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Minimize Disease and Competition Problems


Stands should be managed to prevent or reduce losses from all disease and insect pests. Studies have shown a close association between annosum root rot and SPB attack (fig. 11). Precautions should be taken to reduce the danger of annosum infection. Intermediate cuttings to remove high-hazard SPB trees or to promote stand vigor should be scheduled during summer, when fewer annosum spores are produced and high temperatures kill those that are produced. Treating stumps with borax or Peniophora spores also reduces the incidence and spread of infection.

Figure 11. - Annosum root rot is closely associated with SPB attack.
Figure 11. - Annosum root rot is closely associated with SPB attack.

Stands with littleleaf disease are generally high-hazard SPB areas (fig. 12). "Locus" trees-those first attacked and preferred by the SPB are often dominant and codominant shortleaf pine trees with large live crown ratios and root systems in incipient stages of decline. Trees in advanced stages of littleleaf decline are seldom killed by the SPB. Sanitation cuttings are recommended to utilize both diseased and SPB attacked trees. Stands should be regenerated before they reach advanced stages of decline, usually between the ages of 30 and 40. Loblolly pine is not as susceptible to littleleaf disease as shortleaf pine and should be favored when regenerating stands.

Figure 12.-Littleleaf sites are high-hazard SPB areas. In the Southeast, SPB infestations (1972) were closely  associated with the range of severe littleleaf disease.
Figure 12.-Littleleaf sites are high-hazard SPB areas. In the Southeast, SPB infestations (1972) were closely
associated with the range of severe littleleaf disease.

Trees heavily infested with fusiform rust galls should be salvaged. Diseased stems are subject to breakage by wind and ice, and may be infection courts for numerous insect and disease organisms. Sanitation cuttings will lower the potential for attack and spread of insect pests and provide cash returns from salvaged materials.

Prescribed burning should be considered as a pest management practice. Burning can be used to eliminate suppressed high-hazard trees from overstocked stands (fig. 13). Stand vigor will be further increased by reducing competition from understory hardwoods and vegetation. Prescribed burning before and after thinning also reduces severity of annosum root rot in the South. Controlled use of fire does not increase SPB activity: it can be a useful tool in reducing losses from pests.

Stands and forests that are highly resistant to SPB attack should be equally resistant to attack by other bark beetles. Maintaining healthy stands is the key to integrated pest management (IPM).

Figure 13. - Prescribed burning can be used to reduce competition in high-hazard stands.
Figure 13. - Prescribed burning can be used to reduce competition in high-hazard stands.

 

Planning and Application.- The risk of SPB attack and rapid spot growth is lowest when insect populations are down. This is the best time to plan and implement silvicultural treatments related to IPM. Mill quotas are not filled with salvage wood, and operators are available to conduct intermediate cuttings. The "reservoir" of SPB-infested and high-hazard trees is removed, and more growing space is provided for residual trees. High-hazard 'stands can be identified and treated to reduce their susceptibility to beetle attack and the potential for spot growth in a future outbreak. Low-hazard stands can be tended to maintain vigor and rapid growth. Stands and forests that are highly resistant to SPB attack should be a primary objective of management. Prevention silviculture offers the most practical and long-lasting means of achieving this goal. In short, good forest management is good pest management.

 

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