Agriculture Reference
In-Depth Information
Fig 16.18 Plant collapse caused by Phytophthora heart rot.
Management
•
Use systemic chemicals to reduce heart rot. This program
should start with the treatment of planting material before
planting. After planting, drenching or spraying with
registered chemicals at recommended rates and intervals
is necessary to ensure against losses. Infected plants can be
saved only if treated soon after symptoms appear.
Avoid excessively deep planting and prevent soil entering
the hearts during planting.
•
Well-drained soils are essential for minimising the risk
of Phytophthora infection. This can be achieved through:
•
-
careful fi eld selection
-
planting on raised beds at least 23 cm high
-
constructing drains to intercept run-off before it
reaches the plantation
Fig 16.17 Phytophthora invasion of a pineapple stem.
-
constructing drains within the fi eld so that water is
removed rapidly without causing erosion
Phytophthora nicotianae
prefers warm to hot conditions
(25-36
C), and is less dependent on high soil moisture.
Damage is most severe at pH 7 and above, but will occur at
pH 5. It destroys young roots, but rarely kills the entire root
system.
Phytophthora nicotianae
is mainly responsible for a
heart rot that may occur without preliminary invasion of
the root system. In areas with a high incidence of heart rot
caused by
P. nicotianae
, surviving plants can remain
healthy without the roots being attacked.
°
-
installing underground drains
Importance
Heart and root rots are the most serious and widespread
diseases of pineapple in Queensland.
Phytophthora
cinnamomi
is the predominant pathogen of pineapples
grown south of the Mary Valley in south Queensland; both
species are found in central Queensland, and
P. nicotianae
is more common than
P. cinnamomi
in north Queensland.
Fig 16.19 Crop devastated by Phytophthora heart rot.
