predators in, and the aphids out!