Avoiding Celery Pests and Diseases

How to keep your celery healthy and strong!
Avoiding Celery Pests and Diseases

There are a number of diseases and pests that can potentially harm your celery crop. Luckily, there’s a fairly simple solution to avoid most of these issues: plant a less-vulnerable variety like Tall Utah.

Below, we've listed common diseases and pests, and what you can do to either avoid or fix the issue!


Bacterial blight: A disease causing small water-soaked spots to form on the leaves that are circular or angular in shape.

What to do: Make sure to space out your celery plants properly. As well, keep in mind that the most severe symptoms will happen when temperatures are above 85°F (30°C). Finally, you can reduce your risk of blight by planting less vulnerable varieties (like Tall Utah) and only trimming leaves when they’re dry. 

Soft rot: Small water-soaked lesions will form that become soft, sunken and brown. The bacteria for this disease will enter your plant through wounds (like tears in the stem), and it usually comes out when soil has been water-soaked for a long period of time.

What to do: Avoid soft rot by planting your celery in well-drained soil, allowing it to dry in between watering. Also, make sure it’s planted in its appropriate depth, because when you plant celery too deep, it can increase the disease and its severity. As well, try your best not to throw soil on your plants while cultivating.

Celery mosaic: The leaves may be twisted, curled or cupped, and young plants may be stunted. This virus is transmitted by several types of aphid pests, and symptoms usually develop within 10 days or so.

What to do: Prevent this disease by using insecticides against the aphids. Having a “celery-free” period of 1-3 months prior to planting is also helpful! Be sure to control the growth of weeds, though, as they can spread the virus to your celery.

Damping-off: A disease causing soft, rotted seeds that fail to germinate. The fungus can be spread three different ways, either in water, by contaminated soil, or on your equipment.

What to do: Avoid planting your celery in cool, poorly drained, wet soil. Instead, plant them in raised beds if possible, which will help with your soil drainage and can prevent a damping-off mishap. Also, if you reuse any pots or trays, be sure to clean them thoroughly before using them again!

Early blight: Small yellow spots will form on the upper and lower leaf surfaces, which then grow into brown-grey spots with a papery texture. Typically, this disease thrives in warm temperatures and high humidity.

What to do: You can avoid this disease by rotating your crops every year, and making sure you space out your celery plants properly. As well, certain oils and bacterial fungicides can also help to treat this disease.

Downy mildew: At first, this disease causes leaves to turn yellow, typically starting from the main vein then spreading outward. Fungal spores (ew!) will then grow on the undersides of leaves, appearing as gray to almost purple fuzzy spots. Downy mildew typically affects young, tender leaves.

What to do: Downy mildew is usually spread when leaves are wet for too long, so avoid overhead watering and space out your plants properly so that their leaves can dry. Also, you can plant disease-resistant varieties while rotating your celery with other crops. 

Late blight: You’ll notice black spots that look like peppercorns embedded in the leaf tissue. It becomes a problem when heavy rainfall and dense leaf canopies keep your plants from drying properly.

What to do: Avoid late blight by planting disease-free seeds, and make sure your celery is spaced out properly so that its leaves can dry out. If the disease is already present, you’ll want to remove and destroy your infected plants to keep it from spreading. 

Fusarium yellows: Yellowing plants that are severely stunted, with brown, water-soaked roots. This fungus can survive in your soil indefinitely once it’s there, and it’s usually introduced by infected transplants or contaminated equipment

What to do: Make sure to regularly sanitize your tools, plant your celery in disease-free soil, and plant tolerant or resistant varieties when possible.

Pink rot: Soft brown lesions on the base of celery stalks that cause the surrounding area to turn pink. Later, large black spots will develop on the infected spot. Typically, pink rot is caused by soil that’s been heavily wet for more than two weeks.

What to do: Drip watering is a good way to control your plants’ moisture level, avoiding pink rot in the process As well, plowing and mulching your soil promotes air circulation to fight against this fungus.

Powdery mildew: White patches that start on older leaves and eventually spread to other plant parts. It’s brought on by high humidity and moderate temperatures, with symptoms becoming most severe in shaded areas.

What to do: Avoid this disease by planting resistant varieties, and water your plants early so that they have time to dry during the day. You can also apply 1 tablespoon of baking soda with 2.5 tablespoons horticultural oil each week, or you can use a compost tea (one part finished compost with six parts water).



Armyworm: Larvae that heavily feed on leaves, turning them into “skeleton” leaves. These pests are most active in the early morning and the late evening, which are the best times to check for damage.

What to do: You can use natural enemies like wasps and flies to help keep this pest in check. Also, if you’re using insecticides, it’s best to do so in the twilight hours. This is when it will be the most effective!

Aphids: Usually green or yellow, but they can also be pink, brown, black or red. A heavy infestation may cause your celery leaves to appear yellow and distorted. Sooty mold can also develop as a result of the sugary/sticky substance they leave behind.

What to do: You can use insecticides and oils when you have a heavy infestation, which are usually your best method for control. You can also use a garden hose to spray them off of your stronger plants. 

Nematodes: Microscopic worms that live in soil and plant tissue. They stunt your celery’s growth, and cause galls (swelling growths)
to form on the roots. Because of their wide host range, it’s difficult to manage this disease sufficiently.

What to do: Avoid spreading nematodes by thoroughly cleaning your equipment and not moving any infected soil. As well, you can rotate with non-infested crops. Just be sure to remove and destroy any plants that have been affected.

Black heart: This disease appears as black spots in the middle of the plant, and the damage typically isn’t visible until later in the season. Black heart is a nutrient imbalance that’s caused by a calcium deficiency

What to do: Apply calcium rich fertilizers to your soil, and make sure you keep your celery well-watered.


If you're having an issue with your celery that wasn't listed above, be sure to let us know! Send us a message so that we can help your plants thrive :)

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Posted 1 month ago