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Preventing leaf curl and die-back on fruit trees

It's coming up to bud season and I'm worried about leaf curl and die-back on my fruit trees. What can I do now to prevent this?

 

As fruit trees come into full blossom we do get problems with stone fruit — peaches and nectarines in particular. One of those problems is the famous leaf curl.

Leaf curl is caused by a fungus called Taphrina deformans — a logical name because it deforms the leaves. The leaves turn a pinky colour, then fall off the tree. That's where the life cycle of the fungus continues.

To stop this cycle you need copper and a good diary. Those fallen leaves keep on culturing this fungus, and sooner or later the tree gets weaker because it loses leaves. But the fungus continues on. Finally it releases its spores in autumn back into the trees, into the new buds being formed for next spring.

Timing, therefore, is crucial. Your tree will need regular spraying with Copper Oxychloride to keep the disease at bay. Spray soon after pruning in winter, just before the tree comes into leaf in spring and again 10-14 days later.

Another solution is to protect the buds at the time they get infected by the fungus in autumn. When half your leaves have fallen in autumn, give the tree one spray with a double dose of copper. If you time that well, you'll get rid of it for the whole season.

Another common problem in the North Island on peaches and nectarines is die-back of new twigs. It's caused by oriental fruit moth, which only occurs in the North Island.

The first generation of caterpillars make their home in the new twigs. The twigs fight back, gumming up the tunnel, trying to flush out the caterpillar. But the caterpillar just keeps on feeding and kills the new growth, giving you die-back.

The second generation of this species of moth will go not for the twigs, but straight into the peaches. That is similar to codling moth on apples, and that's what damages your peaches.

Spray with Carbaryl, or simply remove the offending twigs and burn them. By doing that, you're removing the first generation of these moths. That way your second generation will be lower and you've protected many of your peaches.

UnitecAdvice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

Reproduced with permission from NZOOM Home and Garden content,
from the previous website of  TVNZ News

The views expressed here are not necessarily those of the RNZIH
 
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Last updated: June 27, 2005