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Recycle A to Z

alternatives to pesticides - bugs/pests - leaf miners

leaf miner                  leaf miner damage
Actual size: Larva 1/4”                               Leaf miner damage
                    Adult 1/10”

Leaf miners are insects that tunnel between the upper and lower surfaces of leaves. Hatching larvae will tunnel through mid-leaf tissue, feeding as they go, and leave characteristic wavy lines that are visible on the top of the leaf. When ready to pupate, the larvae leave the leaf and drop to the soil, emerging in 10 to 15 days as adult flies. A certain amount of tunneling can usually be tolerated, but the damage is especially troublesome on spinach, chard and sometimes beets since these plants are grown in order to harvest the leaves.

Prevention
Covering - Covering the vegetable crop with a floating row cover for the entire life of the plants can be extremely effective.
Planting - Fall-sown crops are less susceptible. Move plantings at least several feet away from where you planted last year.

Physical control
Pick Off and Destroy - For small infestations, pick off and destroy the affected leaves.
Scratch Off - Scratch the small white egg clusters from the backs of the leaves with your fingernail.
Sticky Traps - In enclosed areas such as greenhouses, use yellow sticky traps to catch adults.
Plastic Mulch - Plastic mulches prevent leaf miner larvae from reaching the soil to pupate.

Biological control
Beneficial Predators - Encourage beneficial predators such as lacewings and spiders for egg and adult control. Other natural enemies include ants, true bugs, flies and birds. Parasitic wasps are able to attack the larvae through the leaf.

Least-toxic chemical control
Neem Oil - Neem oil operates as a repellent to adult leaf miners and as a systemic insect growth regulator on larvae.  Neem is a relatively new botanical insecticide derived from a tree. This product is reported to be very effective, with slightly more staying power than some other botanical insecticides. It does, however, break down completely and is less toxic to humans than some botanicals.
Horticultural Oils - Recent studies also indicate that horticultural oils (not dormant oils) may work against leaf miner eggs, but timing the spray is crucial.  Horticultural oils are also called summer oils; these are more highly refined than dormant oils, making them appropriate for use on leaves during the growing season.  Consult a nursery to locate a suitable product and follow all precautions. Don’t use horticultural oils when plants are flowering.

 

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