Pomegranate Problems: Splitting, Fruit Drop, Rot and Pests

Start by ruling out the three non-diseases

Before you reach for anything to spray, check three things, because they account for the large majority of complaints about pomegranates and none of them is a pest or a pathogen.

First, are the flowers double? A rosette of many petals with no swollen vase behind it will never set fruit. Second, is the autumn long enough and dry enough? Fruit that stays green and hard until frost has simply run out of season. Third, is the watering even? Erratic water causes both the heavy flower drop in midsummer and the split fruit in autumn. Work through those three before you diagnose anything else, and you will usually find your answer.

Splitting and fruit rot

Splitting is a physiological failure, not an infection, but the infection follows within days. Once the skin opens, gray mold and blue mold move into the exposed arils and the fruit is finished. There is no spray for splitting; the controls are even watering, a thick mulch to buffer soil moisture, thinning so fruit do not press against each other, and picking ahead of forecast heavy rain when the crop is close to ripe.

A different and more insidious rot lives inside apparently perfect fruit. Fungal spores enter through the open flower at bloom, colonise the interior, and produce fruit that look flawless outside while the arils inside are brown, dark and dry. You only find it when you cut the fruit. Affected fruit are often slightly lighter for their size and sometimes sound dull rather than metallic when tapped. There is nothing to do once it is present; remove and destroy affected fruit rather than composting them, avoid overhead watering during bloom, and prune to keep the canopy open so flowers dry quickly after rain.

Flower and fruitlet drop

A pomegranate produces two kinds of flower. Some are complete and fruit-forming with the vase-shaped ovary behind the petals; others are short-styled and male in function, and those are meant to drop. A carpet of fallen flowers under the tree in midsummer is therefore normal and not a symptom. What is not normal is the loss of fruitlets that had already begun to swell.

Fruitlets that reach pea or marble size and then yellow and fall are almost always reacting to water stress, to a sudden heat spike above about 100F (38C) during set, or to sheer competition in an overloaded cluster. Steady deep watering through flowering and early set is the main fix. Thinning clusters to one fruit at walnut size prevents the tree from doing a cruder version of the same thing later. Excess nitrogen also contributes, by pushing the tree toward shoot growth at the moment it should be holding fruit.

Note the date of the first heavy flower drop each year and what the weather did that week. After two seasons you will be able to tell your normal male-flower drop from a genuine stress event at a glance.

Insects worth knowing

Pomegranate has relatively few serious pests, and a healthy unfed tree in a sunny open position rarely needs any intervention. Aphids colonise the soft shoot tips in spring, curl the leaves and leave sticky honeydew that goes sooty black. A jet of water and patience usually settles it, because predators follow the aphids within a fortnight; reaching for a broad spray tends to make the following flush worse by removing those predators.

Large sap-sucking bugs are the more damaging group in warm regions. They pierce the developing fruit, and the puncture both admits rot organisms and causes hard corky patches in the flesh. They are conspicuous, so hand-picking into soapy water in the early morning while they are sluggish is genuinely effective on a garden-scale tree. Scale insects appear as immobile brown or white bumps on stems and are best managed with a dormant-season oil spray and by cutting out badly encrusted wood. Wasps and birds arrive only once fruit has split, so controlling splitting controls them too.

Leaf and bark trouble

Small dark spots on leaves and dark sunken lesions on fruit skin appear in wet seasons and are fungal. On a tree in a climate dry enough to ripen the crop they are cosmetic and need no action beyond raking up fallen leaves and fruit in winter, which removes the overwintering source. In a wetter climate they become one more reason the fruit will not finish, and the honest response is to grow the plant in a container under cover rather than to spray repeatedly.

Yellow leaves with green veins on alkaline ground indicate iron lock-up rather than a shortage in the soil, and a chelated iron treatment plus a check that the roots are not sitting wet will correct it. Sudden death of a whole trunk in a multi-stem bush, with dry cracked bark, usually follows a hard winter; cut the dead trunk out at the base and let a replacement sucker take its place, which is exactly the reason to grow a multi-stem bush in a marginal climate.