Common pepper plant problems
Pepper plants are susceptible to a range of insects, fungal and bacterial diseases, viruses, and environmental disorders that can reduce yield or kill plants outright. Identifying the problem early — by the specific symptoms — is the first step to effective management.
Bacterial leaf spot
Bacterial leaf spot (Xanthomonas euvesicatoria and related species) is the most common and destructive pepper disease. Symptoms begin as water-soaked lesions that enlarge and develop a tan to gray center with darker brown margins, usually surrounded by a yellow halo. Severe infections cause heavy leaf drop, flower loss, and small scabby lesions on fruit.
The disease spreads fastest during prolonged hot, humid weather in mid to late summer. Water splash and wind move the bacteria from plant to plant. Management includes using disease-free or bleach-treated seed, planting resistant cultivars, applying copper-based bactericides before rainy periods, and avoiding overhead irrigation.
Phytophthora blight
Phytophthora blight (Phytophthora capsici) is described by UConn Extension as "the toughest pepper pest to manage." It requires 24–48 hours of soil saturation to initiate infection and can kill every plant in a planting once established in a wet year. Above-ground symptoms include rapid wilting, stem collapse, and water-soaked spots on foliage and fruit. Below ground, the bark on roots sheds easily from discolored, dead tissue.
Prevention is the only reliable strategy. Plant on raised beds or well-drained sites, avoid overhead irrigation, do not plant peppers after tomatoes or other solanaceous crops for at least 3–4 years, and select tolerant cultivars where available. Metalaxyl fungicides are registered but are ineffective once infection is established.
Common insect pests
Aphids colonize plants in large numbers, causing leaf curling, yellow discoloration, and a sticky honeydew residue on leaves. The treatment threshold is roughly 5–10 aphids per leaf before fruit set. Reflective silver plastic mulch reduces colonization. Broad-spectrum pesticides often worsen aphid problems by killing natural predators.
Cutworms sever seedling stems at the soil line, typically causing overnight losses of new transplants. Tomato hornworms chew large holes in fruit and foliage. European corn borers bore directly into pepper fruit and are the most common cause of soft rot inside developing pods; pheromone trap monitoring helps time sprays when weekly trap captures exceed 7 moths.
Viruses
Several viruses affect peppers and cannot be cured once a plant is infected. Tobacco mosaic virus (TMV) causes raised bumps and mottled light-and-dark-green areas on leaves, uneven fruit ripening, and reduced fruit size. It persists for years in dried crop debris and spreads mechanically through hands and tools. Wash hands and disinfect tools with a 10% bleach solution when working with plants.
Pepper mottle virus (PMV) and cucumber mosaic virus (CMV) are both aphid-transmitted and cause puckered, misshapen leaves with a mottled appearance plus small distorted fruit. Tomato spotted wilt virus (TSWV), spread by thrips, produces off-color spotting on green fruit and yellow patches on red fruit that never fully ripen. Remove and discard infected plants promptly; control aphids and thrips to limit spread; rotate away from susceptible hosts.
Blossom drop
Blossom drop is one of the most common complaints from home pepper growers and is almost always caused by temperatures outside the range needed for pollen germination and tube growth. Pollen function fails above 90°F or below 55°F. MSU Extension identifies daytime temperatures at or above 90°F and nighttime temperatures below 60°F as the two primary triggers. Plants exposed to these conditions for several days in a row will abort flowers; extreme heat above 105°F or cold below 50°F can cause drop within hours.
Inconsistent watering — especially allowing the soil to dry out completely during flowering — is the other major cause. Keep soil evenly moist during bloom. High nighttime temperatures are particularly damaging because the plant never gets the cool resting period it needs for normal reproductive function. Blossom drop caused by weather extremes is not fixable mid-season; the plant will typically resume fruit set once temperatures return to the normal range.
Blossom-end rot and sunscald
Blossom-end rot appears as a water-soaked, light-brown spot at the fruit's blossom end that expands into a sunken, leathery lesion. It is caused by inconsistent soil moisture and calcium deficiency in the developing fruit — not a lack of calcium in the soil. The most effective management is consistent, even watering throughout fruit development.
Sunscald affects fruit that is suddenly exposed to intense direct sun, typically after disease or pruning removes shading foliage. Affected areas become light-colored, soft, and wrinkled, eventually turning whitish-tan and papery. Preventing excessive defoliation from disease is the primary control.