PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Management (IDM)
1. Prepare a plan that fits your situation, as a
commercial orchardist or home gardener.
2. Crop, region. Obtain local information sheets on
peach leaf curl.
3. Identification of disease must be confirmed. Do
not confuse with aphid injury. Consult a diagnostic
service if symptoms are confusing (page xiv).
4. Monitor disease and/or damage during spring to
determine which trees/varieties will require
treatment the following spring and to determine
the effectiveness of any treatments already carried
out. Mark affected varieties if necessary. Record
results.
5. Threshold. How much damage can you accept?
Have any thresholds been established? If so, what
are they, eg economic, aesthetic, environmental?
Do you need to calculate your own threshold?
Remember know when, where, what and how
to monitor.
6. Action. Take appropriate action when any
threshold is reached. During the growing season,
fertilize severely affected trees, etc.
7. Evaluation. Review IDM program to see how
well it worked. Recommend improvements if
required, eg replacing susceptible varieties. Note:
An occasional curly leaf on an otherwise healthy
tree is not important.
Control methods
Peach leaf curl may be controlled more efficiently
and more easily than any other major disease of
stone fruits.
Cultural methods.
If trees have been severely defoliated by the
disease through failure to spray at the correct time,
a light application of a quickly-acting fertilizer
such as sulphate of ammonia, may help them to
produce new foliage.
Sanitation.
Prune out all infected shoots at pruning time to
reduce infection sources for the following season.
Infected shoots can be difficult to see.
Resistant varieties.
Some varieties of peaches are very susceptible, eg
Elberta and Blackburn.
Fungicides.
Peach leaf curl can be controlled satisfactorily with
a single spray of a registered fungicide just before
budswell. Some fungicides are not suitable for
some stone fruits, eg peach or apricots. Follow
label instructions.
Table 66. Peach leaf curl – Some fungicides.
What to use?
NON-SYSTEMIC FUNGICIDES (protectants)
Group M fungicides carry an inherently low risk of
fungicide resistance developing.
Group M1, Copper compounds, eg copper hydroxide,
copper oxychloride, cupric hydroxide, cuprous
oxide, copper ammonium acetate, tribasic copper
sulphate, copper octanoate, buffered copper
complex
Group M2, Sulphur compounds, eg Kumulus ,
Lansul , Sulfine , Wettable sulphur (dispersible
sulphur); Lime Sulphur (polysulphide sulfur)
Group M3, eg Ziram (ziram)
Group M1/M3, eg Mankozeb DF (cupric hydroxide/
mancozeb)
Group M5, eg Bravo , Rover , various (chlorothalonil)
Group M7, eg, Syllit (dodine)
Group M9, eg Delan (dithianon)
When and how to apply?
Correct timing is critical for effective control.
For effective control spray when buds are swelling but
before they have opened. It is not possible to
satisfactorily control peach leaf curl once the fungus has
entered the leaf.
As initial infection occurs during a short period
when leaves are emerging from buds, 1 application of a
copper fungicide (or lime sulphur) just before buds start
to swell (when buds are beginning to get plumper) in
spring may give satisfactory control.
To ensure correct timing and complete coverage,
sometimes 2 sprays, the 1st at the very first sign of bud
movement and a 2nd spray a week later are applied. It is
better to apply the 1st spray too early rather than too late.
Do not apply after mid-budswell or control will be
unsatisfactory and sprays may burn young leaves.
Where disease has been difficult to control in
previous seasons the following 3 sprays is suggested:
1 st spray in autumn at leaf fall.
2 nd spray immediately before budswell.
3 rd spray about 1 week later at budswell.
Failure to control peach leaf curl adequately
with 1-2 copper sprays is usually due to incorrect timing,
usually too late due to difficulty in recognizing the
1st sign of budswell or wet weather (spraying
impossible). In a planting containing peach and nectarine
cultivars, sprays must be timed for the cultivar which
shows the earliest movement of buds.
Copper fungicides are more effective than sulphur
when conditions favour disease. Whichever spray is
used, the whole tree must be thoroughly sprayed,
taking care not to miss limb and twig extremities.
After budswell. Some protectant fungicides are
registered for use just after budswell, these can be useful
where the disease has been a problem in previous
seasons.
Some of these fungicides will also control other diseases
of stone fruits.
360 Fungal diseases - Examples of fungal diseases