Nematodes immune to anthelm.

Dan Holdsworth drh92 at aber.ac.uk
Thu Jan 30 11:59:03 EST 1997


In article <oobarrig.101.32EA3C3C at pop.service.ohio-state.edu>,
oobarrig at pop.service.ohio-state.edu (Omar O. Barriga) writes:
:Sorry, but I forgot something important.
:
:	Dan Holdworth mentioned a fairly popular theory that says that
:susceptible 
:parasites are better fit than resistant parasites (Why, otherwise,
:the 
:susceptible population would exist in nature instead of the resistant
::population?).

I should clarify this.

Pests that have adapted to heavy pesticide spraying normally do so by 
massively increasing the amounts of enzymes like esterases or oxydases.
This increase in production of enzyme is often at the expense of something
else, where the "something else" was a predator-avoidance mechanism.

Stopping spraying briefly changes the rules. Under the spraying regime, the
pests had their predator problems taken care of by the pesticides. Under the
no-spray regime (maybe combined with some re-introduction of predators)
the pests have to try to cope with predation.

This is effectively the same technique as changing from pyrethroids to 
carbamates; you are changing the control strategem and thus rendering useless
the previous adaptations of the pest.

In some cases, changing the pesticide can have marvelous effects; insects 
tend to oxidize poisons, then hydrolyse. Changing from a pesticide which is
inactivated by this pathway to one which by lethal synthesis is activated
by it is very good. 

Under those conditions you are effectively pre-adapting the pests for 
one control strategy...

Remember, natural predators are just one more control strategy. 

It is by caffeine alone I set my mind in motion, it is by the beans of Java
that thoughts acquire speed, the hands acquire shaking, the shaking becomes a
warning, it is by caffeine alone I set my mind in motion.
Dan Holdsworth, drh92 at aber.ac.uk **SPAMMERS WILL BE FILTERED**



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