Agriculture Reference
In-Depth Information
liquids (such as those containing citrus extracts).
Amateur and professional horticulturists may apply
a spray of copper (Bordeaux solution) at bud burst
(spring) and leaf fall (autumn) to prevent entry of
germinating spores.
Coral spot (
Nectria cinnabarina
)
This
belongs to the Ascomycota group of fungi.
Damage
. This disease is found on dead branches of
trees and shrubs. Closer inspection shows a mass of
pink pustules (about 1 mm across) sticking out from
the dead wood (Figure 19.13b).
The disease is commonly seen on broadleaf species
such as maple, horse chestnut, beech, hornbeam,
lime, walnut,
Magnolia
and
Elaeagnus
. Cane fruit
such as currant and gooseberry bushes are also quite
susceptible. The conifer group of trees such as pine is
not usually affected.
Life cycle and spread
. This fungal species is a weak
parasite, often living as a saprophyte on dead trees
and on canes used to support climbing beans. The
trees and shrubs mentioned above are infected by
spores landing on dead wood, or through young
tissue killed by frosts in late spring, or through
lenticels (see p. 86). The fungus is then able to
invade further into living wood. This infection is
often made worse when the host plant has been
subjected to stress such as drought, water logging
or root disease. The pink pustules develop when the
infected area of wood has died. The spores released
from the pustules are spread by both wind and water
splash.
Control
. Pruning should be carried out in dry weather
to reduce the chances of infection. Cuts are best
located slightly away from junction points with the
main branch or the stem, as wound healing is more
rapid in this location. Infected stems should be cut
out to leave healthy tissue and to minimize further
spore production. Infected prunings should be taken
away from the recently pruned area and burnt. Pruning
paints (such as the one containing octane acid salts)
are not normally recommended in dry weather, but
may be of value when rain is forecast immediately
after pruning, or where a particularly susceptible
species has been pruned.
Figure 19.12
Botrytis cinerea
infecting a strawberry
fruit
tomatoes. Amateur gardeners at present have no
effective chemical control against this disease.
Apple and pear canker (
Nectria
galligena
)
This
belongs to the Ascomycota group of fungi.
Damage
. This fungus causes sunken areas in the bark
of both young and old branches of ornamental Malus,
apples or pears (Figure 19.13a). Poor shoot growth is
seen, and the wood may fracture in high winds.
Life cycle and spread
. The fungus enters through
leaf scars in autumn or through pruning wounds
during winter. Care is therefore necessary to prevent
infection, particularly in susceptible apple cultivars
such as the 'Cox's Orange Pippin' by avoiding pruning
in mild, damp conditions. Spores produced in red
spore cases (found embedded in the canker tissue)
are spread by rain splash.
Control
. Removal of cankered shoots may be
necessary to prevent further infection, while in
cankers of large branches, cutting out of brown
infected tissue may allow continued use of the
branch. Removed tissue should be burnt. The
exposed wood area may be protected by a protective
paste applied to the wound, especially in areas of the
Britain and Ireland with high rainfall. Pruning knives
should be cleaned after use on cankered tissue with
Rust fungi
This
belong to the Basidiomycota group of fungi.
Rusts produce characteristic orange, brown or black
raised leaf spots caused by the fungal tissue breaking
through the leaf epidermis of the host (Figure 19.14).
