Reader's question: I have a pear tree, which three years ago fruited heavily with beautiful juicy fruit. For the past two years the fruit has grown until it is about 4½cm long then it has gone black, shrivelled and dropped off. Have you any idea of the cause and is there any treatment?

Anne Navin, Bishop Auckland

ALTHOUGH frost can scorch back blossom and shoots, it sounds as though your pear tree is suffering from pear blossom wilt (or twig blight, spur blight, wither tip and brown rot, which are all caused by the same fungus). It’s a menace to fruit tree blossom and in wet years to twigs, going on to rot the fruit. These diseases are all much the same. The fungus damages new growth early in the season. It gets into flowers, causing them to wilt within two weeks of opening. Shoot infections follow and cankers form on shoots, twigs or spurs, girdling the bark and causing leaves above the damaged area to die.

In wet weather, this disease can be widespread. It results in limp, watersoaked flowers hanging on the twig.

The fungus sclerotinia laxa is responsible. Look out for grey pustules on the flower stalks. From there, the fungus enters the shoots and infects the twigs. It looks as if the affected parts have been scorched. Often, the whole tree becomes covered with browned shoots.

The fungus overwinters in cankers on the shoots, in mummified fruits still on the branches or in fallen fruit. In fact, the mummified fruit seem able to persist as sources of infection for several years. In the spring, spores are released which go on to cause blossom infections. They get to new sites on the breeze, by rain splash or are carried by insects. The spores multiply quickly in the floral parts when the weather is wet, releasing more spores which go on to infect additional flowers.

There is no cure for the disease, but good housekeeping, such as sweeping up and disposing of leaves or removing rotten fruit from the tree, and pruning the branches so that there is plenty of air circulation within the crown will all help keep the disease at bay.

Jobs this week

■ Lift the corms of gladioli when the leaves turn yellow, cut off the stems, dry the corms, rub clean, label varieties and store in a cool, mouse-free place.

■ When the leaves have been blackened by frost, dahlia tubers should be dug up. Cut off the stems at two to three inches above the tuber, remove all the loose soil, dry them in an airy place, dust with flowers of sulphur, and label and store in a cool dark place. The easiest way to apply sulphur is to shake the tubers in a plastic bag with handful of flowers of sulphur. Large old clumps of tubers are better divided next spring, when you plant them out again. Division now only makes wounds for mould to enter.

■ Cut down canes of Jerusalem artichokes to around a foot long. Dig out the tubers freshly as required over the coming months. Where eel worm is a problem, lift the tubers of Jerusalem artichokes and store them as you would potatoes.

■ Brigid presents the Green Gardening and Great Outdoors show every Sunday from 11am to 2pm on BBC Tees, 95FM.

Questions can be rung into the show on 01642-225511, or texted on 07786-200995.

Emails can be sent to brigid.press@bbc.co.uk.