A GOOD apple crop depends on the weather and how we treat our trees. Even if you can rely on plenty of large, tasty apples 99 per cent of the time, the weather can still put paid to a happy harvest. A cool, wet autumn may prevent the next year’s fruit buds from ripening well and a sharp frost at blossom time can put paid to much of the yield. Early in May the temperature in my garden went down to -4C, which damaged the blossom and gave me a poorer crop than usual.

Even when apple blossom survives the ravages of frost, apples may still show signs of frost damage. A ring of brown, corky tissue, usually towards the eye of the apple, can be blamed on sub-zero temperatures. This has happened to some of my apples at a more exposed end of the cordon. They’re fine to eat, but won’t store.

I’ve also been struck by the number of cracked fruits this year and reckon I can blame the weather for that as well. Although irregular watering can cause cracking, huge fluctuations in temperature are equally bad. Looking at my records for April, I see that on 10 days there were swings of more than 15C. Though much less bad the following, the trend did continue.

Weather aside, pests are often the cause of small and misshapen apples and, as ever, you can often solve the problem once you understand what’s causing it. There are four species of aphid which feed on apples. In different ways, the rosy apple aphid, the rosy leaf curling aphid, the grass-apple aphid and the green apple aphid attack leaves, blossom and developing fruit.

These aphids have a similar life cycle and can be treated in the same way. They overwinter as eggs in the bark of apple trees and hatch in March. The larvae then start feeding on opening buds and blossom. Two of the species – rosy apple and apple-grass aphids – migrate in summer to other hosts, but the others remain on apple trees.

Use an organic winter wash to deal with these aphids. Based on natural plant oils, the winter wash is perfectly safe to use any time between now and December, or in late March, as the pests hatch out. But only do this in the evening when no pollinating bumblebees are around.

Apple sawfly also cause misshapen fruit. The creamy white larvae start eating into young fruitlets in May and June. Cavities in the tiny fruits are filled with reddish-brown rot, and though many apples drop, some hang on till harvest. To check, cut open any suspect fruit.

The pests overwinter as cocoons in soil close to the tree. When the adults emerge in spring, they lay around 30 eggs in open flowers. After hatching, the larvae consume tiny seeds in the developing fruits. Once done, they move to a second or third fruit before dropping to the ground for winter.

Reduce the problem for next year by clearing away any fallen fruit and forking over the soil round the tree, if that’s possible. You can also apply the organic winter wash in spring. Timing is all. Do this a week after petals have dropped and before the larvae enter the fruitlets. It’s essential you apply the wash in the evening when there will be no pollinators around. Worcester Pearmain, Charles Ross, James Grieve and Ellisons Orange are especially susceptible and sawfly aren’t attracted to cookers.

There’s no shortage of pests and diseases that afflict apple trees, and the fungus, apple scab, is all too common. It disfigures and can even crack the skin but doesn’t affect the taste, though scabby apples don’t store well. The fungus overwinters in fallen leaves and fruits and re-emerges in the spring. So, to reduce the spread, remove and destroy all fallen leaves and fruit. It thrives during a wet summer and when trees haven’t been pruned to allow good air circulation. So, when pruning trees over the next few months, remove any congested and crossing branches to allow for good air circulation.