By Carl Wilson, horticulture agent, Colorado State University Cooperative Extension, Denver
Tan blotches on spinach leaves may be a sign of insect damage caused by spinach leaf miner. The immature maggot stage burrows within leaves of spinach, beets and chard, causing blotchy dead patches. The remainder of the leaf is edible.
This insect overwinters in the soil, emerging in midspring. It flies to young plants and lays white egg masses on the undersides of leaves. The maggot hatches to tunnel into the leaves for two to three weeks before dropping to the ground to pupate.
If you plant your spinach in a new area where leaf miners won't be emerging from the ground, use floating row cover fabric to cover your plants and exclude adult flies. Regularly inspect leaves for egg masses on the undersides and crush any you find before they hatch.
If you find larvae tunneling within the leaves, pick and destroy the leaves because insects will continue to live there. Very early spring plantings and fall plantings tend to escape damage.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010