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Control of Pales and Pitch-Eating Weevils in the South
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Control Alternatives


Delayed Planting

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.

Chemical Control

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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 the Appendix.

Chemical Control Strategy

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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

Cutting History Hazard Rating Control Recommendation
Logging date Site-preparation date

-

Planting date Treatment
winter-spring spring to early summer1 cold (low) December to mid-Feb. None
summer summer-fall warm (moderate) mid-Feb. through March Furadan granules
Imidan 50W+ extender
Dursban 4E
March Furadan 4F
fall fall hot (high) mid-Feb. through March Furadan granules
Imidan 50W+ extender
Dursban 4E

-

-

(unexpected damage)

-

Dursban 4E
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 be prevented.

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" sites.

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 area.

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

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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 seedlings.

 
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