Why Are My Currants Dropping Before They Ripen?

Finding green or half-ripe currants on the ground beneath the bush is worrying — it suggests the crop you were counting on will be smaller than expected, and if the dropping continues, you may end up with very little to harvest at all. Premature fruit drop in currants can be a natural self-thinning response, a symptom of stress, or a sign of disease in the developing berries, and distinguishing between these is the key to knowing whether to intervene.

Natural self-thinning after a heavy set

After exceptionally good pollination, a currant bush may set more fruit than it can mature and will shed the excess — typically in late May or early June in a process sometimes called the June drop. This is a perfectly normal physiological response and does not indicate a problem. The remaining berries will often be larger and better flavoured than if the full set had been retained. If only a small proportion of the fruit is dropping and those that remain look healthy, wait and observe rather than intervening.

Drought stress during fruit development

Currant bushes draw heavily on soil moisture during June and July when fruit is developing rapidly. An acute water shortage at this stage causes the plant to abort some or all of its developing fruit to preserve its own tissues. Water thoroughly and regularly during dry spells, applying water directly to the root zone. Mulching the soil around the bush with a 10 cm layer of bark chips or compost reduces evaporation markedly and moderates soil temperature.

Botrytis (grey mould) in the fruit clusters

Botrytis cinerea infects individual berries within a strig, causing them to turn grey-brown, develop a fuzzy mould covering, and drop prematurely. Cool, wet summers with poor air circulation around the bush create ideal conditions for this fungus. Infected berries fall first but healthy-looking ones can follow if the mould spreads. Improve air circulation by pruning the centre of the bush open and removing any dead or dying shoots. Pick off and destroy visibly infected strigs as soon as you notice them.

Currant fruit fly or sawfly damage

In some regions the currant fruit fly (Epochra canadensis in North America, or related species in Europe) lays eggs in developing fruit, and the larvae feeding inside cause berries to drop early. Examine a few dropped berries by cutting them open — if a small grub is present, this is the cause. Collect and destroy all dropped fruit immediately to break the life cycle, as the larvae pupate in the soil beneath the bush to emerge the following year.