Pomegranate Tree Diseases: Black Heart Rot Starts at Bloom — How to Tell 6 Fungal Problems Apart (and Where Bacterial Blight Fits)

November 10, 2026

Updated on November 10, 2026

12 mins read

Pomegranate rotten inside but fine outside? Black heart starts at the flower. Tell 6 fungal pomegranate diseases apart and see where bacterial blight fits.

In short

Brown or black arils inside a pomegranate that looked fine outside often point to black heart (Alternaria), which enters through the flower around bloom.
Preharvest sprays are generally ineffective against it; extension advises sanitation, a gentle shake at harvest and insect control.
In Florida, anthracnose is among the most important diseases; bacterial blight appears in none of the US extension pages we read.
Checked against: UC IPM, UF/IFAS, Texas A&M.

Cut open a pomegranate that looked perfect on the tree and find the arils brown and black, and black heart is a prime suspect. It’s also called heart rot, Alternaria fungi cause it, and the surprise is the timing. A study of six Israeli orchards found that the fungus gets in through the open flower, then, in some fruit, waits inside the young fruit for about three to four months before the rot starts.

Black heart is one of six groups of fungal problems that US extension sources describe on pomegranates (the last table row combines the Coniella and Botryosphaeria canker fungi). Add a few look-alikes that aren’t diseases at all (an insect, a watering problem, ordinary bark) and you have the full list of what home growers get worried about. This guide sorts them by where on the tree the damage shows, says what the California, Florida and Texas sources recommend, and answers a question the usual guides skip: where does bacterial blight, which features in recent research from Pakistan and India, fit for a US grower?

One caution about the evidence. Nearly all of it comes from California’s large orchards, Florida (an experimental crop on about 200 acres, per UF/IFAS in 2019) and Texas. If you grow in zone 6 or 7, as in our zone 6 pomegranate guide, you’re reading across climates. For problems on other plants, start with our plant disease identification guide.

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Which Problem Do You Have? Start With Where You See It

Match where the damage sits to the likely cause. Decay that starts inside the fruit with a normal-looking rind points to Alternaria; decay that starts at the rind or calyx points to Aspergillus, anthracnose or Coniella; a gray coating after storage points to Botrytis.

Where it shows	What you see	Likely cause	Reported in
Inside the fruit only	Rind normal or slightly paler red; fruit lighter than its neighbors; brown, then black arils when cut open	Black heart (Alternaria alternata)	California, Texas, Israel
Rind, usually near the calyx	Paler red to brownish-red patches; black powder on the rind or in cracks; brown, black-sporing arils inside	Aspergillus fruit rot (A. niger)	California, Texas
Fruit surface in wet weather	Hard dark brown to black lesions at the calyx of green fruit, later sunken spots; gray to orange spore masses	Anthracnose (Colletotrichum)	Florida, Southeast
Skin and leaves	Small dark spots on the skin only; leaf spots with a dark margin and a greenish halo	Leaf and fruit spot (Pseudocercospora or Cercospora punicae)	Florida, Texas
Fruit after storage	Gray fuzzy coating after washing or humid storage	Gray mold (Botrytis cinerea)	California
Rotten fruit with black dots; dying stems	Raised black dots on a brown rind; dried fruit (mummies) hanging on; swollen, cracked stem cankers	Coniella (Pilidiella) rot and Botryosphaeria canker	California, Florida

Sources for the table are UC IPM, UF/IFAS and Texas A&M AgriLife; the sections below give each claim its own link.

Black Heart: The Rot You Can’t See From the Outside

Black heart is a rot of the fruit’s interior that usually shows no outside sign. UC IPM says “the fungus can grow inside the fruit without external decay symptoms.” The only hints are a fruit that weighs less than it should and a rind that looks slightly off-color, such as a paler red. Texas A&M adds that the problem usually isn’t apparent until fruit is sorted after harvest.

The mechanism explains why. In the Israeli study, Ezra and colleagues isolated Alternaria alternata from the pistils of more than 85% of open flowers and from about 20% of the seed chambers (loculi) of fruit that looked healthy. Spores germinate on the stigma, grow down the style into the lower seed chamber at the calyx end, and sit there, latent, for about three to four months. When ripening starts, a small number of fruits turn on the fungus: it invades the arils, first as a brown soft rot, then black and dry, and works up into the upper chambers until the whole fruit rots.

So the fungus is common, and most fruit that carry it never rot. UC IPM puts losses in California orchards at usually under 1% and up to 6%. Those are commercial figures, but they suggest a few bad fruit in a season is the normal cost, not a sign the tree is failing. That reading is ours, not a number from a home orchard.

Sources differ slightly on the risky window. UC IPM cites San Joaquin Valley research that petal fall is the most susceptible stage, while noting infection can happen throughout bloom and fruit development; Texas A&M names the open-flower stage. Either way, UC IPM says infections commonly begin after rain during flowering and early fruit development, which puts the risk at bloom, months before the symptoms.

Why sprays rarely help

UC IPM and Texas A&M give the same reason in the same words: because the fruit’s crown covers the blossom tissues, preharvest sprays are generally ineffective. By the time a fruit shows any sign, the fungus has been inside it for months. What the sources recommend instead:

Remove old fruit and dead branches. The fungus overwinters on debris in or on the soil and in mummified fruit.
Shake the tree gently at harvest. UC IPM says this can drop infected fruit that looks healthy.
Avoid water stress and overwatering. Both can crack fruit, and cracks are entry points.
Sort before you store. UC IPM advises sorting and grading for discoloration and cracking so diseased fruit doesn’t get packed.
Control the bugs that puncture fruit. Texas A&M names leaffooted bugs (more on them below).

A hand test fits that advice. Before storing a harvest, set aside any fruit that feels clearly light for its size or looks paler red than its neighbors. That is our suggestion, built on UC IPM’s symptom list. It isn’t a published test, and it won’t catch every infected fruit.

Rots and Spots You Can See: Anthracnose, Leaf Spot, Aspergillus

If the damage shows on the skin or the leaves, the likely suspects depend on where you garden. California sources describe Aspergillus, gray mold and Coniella; Florida and Southeast sources list anthracnose and leaf and fruit spots among the main problems.

Anthracnose (Colletotrichum): one of Florida’s most important diseases

UF/IFAS lists anthracnose among the most important pomegranate diseases in Florida. When the rainy season starts in late May to June, the first sign is hard, dark brown to black lesions on the calyx of green fruit. After prolonged summer rains, ripening fruit get scattered, irregular, sunken rotted spots that progress through the rind into the arils, and in wet, humid weather gray to orange spore masses appear on the lesions. On leaves it makes irregular brown spots, with severe defoliation after prolonged rain, and it kills the tips of new shoots.

A 2014 to 2016 survey of Southeast US orchards, published in Acta Horticulturae, identified Colletotrichum as a prevalent pathogen based on how often it was isolated; more than 75% of the isolates belonged to the C. gloeosporioides group. Isolates from the other group, C. acutatum, were more aggressive on detached fruit. The trigger in these descriptions is sustained wet weather, not a date, so a rainy June in zone 6 may deserve the same attention; that’s our reading, since none of the sources studied northern orchards.

Leaf and fruit spot: look for the halo

UF/IFAS describes Pseudocercospora punicae lesions that start at 0.1 to 0.3 cm and dark brown, then grow to 0.5 to 1.2 cm with a dark brown margin and gray coloration, sometimes with concentric rings, and a greenish halo that stands out as the leaf yellows. On fruit the spots are small, irregular and black, can merge into blotches, and are superficial only, unlike anthracnose and other fungi that reach the rind and arils.

Texas A&M’s fact sheet calls its pathogen Cercospora punicae, a different genus name, but the symptoms it lists line up: dark spots with a faint halo, and fruit spots that are “darker, of various sizes, without cracks, and no stickiness.” It says losses are usually small, though in some host plants they can be significant, and that leaf spots cut yield by lowering photosynthesis. (A graduate student wrote the page as a class exercise, which it states.) For how fungal leaf spots spread in general, see our guide to fungal plant diseases.

Aspergillus, Coniella and mummies

In California, UC IPM describes Aspergillus fruit rot as more visible than Alternaria: decay usually near the calyx, a rind that’s paler red or yellowish to brownish-red, and black powdery spores inside and, once decay reaches the surface, outside. It tends to follow injuries: insect feeding, bird pecking, sunburn, overwatering and russeting.

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The fungus UC IPM calls Coniella (=Pilidiella) granati is the one UF/IFAS calls Pilidiella granati. It browns the rind, rots the arils and leaves raised black dots on the surface. In Florida, UF/IFAS says infected fruit dry out into mummies by the end of the season, and nearly 50% of them drop while the rest stay on the tree. UF/IFAS calls fruit rot a serious problem that can cost more than 80% of the fruit in Florida. Several pathogens were isolated from the mummies, which is why it says to remove all mummified and rotted fruit during and between seasons.

Gray mold is mostly a storage problem. UC IPM says Botrytis infects flower parts at bloom and stays inactive until ripening; washing the fruit or storing it at high humidity activates it, and decay develops quickly at shelf temperatures of about 65 to 75°F (18 to 24°C). UC IPM’s commercial storage figures are 41°F (5°C) for up to two months at 90 to 95% relative humidity. For a home harvest, the one thing the page clearly flags is washing, so our inference, not a tested recommendation, is to wash fruit only before eating and keep the rest cool.

Dieback: Canker, Winter Injury, or Just Bark?

Cutting into a dying stem is the first check for canker: look for discoloration in the cross-section, which helps narrow the cause. Check before you pull anything, because ordinary bark can look alarming and winter injury opens the door for canker fungi.

UF/IFAS describes Botryosphaeria canker, caused by Neofusicoccum parvum and Lasiodiplodia theobromae, as small brown lesions on succulent stems. In inoculation tests the stems showed blight-like symptoms after three months, and a year after infection they carried large swollen cankers with deep cracks and many fruiting bodies. Stems are slowly girdled and, per UF/IFAS, the tree dies after one to two years. UC IPM describes a similar canker from Coniella granati on young shoots, with black dots on bark and thorns.

Stress is the link to winter. A University of Maryland Extension answer says Botryosphaeria tends to infect plants stressed by drought, heat or winter injury, and that pomegranate is barely winter-hardy in Maryland. In the same exchange, the university’s plant pathologist looked at photos of rusty, flaking bark on a five-year-old tree and saw no sign of disease. The raised bumps looked like lenticels (the bark’s gas-exchange pores) or normal bark development with age.

The Maryland advice on how to check is simple: look at a cross-section of freshly dead or dying stems for discoloration, since where it sits and how it looks helps narrow the cause. If it’s a canker, UF/IFAS advises pruning diseased branches and the leftover pedicels (the short stalks that carry the fruit), because the canker fungi were often isolated from pedicels. Prune in dry weather, cut at an angle so water drains off the wood, and sanitize tools between trees. UF/IFAS puts the best pruning time in winter, when spore production is low, or in late fall, when wounds are less susceptible and heal faster. Those timings come from Florida; adjust them for a cold-winter site. If the tree died back after a hard winter, rule out cold damage first; our guide to growing a pomegranate tree that fruits covers hardiness.

Look-Alikes That Aren’t Diseases: Leaffooted Bugs and Cracked Fruit

Brown spots inside the rind and withered arils are often an insect, not a fungus. UC IPM calls the leaffooted bug “a frequent and highly damaging pest of pomegranate.” Adults are 0.75 to 1 inch long, gray to dark gray, with a narrow white zigzag band across the back and flattened, leaf-like hind legs. Feeding damage is hard to see from outside; cut the fruit open and you find brown spots on the inside of the skin where the mouthpart went in, and arils that feeding has withered.

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The tie to disease is the wound. UC IPM says opportunistic pathogens sometimes enter feeding wounds and cause soft rot on the surface or black rotten areas inside, and Texas A&M links Aspergillus to this kind of feeding. To tell the two apart, black heart starts in the lower seed chambers at the calyx end (Ezra and colleagues), while bug feeding leaves brown spots on the inner skin.

UC IPM’s California timing has bug numbers building from mid-August through harvest. It advises removing all fruit before winter, notes that orchards with cracked and split fruit left on the trees are a favored overwintering site, and says that about 21°F for at least six hours kills about half of exposed bugs. Texas A&M’s page says cold near 23°F kills most; the two sources differ, so don’t count on one cold night.

Cracked fruit is a symptom and a door. Coniella enters through insect exit holes, bird pecks, thorn punctures and natural cracking (UC IPM), and Aspergillus follows cracking from overwatering, sunburn and similar injury. UC IPM’s advice is to avoid the water stress and overwatering that may result in fruit cracking.

Where Bacterial Blight Fits (and Where It Doesn’t)

Bacterial blight is real, serious and documented in other countries, but none of the US extension pages we read lists it for pomegranate, so don’t diagnose it from one spotty leaf. The pathogen is Xanthomonas axonopodis pv. punicae, which the EPPO database now lists as Xanthomonas citri pv. punicae.

A 2025 paper in Frontiers in Plant Science calls it a major constraint to pomegranate production and fruit quality, and says it has been declared a quarantine pest in various growing areas, especially Pakistan, India, South Africa and Turkey. Turkey’s 2014 first report cites earlier reports from India, Pakistan and South Africa.

Researchers in India describe the symptoms in Scientific Reports: water-soaked lesions on leaves (seen on the lower surface in their tests) that develop into dark brown spots surrounded by bacterial ooze, and on fruit, isolated water-soaked lesions followed by necrosis with small cracks that can lead to splitting of the whole fruit.

AI illustration of dark, water-soaked spots on a pomegranate leaf, the symptoms described for bacterial blight in India — AI illustration of the water-soaked, dark-spotted lesions described for bacterial blight in India. It is not a photo of a US case; the fungal leaf spots seen in Florida have a dark margin and a greenish halo instead.

Now the US side. UC IPM’s pomegranate guidelines list five diseases (Alternaria rot, Aspergillus rot, blue and green mold, Coniella canker and rot, and gray mold), and none is bacterial. UF/IFAS’s Florida disease list is entirely fungal. Texas A&M’s Cercospora page mentions bacterial spot only as what the fruit spots resemble. There is a catch: the Southeast survey plated tissue on agar containing two antibiotics (rifampicin and ampicillin) and identified fungi, so it was built to isolate fungi and was not designed to detect a bacterial pathogen. The honest status is “not documented in the US sources we read,” not “proven absent.”

In the yard, the difference to look for is the one the sources give. Texas A&M describes Cercospora fruit spots as darker, without cracks and not sticky; the Indian description is water-soaked, oozing and cracking. The Scientific Reports authors also warn that symptoms of one disease can be confused with another, and that the pathogen can persist in a latent form in healthy-looking parts of a diseased tree. If you see water-soaked, oozing, cracking spots, take a sample to your state’s plant diagnostic lab instead of guessing. That advice is ours.

Don’t copy the control program from the research papers either. In the Pakistani trial, six bactericides were sprayed every 15 days from April to July, and copper oxychloride with streptocycline worked best. That is a field-trial program for a disease that is endemic there, and we found no US extension source that endorses it for home trees.

Do Fungicides Work? What Three Extension Sources Say

The honest answer is “not against the rots that matter most.” The sources show an effective option only for postharvest gray mold, and Texas A&M lists fungicides for leaf spot without stating how well they work. The table sets the statements side by side.

Source	Disease	What it says
UC IPM (California guidelines, commercial)	Alternaria and Aspergillus rot	Preharvest sprays are generally ineffective because the crown covers the blossom tissues
UC IPM	Gray mold	The crown covers the blossom, which prevents the use of preharvest sprays; postharvest sprays can be very effective
UF/IFAS PP349 (Florida, 2019)	Anthracnose, leaf spots, canker, fruit rots	“Fungicides currently labelled for pomegranate are ineffective against the fungal pathogens reviewed”; several products were under EPA evaluation
Texas A&M fact sheet (2020, student-written)	Cercospora leaf spot	Lists fungicides with thiophanate, carbendazim or propiconazole; says to follow the label and disinfect pruning tools with 10% bleach

These statements come from different places, diseases and years, so they don’t contradict each other as cleanly as they look. The UF/IFAS statement is from 2019 and says new products were under review, so ask your county extension office what’s current. The safe rule is the label’s: use only a product whose label lists pomegranate.

Frequently Asked Questions

Can you eat a pomegranate with black heart?

Texas A&M says heart rot makes the seeds inedible, and the affected arils are brown to black and rotted. Cut the fruit open before you commit to it, and discard any fruit with brown or black arils.

Do I need to spray my pomegranate tree for fruit rot?

UC IPM and Texas A&M both say preharvest sprays are generally ineffective against Alternaria rot, and UC IPM says the same for Aspergillus rot, because the crown covers the blossom tissues. Sanitation, a gentle harvest shake, even watering and insect control are what they recommend. If you do spray, use only a product labeled for pomegranate.

Is bacterial blight in the United States?

None of the US extension pages we read lists bacterial blight for pomegranate, and it is documented in India, Pakistan, South Africa and Turkey. That makes it “not documented,” not “ruled out.” A state plant diagnostic lab can tell a bacterial spot from a fungal one.

Your Next Step

If it’s winter where you are, do the dormant job now: pick every fruit and mummy off the tree and the ground, clear the leaf litter, and cut into any dead stem before you blame a disease. Next year, water evenly through bloom, shake the tree before you pick, and cut a few fruit open before you store the lot. If pomegranate isn’t your only fruit tree, our fruit tree growing guide covers the rest of the orchard.

Sources

Also free:

Pomegranate Tree Diseases: Black Heart Rot Starts at Bloom — How to Tell 6 Fungal Problems Apart (and Where Bacterial Blight Fits)

Which Problem Do You Have? Start With Where You See It