Leaf Miners in Garden Spinach Leaves

Identification

• Spinach leaf miners are the larva of the spinach leaf miner fly, a small gray fly that emerges in spring. The fly lays clusters of white eggs on the undersides of spinach, beet and chard leaves. The larva emerge as white maggots that tunnel into the leaves to feed. They remain inside the plants for several weeks before dropping to the soil to pupate. The whole life cycle takes 30 to 40 days. Spinach leaf miners may produce three to four generations in one season.

Damage

• Initially, the spinach leaf miner may produce small blotchy marks on leaves. Later, the damage spreads to include tunneling marks or large blotches. Infected leaves are unappealing to eat and dry out and die.

Prevention

• Spinach leaf miners are a larger problem when grown year-round through the use of cold frames or hoop tunnels. To prevent spinach leaf miners, rotate the location of spinach crops annually and remove weeds and plant debris that serve as shelter for the insects. Till the soil in fall or early spring to kill any overwintering pupae.

Treatment

• Set floating row covers over spinach crops after planting to prevent spinach leaf miner flies from laying eggs on spinach plants. Keep in mind, though, that floating row covers will not prevent damage from pupae emerging from the soil. Scout for eggs in mid to late spring, by looking under the leaves. Hand-pick and crush any eggs you find. Pick and destroy any leaves that show evidence of leaf miner damage so the insects can't complete their life cycle.