Rating the Susceptibility of Stands to Southern Pine Beetle Attack

G.N. Mason - Research Coordinator, IPM RD&A Program for Bark Beetles of Southern Pines,
P.L. Lorio, Jr. - Project Leader and Supervisory Soil Scientist, Forest Insect Research, USDA Forest Service, Southern Forest Experiment Station, Pinesville, LA,
R.P. Belanger - Principal Silviculturist, USDA Forest Service, Southeastern Forest Experiment Station, Athens, GA, and
W.A. Nettleton - Entomologist, Forest Pest Management, USDA Forest Service, Southern Region, State and Private Forestry, Pineville, LA.

Integrated Pest Management Handbook, USDA, Forest Service, Agriculture Handbook No. 645, April 1985.

Model Summaries - TFS Grid Hazard

Description

TFS Grid Hazard is a large-area Hazard-rating system designed to rate Texas Forest Service Grid blocks (18,000-acre units) as high, moderate, or low Hazard based on site and stand conditions likely to support outbreak populations of SPB. The model is based on a discriminant analysis of photo-interpreted stand and land-form variables obtained by sampling small-scale aerial photographs (1:60,000). The system was developed and validated in east Texas using historical beetle infestation records. It is easily applied and used broad data categories for input. Although specifically designed for east Texas, the technique is easily adaptable to other areas in the Gulf Coast States that have similar historical information.

Inputs

Information on host type, percentage pine, stand density, and landform position from each of 20 uniformly distributed, circular 30-acre photo plots per Grid block. Photo samples may be interpreted from 1:60,000- to 1:120,000-scale color infrared photography. The site/stand factors and classification considered are: 1) Presence of host type (nonhost type, or if pine, whether it is less than or more than 15 years of age) 2) Percentage of pine (>/= 70 percent or <70 percent) 3) Percentage crown closure (>/= 80 percent or <80 percent) 4) Landform classification (bottomland or other terrain)

Step I.
Classify each of 20 photo plots per Grid block according to the following key:

Step II.
For each photo plot, tally by category:

* Not used to determine hazard.

Step III.
Enter plot tally in equation:

Discriminant score =

- 1.35 - 0.108(A) + 0.135(D) + 0.330(E) + 0.404(F) + 0.305(I) + 0.271(J).**

**Values for input variables (A through J) are the numbers of photo plots in each of the combinations of site/stand conditions under Step 1 (only values for A, D, E, F, I, and J are utilized in the discriminant equation.)

Outputs	A numerical discriminant score where:   Score Hazard class > 1.2 High 0.4 - 1.2 Medium < 0.4 Low
General Reference	Billings and Bryant 1983.
For additional information, contact	Dr. Ronald F. Billings Texas Forest Service Lufkin, TX 75901 Telephone: (409) 632-7761

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