Agriculture Reference
In-Depth Information
These wounds can have a significant impact in the
commercial value of the crop and may be the site of entry
for pathogens.
ranges and breeding seasons, leading to the naturalization
of some pests and an increase in the number of generations
of current pathogens and pests produced per year. In
particular, warmer conditions will extend the range of a
number of fungal rots that are not typically a problem in
temperate climates. These “new” diseases and pests of
field potato will inevitably provide further challenges for
storage.
There are currently a limited number of effective chemi-
cals available for disease control on potatoes and even
fewer available for use on potatoes destined for human
consumption. Almost inevitably the use of these will,
because of concerns for environmental and health and
safety fears, become more restrictive. Although effort is
being expended on the search for new and replacement
products there are long lead times for their introduction,
meanwhile development of pathogen and pest resistance
to current chemical controls is always an ongoing issue
and threat.
Currently in the armoury of tools for pest and disease
control and management include improved and improving
diagnostics and very extensive and accessible web based
information and knowledge systems. Our capacity to very
quickly and precisely diagnose problems is increasing, for
example there are now PCR (Polymerase Chain Reaction),
and particularly real-time PCR diagnostics for most
significant pathogens. Field based PCR and immunologi-
cal testing is already possible to inform the status of potato
disease brought into store. The development of web pages
and networks allows access to the expert knowledge and
experience of plant pathologists across the globe. These
tools are continuously being refined and updated, and can
help redress the balance that problems with climate change
and chemical control may bring.
Vertebrates
Animals, particularly rodents and birds, must be excluded
from stores to prevent physical damage which can lead to
secondary infection and also to prevent contamination by
faeces.
Physiological disorders
There are a number of physiological responses to environ-
mental conditions by the tuber whose symptoms can appear
to be the result of disease. In these cases there is usually no
external sign of pathogen attack and there has been little or
no sign or symptom of infection on the growing crop.
Enlarged lenticels, a response to excessive surface water,
can provide entry sites particularly for bacterial pathogens.
Jelly end, which superficially resembles a rot, is a breakdown
of starch to sugars in response to hot and dry conditions in
the early growing season, and can be seen at low tempera-
ture storage. Blackheart which superficially resembles an
internal rot, is a response to oxygen deprivation, particularly
during storage at higher temperatures. Low temperatures or
freezing during or prior to storage can cause significant
damage, particularly to internal tissues, and leave the tuber
more prone to disease. Vascular necrosis, a brownish
discolouring of the vascular ring may be a response of the
plant to hot, dry conditions during growth and resembles
infection by potato leafroll virus or
Verticillium
spp.
Pressure bruising causes grey to black discoloration of the
flesh as a result of compression due to high potato piles.
General store hygiene
Diseases can be difficult to control within a store. The long
time scales of tuber storage and the particular circum-
stances of storage can maintain and allow the spread of
some damaging diseases. Consequently effort should be
expended to ensure that stores are clean and hygienic, for
example by annual deep cleaning and perhaps disinfection/
sterilisation. Minimize the introduction of diseases brought
in on tubers.
A summary of the key issues in pest
and disease control
The most effective method of minimising pest and disease
problems is active prevention and control of diseased
potato from entering storage. This requires control of
potato production from seed to store. Unfortunately, there
are no shortcuts or quick fixes available. To reiterate:
Future prospects for managing post-harvest
pest and disease control
A number of issues can be foreseen that will affect the
capacity to effectively manage the pests and diseases in
store. Climate change will alter the current distribution of
pathogens and pests of potato cultivation and storage.
Warmer and wetter conditions may extend geographic
• Use disease-free seed and use best cultural practices to
manage diseases and pests in the field
• Harvest and handle carefully to avoid physical damage to
tubers
• Use an effective drying and curing regime to allow
wounds to heal effectively
• Load carefully into clean and hygienic stores
