Rescue plan for cherry

QWhy have my cherry ‘Stella’ leaves turned sooty?

ACherries can be affected by a number of diseases and pests such as black aphids. These drip sticky honeydew onto lower leaves, which is then colonised by sooty mould. Spray with a suitable insecticide such as Provado Ultimate Fruit and Vegetable Bug Killer (£4.19 for 1L spray) as soon as you spot the problem. This will also control other pests such as scale insect, which may also have caused the sooty mould. Prune off affected shoot tips in July or August. Bacterial canker (shothole disease) could also be the cause: look for lots of small holes in the leaves. Foliage and shoots often die back and resin oozes from the stems. I do hope it’s not canker, as I’m afraid there’s no cure. Q Can I help apple trees fruit again? A It’s unusual for healthy trees to stop fruiting suddenly, but improper pruning might be to blame. Hard pruning every winter will prevent fruiting, so just give a light prune or leave them alone this year. If trees aren’t growing well they won’t flower or fruit either. Try feeding with general fertiliser in spring. Q Were leaf spots to blame for brown flesh on quince fruits? A Quince foliage is prone to powdery mildew, which is unsightly but rarely causes much harm to the plant or fruit. Instead, the brown flesh may have been caused by a calcium deficiency, leading to a problem similar to bitter pit in apples. This commonly affects young trees and is associated with drought. If you have acidic soil, apply lime and keep the tree well watered in dry weather. If the browning occured throughout the fruit flesh, your quince may simply have been overripe when picked. Q Is Prunus avium self-fertile and when should we prune it? A Prunus avium is the wild cherry from which edible cherries have been bred; without its cultivar name I can’t tell if yours is self-fertile. It’s much better to buy named trees from specialist fruit nurseries or garden centres. Prune it in summer, when in full leaf. Reduce long stems by half their length to increase bushiness. Q What’s this woolly deposit on my apple tree? A The stress of heat and lack of water last year made plants more susceptible to pests and diseases. Your apple is suffering from woolly aphid – a pest that infests shoots and sometimes leaves. The aphids cover themselves with a waxy, woolly coating and suck sap from trees, weakening them and reducing the crop. Remove aphids from large branches by scrubbing them with a brush. In summer, if the tree is small enough to spray, use a suitable insecticide such as Westland Resolva Bug Killer (£9.99 for 250ml concentrate). Q How do I treat scab on crab apple ‘John Downie’? A ‘John Downie’ is an old crab apple cultivar planted for its large fruits that are useful for crab apple jelly. Unfortunately it’s prone to common apple diseases such as scab, which affects the leaves and fruit. It’s not easy to spray against scab, so the best precaution is to make sure the tree is healthy, by keeping grass away from its trunk, mulching well and feeding to promote good growth. Last year’s hot, dry summer wasn’t easy for most trees. Prune out any weak and crowded shoots this winter to improve air flow around leaves and fruits. Modern cultivars have better resistance to the disease.