Agriculture Reference
In-Depth Information
Future research directions
Knowledge banks from natural systems studies and comparisons with agroecosystems
The application of ecological principles to pest regulation in agroecosystems is extremely impor-
tant for advancing crop protection through ecosystem services. However, the staggering amount
of diversity in habitats and life histories among pests and pathogens defies any strict adherence to
generalities. Therefore, technological advances in data management and expert systems can now
be used to synthesise detailed results from relevant ecological studies as a basis for making
specific decisions in pest management. Further, the degree to which results from ecological
studies in natural systems can be transferred to understanding plant-arthropod, disease-host,
and predator-prey interactions in agroecosystems is, for the most part, speculative. Future com-
parative studies between natural and managed habitats are needed to test common assumptions
(Barbosa 1998) and create a realistic set of goals and practices for organic growers.
Development of cultivars suited to organic farming conditions and needs
Breeding for resistant cultivars under organic management conditions should be a high
priority. Herbivores that exploit cultivated varieties often encounter resources that differ in
fundamental ways from the plants' wild relatives. Attributes that have arisen out of a selection
process for enhanced productivity and palatability under conventional conditions tend to
increase the crop's suitability as a host for phytophagous arthropods and pathogens. First,
compared to their progenitors, crop plants can contain lower levels and simplified suites of
antiherbivore defences (Kennedy and Barbour 1992), can possess a more uniform genetic
composition, and may experience lower levels of plant stress. Second, the presentation of these
plants to herbivores and pathogens differs from the conditions found in most of the communi-
ties of their wild relatives in its tendency for uniformity in species composition, age distribu-
tion of the population, and structural pattern. Each of these factors contributes to the need for
research into optimised plant resistance in different management contexts and cropping
systems.
Optimisation of production of healthy seed and vegetative propagating materials
Organic crop production can be very successful provided that healthy seed and vegetative
propagating materials are used, since the options for intervention are limited once the crop is
in the field. The best option would be to produce seeds and vegetative materials in pest and
disease-free areas (i.e. in isolated regions with arid climates). However, organic agriculture
may not be well established in such regions, and facilities for tissue culture and seed health
testing may not be available, for example in northern Africa. A combination of biological,
social and economic research would be needed to optimise the production in such regions in
close collaboration with local farmers. Additional research would be desirable to develop and
test plant extracts and microbial communities for biological control of seedling diseases, and
to formulate these products so that they can be approved by organic certification agencies.
Assessment of the role of landscape factors for colonisation of pests, pathogens and natural
enemies
Vegetation at the field margin or in surrounding areas serves as coloniser sources for mobile
pests, vectors, and pathogens. The degree to which organic crop fields are colonised, exploited
and damaged may depend upon the quality of these source pools. Vegetation management
may reduce pest and pathogen levels directly or may serve to stabilise and enhance predators
and parasitoids for biological control of crop pests. Rigorous analyses of landscape-scale phe-
nomena, though recognised as critical for decades (e.g. a 'wide-area view'
sensu
Rabb 1978),
are only recently becoming feasible with new geographical information systems capabilities
