Birds, run off, and disease

Problems

Birds love cherries, the RHS says, so it’s best to net the tree or grow it in a fruit cage if you want the whole crop for yourself. RHS Netting will help to deter birds, the RHS says. Cover the tree or individual branches, raise the netting above the fruits, and keep it taut and fastened securely so birds and other wildlife don’t get entangled. Cover the tree before the fruits start to colour up. RHS

Common insect pests include scale, aphids, and fruit flies, Britannica says, and backyard trees must be protected from bird predation. At a commercial level, that article says, crop losses from birds are usually considered insignificant. Britannica

Cherry fruit drop

In some seasons, the RHS says, sweet cherries lose much of their fruit before it ripens. This loss is called cherry fruit drop or run off and, in severe cases, it can lead to an almost total failure of the crop. RHS In Britain, the most common fruit to suffer this drop is the sweet cherry, the RHS says, and this is referred to as cherry run off. RHS

In 2000 in the UK, the RHS says, as much as 90 percent of fruit that initially set on sweet cherries was lost before maturity. RHS The severity of the drop also varies by location, the same page says: cherries in northern areas such as the UK or Norway suffer more than those grown in the south of Europe or the USA. RHS

Many fruit trees, including apples, pears, plums and cherries, naturally shed some of their immature fruits in early summer, the RHS notes. The fruitlets fall over a short period, which may look alarming but is not generally a cause for concern, as a good crop usually remains on the tree. RHS As ripening becomes imminent, much, and often most, of the fruit can fall to the ground. The fruit is immature, so can’t be eaten, the RHS says. RHS

Recent research, the RHS says, suggests that in sweet cherry a combination of climatic factors can be linked to heavier fruit drop, including poor weather and low light intensity at blossom time, and low temperatures in the early stages of fruit development. Fruit yields were lower following wet and cold autumns. RHS

Pruning trees to give an open canopy is one potential remedy, the RHS says, as it maximises light to the leaves. RHS The RHS suggests reducing the number of fruits when there are more than 10 fruitlets per spur, when the fruitlets are less than 5mm (¼in) in diameter — usually when petals are still present and before the pit hardens. It also says more research is needed before clear guidance can be given on the balance between leaf area and fruit. RHS

Diseases named in the sources

Sweet cherries are vulnerable to a number of plant diseases, Britannica says, including scab, bacterial canker, black knot, crown gall, leaf curl, and powdery mildew, among others. Britannica

Die-back of branches and discoloured leaves can be caused by the fungal disease silver leaf, the RHS says. To avoid infection, prune in summer after harvesting. RHS Dead patches of bark and small holes in leaves can be signs of bacterial canker, the RHS says, which may eventually result in branches or whole trees dying. RHS