Why Are There Spots on Your Spinach Leaves?

Dark spots on your spinach leaves probably indicate a problem with pesky spinach leafminers

Credit: Farmer Jay

If you notice blotches on your spinach leaves, remove them right away

Q: All the leaves on my spinach have blotches. What is causing this problem?

Spinach leafminer (Pegomya hyoscyami) is an insect that at the immature-maggot stage tunnels through old leaves in plants like spinach, Swiss chard, beet, lamb quarters (weed) and other related weeds.

The insect then overwinters in the soil as a pupa. Adult flies emerge in midspring. They lay masses of white eggs on the undersides of old leaves. Once the eggs hatch, the young maggots tunnel into the leaf to feed for about two to three weeks until the larvae drop to the ground to pupate in the soil . . . and so on.

There are several generations per season. Most damage occurs during the cooler times of the year.

There are no sprays that are effective. Remove infested leaves when noticed and dispose into the garbage. Next season, try to rotate to a fresh plot. Cover plants with a polyester fibre to keep adult flies from laying eggs. If ground space is limited for proper rotation, try growing plants in pots.