PREVENTION is better than cure for nipping brown rot disease in the bud - and you can start by pruning in coming weeks

Despite the fact this disease is striking hard right now, February is probably the wrong time of the year to write about brown rot disease and how to control it.

After all, the key time for preventative measures is during late winter and early spring.

But the fact the most destructive, revolting and frustrating stage of this stone fruit disease is destroying crops before our eyes is reason enough to write about what to do about it - even if it is almost too late.

The present outbreak started late last winter and spring.

Most of southeastern Australia had a series of unusually heavy and persistent rainfalls.

They occurred while most stone fruit trees - apricot, plum, peach, nectarine and cherry - were in blossom.

Many flowers remained wet for too long, allowing a fungus to move in from mummified, shrivelled fruit still clinging from the previous summer, or lying on the ground.

The infected blossoms wither and turn black, a fungal stage called blossom blight.

Almost immediately the disease organisms also penetrate the soft bark of the youngest, fruit bearing branches, so the trees now become infected carriers.

It is the first deadly stage of brown rot disease which will remain, semi-dormant and inconspicuous, waiting for the fruit to develop.

All we see are insignificant-looking cankers, tiny, half-healed splits in the young bark, some of which ooze sticky blobs of toffee-like sap.

Then months later as the fruit begins to swell, tiny, pale khaki disease spores begin to appear within the cankers and on remaining mummified fruit.

As stone fruits mature the flesh softens and sweetens.

That's when brown rot fungal organisms strike to feed off the developing fruit sugars.

The first tiny brown dots appear on skins, then over a few days they expand and spread quickly until ripening fruit becomes completely rotten.

Usually great decayed clusters of fruit cling together, at first towards the ends of branches.

Soon they too start to shrivel, dry off and they too become dotted with infective spores, which drift to other fruit and nearby stone fruit trees.

Once brown rot begins to destroy large numbers of fruit, it is virtually too late to do much.

That's a job that must be started during and immediately after harvest then continued through the year.

The main preventative spraying controls are carried out at leaf fall in autumn and again during August and September, just before the leaves appear.

In essence, control of brown rot disease on stone fruit is nothing more than strict hygiene, while ensuring that sources of re-infection are removed from all parts of every tree.

The first job is to cut free all diseased fruit and continually rake up all fallen fruit and take it well clear.

As soon as all fruit have been picked, start pruning. This is not a winter job with stone fruit.

Pruning is best carried out in summer while trees are still in active growth.

That ensures quick healing of pruning wounds.

All young infected branches must be cut back to healthy wood.

Every bit of pruning debris must then be carefully collected and carted away to remove sources of infection.

If necessary, mow any grass beneath trees hard to the ground using a catcher, so every bit of fruit and other debris is sucked up leaving the ground clean.

At leaf fall spray every stone fruit tree with Bordeaux or Burgundy mixture.

During winter, check closely and remove any branches with cankers or mummified fruit.

In late winter, just as the blossom buds are swelling and starting to colour-up, spray again with the same full-strength sprays.

They also control peach leaf curl disease.

Again check for and cut out any cankered wood.

In early spring, watch out for signs of blossom blight and prune out all infected branches.

It is worth the effort because with strict hygiene, ruthless pruning and perfectly-timed sprays we can beat this deadly disease - even after a wet spring.