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Swiss Chard pests and diseases

Published: 09.04.2023
Pest/Disease Type Symptoms on Swiss chard Control/Prevention
Aphids Insect Curling, yellowing leaves, stunted growth Use insecticidal soap or neem oil, regularly inspect for infestations
Leaf Miner Insect White, winding tunnels on leaves Remove affected leaves, use insecticidal soap or neem oil, cover with row covers
Slugs and Snails Insect Holes in leaves, slime trails Handpick, use slug bait, keep garden clean and free from debris
Flea Beetles Insect Small holes in leaves, stunted growth Use row covers, vacuum up larvae, use insecticidal soap or neem oil
Root Maggots Insect Wilting, yellowing, stunted growth Use insecticidal soap or neem oil, cover with row covers, rotate crops
Downy Mildew Fungal Yellowing, stunted growth, white mold Remove affected leaves, use fungicides containing copper, improve air circulation
Powdery Mildew Fungal White, powdery coating on leaves Remove affected leaves, use fungicides containing sulfur or potassium bicarbonate, improve air circulation
Bacterial Leaf Spot Bacterial Brown or black spots on leaves, stunted growth Remove affected leaves, use copper-based fungicides, keep garden clean and free from debris
Verticillium Wilt Fungal Wilting, yellowing, stunted growth Remove affected plants, sterilize tools and soil, avoid planting susceptible crops in the same area
Clubroot Fungal Swollen roots, stunted growth, yellowing Use resistant cultivars, rotate crops, improve soil drainage and fertility.


Aphids are tiny, soft-bodied insects that suck sap from plants. They are common pests that can infest Swiss chard and other vegetables in your garden.


The first sign of an aphid infestation is distorted and curled leaves, as well as sticky honeydew on the leaves and stems. The leaves may also turn yellow and drop prematurely.

Control or Prevention:

The best way to prevent aphids is to keep your garden healthy and free of weeds. You can also use physical barriers like row covers to keep them away from your plants. Insecticidal soaps and neem oil sprays can also be effective in controlling aphids.

Another option is to introduce natural predators like ladybugs, lacewings, and parasitic wasps into your garden. These predators feed on aphids and can help keep their populations under control.

Regularly inspecting your Swiss chard plants for signs of aphid infestations can help you catch the problem early before it gets out of hand. With a little bit of effort, you can prevent and control aphids in your garden and keep your Swiss chard healthy and thriving.

Leaf Miner

Leaf miner is a common pest that attacks Swiss Chard and other leafy vegetables. These tiny insects lay eggs on the leaves, and when the larvae hatch, they burrow through the leaf tissue, creating tunnel-like mines. The damage caused by leaf miners can weaken the plant and make it more susceptible to other diseases and pests.


The most obvious symptom of leaf miner infestation is the presence of squiggly lines or trails on the leaves of Swiss Chard. These lines are actually tunnels created by the larvae as they feed on the leaf tissue. As the infestation progresses, the leaves may turn yellow, and the plant may start to wilt.

Control and Prevention

The best way to control leaf miners is to prevent them from infesting your garden in the first place. You can do this by practicing good garden hygiene, removing weeds and debris, and rotating your crops regularly. If you do notice leaf miners on your Swiss Chard, you can try removing the affected leaves or spraying the plant with an insecticide that is labeled for leaf miners.

Another effective way to prevent leaf miners is to cover your plants with a fine mesh netting. This will prevent adult leaf miners from laying their eggs on the leaves. Overall, with good prevention and control measures in place, you can keep your Swiss Chard healthy and free from pests like leaf miners.

Slugs and Snails

Slugs and snails are common pests that can wreak havoc on Swiss Chard plants. They are most active during damp and humid weather conditions, which is when they cause the most damage.


The most obvious symptom of slug and snail damage is irregular holes in the leaves of Swiss Chard plants. These holes may have a smooth edge, indicating the work of a slug, or a ragged edge, indicating the work of a snail. Additionally, slime trails on leaves and on the ground around plants may be visible.

Control or Prevention

To control or prevent slug and snail damage, it is important to keep the garden clean and free of debris where they can hide. Handpicking them off plants and using beer traps can also be effective. Copper tape around planters can deter slugs and snails from climbing up into the plants.

Another prevention method is to reduce moisture levels around plants by watering in the morning or early afternoon so that leaves have a chance to dry before nightfall. Applying diatomaceous earth or using iron phosphate baits can also help control slug and snail populations.

Overall, being vigilant and taking preventative measures can help keep these pesky pests at bay and ensure healthy Swiss Chard plants in your garden.

Flea Beetles: A Common Pest of Swiss Chard

Flea beetles are a common pest that can wreak havoc on your Swiss chard crop. These small, shiny beetles get their name from their ability to jump like fleas when disturbed. They are about 1/10 inch long and vary in color from black to brown or bronze.


Flea beetles feed on the leaves of Swiss chard plants, leaving small holes that can eventually cause the leaves to wilt and die. If left untreated, they can quickly cause significant damage to your crop.

Control or Prevention

There are several steps you can take to prevent and control flea beetles:

  • Row Covers: Covering your plants with row covers can prevent flea beetles from reaching your Swiss chard plants.
  • Natural Predators: Encouraging natural predators like ground beetles and parasitic wasps can help keep flea beetle populations in check.
  • Neem Oil: Neem oil is an effective natural insecticide that can be sprayed on your plants to control flea beetles.
  • Crop Rotation: Rotating your crops each year can help reduce the chances of flea beetle infestations.

By taking these preventative measures and monitoring your plants regularly, you can keep flea beetle damage under control and enjoy a healthy Swiss chard crop.

Root Maggots

Root maggots are a common pest that attacks the roots of many vegetable plants, including Swiss chard. These small, white, legless larvae are the offspring of the root maggot fly and can cause significant damage to the plants.

Symptoms: The first sign of root maggots is usually wilting or yellowing leaves, which can quickly progress to stunted growth and death of the plant. Upon closer inspection, you may notice small tunnels in the roots and the presence of small, white maggots.

Prevention and Control: To prevent root maggots, avoid planting Swiss chard in soil that has previously been used for cruciferous vegetables like cabbage or broccoli. You can also use row covers to prevent adult flies from laying eggs on your plants. If you notice signs of root maggots, try removing and destroying any affected plants and rotating crops in future seasons. You can also use beneficial nematodes or insecticidal soap to control the larvae.

Overall, the key to preventing and controlling root maggots is good garden hygiene and vigilance. By monitoring your plants regularly and taking proactive measures to prevent infestations, you can keep your Swiss chard healthy and thriving.

Downy Mildew

Downy mildew is a common fungal disease that affects Swiss chard and other leafy vegetables. It thrives in cool and moist weather conditions, making it a common problem for gardeners in the spring and fall seasons.

Symptoms: The first signs of downy mildew are yellowish or light green patches on the leaves, which later turn brown and die. A grayish mold growth appears on the underside of the leaves, while the upper side may have oily-looking spots. The plants may become stunted and produce fewer leaves than usual.

Control or Prevention: To control downy mildew, make sure you plant resistant varieties of Swiss chard. If you notice the symptoms of downy mildew, remove the affected leaves and destroy them immediately. Do not compost them as this will only spread the disease. Keep your garden clean and free from debris to prevent fungal spores from developing. Water your plants early in the day so that the leaves have time to dry before evening. A preventive measure against downy mildew is to apply fungicides early in the season.

By following these simple steps, you can prevent downy mildew from affecting your Swiss chard plants and enjoy a healthy harvest.

Powdery Mildew

Powdery mildew is a common fungal disease that affects many types of plants, including Swiss chard. The disease is easily recognizable by the powdery, white or grayish coating that appears on the leaves, stems, and flowers of infected plants.


The first signs of powdery mildew include small, circular white spots on the leaves of Swiss chard plants. As the disease progresses, the spots become larger and more numerous, eventually forming a powdery coating on the entire leaf surface. Infected leaves may also become yellow or brown and may eventually wither and die.

Control and Prevention

Preventing powdery mildew requires keeping the foliage dry and reducing humidity around plants. Avoid overhead watering, as this can promote the spread of the disease. Instead, water Swiss chard at the base of the plant to keep the leaves dry. Good air circulation around plants is also important for preventing powdery mildew.

To control powdery mildew, remove infected leaves as soon as possible to prevent further spread of the disease. Fungicidal sprays are also available to treat powdery mildew, but they should be used as a last resort and only if cultural controls fail to prevent the disease.

Bacterial Leaf Spot

Bacterial Leaf Spot is a common disease that affects Swiss chard plants. The disease is caused by the Xanthomonas campestris bacteria and can cause significant damage to the plant if left untreated.


The first sign of Bacterial Leaf Spot is the appearance of water-soaked lesions on the leaves. These lesions are typically dark green or black and can be circular or irregular in shape. As the disease progresses, the lesions will become larger and may merge together. Eventually, the affected leaves will turn yellow and die.

Control or Prevention

To prevent Bacterial Leaf Spot, it's important to practice good hygiene in the garden. This includes removing any infected plants, sanitizing gardening tools, and avoiding overhead watering. If your Swiss chard plants are already infected, there are several steps you can take to control the spread of the disease. These include removing infected leaves, applying copper-based fungicides, and improving air circulation around the plants.

Overall, Bacterial Leaf Spot is a serious threat to Swiss chard plants, but with proper prevention and control measures, it can be managed effectively. If you're a beginning gardener, it's important to stay vigilant for signs of this disease and take action as soon as possible to protect your plants.

Verticillium Wilt

Verticillium Wilt is a fungal disease that affects a wide range of plants, including Swiss chard. It is caused by the soil-borne fungus Verticillium dahliae, which invades the plant's vascular system and disrupts the flow of water and nutrients.


The symptoms of Verticillium Wilt in Swiss chard include yellowing and wilting of the leaves, starting at the bottom of the plant and progressing upwards. The veins of the affected leaves may turn brown or black, and the plant may eventually die. The fungus can survive in soil for several years, making it difficult to eradicate.

Control or Prevention

There are several steps you can take to control or prevent Verticillium Wilt in Swiss chard. First, make sure to plant resistant varieties if possible. Rotate your crops every year, avoiding planting susceptible plants in the same area for at least three years. Use sterilized soil and avoid overhead watering, which can spread the fungus. If you suspect an infection, remove and destroy affected plants, and do not compost them. Fungicides may also be effective in controlling the disease, but prevention is the best approach.

By taking these preventative measures, you can help ensure healthy Swiss chard plants and a successful garden.


Clubroot is a fungal disease that affects many plants in the Brassicaceae family, including Swiss chard. The fungus invades the roots of the plant, causing them to become swollen and distorted. This can lead to stunted growth, yellowing of the leaves, and eventually death of the plant.

Symptoms of clubroot usually appear in the later stages of plant development. The leaves may become pale or yellow and wilt easily, even with adequate watering. The roots of the plant will appear swollen and deformed, often with small bumps or nodules on them. If left untreated, clubroot can spread quickly through the soil and infect other plants in the garden.

To control or prevent clubroot, it is important to maintain good soil health. Avoid planting Brassicaceae crops in the same area year after year, as this can promote the buildup of fungal spores in the soil. Instead, rotate crops and consider adding organic matter to improve soil structure and drainage.

If you suspect clubroot is present in your garden, remove infected plants immediately and dispose of them in the trash (not compost). Fungicides may be used to help control the spread of the disease, but prevention is the best approach for long-term management.

Author: Michael Chen
Bio: I'm gardening specialist with a mission to empower people to grow their own fruits and vegetables. With my background in Plant Science from the University of California and experience working with farmers and community gardens, I'm dedicated to promoting sustainable agriculture practices and helping individuals achieve bountiful harvests. Let's get growing!