Agriculture Reference
In-Depth Information
Interestingly, in China, which grows in excess of 28 million hectares of wheat,
'ecological' control of the stripe rust fungus,
Puccinia striiformis,
has been considered
as a major strategy for sustainable disease control (Chen
et al.
,
2007). This approach
involves: (a) improving cultivar resistance, (b) changing cultural practices, (c) eradicating
volunteer wheat seedlings, (d) regulating wheat planting date and (e) returning land to
forestry and pastures (Chen
et al.
,
2007).
Irrespective of the system into which biologically based disease control methods are
slotted, their use in crop protection programmes will fi rst require a number of issues to be
resolved and barriers to be overcome.
14.3
Biologically based disease control: barriers to
implementation
Effi cacy of disease control
14.3.1
In most developed countries, high crop yields are maintained through the use of improved
varieties, together with fertilisers and pesticides. Indeed, farmers and growers in these
countries are accustomed to achieving high levels of disease control with fungicides,
although as indicated above and in Chapter 1, the development of fungicide resistance
can erode fungicide effi cacy. In contrast, levels of disease control obtained with many
biologically based control methods are lower than those achieved using fungicides. In
addition, many biologically based methods tend to provide inconsistent disease control.
For example, although induced resistance can provide high levels of disease control on
some crops, with many crops, disease control is less impressive. Expression of induced
resistance in crop plants can also be variable, depending on a number of factors, includ-
ing genotype and environment (see Chapter 4). There are also problems of variability and
inconsistency of disease control with some biological control agents (BCAs) (Whipps,
2007; see also Chapter 3). Perceived problems with inadequate and inconsistent disease
control will not persuade farmers and growers to adopt biologically based approaches.
Minimising the effects of these problems requires further research.
14.3.2
Regulatory issues
Despite the considerable effort by researchers to develop novel biologically based solutions
for disease control (e.g. BCAs, plant-derived substances, induced resistance agents), few
products have reached the marketplace. The high cost of registration, coupled with limited
market size for some products, has been identifi ed as a major barrier (Richardson, 2005;
Kleeberg, 2007). However, this problem has been recognised by regulatory authorities and
in the United Kingdom, for example, the Pesticides Safety Directorate (PSD) launched a
pilot scheme for biopesticides in 2004, allowing the requirements for registration to be
tailored to the product type and importantly, offering a signifi cant reduction in the appli-
cation fee (Richardson, 2005; Whittaker, 2007). This pilot scheme has since evolved into
a permanent Biopesticides Scheme run by the PSD. However, this experience contrasts
with elsewhere in Europe, where the biopesticide industry has failed to engage effectively
with the regulatory authorities (Whittaker, 2007). Unless this situation changes, signifi cant
problems, getting biopesticides into commercial practice, will continue.
