Grape: fruit splitting or cracking

What it is likely to be on grape

1. Fruit splitting

   Candidate 1very common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Grapes — problems
   • Cornell Fruit Resources — Cornell University, College of Agriculture and Life Sciences: Grape berry splitting

   Checked 2026-08-13

   Fruit splitting open on the plant, usually after rain following a dry spell. Nothing is attacking it: the inside has taken up water faster than the skin can grow, and the skin gives way. The split then lets brown rot in, which is where the real loss comes from.

   Points towards it

   • · the split happens when the root takes up water faster than the skin can grow, which is a wet spell after a dry one
   • · it is worst in the tightest bunches, where berries press on each other and cannot expand — so one bunch splits while a looser one alongside does not

   Argues against it

   • · the vine has had no sudden water, so a pressure split is not the explanation and something on the skin is more likely

   Check this next

   Look at where the split is and how tight the bunch is. A water split runs on berries wedged tightly against their neighbours, the skin is clean around the split, and it appears within a day or two of heavy rain or a heavy watering after a dry fortnight. A berry that split where a grey or scarred patch already sat on the skin has a different story.

   What to do now

   Thin the bunches when the berries are still small — removing up to a third of the berries with long scissors so that no berry touches another is the single measure that prevents this — and keep the water supply even rather than swinging between drought and soaking, particularly for a vine in a container or against a wall. Split berries should be picked off promptly, because grey mould enters through them and will take the whole bunch.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Grapes — thinning and watering

   Checked 2026-08-13

2. Powdery mildew

   Candidate 2common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Grape powdery mildew
   • Cornell Fruit Resources — Cornell University, College of Agriculture and Life Sciences: Powdery mildew of grape

   Checked 2026-08-13

   A white, floury coating on the upper leaf surface, most familiar on courgettes and cucumbers late in the season. Unlike most fungal diseases it does not need the leaves to be wet — it needs the roots to be dry and the air to be humid, which is why it arrives in a warm dry August.

   Points towards it

   • · the split follows a grey-white bloom or a corky scarred patch on the skin, which is the infection that stopped that part of the berry growing
   • · grapes under glass get powdery mildew far more readily than outdoor vines, because the air is still and dry
   • · unlike most fungal problems this one does not need wet leaves, and a dry-rooted vine in humid still air is its ideal

   Argues against it

   • · clean unmarked skin around every split points at water pressure alone rather than at an infection that scarred the berry earlier — this rules it out entirely.

   Check this next

   Look closely at the skin around the split, and at the berries that have not split yet. Where splitting follows mildew there is a dull grey bloom or a brown corky scar beside the tear, and unsplit berries in the same bunch carry the same marking — the fruit was infected weeks earlier and simply could not stretch. Clean skin on every berry means the water was the whole story.

   What to do now

   Improve the airflow first: thin the bunches, take out crowded laterals, and ventilate a greenhouse vine hard, because still humid air is what this fungus wants and wetting the leaves is not. Remove affected berries and shoot tips as they show, and expect the following season to be better on a vine that has been opened up — the infection overwinters in the buds and dormant wood, so winter pruning is part of the control.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Grape powdery mildew — control

   Checked 2026-08-13

Narrow it down

This page lists everything at once, which is the right shape for reading and the wrong shape for deciding. The interactive tool asks one question at a time, starting with whichever would separate these causes fastest, and stops as soon as further answers would not help.

Opens with the plant and the symptom already set. Nothing you answer is stored or sent anywhere — the answers live in the address bar and nowhere else.

What this does not cover

These are the causes GrowingHQ holds rules for on grape — not every cause there is. Where several problems look alike, the honest answer is often that they cannot be told apart by eye, and a page that named one would be guessing. If none of the above fits, the general fruit splitting or cracking page lists causes across all plants, and the Grape profile lists the problems it is prone to.