Midwest Vegetable Guide - 2022 - 70

Insect Management Strategies
Conservation Biological Control: Conserving natural
enemies is one aspect of biological control that can
effectively reduce pest populations and damage. This can be
accomplished in several ways, but the most important is
careful selection of pesticides and reducing the overall
number of applications. When selecting an insecticide,
consider the impact that application will have on beneficial
insects. Bacillus thuringiensis (Bt) products, for example,
only have efficacy against the targeted organisms (most often
caterpillars). Other products, such as flonicamid, are selective
at killing insects with piercing-sucking feeding habits,
targeting aphids and plant bugs. Choosing a chemical option
that has been approved by the EPA as a Reduced Risk
product is another way to minimize the impact on nontarget
organisms, including natural enemies and parasitoid, when an
application is necessary.
Proper Identification
Properly identifying pests is the foundation on which a good
insect management program is built. If the pest is not
properly identified, the chances of selecting the correct
control strategies are greatly diminished. Many insects and
mites can be correctly identified simply because they are
encountered so often. However, it never hurts to back up your
knowledge base with some reference materials. Your county
Extension office has a number of bulletins available that will
help you properly identify insect pests. There also are a
number of good books available with color photographs of
many of the common insect pests. Most entomologists don't
like to admit it, but we often identify unfamiliar insects by
comparing them to pictures in a book. For a small fee,
samples can be submitted to a local plant and pest diagnostic
lab.
Beneficial organisms can be important components of an
effective insect management program. Being able to
distinguish the good insects from the bad insects may help
you avoid unnecessary and possibly disruptive pesticide
sprays.
Some common beneficial organisms all growers should be
able to identify include lady beetle larvae and adults,
lacewing eggs, larvae and adults, parasitized aphid
" mummies " , minute pirate bugs, and syrphid fly larvae.
In addition to proper identification, it is helpful to know as
much as possible about the insect's biology including how to
identify the various life stage, location or habitat where each
portion of their lifestage occurs and the host range of the pest.
Insects with incomplete metamorphosis have juvenile stages
- called nymphs - that resemble the adults, except that
they are smaller and don't have wings. The feeding behavior
is usually the same for nymphs and adults. For example,
squash bugs and aphids are insects with incomplete
metamorphosis.
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Insects with complete metamorphosis have a larval stage that
is completely different in appearance from the adult. Adult
insects never grow, so little beetles don't grow up to be big
beetles. For example, caterpillars are the immature (larvae
form) of moths and butterflies. Insects who undergo complete
metamorphosis also have an intermediate stage, known as a
pupa, between the larval and adult stages. For caterpillars this
is called a chrysalis or cocoon. Larvae never have wings and
are not capable of reproducing. Larvae go through a series of
molts (shedding their skins) in order to grow. Larvae and
adults frequently, although not always, feed differently and
move between plants or plant parts as they develop. In many
instances, the immature stage feeds below ground while the
mature is found above, or vice versa. Beetle larvae (think
Japanese beetles, wireworms, rootworms) feed below ground
on plant roots while the adults (again Japanese beetles, click
beetles, rootworms) are found above ground feeding on plant
foliage. Thrips spend their larval and adult stages above
ground, but pupate in the soil.
For important insect, mite, and slug pests, it also is helpful to
know the overwintering stage, life cycle length, and number
of generations per year that can be expected. Again, most of
this information can be found in Extension bulletins.
Monitoring
Vegetable growers must make insect, mite, and slug pest
management decisions on an almost daily basis during the
growing season. To make the best decisions, it is often useful
to have information regarding the current status of a pest's
population. This can be accomplished through some sort of
sampling or monitoring program. There are several methods
to monitor insect populations.
Pheromone traps can be used to determine when pests are
flying, often times in relation to searching for a mate. This
information can be used in several ways. First, catching pests
in the trap can alert growers to begin looking for the pest in
the field. This can save time because the grower won't be
looking for the pest before it is present. Second, pheromone
trap catches can be used to time insecticide applications.
Third, for some pests, such as corn earworms, the need to
spray can be determined from the number of moths caught in
the trap. Pheromones are available for many of the moth
stages of caterpillar pests of vegetables, and swede midge.
Another method for monitoring insects is by scouting fields.
Scouting can be formal, such as counting insects on a given
number of plants throughout the field, or it can be informal,
with the grower walking through the field and looking for the
signs and symptoms of insects on the plants. Formal scouting
may be more accurate, but the most important thing is for
growers to regularly walk their fields looking for insects or
insect damage. Most can be monitored just by close
inspection of the plants. Others may require the use of
equipment such as a sweep net or a beat cloth. Some pests,
such as mites, may require the use of a hand lens to see.
Midwest Veg Guide 2022
Midwest Vegetable Guide - 2022

Table of Contents for the Digital Edition of Midwest Vegetable Guide - 2022
