Swiss chard (Beta vulgaris subsp. cicla) is a cool-season garden crop prized for its large and colorful foliage, enjoyed for its flavor and nutritional value as well as for its ornamental contribution to a vegetable garden. A handful of different pests may occasionally threaten the appearance and vigor of a Swiss chard plant.
Aphids are small, soft-bodied, pear-shaped insects that use slender mouthparts to pierce plant tissue and feed on fluids, causing leaf curling, yellowing and distortion and stunting plant growth. Aphids also excrete a sugary substance, honeydew, that looks shiny, hosts sooty mold fungal growth and attracts ants. Regularly spraying the Swiss chard with a forceful stream of water will knock these weak fliers off of the chard while also rinsing honeydew off the leaves. Avoid excessive nitrogen fertilizer applications, which stimulate a flush of tender new growth particularly attractive to aphids, and consider covering seedlings with row covers or fine netting until they have a few leaves.
Flea beetle damage on a Swiss chard plant appears as small pits or holes where they feed on leaf undersides. The flea beetle adult is a small, shiny beetle about 1/10 inch long that jumps when disturbed. Large, established plants with at least about five true leaves can tolerate feeding, with their lowest, older leaves taking the brunt of the damage, but flea beetles can stunt or even kill seedlings. To avoid serious problems, till plant residue into the soil at the end of the growing season and keep the garden and surrounding area free of weeds that can harbor this pest.
Leafminers on chard are the larvae of small black and yellow flies in the genus Liriomyza. These larvae feed between leaf surfaces, creating white, twisting trails or mines where they feed. To avoid problems with leafminer, practice crop rotation, cover seedlings with row covers or protective netting until they develop several leaves, and keep the area free of weeds. Where leafminers do attack the chard, cut out infested portions of leaves while the larvae are still inside and destroy that portion of the leaf. You can still use the remainder of the leaf.
Other Possible Pests
A few additional pests may occasionally plague Swiss chard but do not generally cause serious problems unless they attack seedlings. Slugs chew holes in leaves and deposit silvery trails of dried mucus. Cutworms and loopers are the larvae of moths. Feeding by these pests can cut seedlings off near the soil line or leave notched edges or holes on the leaves of older plants. Physically removing these chewing, sometimes nocturnal, pests is often the most efficient treatment. Keep nearby areas free of debris and weeds that can harbor these pests.
- Utah State University Cooperative Extension: Swiss Chard in the Garden
- University of California Statewide Integrated Pest Management Program: Flea Beetles
- University of California Statewide Integrated Pest Management Program: Leafminers—Liriomyza spp.
- Jefferson Farm and Gardens: Swiss Chard
- Washington State University Extension: Common Insect and Mite: Cutworms and Loopers
- Photo Credit Digital Vision./Photodisc/Getty Images