Forest Pests: Insects, Diseases & Other Damage Agents

Anderson, R. L.; Mistretta, P. A. Management strategies for reducing losses caused by fusiform rust, annosus root rot, and littleleaf disease. Agric. Handb. 597. Washington, DC: U.S. Department of Agriculture, Forest Service, 1982. 30 p.

Introduction

Fusiform rust, annosus root rot, and littleleaf disease cause extensive damage to the pine resource in the Southern United States. Most commonly damaged are slash (Pinus elliottii Engelm. var. elliottii), loblolly (P. taeda L.), and shortleaf (P. echinata Mill.) pines.

Plantation failures, reductions in growth and timber quality, and tree mortality commonly result from infection by these three diseases. Annual losses are estimated to exceed $130 million.

Research has now identified the characteristics of susceptible sites, vulnerable tree species, and insects associated with these diseases. This handbook summarizes research results in these areas for the manager who needs up-to-date information for making management decisions.

Material in this handbook is based on these underlying assumptions:

1. Fusiform rust rarely infects shortleaf pine; loblolly and slash pines are the only ones considered to be hosts.
2. Slash pine appears resistant to littleleaf disease and is not considered in littleleaf disease management.
3. Shortleaf and loblolly pines are subject to both annosus root rot and littleleaf disease, but the two diseases tend to occur on sites with very different soil characteristics. Fusiform rust, however, is relatively nonspecific to site and infects loblolly and slash pines on both annosus and littleleaf sites.
4. Black turpentine beetles (Dendroctonus terebrans (Oliver)) and caterpillars of the southern pine coneworm (Dioryctria amatella (Hulst)) commonly attack fusiform rust cankers.
5. Southern pine beetles (Dendroctonus frontalis Zimmerman) favor trees weakened by littleleaf disease or annosus root rot for their initial attacks.
6. Pine engravers (Ips spp.) attack pines infected by all three of these diseases.

Figure 1 (above), an integrated host/disease cycle, depicts the interactions in time of the three diseases described in this handbook. Note that this figure focuses on parts of the life cycle where tree age and size class are of greatest concern to managers. New fusiform rust infections occur in older age classes, but managers must be concerned primarily with those infections occurring before age 10. Similarly, while some loss to annosus root rot does occur within 5 years of planting, concern is greatest in older, thinned stands.

The consolidation of data on all three diseases in one handbook should enhance the manager’s decision making process. Significance, symptoms, and hazard rating are presented separately for fusiform rust, annosus root rot, and littleleaf disease. A separate section covers management practices. All of the accepted prevention and suppression practices for each disease are integrated into a decision key (in flow-chart form). After resource managers answer specific questions about site and stand conditions, they will arrive at a list of suggested stand management options. The options are explained in the Management Practices section. This section is not intended to be a stand prescription, but rather lists all available options to consider when developing stand prescriptions.

Figure 1. - Management integration of the disease cycles of fusiform rust, annosus root rot, and littleleaf disease into a generalized pine life cycle.

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