Five categories cover almost every complaint a pepper plant makes: environment, nutrition, pests, pathogens, and normal traits that look like damage. The table below maps 55 symptoms to causes and fixes. Three mappings that circulate on charts like this one do not survive contact with the extension literature, and blossom end rot is the worst offender. Corrections follow the table.

How to work the chart

Start with the cheapest tests. Soil moisture, root-zone temperature and pH cost nothing and explain more pepper symptoms than every pest and pathogen combined. Only after those three come back clean does a deficiency diagnosis mean anything, because a nutrient the plant cannot absorb looks exactly like a nutrient that is not there. Then check where on the plant the symptom sits. Mobile nutrients (nitrogen, phosphorus, potassium, magnesium) move out of old leaves to feed new growth, so the bottom of the plant fails first. Immobile ones (calcium, boron, iron, sulfur, manganese, zinc) strand the growing tip, so damage shows in the newest leaves. That single split cuts a deficiency list in half before you touch a fertilizer bag.

Pattern matters as much as color. Interveinal chlorosis, where veins stay green and the tissue between them yellows, points at magnesium, iron or manganese. Uniform yellowing points at nitrogen or sulfur. Marginal scorch, a brown rim working inward, points at potassium or at salt. For symptoms that fit no standard category, the diagnostic table for odd symptoms covers the leftovers.

Pepper plant diagnosis chart

SymptomCauseWhat to do
Environmental
Stunted growth, slow or patchy germination.Root zone too cold.Germinate at 80 to 85°F (27 to 29°C) soil temperature on a heat mat; delay outdoor sowing.
Flower and young pod drop, leaf curl in a heat wave.Temperature past the pollen threshold.Afternoon shade cloth, mulch, irrigate ahead of the peak; pollen fails above roughly 90°F (32°C) days or 75°F (24°C) nights.
Long internodes, pale thin stems, no fruit set.Light intensity too low.Move to full sun or raise PPFD; adding hours will not fix a stretch caused by weak light.
Bleached white patches on the topmost leaves.Intensity too high, or no hardening off.Raise the fixture, add 30 to 40 percent shade cloth, harden off over 7 to 10 days.
Brown crisp leaf margins, inward curl.High evaporative demand, but rule out salts and drought first.Check fertilizer strength and watering before blaming humidity; group plants, add a humidifier indoors.
Mold and fungal outbreaks.High humidity with still air.Move air, widen spacing, water the soil rather than the leaves.
Leaf spotting that spreads after every rain.Poor air circulation and long leaf wetness.Fans, wider spacing, drip irrigation instead of overhead.
Yellowing from the bottom up, mushy dark roots.Saturated medium favoring Pythium and Phytophthora root rot.Dry down between waterings and fix drainage; water creates the opening, the pathogen does the damage.
Wilting, dry brittle leaves.Underwatering.Water more often, mulch, check that the root ball is not hydrophobic.
Brown leaf tips, slow growth, white crust on the pot rim.Salt accumulation in a container.Leach with two to three pot volumes of low-EC water, then cut the feed rate.
Stunted growth despite good light and feed.Container too small.Repot; 3 to 7 gallons (11 to 26 L) suits most fruiting plants.
Wilting and leaf drop days after a move.Transplant shock.Shade for several days, water in once, leave the root ball alone.
Torn leaves, snapped branches.Wind stress.Windbreak or stake before the plant carries a fruit load.
Nutrient deficiencies
Uniform yellowing of the oldest leaves, working up.Nitrogen deficiency (mobile).Feed a balanced fertilizer carrying nitrogen; excess pushes leaf at the expense of pods.
Purple stems and leaf undersides with stunting.Phosphorus deficiency, or cold roots mimicking it.Warm the root zone first; cold soil blocks phosphorus uptake in ground that tests adequate.
Brown scorched margins on middle-canopy leaves.Potassium deficiency.Potassium sulfate or kelp meal; heavy magnesium or calcium competes for uptake.
Sunken leathery brown patch at the pod tip.Blossom end rot: a calcium shortfall inside the fruit, rarely a soil calcium shortage.Even soil moisture, mulch, steady irrigation; foliar calcium never reaches the fruit.
Interveinal yellowing on older leaves, veins still green.Magnesium deficiency (mobile).Epsom salt at 1 to 2 tablespoons per gallon as a foliar spray; correct pH as well.
Interveinal chlorosis in the newest leaves.Iron deficiency, almost always high pH rather than low iron.Bring pH into 6.0 to 6.8; chelated iron buys time while pH comes down.
Small distorted leaves, short internodes, rosetted tip.Zinc deficiency.Zinc sulfate foliar spray; high pH and heavy phosphorus both suppress zinc.
Dead growing tips, corky fruit, poor set.Boron deficiency (immobile).Very dilute borax; the margin between deficient and toxic is the narrowest of any nutrient.
Uniform yellowing of the newest leaves.Sulfur deficiency.A sulfate-carrying fertilizer such as potassium sulfate or gypsum.
Interveinal chlorosis in young leaves, then leaf drop.Manganese deficiency.Manganese sulfate; high pH locks manganese the same way it locks iron.
Several deficiency patterns at once on one plant.pH lockout rather than a missing nutrient.Test, then correct to 6.0 to 6.8 in soil and 5.5 to 6.5 in soilless media.
Pests
Sticky honeydew, curled growing tips, sooty mold.Aphids.Water jet, insecticidal soap, neem; aphids also move cucumber mosaic virus.
Clouds of tiny white insects off the underside.Whiteflies.Yellow sticky cards, soap, neem; Bemisia tabaci carries pepper leaf curl viruses.
Fine webbing, stippled bronzing leaves.Spider mites.Soak the undersides, repeat every 3 to 5 days, miticide if it persists.
Silvered scarring on leaves and pod shoulders.Thrips.Spinosad, blue sticky cards; thrips vector tomato spotted wilt virus.
Small dark flies over the soil, seedlings collapsing.Fungus gnats.Dry the surface, sticky cards, Bacillus thuringiensis subsp. israelensis drench.
Chewed holes with dark frass pellets.Caterpillars.Handpick; Bt kurstaki works on small larvae only, so scout early.
Shot holes peppering seedling leaves.Flea beetles.Floating row cover at transplant, off at flowering; neem on small plants.
Winding pale trails inside the leaf blade.Leaf miners.Pull mined leaves, spinosad if severe; broad sprays kill the parasitoid wasps that control them.
Bronzed, glossy, twisted new growth.Broad mites.Discard heavily infested plants; sulfur or a labeled miticide; damage mimics herbicide injury.
Wilting and stunting with clean foliage.Root aphids or root mealybugs.Inspect the root ball and drench; uncommon on pepper, so rule out Phytophthora root rot first.
Diseases
White powdery growth, mostly on leaf undersides.Powdery mildew, Leveillula taurica.Sulfur or potassium bicarbonate, rotating modes of action.
Bright yellow blotches on top, white fuzz underneath.The same Leveillula infection, routinely misread as downy mildew.Treat it as powdery mildew; true downy mildew of pepper (Peronospora tabacina) stays rare.
Water-soaked lesions turning brown with yellow halos.Bacterial leaf spot, Xanthomonas spp.Clean seed and resistant cultivars first; copper resistance is common, so tank-mix copper with mancozeb.
Dark sunken fruit spots with concentric rings.Anthracnose, Colletotrichum spp.Strip infected pods, rotate, protect fruit from set onward.
Gray fuzzy growth on stems, flowers and pods.Botrytis gray mold.Prune for airflow, cut humidity, remove infected tissue promptly.
Dark girdling lesion at the soil line, sudden wilt.Phytophthora blight, Phytophthora capsici.Raised beds and drainage; tolerant cultivars or grafting; no cure once a plant wilts.
One-sided yellowing, brown streaks in the stem.Fusarium wilt.Pull plants, rotate long, solarize; the fungus persists in soil for years.
Diffuse lower-leaf yellowing and wilt, vascular browning.Verticillium wilt.Rotate out of solanaceous crops; the wide host range makes rotation slow.
Seedlings topple at the soil line.Damping off: Pythium, Rhizoctonia or Fusarium.Clean trays and media, bottom heat, airflow, no standing water.
Sunken leathery brown patch at the pod tip.Blossom end rot, a physiological disorder, indexed here because growers hunt for it among diseases.Fungicide does nothing; see the nutrition row and fix irrigation.
Severe upward curl, stunting, crowded short internodes.Pepper leaf curl virus, a begomovirus.Remove plants and control the whitefly vector; the virus itself has no treatment.
Concentric ringspots on leaves and pods.Tomato spotted wilt virus.Remove plants, suppress thrips, plant resistant cultivars where the virus is endemic.
Mottled light and dark green leaves.Cucumber mosaic virus.Remove plants; insecticides barely slow aphid spread of a non-persistent virus, so use reflective mulch.
Mottled, narrowed, strap-like distorted leaves.Tobamoviruses: TMV, ToMV, pepper mild mottle virus.Destroy plants, sanitize tools and hands, keep tobacco products away from the bench.
Normal variation
Tan corky lines across the pod skin.Corking, a stretch mark in the cuticle.Normal, and a quality mark on Jalapeño.
Purple pigment on stems and leaf undersides.Anthocyanin from strong sun or cool nights.Normal in many cultivars; suspect phosphorus only alongside stunting and old-leaf symptoms.
Leaf loss for a week or two after a move.Post-transplant leaf drop.Normal; the plant trims its canopy to match disturbed roots.
Almost no growth in the first six weeks.Slow chinense and baccatum seedlings.Normal; start those species two to four weeks ahead of annuum.
Pods passing through purple, brown or cream.Ripening pigment sequence.Normal; confirm the variety's final color before you pick.
Dense fuzz on leaves and stems.Trichomes.Normal in C. pubescens, whose name means hairy.
Twisted or strap-shaped first true leaves.Seedling leaf distortion.Usually outgrown; if new growth stays twisted, suspect broad mites or herbicide drift.

Why does blossom end rot appear when my soil test shows plenty of calcium?

Because blossom end rot is a transport failure, not a supply failure. Calcium moves up the xylem with the transpiration stream and does not travel back down the phloem. Fruit transpires very little, so it competes poorly with leaves for whatever calcium the roots pull in. When soil moisture swings, a dry spell after heavy rain being the classic trigger, that flow stalls and the pod tip starves while the soil stays rich. Clemson's Home and Garden Information Center files calcium sprays under gardening myths for exactly this reason: fruit skin cannot absorb foliar calcium. Even irrigation, a mulch layer and undisturbed roots fix far more cases than any amendment. If a soil test genuinely shows low calcium, deliver it to the root zone, never to the leaves.

Is the white mildew on my pepper downy or powdery?

On pepper it is nearly always powdery, caused by Leveillula taurica. This fungus grows inside the leaf and pushes its conidiophores out through the stomata on the underside. The white bloom therefore sits on the lower surface, while the upper side shows light green to bright yellow blotches that later go necrotic. That combination reads as downy mildew to anyone who learned the disease on cucurbits. The Pacific Northwest Pest Management Handbook names Leveillula as the pepper powdery mildew organism and lists sulfur, potassium bicarbonate and rotating fungicide classes. Downy mildew of Capsicum does exist, reported as Peronospora tabacina from nurseries in the United States, Greece, Australia and Spain, but it stays rare enough that powdery mildew is the safer first call.

Deficiency or lockout

Peppers take up nutrients best between pH 6.0 and 6.8 in soil, and between 5.5 and 6.5 in soilless mixes. Push past 7.0 and iron, manganese and zinc drop out of solution while the fertilizer bag still promises them. Drop below 5.5 and manganese and aluminum turn toxic. A plant showing three deficiency patterns at once is telling you about pH, not about three separate shortages. Test before you feed, because stacking micronutrient products onto a locked-out root zone adds salt and makes the next diagnosis harder. The nutrient lockout guide works through the interactions, and the fertilizer guide covers rates.

Which symptoms mean nothing is wrong?

Four show up constantly in help requests. Corking, the tan netting across a jalapeño's shoulders, is cuticle stretched by fast fruit growth, and packers grade for it rather than against it. Purple stems come from anthocyanin, a sunscreen response, and only suggest phosphorus when stunting and old-leaf symptoms arrive alongside. Slow early growth is standard for C. chinense and C. baccatum, which is why growers start them weeks ahead. Fuzzy leaves are simply what pubescens looks like. Pods moving through an intermediate shade are ripening on schedule, and the harvesting guide sets out what that sequence should look like. Everything else, pest identifications included, gets more depth in the pest guide and the fruiting problems guide.

Sources & Further Reading