Pests are considered resistant to a certain chemical compound (natural
or synthetic compounds) when it is no longer killed or adversely affected by
the chemical. Most pesticides target biological systems in order to control
pest populations – “control” meaning; to reduce pest populations to levels that do
not cause great plant or economical loss.
Pesticides can affect the nervous systems of insects, killing them
directly or affect reproduction, such as decreasing the amount of offspring each
generation. Pesticides can also be general, affecting a wide variety of insects,
or target-specific, affecting a specific insect (aphids) or an insect suborder (Sternorrhyncha: Aphids, scale bugs and whiteflies).
Pesticide resistance is due to a beneficial mutation. The mutation usually
occurs in the biochemical site affected by the pesticide, which is then rendered
unrecognisable by the pesticide. Resistance can also be due to an increase of
detox systems in the insect cell or chemical pumps that pump the pesticide out
of the insect cell. These resistance mechanisms are inherited by the offspring
of resistant parents. The evolutionary process behind the survival of the
beneficial mutation each successive generation is known as natural selection,
the Darwinian mechanism of survival of the fittest.
 |
Blue: Susceptible
Red: Resistant
|
Resistant mutations accumulate through natural replication errors
within the DNA of the organisms. Resistant organisms (Parental generation) will
survive and reproduce. Their offspring (F1: First generation) will survive
subsequent pesticide treatments, and over several insect generations (can be as
little as 1-2 years) a resistant population will develop.
Pesticide resistance can remain in insect populations after the product
has been discontinued for as much as 2 years. After which the resistant
mutation will decrease slowly. After a few years pesticide susceptible insects
will dominate the population once more. Resistant insects have a reproductive deficit
in an environment with no pesticides, they produce less offspring than
susceptible insects and subsequently decrease in the population.
The prevention of pesticide resistance is to use pesticides correctly:
ü Use pesticides according to the manufacturer’s
instructions (not more and not less). This goes for both the concentration at
which the pesticide is made and the frequency of use. This prevents resistance
and reduces the impact on the environment.
ü Changing the Class of pesticide (such as chlorinated
hydrocarbons, cyclodienes, organophosphates, carbamates, pyrethroids, neonicotinoids)
every season will prevent resistance to a single type of pesticide. Mixed, combination or multiple
class pesticides will result in multiple-pesticide resistant insects.
ü Specific pesticides (such as those just for aphids)
will reduce the chance of poisoning other beneficial insects or the induction
of resistant in non-target insects.
ü Make up enough pesticide for your present application. If you are left with some remaining pesticide-solution, pour it into a plastic bag, tie off and throw into the dustbin - this prevents any pesticides going into the water supply. Wash out pesticide equipment with soap (dish-washing liquid is fine); this will help break down any residual pesticides in the water.
ü Make up enough pesticide for your present application. If you are left with some remaining pesticide-solution, pour it into a plastic bag, tie off and throw into the dustbin - this prevents any pesticides going into the water supply. Wash out pesticide equipment with soap (dish-washing liquid is fine); this will help break down any residual pesticides in the water.
Preferable
pest management systems include the use of pest predators, crop rotations and preventing
pests from attacking stressed plants (good soil, regular water = healthy and
resilient plants) in the first place - AKA Integrated Pest Management: IPM. Planting pest and disease resistant
cultivars also go a long way in preventing pest populations form reaching epic
proportions in the garden. If a plant does not grow well in your garden or is a
weak specimen it is better to remove it than face a constant battle with it
harbouring pests (one of the reasons I don’t really like sacrificial companion
plants).
I don’t
advocate against the use of pesticides, but I don’t judge those who do use them
either. In rural communities, the use pesticides on crops is the only way for
them to sustain themselves and feed their families. So instead of telling
everybody not to use pesticides, I supply information on safe and effective
use. I prefer natural remedies to pesticides. For some environmentally safe and
home-based pest control recipes, check out Pest Control.
That
basically sums it up J.
Related Posts
Insectary - attracting pest predators and beneficial insects to your garden
Pest Control - Organic control recipes
Biological Control:
Mantis
Wasps
Flies
Ladybeetles
Pest Profiles
Leafhoppers
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Related Posts
Insectary - attracting pest predators and beneficial insects to your garden
Pest Control - Organic control recipes
Biological Control:
Mantis
Wasps
Flies
Ladybeetles
Pest Profiles
Leafhoppers
______________________________________________________________________________
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