Southeastern U.S. Vegetable Crop Handbook - 2022 - 44

* The economic action threshold level (when the cost of
control equals or exceeds potential crop losses attributed
to real or potential damage)
* Other factors are listed in the Recommended Control
Guidelines section that follows
To employ an IPM program successfully, basic practices need
to be followed. Whether participating in a univer sity- or grower-supported
IPM program, hiring a private consultant, or doing
the work personally, the grower still practices:
* frequent and regular examination of fields to assess pest
populations
* applying a control measure only when the economic
threshold level has been reached
* where possible, employing a cultural practice or a biological
control or using a pesticide that is less harmful to natural
enemies of the target pest
Resistance management. The way pesticides are used affects
the development of resistance. Resis tance develops because
intensive pesticide use kills the susceptible individuals in a
population, leaving only resistant ones to breed. Adopting the
following practices will reduce the development of pest resistance:
1.
Rotate crops to a nonhost crop, thus reducing the need for pesticide
treatment and, thereby reducing the ratio of resistant to
susceptible individuals in the breeding population.
2. Use control guidelines as an important tactic for reducing the
pesticide resistance problem. For more informa tion concerning
control guidelines, refer to the following section and the
crop-specific sections of this handbook.
3. Spot treat when possible. Early-season insects are often concentrated
in areas near their overwintering sites. Diseases
often can be first detected in favorable microclimates, such as
low or wet areas of the field. Perennial weeds and newly introduced
or herbicide-resistant annual weeds often occur first in
small numbers in a part of a field. Treating these areas, rather
than the entire field, can prevent the development of resistant
populations.
4. Control pests early, because seedling weeds and immature
insects are more susceptible to pesticides and less likely to
develop resistance compared to older and more mature crop
pests.
5. Do not overspray. Attempts to destroy every pest in the field
by multiple applications or by using higher than labeled rates
often eliminate the susceptible pests but not the resistant pests.
6. Rotate pesticides to reduce the development of resistance, particularly
with pesticides that differ in their mechanism of action.
Rotation among different chemical groups is an excellent
method of reducing resistance problems.
7. Use appropriate additives when recommended on the pesticide's
label. For example, adding a crop oil concentrate or a
surfactant to certain postemergence herbicides will increase
the effectiveness of the herbicides.
Control Pests According to Recommended Control Guidelines
or Schedule. Control guidelines provide a way to decide
whether pesticide applications or other management actions are
needed to avoid eco nomic loss from pest damage. Guidelines for
pests are generally expressed as a count of a given insect stage
or as a crop damage level based on certain sampling techniques.
They are intended to reflect the pest population that will cause
economic damage and thus would warrant the cost of treatment.
Guidelines are usually based on pest populations, field history,
stage of crop's development, variety, weather conditions, life
stage of the pest, parasite, and/or predator populations, resistance
to chemicals, time of year, and other factors. Specific thresholds
are given in this handbook for a number of pests of many crops.
Insect population sampling techniques include:
* Visual observation. Direct counts of any insect stages
(eggs, larvae, adults, etc.) are accomplished by exam ining
plants or plant parts (leaves, stems, flowers, fruits). Counts
can be taken on single plants or a pre scribed length of
row, which will vary with the crop. Usually, quick moving
insects are counted first, followed by those that are less
mobile.
* Shake cloth (also known as a ground cloth). This sampling
procedure consists of using a standard 3-foot by 3-foot
shake cloth to assess insect popula tions. Randomly choose
a site without disturbing the plants and carefully unroll the
shake cloth between two rows. Bend the plants over the
cloth one row at a time and beat the plants vigorously to
dislodge insects held on stems, leaves, and branches. Count
only insects that have landed on the shake cloth. The number
of sampling sites per field will vary with the crop.
* Sweep net. This sampling procedure uses a standard
15-inch diameter sweep net to assess insect popula tions.
While walking along one row, swing the net from side to
side with a pendulum-like motion to face the direction of
movement. The net should be rotated 180 degrees after
each sweep and swung through the foliage. Each pass of
the net is counted as one sweep. The number of sweeps per
field will vary with the crop.
Weed population sampling techniques include:
* Weed identification. This first step is frequently skipped.
Perennial weeds and certain serious annual weeds should
be controlled before they can spread. Common annual
weeds need only be controlled if they represent a threat to
yield, quality, or harvestability. It is critical to know the
weed history of a field prior to planting as many herbicides
need to be applied pre-plant. Your county Extension office
is an excellent resource for reliable weed identification.
* Growth stage determination. The ability of weeds to compete
with the crop is related to size of the weed and size of
the crop. Control of the weed using herbicides or mechanical
methods is also dependant on weed size. A decision to
control or not to control a weed must be carried out before
the crop is affected and before the weed is too large to be
controlled.
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2022 Vegetable Crop Handbook for Southeastern United States
Southeastern U.S. Vegetable Crop Handbook - 2022

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