Agriculture Reference
In-Depth Information
limitations on the ability to 'fine tune' the spray programme. Where spray intervals
cannot be altered for practical reasons it may be possible to reduced dose according
to forecast risk as suggested by Nielsen (2004). Spraying on a large scale also poses
logistical problems in terms of sprayer capacity, adequate stock of fungicides and
competing demands for the treatment of other crops (Hinds, 2000).
Where there is a one disease per crop situation, as with blight of potatoes and in
some parts of the UK, mildew on spring barley, decisions can be relatively simple.
Where several diseases are involved, timing and choice of product become more
important. Dose and whether the product has protectant or eradicate activity are also
important factors as these impinge on timing. The increased complexity of the
decision-making process has lead to a more integrated approach to disease control
through managed or decision support systems. EPIPRE (Zadoks, 1981),
PRO_PLANT (Frahm
et al
., 1996) and DESSAC (Parsons
et al
., 2004) are such
examples. However, Forrer (1992) suggests that such systems are short-lived after
farmers have got used to them. They are also demanding of the farmer in terms of
monitoring the crop for disease. Such systems also depend on the farmers' ability to
identify disease, for example, being able to distinguish between eyespot and sharp
eyespot is difficult even for experienced plant pathologists. Improved diagnostic
techniques, using molecular methods (see Chapter 1), can provide assistance, but
care in interpretation of the results is still required. However, decision support
systems do provide a valuable training aid in crop management for farmers,
consultants and students of crop protection.
With continuing reductions in financial support to agriculture, it is an inevitable
consideration that forecasting systems become a substitute for the necessary number
of experts required to provide an input into the daily decision-making process of
disease management. However, what is forgotten is that these 'expert' systems very
often require the expert to interpret the data generated from them. Accurate disease
diagnosis and assessment (Chapter 2) are difficult for the non-specialist and they are
not necessarily helped by the advent of immunodiagnostics and PCR methodology.
Modern methods do not necessarily address the consequence of a specific diagnosis
until there is a quantitative rather than qualitative basis for the result, or necessarily
address growers' concerns in addressing their particular problems. Problem-solving
is more complex as it is concerned with the practical possibilities, aspirations and
even psychological security of the individual farmer. Decision support systems are
what they say, they are a support to decisions and should not be viewed as an
attempt to become a substitute for the absence of an effective extension service. It is
important that the systems are over-ridden when the decisions being made are at
variance with the 'sixth sense' of the experienced advisor. Douglas Bader (British
World War II pilot) said that “Rules are for the obedience of fools and the guidance
of wise men”. Knowledge developed over a number of years of experience of local
conditions together with results from appropriate experiments are sometimes more
important than a computer read-out. However, forecasting systems will continue to
be an essential part of the decision-making process on disease control, whether
analytical or intuitive.
