Estimates and measurements of pine weevil feeding on conifer seedlings: their relationships and application

In assessments of pine weevil (Hylobius abietis (L.)) feeding on conifer seedlings in Sweden, positive linear relationships were found between the numbers of attacked seedlings and each of the numbers of seedlings killed by pine weevil feeding, the damage score, and the mean estimated extent of feeding on damaged seedlings. Hence the damage score was described by polynomial regression on number of attacked seedlings. The influence of environmmental conditions was reflected in variations of the extent of feeding and seedling mortality. Independent assessments of the extent of feeding on an ordinal or percent scale were made by four investigators. The numbers of seedlings with feeding scars observed in field inspections were consistently lower than the actual numbers attacked. The estimates of mean extent of feeding on damaged seedlings varied between investigators within a range of about 10%. The relationship between the measured area of damaged bark and the estimated extent of feeding was expressed by linear and exponential regressions.