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With most of the summerfruit harvest over, and the early varieties of apples and pears off the trees it is time to start thinking about setting the orchard up for next season.
The diseases which may require attention include:
Summerfruit
- Silver Leaf
- Bacterial diseases
- Brown Rot
Pipfruit
- Phythophthora
- Black Spot
- European Canker
- Specific Apple Replant Disease (SARD)
- Fireblight
Silver Leaf
Summerfruit trees are least likely to be infected by silver leaf if their pruning is carried out during periods of dry weather between harvest and leaf fall.
Before pruning it is good orchard practice to clean up any dead wood which may be lying around the orchard environs because if this wood happens to be infected with silver leaf, rain will trigger the disease to begin producing spores. If you are keeping it for firewood, cover it so it cannot get wet.
With highly susceptible species such as cherry or apricot, only prune during fine clear sunny weather and apply fungicidal wound protectants to all saw cuts.
Bacterial Diseases
Immature leaf scar tissue exposed as the leaves fall are considered to be major entry points for stonefruit blast and bacterial spot. The first step in control of these diseases is the application of a copper spray just prior to the commencement of leaf fall or the first significant air frost.
Persistent coppers such as Bordeaux mixture or its commercial copper substitutes should be used because these formulations stick around on the plant surface and will be splashed around every time it rains.
In locations or on orchards which have a history of bacterial infection, further copper sprays during leaf fall are advisable.
Brown Rot
Mummified fruit and twig infections are major sources of re-infection for the crop next spring. During the pruning try to cut out these infections.
Phythophthora
This disease is very active during the autumn, and infection is very much favoured by wet weather following a long dry period such as we have had this season.
Foliar application of a phosphorus acid based fungicide such as Aliette or Foli-R-Fos as soon as practical after harvest will reduce risk of infection.
For crown and root rots, poor drainage and wind rock are key factors in infection. Improving drainage and tree support will also help.
Black Spot
Frequently black spot can become quite active after harvest, even though evidence of infection was not obvious prior to or during harvest. In newer orchards the autumn is often a key time for growth, so it is advisable to maintain black spot cover sprays while this growth is going on.
Established blocks will not need fungicide protection for control between now and leaf fall, but if black spot is present will need leaf fall clean up sprays of Urea at 5% to minimise disease carryover.
European Canker
Leaf scar tissue is an important entry point for this disease. Pre-leaf fall and leaf fall fungicide sprays are essential in orchards where the disease is present.
The first spray should go on right at the commencement of leaf fall.
SARD
Where apples are replanted following apples, this disorder adversely affects both growth and fruit size in the replant trees.
Incidence varies with soil type, with lighter textured soils showing more severe symptoms than heavier soils.
Blocks to be replaced should be pulled out as soon as possible, root raked so that as much of the root system as possible can be removed, then fumigated before soil temperatures drop below about 120C.
Fireblight
During the post harvest period fireblight infections are very easy to see because their dead leaves and twigs stand out against the healthy green leaves around them. This is a good time to prune them out.
Leaf fall sprays of copper or other bactericides are ineffective against fireblight because the organism is not active at this time of the year.
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