Soft green scale (Coccus alpinus/ C. viridis)
Various species of scales attack coffee in East Africa. The soft green scales are common but minor pests of Arabica coffee. More serious on transplanted seedlings during the first 2 years in the field. The yellowish to greenish flat oval scales are about 5 mm in length. They prefer to attack green wood and leaves, and usually appear as rows of flat oval green scales along main leaf vein and near tips of green shoots. Soft green scales produce large amounts of honeydew. This honeydew attracts ants, which while tending the scales protect them from their natural enemies. The sticky honeydew covers the leaves and sooty mould develops on it. As a result leaves appear black and sticky. Too dry microclimate favours infestation with soft green scale.
- Natural enemies of the soft green scale include predators such as ladybirds (Chilocorus melanophthalmus, Chilocorus nigrita), parasitic wasps (Coccophagus cowperi, Diversinervus stramineus, Metaphycus stanleyi). The parasitic fungus Cephalosporium (Verticillium) lecanii is particularly effective in the rainy season when it can kill large colonies of the green coffee scale in a short period of time.
- Control of soft green scale is possible indirectly by controlling ants by banding the tree stump. This keeps the attending ants away and allows natural enemies to clean up the infestation. The band should be at least 15 cm wide. Be careful not to leave any bridges.
- Improve shade on the plantation.
- Neem treatments have some effects on scales.