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• 1. [Article] Western spruce budworm egg masses for predicting defoliation potential in the northern region : progress report

  An attempt was made to predict western spruce budworm defoliation using egg counts from plots in the Douglas-fir type east of the Continental Divide in Montana, the Douglas-fir type west of the Continental ...

  Citation × Citation Citation Abstract Copy Title: Western spruce budworm egg masses for predicting defoliation potential in the northern region : progress report Author: United States. Forest Service. Northern Region. State & Private Forestry, Tunnock, Scott An attempt was made to predict western spruce budworm defoliation using egg counts from plots in the Douglas-fir type east of the Continental Divide in Montana, the Douglas-fir type west of the Continental Divide in Montana, and the mixed grand fir Douglas-fir type of northern Idaho. The parameters used in a linear regression model for the three ecotypes were eggs per 100 buds in 1972 as the independent variable and percent defoliation in 1973 as the dependent variable. Correlation coefficients (0 were: 0.39, 0.54, and 0.66 for the data from grand fir in northern Idaho and Douglas-fir in eastern and western Montana respectively. A covariance analysis of the three regression lines showed there were differences between the three ecotypes. Title: Western spruce budworm egg masses for predicting defoliation potential in the northern region : progress report Author: United States. Forest Service. Northern Region. State & Private Forestry, Tunnock, Scott An attempt was made to predict western spruce budworm defoliation using egg counts from plots in the Douglas-fir type east of the Continental Divide in Montana, the Douglas-fir type west of the Continental Divide in Montana, and the mixed grand fir Douglas-fir type of northern Idaho. The parameters used in a linear regression model for the three ecotypes were eggs per 100 buds in 1972 as the independent variable and percent defoliation in 1973 as the dependent variable. Correlation coefficients (0 were: 0.39, 0.54, and 0.66 for the data from grand fir in northern Idaho and Douglas-fir in eastern and western Montana respectively. A covariance analysis of the three regression lines showed there were differences between the three ecotypes. Close

• 2. [Article] Western spruce budworm defoliation trend relative to weather in the Northern Region, 1969-1979

  Western spruce budworm defoliated area in the Northern Region has differed significantly across three discrete geographic zones during the past decade. Aerially visible defoliation in northern Idaho increased ...

  Citation × Citation Citation Abstract Copy Title: Western spruce budworm defoliation trend relative to weather in the Northern Region, 1969-1979 Author: United States. Forest Service. Northern Region. State & Private Forestry, Hard, John S., Eder, Robert G., Tunnock, Scott Western spruce budworm defoliated area in the Northern Region has differed significantly across three discrete geographic zones during the past decade. Aerially visible defoliation in northern Idaho increased from 1.7 million acres in 1969 to a high of 2.2 million acres in 1974, and declined to none in 1979. Defoliated area in western Montana increased from 1.8 million acres in 1969 to a high of 2.8 million acres in 1972 and declined to 0.6 million acres in 1979. Conversely, defoliated area in eastern Montana fluctuated at low levels between 0.1 and 0.7 million acres between 1969 and 1974, and then rose to a high of 1.6 million acres in 1979. Analysis of defoliation trend, the ratio of acres defoliated in the current year by acres defoliated the prior year, and weather during budworm larval and pupal periods during the past decade revealed the following relationships: Defoliation trend in all three geographic areas varied (a) directly with mean maximum temperature during May, June, and July of the year before, and (b) inversely with frequency of measurable precipitation during May, June, and July of the year before. Based on warm, dry conditions throughout the Region in 1979, we predict a general increase in budworm populations in the Northern Region in 1980. Title: Western spruce budworm defoliation trend relative to weather in the Northern Region, 1969-1979 Author: United States. Forest Service. Northern Region. State & Private Forestry, Hard, John S., Eder, Robert G., Tunnock, Scott Western spruce budworm defoliated area in the Northern Region has differed significantly across three discrete geographic zones during the past decade. Aerially visible defoliation in northern Idaho increased from 1.7 million acres in 1969 to a high of 2.2 million acres in 1974, and declined to none in 1979. Defoliated area in western Montana increased from 1.8 million acres in 1969 to a high of 2.8 million acres in 1972 and declined to 0.6 million acres in 1979. Conversely, defoliated area in eastern Montana fluctuated at low levels between 0.1 and 0.7 million acres between 1969 and 1974, and then rose to a high of 1.6 million acres in 1979. Analysis of defoliation trend, the ratio of acres defoliated in the current year by acres defoliated the prior year, and weather during budworm larval and pupal periods during the past decade revealed the following relationships: Defoliation trend in all three geographic areas varied (a) directly with mean maximum temperature during May, June, and July of the year before, and (b) inversely with frequency of measurable precipitation during May, June, and July of the year before. Based on warm, dry conditions throughout the Region in 1979, we predict a general increase in budworm populations in the Northern Region in 1980. Close