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Insect Management Strategies
Familiarizing yourself with the damage they induce can aid in
their detection. For example, the stippling of leaves from
mites. Alternatively you can shake the plant over a sheet or
piece of paper to dislodge the pest. This is effective for mites
and thrips. Regular (weekly) monitoring will allow growers
to make informed management decisions.
In protected environments, yellow sticky cards may serve as a
passive monitoring method. The cards should be placed
strategically around the crops to intercept pests as they move
into the growing space (near ventilation openings) or between
crops in the same space. Cards will not control pests but can
aid in their detection. They should be checked often (at least
weekly) and changed when the surface gets full or is no
longer sticky.
Determining the Potential for
Economic Loss
Unfortunately, we do not have economic thresholds for many
vegetable insect pests. Whenever possible, we have listed the
best thresholds available along with control options in the
crop-specific sections of this manual.
Although some of these estimates have not been verified by
research in each state, they have been derived from scientific
research or extensive observations. Growers may wish to
adjust these thresholds based on past experience. Extension
bulletins also are useful sources of information regarding
potential losses from insects.
Growers should remember that some crops, such as snap
beans and potatoes, can suffer a great deal of defoliation
before there is any effect on yield. Sometimes, plants with
considerable amounts of insect damage will yield as well as
plants that have no insect feeding. If the pest is one that feeds
on the marketable portion of the plant, then less damage can
be tolerated.
Proper Selection of a Pest Control
Option
In vegetable crops, the selection of a control option during
the growing season usually means doing nothing or selecting
a pesticide. Although we always encourage growers to read
and follow label directions, the one area where the label is not
necessarily the best source of information is concerning
which insects the insecticide will control. The insecticides
recommended in this book for control of various pests are
listed because they are legal to use and because they have
been found to be effective by the authors. Consider
insecticide or biological control agent costs, application costs,
relative effectiveness, gain in profits that can be expected
from the application, whether it will control other pests, and
how it will affect predators, parasites, and pollinators.
Growers should refrain from " revenge spraying, " that is,
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spraying after the damage is already done. At that point,
spraying is a waste of money and may actually increase pest
damage by killing beneficial insects.
Evaluation
Growers should always evaluate the effectiveness of a pest
control action. Inspecting the field a couple of days after an
insecticide is applied will help the grower determine the
necessity for additional control measures in that field, as well
as provide information about the insecticide's effectiveness
for future reference. Growers should pay attention to whether
the insecticide killed all stages of the pests or if only small
larvae or nymphs were killed. They should also notice the
effects on other pests in the field and on beneficial insects.
Resistance Management
It is important to rotate products with different modes of
action in order to reduce the potential of insect, mite, and slug
populations developing resistance to products with specific
modes of action. A pesticide's mode of action is how it
affects the metabolic and physiological processes in the pest
(in this case, the pests are insects, mites, or slugs). Many
product labels contain resistance management information or
guidelines that will help vegetable growers determine which
products they should rotate with others, including an
Insecticide Resistance Action Committee (IRAC) code, that
describes the mode of action with a number and/or letter. Try
to avoid using products with the same IRAC code repeatedly
to conserve its efficacy on pests. Biopesticides derived from
fungal and bacterial insect pathogens and live biological
control insects can also be deployed against insect pests,
further preserving the efficacy of certain insecticides. For
more information associated with rotating different modes of
action, contact your state or regional extension entomologist.
Midwest Vegetable Guide - 2022

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