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and environmental effects must be determined using prescribed OECD
guidelines.
If the botanical compound is acceptable under tier I criteria, all other phases
can be carried out. Preliminary cropping trials and collection of information
on effects on the target pest and related environmental data must also be
carried out. During toxicity testing, data on vector ecology, transmission sites,
peak periods of infection, and human use can be collected. Additionally,
agrobotanical studies to identify methods of propagation, insect and disease
resistance, and cultivation trials can be carried out.
If toxicity tests indicate that the compound is safe to use, the final set of tests
will be the field trials. These must follow WHO protocols to determine time
and mode of application, concentration, environmental fate, rate of degradation,
and efficacy toward the target organism. The trials should be similar to
those used for synthetic products. The approval process for botanicals will not
take any less time than that needed for synthetic pesticides.
We are seeking pesticides that are rapidly biodegradable and attack sites at
which pests cannot readily develop resistance through mutation. Although
botanical pesticides have been present for millennia, few pest species have
developed resistance, unlike the situation with synthetic chemicals.
If, as we expect, endod proves to be safe for the control of schistosomiasisbearing
snails, then it coiild replace niclosamide. Using a cheaply produced,
easily extracted molluscicide, integrated with chemotherapy, the health of
people in endemic regions could be improved.
Conclusion
The potential for further and meaningful developments in botanical pest
control is enormous. We are aware that the cost of developing botanical
pesticides can be as great as those for synthetic pesticides. Nevertheless, we
believe it is an avenue that should be pursued because plant and animal
chemical defense mechanisms have proven highly effective in inhibiting
predator or pest activity.
One should also consider other avenues. For example, more work is required
on the behaviourial, physical, and biochemical adaptations of insects exposed
to phototoxins, antifeedants, and the other types of compounds produced by
plants. Insects are able to metabolize the defense compounds of their natural
hosts, whereas those not usually feeding on those hosts cannot. This is an
important consideration in the identifying selective botanical insecticides and
the potential for resistance.
At the molecular level, more information is required on adaptation, such as
the quenching of molecules through compounds such as ascorbic acid, carotenes,
tocopherols, or enzymes (e.g., superoxide dismutase, catalase, and
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