A Guide to Pepper Plant Diseases

How to Fight Common Pepper Plant Pests and Diseases

A Guide to Pepper Plant Diseases

Hot, sweet, purple, yellow, wrinkly or bell – I love all peppers. If you find yourself wanting to harvest your peck of peppers, but are having trouble with plant blight, here are some troubleshooting solutions to fight pepper plant diseases.

Blossom End Rot

Blossom end rot is associated with low levels of calcium. Irregular watering and temperatures above 90°F will also cause sunken, water-soaked spots to develop on blossoms or the tips of fruit. Keeping soil evenly moist, mulching around plants and adding limestone if the pH is below 6.0 will reduce this pepper plant disease.


Plants infected by root-knot nematodes grow less than healthy plants. The range of nematodes is very large and can affect many food crops in addition to peppers. Due to the reduced role of the root system, the leaves show nutrient deficiencies and daytime wilting. Gently digging up the roots and observing the bead-like galls will give you confirmation of the presence of nematodes. This disease is most commonly seen in warm areas with long growing seasons. Light, sandy soils (like Florida) also favor nematode infections. To reduce my chances of pepper plant diseases I plant in new beds or large pots with rich soil. I also companion plant marigolds near the peppers to deter the nematodes. Planting root-knot nematode resistant crops such as “Charleston Belle,” “Carolina Wonder” and “Carolina Cayenne” will also help.

Pepper Plant Pests

Aphids, leafhoppers, thrips, and whiteflies are common vectors of viruses that can cause severe damage to pepper plants. Aphids, in warm climates, can reproduce asexually. Aphids can be found on the underside of newer leaves and can cause spotting or chlorosis – a condition that makes the leaves not capable of producing sufficient chlorophyll. This causes the leaves to turn yellow-white or pale. Leafhoppers, found worldwide, also cause yellowing of the leaves. In extreme situations, interveinal yellowing and necrotic areas that look like nutrient deficiencies will develop. Whiteflies whose lifecycle can be as quick as 20 days can attack over 500 ornamental, agricultural and agronomic crops. Whiteflies feed on the phloem and can have similar effects to the pepper plants as aphids. Whiteflies can also slow down the growth of the plant and cause defoliation. Using insecticidal soaps controls the virus vectors and reduces disease incidences. Eliminating virus reservoirs such as ornamentals and weeds near the peppers will also help reduce viruses. Releasing predators such as lacewing flies, ladybugs, and praying mantis is one example of natural pest control for gardening. Inter-planting, rotating crops and keeping the foliage dry are other examples of how to naturally reduce pepper plant pests.


Bacterial Spot

Symptoms of Bacterial Spot are first seen as tiny irregular water-soaked areas. The lesions enlarge and turn brown or black with a pale tan center. This occurs on the leaves, stems, and fruit of sweet peppers and are not as severe in hot peppers. High humidity and heavy dew formation on leaves, as well as warm weather, increases the development of Bacterial Spot. The bacterium can be easily transferred by water splashing from infected debris or transplants on to healthy plants. Pepper fruits are infected through fissures, scuffs and insect punctures. Once Bacterial Spot is present, it is difficult to control. Copper-based sprays can help reduce the development of the disease as well as using clean equipment.

Damping-Off and Root Rot

Damping-Off can affect seedlings pre- and post-emergence. Seeds may rot before germinating or young seedlings develop rot at the crown. Eventually, the tissue becomes soft and restricted making the plant wilt and fall over. In addition to peppers, these fungi have a wide host range and can survive for long periods in soil. I have had good luck using pasteurized seeding mix for sowing seeds rather than trying to save a few dollars by using a regular potting or garden soil. Once the seedlings have emerged and have been transplanted, I dry out the seeding mix completely before reseeding. I use the same seeding mix for a few times and then replace the medium. Damping-Off is at its highest when the soil moisture is high, compacted and there is poor ventilation. Overcrowding of seedlings plus cool and damp weather can also aid in seedlings not growing properly. Water splashing moves diseased soil from unhealthy to healthy plants. The main reason why sterilized seeding mix reduces Damping-Off is that it improves drainage and moisture regulation to help prevent soil saturation.

How to Grow Peppers Disease Free

When learning how to grow peppers, it’s important to note that peppers require soil temperatures to be at a minimum of the mid-60s to grow healthy. When growing seedlings indoors, start your seeds 8 to 10 weeks indoors prior to the transplant date will result in more yields. For the best harvest, plant in full sun. Consistent watering and moisture are important for pepper growth. Keeping peppers upright, by staking or caging, will help the leaves stay dry and reduce the chance of fungus, mold, and pests.

Some of my favorite peppers, which have shown no signs of pepper plant diseases thus far, include variegated foliage and fruit fish pepper and an ornamental, yet extremely hot edible, pepper named “Calico.”

What’s your favorite pepper to grow? Do you struggle with pepper plant diseases? Let us know in the comments below.

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