EVALUATION OF BINOMIAL EGG MASS SAMPLING PLANS FOR LOW-DENSITY GYPSY-MOTH POPULATIONS IN CONTINUOUSLY FORESTED HABITATS

The use of binomial sampling for low density (<618 egg masses per hect are) gypsy moth, Lymantria dispar (L.), populations in continuously fo rested habitats was examined. Fixed- and variable-radius plot egg mass samples were collected in 28 study areas in Virginia, Maryland, and M assachusetts. A model was fit to the egg mass density and the proporti on of trees with zero egg masses. Binomial sampling plans were develop ed for sample sizes of 9, 16, 49, and 98 samples within a 9-ha plot an d compared with complete counts determined by fixed- and variable-radi us plot samples. The relative efficiency, the relative variability alo ng with the total cost of obtaining a sample, of the binomial method w as much lower than the fixed- and variable-radius plot method for the sample sizes of 49 and 98. For the sample sizes of 9 and 16, binomial sampling reduced the time required to take a sample but population est imates had unacceptable precision. Therefore, binomial sampling was de termined not to be an effective sampling method for low density gypsy moth populations.