Agriculture Reference
In-Depth Information
Fig 4.19 Trunk canker lesion on avocado caused by Phytophthora.
Fig 4.17 Large avocado tree infected with Phytophthora root rot.
Inset: sparse foliage exposing small fruit.
may decline rapidly in sandy soils low in nutrients and
organic matter, but may show no symptoms on deep
volcanic soils. Symptoms do not appear unless there is an
upset in the balance between the water requirements of the
leaves and the capacity of roots to absorb water.
The root rot pathogen is widespread in Australia. It is
commonly introduced into clean areas with infected
nursery trees.
When the pathogen is present, the soil environment plays a
very important role in the development of symptoms. Trees
Importance
Phytophthora root rot is the most destructive and
important disease of avocado. It can be extremely serious,
killing most trees in an orchard. Nursery plants and young
replants are particularly sensitive to root rot and often die
soon after infection.
Management
•
Use an integrated approach that relies on pathogen-free
nursery trees, cultural and biological control, resistant
rootstocks and chemicals.
Plant on well-drained soils, or improve drainage by using
mounds.
•
Plant disease-free nursery trees that have been approved
by the Avocado Nursery Voluntary Accreditation
Scheme.
•
Fig 4.18 Haas grafted to resistant and susceptible rootstocks planted
in soil infested with Phytophthora.
