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 - TX Hazard

Description

TX Hazard is a method of rating stands for susceptiblity to SPB attack and their ultimate potential for timber loss. The model was developed for mixed and pure pine forests in east Texas using data collected from 1100 plots during a period of moderately high beetle activity from 1973-1975. The model was tested on an additional 182,000 acres in east Texas and 177,000 acres in Louisiana using aerial photo Hazard ratings and historical infestation records. Testing is continuing in Texas as new infestations occur.

Inputs

Required 1) Pine basal area (square feet per acre) 2) Average stand height or diameter at breast height 3) Landform (bottom, ridge, other) Landform is considered more an an indicator of moisture regime than true topographical position, that is, ridge = drier upland sites, bottom = moist, low-lying pine sites, and other = intermediate conditions. Optional Number of acres in each Hazard class by stand or ownership.

Table 1 - Southern pine beetle Hazard classes based upon average site and stand conditions.

Pine basal area (ft2/acre)	Hazard class1
	Ridge			Other terrain			Bottom
	S	M	L	S	L	M	S	M	L
<80	Low	Low	Low	Low	Low	Low	Low	Low	Low
80-120	Low	Low	Med	Low	Med	Med	Med	Med	High
>120	Low	Med	Med	Med	High	High	Med	High	High

¹S = small trees (<50 ft tall, or > 6 in. d.b.h.), M = medium trees (50-75 ft tall, or 6-12 in. d.b.h.), L = large trees (>75 ft tall, or >12 in. d.b.h.).

Outputs

Normal Hazard classes from table 1. Optional A 5-year loss projection by Hazard class, that is, the number of spots and trees expected to be killed during a 5-year period within a given number of acres of a specific Hazard type (table 2).

Table 2 - Five-year loss projection by Hazard class and stand size.

Hazard class	Estimated 5-year loss
	100 acres		300 acres		500 acres		700 acres		1000 acres
	Spots	Trees1	Spots	Trees	Spots	Trees	Spots	Trees	Spots	Trees
High	2	140	5	420	8	700	11	980	16	1400
Medium	1	14	2	42	4	70	5	98	7	135
Low	.2	4	.5	12	1	20	1.5	28	2	40

¹Estimated trees containing living beetles at time of control; figure does not represent total number of trees killed.

General Reference	Mason et al. 1981
For additional information, contact:	Dr. G.N. Mason USDA Forest Service Southern Forest Experiment Station IPM Program 2500 Shreveport Highway Pineville, LA 71360 Telephone: (318) 473-7250

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