PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Management (IDM)
Are you a commercial grower or home gardener?
1.Obtain/prepare a plan that fits your situation.
There are management programs for this disease in
commercial growing areas, otherwise seek advice for
this disease on your crop in your region.
2.Crop, region. Recognize variations.
3.Identification of disease must be confirmed, by a
diagnostic service (page xiv).
4.Monitor symptoms. Seek advice on when, where,
what and how to monitor. Record results.
5.Threshold. How much damage can you accept? Do
you need to calculate your own threshold for a
particular crop and region?
6.Action. Take appropriate action when any
predetermined threshold is reached.
7.Evaluation. Review IDM program to see how
well it worked. Recommend improvements if required.
Control methods
Generally young trees are affected more seriously
than older trees. Once bacteria are established in
bark or leaf tissue there is little chance of killing
them so control measures aim to protect leaf scars,
pruning and other wounds from infection.
Cultural methods.
There is evidence that bacterial canker
infections in young trees can be reduced by
orchard practices which discourage vigorous
growth.
Do not locate susceptible orchards in areas
where trees are subject to frost damage,
waterlogged soils or prolonged drought.
Prevention of frost damage before bud
movement is also important in stopping entry
through frosted buds.
Pruning generally should be completed as soon
as possible after leaf fall. Pruning cuts are one
of the main points of entry and a large proportion
of infection occurs through winter pruning cuts.
Prune susceptible varieties of young nonbearing
trees after bud burst when they are
actively growing, older trees just before leaf
fall. Prune apricots in late summer or autumn
when warm and dry, or even when leaves are
still on the tree, wounds heal and seal quickly.
Any pruning of cherry trees required should be
done before early autumn.
Trees should be protected from wind driven
rain and overhead irrigation. Irrigate when leaf
surfaces can dry quickly.
Sanitation. .
Remove and destroy infected young trees
less than 4 years old. Sites can be replanted.
Sterilize pruning tools between cuts and between
trees, eg either by dipping in 70% methylated spirit
or wiping with a rag moistened with methylated
spirit.
In older trees, cut out diseased wood. Scrape
away large cankers, burn scrapings. Paint area
with Bordeaux or similar paint. Alternatively
large cankers may be cauterized with a blow
lamp in spring and if necessary, again 2-3 weeks
later. Neither treatments are guaranteed 100%.
Resistant varieties. While all stone fruits
may become infected; apricot and cherry are more
susceptible than others. For cherries:
Highly susceptible - Florence, Napoleon,
St. Margaret.
More tolerant - Merton, Ron's Seedlings,
Williams Favourite. Other imported resistant
cherry cultivars are undergoing testing.
Susceptible varieties should be propagated on
rootstocks resistant to bacterial canker and
should be grafted as high as possible.
Plant quarantine. Bacterial canker of stone
fruit may be introduced into an area by the
purchase of infected nursery stock and possibly by
the use of contaminated secateurs.
Disease-tested planting material.
Only purchase trees from reliable suppliers.
New trees which are ‘suspect’ should not be
planted but destroyed.
Propagate only from trees with no symptoms.
Only healthy budwood and rootstocks should
be used for propagation.
Physical & mechanical methods.
Cankers on trunks and large branches can be
controlled by cauterization with a handheld
propane burner (Agrios 2005) in early to midspring.
If considered necessary it can be repeated
3 weeks later.
Bactericides. Copper fungicides which are
non-systemic and protectant only, are the main
products currently available for controlling
bacterial canker. Overseas streptomycin, which is
systemic, is available for use.
Table 56. Bacterial canker of stone fruit – Some fungicides.
What to use?
NON-SYSTEMIC PROTECTANTS
Group M1, eg various (copper oxychloride)
Group M1/M3, eg Mankocide (cupric hydroxide/mancozeb)
When and how to use?
Copper sprays can only be used as dormant sprays on
stone fruit otherwise leaf and fruit burn may occur. Keep
accurate records of spray programs from year to year.
The number of sprays and timing of sprays will depend
on:
The particular species of stone fruit, eg cherry, etc.
The region of Australia.
Whether the disease is of minor importance,
moderately severe or severe.
Whether the trees are nursery stock, non-bearing, or
bearing.
Bacterial diseases 309