The widespread dropping of immature or green coffee cherries can cause serious losses for farmers as harvest season approaches.
If left untreated, yields may be cut by 40–50%. Prompt and effective action is essential.
During the rainy season, abundant rainfall stimulates vigorous growth in coffee trees but also accelerates natural, physiological, and pathological processes. Premature fruit drop—especially in poorly managed plantations lacking careful pest control—often results.
Three Main Causes
Table of Contents
1. Natural Causes
Coffee flowers grow in clusters. When the tree is very vigorous, each cluster sets many cherries. As the rains progress and cherries swell, competition within the cluster forces some to drop.
This is most common when early rains are light but mid-season rains become heavy, driving rapid fruit growth.
Although each bearing tree may shed handfuls of cherries, this is a natural process and not a major concern. Balanced, adequate fertilization from early fruit set strengthens the fruit stems and helps reduce natural drop.
2. Physiological Causes
Low coffee prices, prolonged drought, and rising input costs can lead farmers to neglect proper fertilization.
Some skip fertilizer altogether or use unbalanced blends—typically deficient in phosphorus (P), potassium (K), and trace elements—so the tree cannot support its crop and cherries drop en masse.
Remedy:
– Provide complete, balanced nutrients.
– In dry weather, foliar-spray young leaves and fruits in the cool morning or late afternoon with a liquid fertilizer.
– In wet weather, apply 200–300 kg/ha each of potassium (for example muriate of potash) and fused phosphate.
– For heavily fruiting trees, increase the dose slightly.
– Review and adjust the fertilization schedule to ensure nutrients are supplied in several split applications.
Monthly foliar sprays of micronutrient-rich fertilizers will further reduce green-fruit drop and improve bean size and quality.
3. Pathological Causes
A key culprit is fungus infecting the fruit pedicel.
Spores survive on withered petals, and nighttime dew creates ideal conditions.
During long, humid rainy spells the fungus thrives, triggering premature fruit drop.
Early detection: look for sooty mold on leaves or check the pedicels for infection.
Treatment:
– Use fungicides containing mancozeb (trade names: DITHANE M-45, MANOZEB 80WP, VIMANCOZ 80WP, ROMIL 72WP, RORIGOLD 720WP, DIPOMATE 80WP).
– If heavy drop is already occurring, switch to fungicides with carbendazim (e.g., INDIAVIL 5SC, BAVISTIN 50FL, CARBAN 50S, CARBENDA 50SC, VICARBEN 50S, APPENCARB Super 75DF).
These can be tank-mixed with insecticides or foliar fertilizers.
Additionally, when irrigating, hose down the branches to wash away old flower petals and newly formed fungal spores.
During the rainy season, prune regularly to open the canopy so sunlight can penetrate, reducing humidity and discouraging fungal growth.