Home gardeners often find insects feeding on the roots of their vegetables, shrubs and flowers. Some plants die from insect infestations and root feeding while others merely suffer from reduced vigour and poor appearance. Properly identifying insects in your garden can help reduce infestations and keep your plants healthy.
Root maggots often damage vegetable plants such as cabbage, radishes, turnips, rutabagas and onions. This root feeding pest is the larval form of flies, which resemble the common housefly. Root maggots live in the soil and are white grubs that typically measure 1/3 inches in length. Adult flies lay their eggs at the base of plants and after hatching, the root maggot eats its way down the plant to the roots. Another common root feeding insect is the larval form of the Japanese beetle. These white, C-shaped grubs live in the soil and feed on plant roots for approximately 10 months before turning into the adult Japanese beetle. Japanese beetle larvae often feed on vegetables, lawn grass and young plant seedlings.
Root maggot feeding destroys the entire root system of plants, eventually causing the plant to die. Vegetable plants often develop sudden yellowing and wilting. Brown scars and tunnelling injuries are visible on the roots of plants infested with root maggots. Eventually, the root system is destroyed and the plant dies. Young seedlings are at an increased risk of root maggot infestation. Japanese beetle larvae live in the soil around infested plants. While adult Japanese beetles feed on the green foliage and flowers of the plant, the larva feeds underground on plant roots. Many plants infested with Japanese beetles do not survive heavy infestations.
Taking precautionary measures can prevent your plants from being attacked by root maggots. Keeping the adult fly from laying her eggs is the key to controlling root maggots. Placing collars around your plants when they are young seedlings is one way to avoid root maggot infestations. Barriers such as agricultural fleece and rock phosphate may help prevent root maggots, as well. Japanese beetles are often difficult to control. Hand-pick adult Japanese beetles from host plants to reduce their numbers. After removing the beetles, place them in a bucket of soapy water to kill them. Alternatively, flick or shake the beetles directly off the leaves into a bucket that you hold under the leaf. You only need a few inches of soapy water in the bucket; more will make it too hard to carry.
Making a lime-drench solution often helps reduce root maggot infestations. According to the Missouri Botanical Garden, a lime-drench solution contains 1 cup lime and 1 quart water. Mix the water and lime together and allow to soak overnight. The next day, pour the clear water from the top of the solution and place it around the base of your vegetable plants. Japanese beetle larvae usually require soil drenches available at your local garden supply centre for control. Japanese beetle traps are not recommended, as they usually bring more adult beetles into the area to lay eggs.