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Cleaning up garden and flower
beds in the fall is an effective way to control various insect
pests. Many insects survive the winter buried in the soil (5-25
cm) or on its surface. Debris left on the soil surface will in
fact help the insects to survive.
In winter, the temperature of
the soil is higher than the air temperature. Various components
in the soil buffer it against severe freezing temperatures. For
this reason. insects are able to survive in the soil, protected
from the winter cold. Debris left on the soil surface further
protects the soil, thus making it more hospitable for overwintering
insects and increasing their chances of survival. If you remove
the debris, the soil will freeze to a greater depth and more
insects will likely die during the winter.
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When and How to Remove the
Debris
The best time to remove the debris
is in early October, after the insects have buried themselves
in for the winter. You can remove the debris earlier or later,
still with effective results in terms of controlling insects.
When removing the debris, it is wise to till the garden and flower
beds. Tilling will bring the insects up the soil surface, where
they are more susceptible to killing temperatures. |
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Drenching the soil in the fall with
an insecticide to control insect pests is not recommended. In
order for an insecticide to be effective, the insect must be
active. Insect larvae, pupae and adults overwintering in the
soil are not active, and therefore pesticide control at this
time of year is ineffective.
Garden Cleanup - Insects that overwinter on the soil
surface under garden debris or buried in the soil include the
beet leaf miner, cabbage maggot, Colorado potato beetle, flea
beetle, imported cabbage worm, onion maggot and spinach carrion
beetle. Incorporating organic matter in the fall is recommended,
but it should be well tilled into the soil; if left on the soil
surface, the organic matter will help protect insects over the
winter.
Flower Beds and Shrubbery - In flower beds and shrubbery, a number
of insects overwinter successfully under debris or in the soil
near the base of ornamentals. Such insects include the currant
fruit fly, imported currant worm, pear slugs, rose curculio and
spring cankerworm. Removal of the leaf litter and a shallow tillage
under ornamentals will help control many of these insects. |
