Spinach is a crop that can appeal to gardeners and a variety of insects and animals due to its quick germination (37 to 45 days) and ability to withstand a wide range of temperatures. It can be planted in both spring and fall and is exposed to pests that are dominant throughout the year. Scouting for problems and preventive measures are the best ways to keep pests from eating spinach in the garden.
The majority of pests that eat spinach are leaf-eating insects. Cutworms, cabbage loopers, corn earworms, snails, slugs and diamondback moth caterpillars are all common pests of spinach. Symptoms are irregularly shaped holes on either the leaf margins or in the middle of the leaves. In the case of cutworms, they will eat the spinach at the base of the plant by eating through the stem about 1/2 inch above ground level. Control can be achieved with organic controls such as neem oil, sucrose-water and other pesticides labelled for use on edible crops.
Aphids are a particular nuisance insect that can feed on spinach leaves by sucking the nutrients. Affected leaves will have a distorted and curled appearance. Leaf miners are another leaf pest that can attack spinach leaves from within. Natural predators such as the ladybug and praying mantis are effective against aphids. Leaf miners can be prevented by placing a fine netting over top of the spinach leaves and affected leaves should be picked off and destroyed.
There are some other causal factors that can appear to be pest-related but is not. Tip burn can be a problem that is caused by high temperatures and uneven watering. It causes the edges of spinach to deteriorate, which can appear as though the leaves are being eaten. Spinach can also contract cucumber mosaic virus, which appears as a leaf blight. Affected leaves should be removed. In severe cases, an organic fungicide can be applied.
Not all pests of spinach are insects or disease. Wildlife can be a pest, as well. Deer, gophers, rabbits and other four-legged mammals can eat spinach leaves. Exclusion is the best method to deter animals from eating spinach. A metal mesh fence partially buried will help to deter smaller and burrowing mammals. A taller fence such as a plastic mesh at least 7 feet tall can be erected to prevent deer from grazing on spinach.