tlfliST SERVICE RESEARCH NOTE NE-273 



r 7bMC{ 1979 



± 



Northeastern Torest 

 Txperiment Station 



FOREST SERVICE, U.S. DEPARTMENT OF AGRICULTURE, 370 REED ROAD, BROOMALL, PA. 19008 



FOREST STAND LOSSES TO GYPSY MOTH IN THE POCONOS 



—DAVID A. GANSNER 

 OWEN W. HERRICK 



Research Foresters 

 Northeastern Forest Experiment Station, 



Broomall, Pa. 



Abstract. A Study of forest stand losses associated with the gypsy 

 moth outbreak of the early 1970's in the Pocono Mountain Region of 

 northeastern Pennsylvania, showed that while most of the stands 

 incurred little or no loss, a few suffered heavy damage. 



How much damage to trees and forests of 

 a region will result from a gypsy moth out- 

 break? The answer depends on a number of 

 interrelated factors such as the frequency and 

 intensity of attack, the susceptibility and 

 vulnerability of host trees, the size and effec- 

 tiveness of insect control programs, and 

 weather. 



Since most of these factors are themselves 

 difficult to predict, it is little wonder that we 

 are unable to accurately forecast impacts of 

 the pest. But, we can turn to recent experi- 

 ences for some indication of what to expect. 

 One is the outbreak that occurred during the 

 early 1970's in the Pocono Mountains of 

 northeastern Pennsylvania. Field-plot data 

 have given us measures of tree and timber 

 losses associated with that infestation. 



BACKGROUND 



Forest stand losses were measured on 143 

 1/10-acre plots in Pike and Monroe Counties, 

 Pennsylvania. This area was on the frontier of 

 gypsy moth infestations in the early 1970's. 

 The plots were established in 1971 in newly 

 infested forest stands. Stand losses for trees 

 3 inches in diameter at breast height (dbh) 

 and larger were measured each year for 5 

 years. The stands were not sprayed to con- 

 trol the gypsy moth during the study period. 



Severity and frequency of gypsy moth at- 

 tacks varied from plot to plot. In general, the 

 study area had moderate to heavy defoliation 

 from 1971 through 1973. Insect populations 

 all but collapsed in 1974 and 1975, and then 

 built up again in 1976. Tree mortality re- 

 flected this pattern of infestation. Four-fifths 



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