Safe Ways to Kill Mealybugs in the Soil

Pyrethrins

• Pyrethrins are toxic chemicals found in pyrethrum daisies that are natural insecticides. Pyrethrin products kill a broad range of insects, including beneficial insects, by poisoning the insect's nervous system. Pyrethrins break down easily in direct sunlight and are more effective in temperatures below 80 degrees Fahrenheit. Pyrethrins are considered an organic method of garden insect control, but its synthetic, more powerful cousin pyrethroid is not.

Neem OIl

• The neem tree produces seeds that contain azadirachtin, a chemical that is toxic to several insects including root mealybugs. Neem has systemic properties, which means the plant absorbs the neem properties through its roots and leaves so that it permeates the plant tissues. When mealybugs try to suck the plant's sap, it becomes unpalatable. And if the root mealybugs continue to feed on the roots, they become deformed and unable to reproduce. Neem oil is nontoxic to humans and mammals, and its effect on some beneficial insects like honeybees, spiders and butterflies is usually minimal. Purchase 100 percent, unrefined neem oil from garden stores and follow the label's application instructions. Neem oil compounds break down quickly, especially in direct sunlight, so repeat applications once a week may be necessary.

Beauveria Bassiana

• Beauveria bassiana is a fungal pathogen of insects that naturally occurs in the soil and makes a few insects sick each season. It's sold in garden stores as an insecticide and is used for a wide range of insects like root mealybugs. However, use B. bassiana only on infested plants because it also kills beneficial insects like earthworms.

Nematodes

• The mention of nematodes may give some gardeners visions of of the root-knot pests that cause damage to plant roots. But certain species of nematodes such as Steinernema carpocapsae and Heterorhabditis heliothidis are welcomed garden allies. The parasitic predators aggressively seek out soil-dwelling insects like root mealybugs and enter the pests' bodies through their mouth or other natural openings. Once inside, the nematode sheds its protective cuticle, releasing an intestinal bacterium that paralyzes and kills the mealybug within 24 to 48 hours. The nematode seals up its protective cuticle and continues its search for its next host. Nematodes subsist in the soil and continue this process for up to a year if moisture and temperature levels remain favorable. Beneficial nematodes are available for purchase at many local garden supply shops.