Agriculture Reference
In-Depth Information
is an interesting alternative for the control of late blight, mainly on organic potato
crops. Two biocontrol strategies have received most attention: use of phylloplane
microorganisms (Ng and Webster, 1997; Garita
et al
., 1998, 1999; Daayf
et al
.,
2003) and microbial-induced resistance (Yan
et al
., 2002; Silva
et al
., 2004).
Unfortunately, we are not aware of any study that demonstrated the effectiveness of
biocontrol agents against potato late blight under field conditions. There have been
limited efforts to thoroughly investigate interactions between
P. infestans
and other
microbes on leaf surfaces and efforts are just being initiated to investigate the
interactions between oospores of
P. infestans
and the soil microbial community.
17.5 CONCLUDING REMARKS
This chapter has attempted to illustrate how the population genetics of
P. infestans
has influenced the epidemiology of the late blight disease, and therefore why it is
important to include population genetics in any consideration of the epidemiology or
management of the disease. The transition from an asexual life history to a life
history that also includes sexual reproduction is changing how we view both the
epidemiology and management. This chapter has also attempted to illustrate that the
population dynamics of
P. infestans
in temperate potato production zones can differ
significantly from that in some tropical production zones. Ignorance of the pathogen
population biology at the local level can lead to failures in disease control, and it is
now clear that the pathogen biology can be dramatically different in one location
compared to another. Unfortunately, even if we have an excellent understanding of
the pathogen biology in a location, the efficacy of available tools to suppress this
disease can be inadequate when the environment is particularly favourable to the
pathogen. Most notably, cultivars with high levels of durable resistance that are
acceptable to the market are needed. Additionally, a curative fungicide that could
halt an established epidemic is also required.
Until advances in disease suppression technology are made, epidemiologists
need to address questions, the answers to which will lead to improved efficacy of
disease management. Some of these are:
•
What is the quantitative relationship between oospores in the field and epi-
demic development?
•
What is the quantitative relationship between late blight in the foliage and late
blight in the tubers?
•
What is the quantitative role in a particular production field of long distance,
aerial transport of sporangia?
•
What are the most effective integrated management systems for particular
production regions?
These questions need to be answered at the local level to be useful, and they need to
be answered generically for universal application. Obtaining the answers will be
challenging, but important. The past fifteen years has seen an explosion in our
understanding of the population dynamics of
P. infestans
and there has also been
very successful application of that information to limit the damage caused by this
