Pest & Disease Guide

Symptoms

Orange-brown spots on leaf undersides, premature leaf drop in late summer.

What to do

Rake and destroy fallen leaves each fall. Copper fungicide sprays in early summer can slow spread. Rarely fatal, but weakens the tree over time.

Symptoms

Yellow mottled/mosaic patterns on leaves, sometimes distorted leaf shape.

What to do

No cure — it's spread by eriophyid mites and through infected cuttings. Doesn't usually kill the tree, but avoid taking cuttings from infected plants to prevent spreading it further.

Symptoms

Fine stippling or bronzing on leaves, sometimes fine webbing on undersides.

What to do

Strong water spray to knock them off, insecticidal soap or horticultural oil for bad infestations. They thrive in hot, dry, dusty conditions — regular watering helps.

Symptoms

Small brown or white bumps on stems/branches, sticky honeydew residue, sooty mold.

What to do

Horticultural oil in dormant season is most effective. Scrape off light infestations by hand. Ants farming scale is a sign to also deal with an ant problem nearby.

Symptoms

Large iridescent green beetles eating ripe fruit, especially split or overripe figs.

What to do

Harvest fruit promptly when ripe. Traps with fruit-scented bait can help. Mostly a nuisance rather than a real threat to the tree.

Symptoms

Stunted growth, yellowing leaves, wilting despite adequate water; knotty galls on roots if you dig one up.

What to do

No easy cure once established. Solarizing soil before planting, and choosing nematode-resistant rootstock for grafting, are the main preventive tools.

Symptoms

Sunken, discolored patches on branches, dieback of individual limbs.

What to do

Prune out affected wood well below the visible damage, sterilizing pruners between cuts. Avoid wounding the tree unnecessarily, especially in wet weather.

Symptoms

Fruit ferments and turns liquidy/sour from the eye inward, often with fruit flies present.

What to do

More common in open-eye varieties in humid climates. Harvest promptly, remove affected fruit right away, and consider closed-eye varieties if this is a recurring problem in your climate.

Symptoms

Blossoms and shoot tips suddenly turn brown-black and wilt into a 'shepherd's crook' shape; oozing cankers in spring. Especially severe on pears and susceptible apples like Jonathan, Jonagold, and Gala.

What to do

Prune out infected wood at least 8-12 inches below visible damage, sterilizing pruners with a bleach or alcohol solution between every single cut. There's no cure once a limb is infected — removal is the only real control. Avoid high-nitrogen fertilizer, which encourages the soft new growth fire blight favors.

Symptoms

Olive-green to brown spots on leaves and fruit that darken and roughen over time; infected leaves often curl and drop early, and fruit can crack.

What to do

Rake and destroy fallen leaves before spring, since the fungus overwinters in leaf litter. Sulfur or copper fungicide in early spring helps on susceptible varieties. Resistant varieties (Liberty, Enterprise, Jonafree, Williams Pride) sidestep the problem almost entirely.

Symptoms

Bright yellow-orange spots on leaves, sometimes with small raised structures; requires a nearby juniper or cedar to complete its life cycle.

What to do

Remove nearby junipers if practical, though this is often impractical in populated areas. Resistant varieties and a fungicide program timed to spring rains are the main practical controls where junipers can't be removed.

Symptoms

Small holes in fruit with reddish-brown frass (droppings) around the entry point; the classic 'worm in the apple.'

What to do

Pheromone traps to monitor and reduce mating. Bag individual fruit with small mesh or paper bags shortly after fruit set for a fully organic option. Remove and destroy fallen infested fruit promptly so larvae can't complete their life cycle in the soil.

Symptoms

Dark smudgy blotches or tiny black dots on fruit skin, mostly cosmetic and appearing in humid late summer.

What to do

Doesn't affect eating quality — often washes or rubs off. Good air circulation from proper pruning and thinning reduces the humid conditions that favor it.

Symptoms

Blotchy yellow mottling on leaves that crosses leaf veins asymmetrically (unlike nutrient deficiency), stunted growth, and small, bitter, lopsided fruit.

What to do

There is no cure — infected trees decline and eventually die. Prevention is everything: buy only certified disease-free trees, and control the Asian citrus psyllid that spreads it. Remove and destroy infected trees promptly to protect neighboring plants.

Symptoms

Silvery, winding tunnels through young leaves, causing distorted, curled new growth.

What to do

Spray preventively with horticultural or neem oil right as new growth (flush) begins — once tunnels are visible, the larvae are already protected inside the leaf and hard to reach. Mature trees tolerate it far better than young ones.

Symptoms

Small brown, white, or cottony bumps on stems and leaf undersides; sticky honeydew and sooty mold buildup.

What to do

Horticultural or white oil is the standard organic control. Encourage ladybugs, a natural predator. Indoor/container citrus overwintered inside are especially prone to both scale and mealybugs — inspect regularly during that period.

Symptoms

Gum oozing from the trunk near the soil line, yellowing and thinning canopy, root decline.

What to do

Almost always caused by soil that stays too wet — improve drainage and avoid planting with the graft union below soil level. Systemic fungicides can help but won't fix an underlying drainage problem.

Symptoms

Leaves emerge puckered, reddened, and thickened in spring, then drop; can significantly weaken the tree if it happens repeatedly.

What to do

Apply a copper-based fungicide in late fall and again in late winter before buds swell — this is a dormant-season disease that can't be effectively treated once leaves have already emerged. Some varieties (like Frost peach) have real resistance bred in.

Symptoms

Blossoms and twigs suddenly blight and die back in spring; ripening fruit develops soft brown spots that quickly spread and cover the whole fruit in fuzzy gray-brown spores.

What to do

Remove and destroy all mummified fruit left on the tree or ground — that's where it overwinters. Improve air circulation through pruning, and avoid wounding fruit near harvest. Fungicide timed to bloom and again near ripening helps in humid climates.

Symptoms

Gummy, sawdust-like frass oozing from the trunk near the soil line; larvae tunnel into the trunk and can girdle young trees.

What to do

Apply a targeted insecticide to the lower trunk in late summer when adult moths are laying eggs. Keep the base of the tree free of mulch buildup and grass, which attracts egg-laying.

Symptoms

Small dark, water-soaked spots on leaves and fruit that can merge and cause leaves to yellow and drop; fruit spots can crack open.

What to do

Copper sprays in early spring help but won't fully control a bad infection. Some varieties have real resistance — ask about bacterial spot resistance when choosing a new plum, peach, or apricot variety for a humid climate.

Symptoms

Hard, black, tar-like swollen growths on branches and twigs, most visible in winter once leaves have dropped.

What to do

Prune out and destroy affected branches 3-4 inches below the visible knot, ideally during the dormant season. This disease can persist and spread for years if the knots aren't physically removed.

Symptoms

Wilting cane tips, often with two rings of small punctures near the top of the cane where an adult beetle laid eggs.

What to do

Cut and destroy wilted tips several inches below the punctures as soon as you spot them, before the larvae can tunnel further down into the cane.

Symptoms

Small purple-to-gray sunken spots on canes, sometimes girdling them; can also spot leaves and fruit.

What to do

Prune out and destroy infected canes after harvest. Improve air circulation by thinning canes to recommended spacing, and avoid overhead watering, which spreads spores.

Symptoms

Dark purple-brown blotches at leaf nodes on canes, weakening or killing the cane above the infection point.

What to do

Remove and destroy infected canes at ground level right after harvest. Thin plantings for better air circulation, since both diseases thrive in crowded, humid conditions.

Symptoms

Skeletonized leaves (only veins remaining) and chewed fruit, usually in mid-to-late summer.

What to do

Hand-pick into soapy water in the morning when beetles are sluggish — genuinely effective for a home planting. Pheromone traps can help but sometimes draw in more beetles than they catch, so use them well away from the plants you're protecting.

Symptoms

Small jumping insects on new growth, sticky honeydew on leaves and fruit, sooty mold buildup, and curled or wilted leaves in a bad infestation.

What to do

A dormant-season horticultural oil spray before buds break is the standard first line of defense. Psylla develop resistance to many insecticides quickly, so avoid relying on the same product repeatedly. Left unchecked, heavy psylla pressure can lead to pear decline.

Symptoms

Poor shoot growth, branch dieback, reddening and rolling of upper leaves, premature leaf drop, and smaller fruit.

What to do

There's no direct treatment once a tree is infected — this is spread by pear psylla, so controlling psylla populations is the real prevention. Choose decline-tolerant rootstock when planting new pear trees in an area where this has been a problem.

Symptoms

Olive-green to dark spots on leaves and fruit, velvety fungal growth on leaf undersides, and cracked or distorted fruit in bad cases.

What to do

Rake and destroy fallen leaves in autumn, since the fungus overwinters there. A dormant copper spray in late winter and a fungicide program timed to spring rain helps on susceptible varieties — very similar management to apple scab.

Symptoms

New shoots and flower clusters suddenly wilt and turn brown in spring; affected berries shrivel, turn tan/gray, and drop early looking like small mummified fruit.

What to do

Rake, mulch over, or till under fallen leaves and old fruit before spring — the fungus overwinters in mummified berries on the ground, and burying them at least 2 inches deep is one of the most effective non-chemical controls. Fungicides timed to bud break help in years with wet spring weather.

Symptoms

Small white legless larvae inside otherwise normal-looking ripe berries, discovered when fruit is soft, mushy, or has visible tunneling.

What to do

Harvest ripe berries promptly rather than letting them sit on the bush. Yellow sticky traps help monitor when adult flies are active so any treatment is timed correctly. Fine mesh netting over bushes during ripening is an effective non-chemical barrier.

Symptoms

Small fruit flies laying eggs directly in ripening (not just overripe) fruit, leading to soft spots and larvae inside berries that otherwise look fine on the outside.

What to do

Harvest as soon as berries ripen — this pest specifically targets fruit while still on the bush, unlike most fruit flies that prefer overripe or fallen fruit. Fine mesh netting and prompt removal of any dropped fruit both help reduce pressure.

Symptoms

Dieback of individual branch tips, wilted or reddish-brown leaves that stay attached, and small dark lesions on stems.

What to do

Prune out and destroy infected branches, cutting well below the visible lesion. Clean up fallen debris around the base of the plant, since the fungus overwinters there.

Symptoms

Fine white-gray powdery coating on leaves, shoots, and developing berries; affected berries stay small, sour, and often crack instead of ripening properly.

What to do

American-heritage varieties like Concord have real natural resistance and are a good starting point if this has been a recurring problem. Sulfur or lime-sulfur sprays timed to bud break are the standard organic control — unlike most powdery mildews, this one thrives in warm, relatively dry conditions rather than damp ones.

Symptoms

Circular brown-black lesions with a yellow halo on leaves, and berries that shrivel into hard black mummified fruit that often stays attached to the vine.

What to do

Remove and destroy mummified berries and fallen leaves — they carry the fungus into the next season. Prune for an open canopy to improve air circulation, and apply a fungicide program starting at bud break in climates with humid summers, where this disease is most damaging.

Symptoms

Small round bumps or galls on the undersides of leaves, and in severe cases, stunted growth and vine decline from root-feeding by the same insect.

What to do

This is the pest that devastated European vineyards in the 1800s — modern vines are protected mainly by grafting onto phylloxera-resistant rootstock rather than by spraying, so if you're buying a new vine, ask whether it's on resistant rootstock. Leaf galls alone are mostly cosmetic and rarely worth treating directly.

Symptoms

Yellowish spots on the upper leaf surface in spring, with orange-yellow blister-like fruiting bodies on the underside; heavy infections cause premature leaf drop.

What to do

This disease is mostly harmless to the currant or gooseberry plant itself — the real damage is to nearby white pine trees, which is why it matters so much legally. ⚠️ Several states restrict or outright ban growing currants and gooseberries (especially black currant) because of this disease, and it was banned federally in the US until 1966. Check your state department of agriculture before planting or shipping Ribes species — Maine, Massachusetts, and North Carolina are among the states with real restrictions as of recent guidance, and this changes over time.

Symptoms

Whitish powdery growth on leaves, shoots, and branch tips starting in early summer; infected berries can crack or shatter, and the coating may turn brown later in the season.

What to do

Prune and dispose of infected shoot tips in early spring before growth resumes. Good air circulation matters a lot here — some growers even trellis gooseberries specifically to improve airflow and make this easier to manage.

Symptoms

Aphids cause distorted, curled new leaves; sawfly larvae skeletonize leaves down to the veins, often very quickly once they appear.

What to do

Hand-pick sawfly larvae when you spot them — they can defoliate a bush fast if left alone. Insecticidal soap works on aphids; encouraging ladybugs and other natural predators helps keep both in check without regular spraying.

Symptoms

Small soft-bodied insects clustering on new growth and leaf undersides, causing curled, distorted leaves and sticky honeydew.

What to do

Honeyberries are generally low-pest plants overall, and light aphid infestations often aren't worth treating. For heavier infestations, insecticidal soap or a strong water spray works well, and encouraging ladybugs helps keep populations down long-term.

Symptoms

White powdery coating on leaves, more common on older varieties and in plantings with poor air circulation.

What to do

Space plants for good airflow and prune out crowded growth — this is usually enough on its own. Fungicide is rarely necessary except in persistently humid, poorly ventilated plantings.

Symptoms

Berries disappearing before they're even fully ripe — honeyberries fruit unusually early in the season, often weeks before anything else, which makes them one of the only ripe food sources around for birds at that point.

What to do

Bird netting over the bush during ripening is the standard, reliable fix. This is genuinely one of the most common honeyberry complaints — expect to lose a meaningful share of the crop to birds without some kind of physical barrier.

Symptoms

Wilting, undersized leaves, stunted shoot growth, and reddish-brown discoloration in the roots and crown if you dig down and check; vines can decline slowly over seasons or collapse suddenly in hot weather.

What to do

This is the single most damaging kiwi disease and it's almost always tied to wet, poorly drained soil — good drainage is the real prevention. Avoid overhead irrigation in favor of drip irrigation, and avoid planting in low spots where water collects.

Symptoms

Small immobile bumps on leaves, canes, and fruit, often with sticky honeydew residue nearby.

What to do

Dormant-season horticultural oil is the standard control, same as for most other fruiting plants. Good pruning to open up the canopy also helps by reducing the humid, sheltered conditions scale insects favor.

Symptoms

Vines decline and can die fairly suddenly; roots appear decayed and blackened when checked, and foliage color and vigor decline even before the plant collapses.

What to do

Good drainage is the real prevention here too — avoid heavy, waterlogged soils. Badly infected plants are usually best removed and replaced rather than treated, since recovery is unreliable once the disease has taken hold.

Symptoms

Small water-soaked spots on young stems that darken and become sunken, and irregular olive-green to brown lesions on leaves, sometimes with a yellow halo; severe cases can girdle and kill stems.

What to do

Prune out and destroy infected stems and leaves promptly. Avoid overhead watering, which spreads bacteria between plants, and improve air circulation around the vine.

Symptoms

Dark, sunken lesions on leaves, flowers, and fruit; on mango specifically this often shows up first as "blossom blight," destroying flower panicles before fruit even sets, and can cause fruit to rot before or after ripening.

What to do

This is by far the most damaging mango disease worldwide, worse in humid climates and rainy weather. A copper spray program timed from flowering through fruit development is the standard approach — spraying young flushes of new leaves and again at bud break matters most, since that's when infection actually establishes even though symptoms show up later.

Symptoms

White powdery coating on leaves, flowers, and young fruit, most active in dry conditions with high early-morning and evening humidity; can cause significant flower and fruit drop in bad years.

What to do

Sulfur-based fungicides applied at flowering are the standard control. This disease specifically favors dry-with-humid-mornings conditions rather than the wet weather anthracnose prefers, so both can show up in the same season for different reasons.

Symptoms

Dark sunken lesions on fruit, and on young twigs specifically a symptom called "pepper spot" — small dark speckling distinct from the fruit lesions.

What to do

Prune for good air circulation and remove dead wood and fallen debris, since the fungus survives on dead plant material between seasons. Fungicide programs are mainly a commercial-orchard measure; for a home tree, sanitation and canopy airflow do most of the work.

Symptoms

Yellowing, sparse foliage and small leaves, dieback of branch tips, and an overall decline in tree vigor over one or more seasons; roots appear dark and decayed when checked.

What to do

This is the single most economically damaging avocado disease worldwide, and it is almost entirely a drainage problem — avocado roots are genuinely intolerant of wet, poorly aerated soil. Plant on a mound or in well-draining soil, avoid overwatering, and avoid piling mulch against the trunk. Resistant rootstocks exist and are worth asking about specifically if this has been a recurring issue in your soil.

Symptoms

Dark sunken spots that develop on the fruit primarily after harvest, as bananas ripen — often the infection was already present on the fruit before picking but stayed dormant ("quiescent") until ripening triggered it.

What to do

Handle fruit gently to avoid wounds that let the fungus in, and harvest at the correct maturity rather than overripe. This is mainly a post-harvest concern rather than something that threatens the plant itself.

Symptoms

Yellowing and wilting of older leaves progressing upward through the plant, splitting at the base of the stem, and eventual collapse of the whole plant; internal stem tissue shows dark discoloration when cut.

What to do

There is no cure once a plant is infected — this is the same soil fungus that wiped out the once-dominant Gros Michel banana commercially in the mid-20th century and now threatens Cavendish types too. The fungus persists in soil for years, so prevention (only planting certified disease-free stock, avoiding moving soil between plantings) matters far more than any treatment after the fact. Remove and destroy infected plants rather than trying to save them.

Symptoms

Yellow mottling and a mosaic pattern on leaves, distorted "shoestring" leaf shape, water-soaked streaking on the leaf stalks, and distinctive ring-shaped or C-shaped spots on the fruit itself; infected plants are stunted and produce little to no usable fruit.

What to do

There's no cure once a plant is infected, and it spreads fast via aphids — remove and destroy infected plants promptly to protect the rest of the planting. This is widely considered the single most damaging papaya disease worldwide, which is exactly why ringspot-resistant varieties like Cariflora and the more recent genetically modified Hawaiian varieties were developed — choosing a resistant variety is the most effective real-world prevention available.

Symptoms

Aphids cluster on new growth, causing curled leaves — and they're the actual carrier of papaya ringspot virus, so an aphid problem is a real disease risk, not just cosmetic. Fruit flies lay eggs in ripening fruit, leading to soft, spoiled spots.

What to do

Controlling aphids matters more for papaya than for most fruit, specifically because they spread ringspot virus. Insecticidal soap helps with light infestations. For fruit flies, harvest promptly and consider bagging individual fruit as it develops.

Symptoms

Larvae tunneling inside otherwise normal-looking fruit, making it unsuitable for eating; this is considered the single most damaging guava pest in Florida and similar climates.

What to do

Bagging individual fruit once it reaches about an inch in diameter is a genuinely effective, low-tech barrier method used by home growers. Prompt harvest and removal of any fallen fruit also helps break the pest's life cycle.

Symptoms

Small white or waxy insects on leaf undersides, sticky honeydew, and sooty mold buildup on leaves and fruit.

What to do

Horticultural oil is the standard control for both. Good air circulation through proper pruning reduces the sheltered conditions these pests favor.

Symptoms

Reddish-brown, hairy, felt-like patches (called erinea) on the underside of young leaves, causing them to curl, thicken, and distort; can also scar flowers and fruit in a bad infestation.

What to do

⚠️ This mite is a real regulatory concern, not just a garden nuisance — it's a prioritized quarantine pest in the continental US, first found in Florida in 2018, and its movement is restricted in some areas. Prune and destroy infested leaves and check with your local agricultural extension office if you suspect an infestation, since it may need to be reported. Neem oil or insecticidal soap can help with light cases.

Symptoms

Dark sunken spots on leaves and fruit, part of the same broad Colletotrichum fungal group that affects most tropical fruit.

What to do

Prune for good air circulation and remove fallen fruit and debris promptly. Wet weather during flowering and fruit development is when infection risk is highest.

Symptoms

Scarring and deformation on developing fruit, plus reddish-brown to black fecal deposits on the skin from feeding — cosmetic damage that can still make a large share of a crop unmarketable in bad years.

What to do

Monitor with yellow or blue sticky traps to catch outbreaks early. Thrips have a short life cycle and can produce many generations a year, so early action matters more than with slower-reproducing pests.

Symptoms

Small soft-bodied insects with waxy, cottony coating clustering on flowers and fruit, along with sticky honeydew and sooty mold.

What to do

Horticultural oil or insecticidal soap works on direct contact. Ants are often found tending mealybugs for the honeydew they produce, so an ant problem nearby is worth addressing at the same time.

Symptoms

Jaboticaba is genuinely one of the lowest-maintenance fruit trees when it comes to pests and disease — most growers report few if any serious problems. Occasional minor issues include aphids, scale, spider mites, and nematodes.

What to do

Routine monitoring is usually all that's needed. If any of the above shows up, standard treatment applies — insecticidal soap or horticultural oil for aphids and scale, and improved soil health for nematode pressure.

Symptoms

Scale: small bumps on stems with sticky honeydew nearby. Bacterial leaf spot: small dark, water-soaked spots on leaves, sometimes with a yellow halo.

What to do

Mulberry is generally a low-pest tree overall. Horticultural oil handles scale in the dormant season. For bacterial spot, avoid overhead watering and prune out affected growth — it's rarely serious enough to need more than that.

Symptoms

Wilting or dying flower clusters in spring, with tiny larvae tunneling inside the flower stalk (peduncle) itself, causing the whole cluster to drop before fruit can set.

What to do

There's no reliable organic treatment once larvae are inside the stalk — removing and destroying affected flower clusters as soon as you notice wilting is the main practical response. Pawpaw is otherwise a genuinely low-pest tree: its leaves and bark contain natural compounds (acetogenins) that make it actively distasteful to deer and most insects, which is a real, well-documented advantage of growing it.

Symptoms

Larvae inside ripening or fallen fruit, most likely to appear in warmer climates where fruit fly pressure is already a concern for other fruit.

What to do

Prompt harvest and removal of fallen fruit is the main defense. Feijoa is otherwise a fairly low-pest plant overall, which is part of why it's been such a popular low-maintenance home garden choice in New Zealand for generations.

Symptoms

Persimmon is widely considered one of the more pest- and disease-resistant fruit trees available, with few serious recurring problems for home growers. Occasional issues include scale, mealybugs, and anthracnose in humid climates.

What to do

Routine monitoring is usually sufficient. When scale or mealybugs do show up, horticultural oil is the standard response; for anthracnose, prune for good airflow and remove fallen fruit and leaves promptly.

Symptoms

Large gray insects, about an inch long, with a distinctive flattened leaf-shaped structure on their hind legs; they pierce developing fruit to feed, causing internal discoloration, dry patches, and sometimes fruit drop — damage that's often not visible from the outside until the fruit is cut open.

What to do

This is one of the most frequent and damaging pomegranate pests. Removing nearby weeds (especially in spring, before fruit forms) reduces the population feeding nearby before it moves into the pomegranate. Hand-picking or knocking them into soapy water in the morning, when they're sluggish, is effective for a home planting.

Symptoms

Excessive, bushy clustering of small shoots ("witches' broom"), yellowing, leaves that look small and distorted, and stunted overall growth; young trees can die within one to two years of infection.

What to do

There's no reliable cure — this is a phytoplasma (a bacteria-like pathogen) spread by leafhoppers, and infected trees are usually best removed to prevent further spread. Controlling leafhoppers and buying certified disease-free nursery stock are the main practical prevention. This disease has caused serious losses in China, the world's largest jujube-growing region, so it's a genuine concern if it's present in your area.

Symptoms

Clusters of small soft-bodied insects on new growth and leaf undersides, often with curled or distorted leaves and sticky honeydew.

What to do

A strong water spray knocks off light infestations. Insecticidal soap or neem oil for heavier ones. Ladybugs and lacewings are effective natural predators — avoid broad-spectrum insecticides that kill them off too.

Symptoms

Fine stippling or bronzing on leaves, sometimes fine webbing on the undersides in bad infestations; worse in hot, dry, dusty conditions.

What to do

Regular watering and occasional strong hosing-down of foliage discourages them. Insecticidal soap or horticultural oil for real infestations. They tend to explode in population when broad-spectrum pesticides wipe out their natural predators.

Symptoms

Small brown, white, or waxy bumps on stems and leaves that don't move; sticky honeydew and sooty mold buildup nearby.

What to do

Dormant-season horticultural oil is the most effective control across nearly every fruiting plant. Scrape off light infestations by hand. Ants farming scale for its honeydew are a sign to deal with an ant problem too.

Symptoms

White or gray powdery coating on leaves and sometimes young fruit, usually starting on new growth.

What to do

Improve air circulation through proper spacing and pruning. Sulfur-based fungicides work well as both prevention and early treatment. Avoid overhead watering late in the day, which keeps foliage damp overnight.

Symptoms

Yellowing, wilting foliage despite adequate watering, dieback starting from the top, and dark, mushy roots if you dig one up.

What to do

Almost always a drainage problem — improve soil drainage or move future plantings to a raised bed or mound. There's no reliable cure once root rot is established; focus on prevention for anything planted after.