DISTRIBUTION AND SAMPLING OF ROOT WEEVIL LARVAE IN YOUNG ORNAMENTAL CONIFER PLANTATIONS

Abstract

AbstractWe determined the distribution of root weevil larvae feeding on the roots of young ornamental conifers in field studies using a new non-destructive sampling technique. Most root weevil larvae fed on the roots during summer, fall, and late spring with significantly more larvae found at 10 cm than at 20 and 30 cm and more at 20 cm than at 30 cm. Larvae moved down into the soil to overwinter and moved closer to the surface (<15 cm) in the spring. Soil samples predicted the population density of larvae under individual trees. Four samples (0.0076 m3), 9 cm in diameter by 30 cm long, taken equidistantly 20 cm from the tree stem provided the best estimate. The equation, T = 64.04 M, where T is the total number of larvae beneath a tree, and M is the mean number of root weevil larvae from four soil samples, described the linear relationship between the number of larvae in soil samples and the total population of larvae beneath a tree. Implications for the timing and location of sampling and control measures are discussed.