Microsoft word - rust _10_.doc

Rust diseases affect currants, gooseberries, blackberries, raspberries and plum trees.
DAMAGE:
Rust diseases are easily recognised in their early stages by
the bright orange coloured spots produced on the leaves from
late spring onwards. Later the spots on the underside of the
leaves turn into dark brown pustules and appear to be woolly
or coarsely hairy.
On raspberries and blackberries it can cause premature leaf
drop and reduction of vigour. The spots on the upper
surfaces of leaves on blackberries differ in colour, being dark
red or purple. On both these fruits the fungus over-winters on
the leaves and in the spring secondary spores are produced
which infect the young leaves. Mild temperatures and high
humidity encourage infection.

Certain rusts have alternate hosts and although unrelated, both plants are needed for the fungus to complete
its life cycle. The disease on currants is always worst in the vicinity of the Weymouth pine and other five-
needled pines. This is because the currant rust fungus passes one stage of its life’s history on to these
species which in turn produces spores which re-infect currant bushes. In severe cases, the disease causes the
defoliation of currants.
The disease on plums is worst in the vicinity of anemones. When plum leaves are severely infected they turn
yellow and fall prematurely. Such defoliation tends to weaken the tree, but as infection is confined to the leaf
and does not affect the fruit, the tree will not be permanently damaged.
CONTROL:
Non Chemical Control

If the symptoms are not too severe, Rust can be controlled by picking off and burning infected leaves as soon
as they are seen. Care must be taken not to remove large numbers of leaves as this can do more harm than
good. Fallen leaves should also be raked up and burned. Care must also be taken to avoid using too much
nitrogen rich fertiliser as this results in an abundance of soft new growth which is more susceptible to rust.
Chemical Control (Currants & Gooseberries Only)

On red, white and blackcurrant crops where the disease has been a problem, spray once after harvest with
copper oxychloride (Bayer 'Fruit and Vegetable Disease Control). Vitax 'Bordeaux Mixture' can be used to
treat rust on gooseberries an blackcurrants by spraying when the plants see first signs of an attack and
repeating every two to three weeks. There are no chemicals approved for use on other crops.
*Please note that Bordeaux Mixture will be withdrawn from sale on 28 February 2013, but that any person can
use and store existing stocks until 28 February 2015.
USE CHEMICALS SAFELY: ALWAYS READ THE LABEL

When using chemicals it is most important to follow the manufacturer’s instructions precisely. Only use on the
fruits that are listed on the manufacturer’s label. An accurate weighing machine and measuring cylinder should
be obtained. Chemicals can be wasted by making concentrations unnecessarily strong or by making them too
weak and ineffective. Furthermore, if chemicals are too strong they may cause damage to the foliage.

Source: http://www.kenmuir.co.uk/image/data/pdf/Fact%20Sheets/RUST%20_10_.pdf