Prevent Leaf Miners on Citrus Trees Organically

Description of the Insect

• Citrus leaf-miners are born of a 0.12 inch moth with silvery, iridescent wings and a brown and white body. There is a distinctive black dot on each wing tip. The moths are active from mid-summer through winter. They spend the daylight hours resting on the underside of leaves and cannot easily be seen. During the hours from dusk to early morning the larvae feed in shallow, meandering lines in the leaves. They molt four times over a 1 to 3 week period and have a life span of two to seven weeks. Citrus leaves become curled and distorted as the leaf-miners feed. Fruit yield is not affected by their unsightly presence.

Organic Citrus Care

• Healthy organic growing practices begin with the life of the soil. Plant the tree in garden loam and use backyard compost as fertilizer on the topsoil level. Do not plant the tree in compost because it impedes root growth into the surrounding soil. Dig a small basin around the tree several feet from the trunk to catch water during irrigation. Fill the basin with water several times after planting to settle the soil and remove any air pockets. Young citrus trees do not extract or deplete soil moisture until they have achieved several inches of new growth,

Preventative Measures

• Chickadee, robin, purple finch, ladybugs and lacewings are natural predators for leaf-miners. Parasitic wasps also help control leaf-miners on citrus trees. Beneficial wasps are attracted to the garden by members of the carrot family (Apiaceae), such as angelica, chervil, fennel, dill, and cilantro. The mint family (Lamiaceae) and the aster family (Asteraceae) of plants also attract the parasitic wasps that feed on leaf-miners. Weeds such as dock and lambs quarter are used as trap plants which attract the insects away from citrus trees. Leaf-miners lay their eggs in clusters on the underside of leaves where they can easily be squashed or the leaves removed entirely.

Horticultural Oils

• Mineral oil, vegetable oil and neem seed oil are effective organic sprays that help control leaf-miners. Cottonseed oil is the most insecticidal of the horticultural oils. They are sprayed on the tree as new growth begins and leaf-miners begin to feed. Oils work by blocking the air holes of the insect or by interfering with its normal metabolism to cause death. Horticultural oil should be sprayed when conditions are dry and temperatures are below 100 degrees Fahrenheit.