Weevil populations in the South tend to be high from
year to year, and serious damage often occurs within a few days or weeks
of planting, even in midwinter when the temperature moderates. Therefore,
control decisions need to be made before planting. To make these decisions,
the forest manager must be able to predict whether significant weevil-caused
damage will occur on the site. The following sections provide guidelines
for making that prediction for both species of weevils, and offer alternatives
for controlling them. Most of the research on which these guidelines were
based was done in areas where pales weevils were more common than pitch-eating
weevils (i.e., eastern North Carolina, the Georgia Piedmont, southeastern
Oklahoma, southwestern Arkansas). However, because of similarities in
biology and behavior of the two species, and the good control obtained
when using these guidelines in areas where both species occur,the guidelines
apply to both species.
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In the past, attempts have been made to correlate the
number of pales weevils trapped on a site prior to planting with the subsequent
seedling damage, in an effort to develop a pales weevil hazard rating
system for recently cutover pine land. Pales and pitch-eating weevils
are easily trapped in nature, and under favorable conditions large numbers
may be collected. Various resin-containing materials can be used for trapping.
The most commonly used materials are pine bolts about 18 inches (0.5 in)
long, split once, or discs freshly cut from living pine stems 5 to 7 inches
(13 to 18 cm) in diameter. Discs should be I V2 to 2 inches (4 to 5 cm)
thick (figure 6). These traps are placed on the ground in an infested
area, with the cut surface flush on the ground. Weevils are attracted
to this material by the odor of the resin. The weevils crawl under the
traps at night where they may remain for many hours (usually until mid-morning),
feeding and mating. Correlations have been poor, however, between the
numbers of weevils found trapped on planting sites prior to planting and
subsequent seedling damage.
Figure 6. - Split pine bolt and pine discs placed around
loblolly pine stump to trap pales and pitch-eating weevil adults.
Until a reliable hazard rating system is developed which
can predict weevil damage based on weevil population estimates, forest
managers must depend on other circumstantial evidence to determine if
control is necessary.
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Weevil problems will not develop in certain planting
situations, such as:
Old fields and areas formerly covered with hardwoods,
since weevils are not attracted to nonconiferous vegetation.
Pine areas being regenerated by direct seeding, since
weevils will have left the area before the seedlings are large enough
to become suitable food.
Pine areas cut and site-prepared before July, because
weevils and their broods will either have died or migrated before
the following planting season.
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Weevil damage is likely to occur on pine lands harvested
in July or later and replanted the following winter. Note, however, that
in sites cut prior to July, a late summer or fall site preparation which
knocks down residual pine stems will result in another influx of weevils,
and seedling mortality should be expected. The size of the attracted population
and the amount of damage apparently depends on the volume of pine cut
during site preparation.
Damage may also occur in areas cut in the spring or even
in I- to 3-year-old pine plantations adjacent to large freshly cut areas,
but this damage is usually confined to 100-foot-wide border strips near
the cutting. Seed tree cuts will also attract damaging populations of
weevils. But by far, the most damage occurs in plantings on recently cutover
or site-prepared pine lands.
Guide to Determining Weevil Damage Hazard
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A rule of thumb has been developed
for the Piedmont and Coastal Plain regions of the South that can be used
by the forest manager to determine weevil hazard: Pine lands
cut and site prepared before July can generally be planted the following
winter without control measures. However, on pine lands harvested in JuIy
and later, or in older cuttings where residual pine is cut during late
summer or fall site preparation, planting should either be delayed one
year or seedlings should be treated with insecticide to prevent weevil-caused
This rule may not apply to pine sites in the southern
Appalachians, where seedlings planted on sites cut before July would probably