If planting on recently cut pine lands is delayed one year, weevil-caused
damage will not occur. Although the delay easily solves the weevil problem,
can you afford to allow land to lie idle for one year? The real cost of
delayed planting versus other alternatives should be carefully evaluated.
A decision to replant high hazard areas at the first
opportunity assumes that the present value of the timber gained through
immediate regeneration is greater than the present value of the control
cost. The value of this extra year's growth--and thus the cost of the
delay--increases as site productivity, intensity of management, and product
value increase. Therefore, investment in control is more profitable for
intensively managed sawtimber stands on good sites than for pulpwood stands
on poor sites. Other factors to consider are: the discount rate used for
investment analysis, the length of time the costs must be carried, and
tax treatment of control costs.
In some areas of the lower Coastal Plain, on sites cut
in the fall and early winter, replanting usually must be delayed one year
for silvicultural reasons. Completion of site preparation may not be possible
until the following spring or summer, when the soil moisture drops. Therefore,
planting cannot be done until the next winter. In those areas, weevils
present no problem as long as site preparation, which might fell additional
pines, is completed before July.
[ top ]
If delayed planting is not required for silvicultural
reasons or is economically unacceptable to the forest manager, chemical
control applied at the time of planting is recommended to ensure successful
regeneration of recently cut pine lands. Seedlings are usually treated
with an insecticide at planting time, because feeding by weevils often
begins soon after the seedlings are planted, especially if the night temperature
is above 60' F.
A wait-and-see strategy is possible, and treatment can
be delayed until damage begins to look serious. However, this requires
weekly surveillance of the plantation and the capability to react swiftly
with treatment, since severe feeding injury may occur within a 1- to 2-week
period when weevil populations are high.
Four treatments are currently registered for control
of pales and pitch-eating weevils: (1) top dip of Imidan, (2) Furadan
granules placed around the base of the seedling or in the planting hole,
(3) Furadan-clay slurry root dip, and (4) Dursban spray.4 Details concerning
treatment, operational procedures, precautions, and safety are given in
Chemical Control Strategy
[ top ]
A chemical control strategy for pales and pitch-eating
weevils has been developed. Land is first assigned a hazard rating based
on logging and site-preparation dates. "Cold" areas, which have
a low hazard rating, are those cut in the late winter and spring and site-prepared
during the spring or early summer. No weevil damage would be expected
there. "Warm" areas, which have a moderate hazard rating, are
those cut in the summer (July and after) and site-prepared in the summer
and fall. Light to moderately heavy weevil damage would be expected. "Hot"
areas, which have a high hazard rating, are those cut and site-prepared
in the fall. Moderate to heavy weevil damage would be expected.
This hazard rating and control strategy is summarized
in table 1. Planting time and control vary with the hazard rating. "Cold"
areas could be planted any time. However, since planting "warm"
and "hot" areas should be delayed as long as possible into the
planting season to minimize seedling exposure to weevils and weathering
of insecticide deposits, "cold" areas should be planted first,
from December to mid-February. "Warm" and "hot" areas
should be planted from mid-February through March.
Table 1. - Pales and pitch-eating
||spring to early summer1
||December to mid-Feb.
||mid-Feb. through March
Imidan 50W+ extender
||mid-Feb. through March
Imidan 50W+ extender
Imidan 50W+ extender (sprays)
1In a winter-spring cutting area, late summer and fall site
preparation that kills residual pine may attract a damaging population
of weevils, thus necessitating treatment.
Furadan granules should remain effective for 3 months
or longer, so this treatment can be used in "warm" or "hot"
areas planted as early as mid-February. But on sites where heavy feeding
is likely immediately following planting, because of warm night temperatures
(above 60'F), Dursban or Imidan would be recommended over Furadan granules.
Because Furadan is a systemic insecticide requiring-a good rain and some
time to be drawn up into the seedling, heavy immediate feeding may not
Since Dursban spray and Imidan top dip will usually last
from mid-February through May, they can be used in early plantings. However,
the Furadan-clay slurry root treatment usually does not last as long,
and therefore is recommended only for March plantings on "warm"
Weevil-caused mortality which is unexpected for any of
several reasons should be of concern to forest managers. For example;
a site may be incorrectly classified as "cold" due to errors
in records for cutting or site-preparation dates. (It is important that
actual cutting dates for the bulk of the harvesting be considered, not
just the starting, ending, or contract dates.)
Possibly, because of unusual weather conditions or some
site characteristic, damaging populations may be present in a June cutting
Furthermore, control obtained with all of the above insecticides
has varied between sites, probably because of differences in weather conditions
or weevil populations. Errors in mixing may occur, and quality of application
varies. Therefore, monitoring weevil damage in treated-as well as untreated
plantations is strongly recommended, so that a remedial treatment can
be applied in time to prevent loss. A Dursban or Imidan spray could be
used in areas where unexpected weevil feeding occurs.
Preventing Large Population Buildups
[ top ]
Extremely large populations of weevils have occurred
when large clearcuts were made adjacent to large areas clearcut the year
before. In such areas, even treated seedlings have been overwhelmed by
the insects. By reducing the size of clearcuts and spreading them out
spatially, mortality has been reduced to an acceptable level among insecticide-treated
seedlings. This practice spreads out the weevil population over a given
area and prevents large populations of weevils from migrating enmasse
only a short distance into a new cutting area where they can overwhelm