AW 



FOREST SERVICE RESEARCH NOTE NE-250 



& * I * 



ores 



ISgrtheastern 

 Txperiment Statioit 



FOREST SERVICE, U.S. DEPT. OF AGRICULTURE, 6816 MARKET STREET, UPPER DARBY, PA. 19082 



A SAMPLING DEVICE FOR COUNTING INSECT 

 EGG CLUSTERS AND MEASURING VERTICAL 

 DISTRIBUTION OF VEGETATION 



— ROBERT L. TALERICO 



Research Entomologist, 



-ROBERT W. WILSON, JR. 



Research Forester 

 Northeastern Forest Experiment Station, 

 Hamden, Connecticut 



Abstract. The use of a vertical sampling pole that delineates known 

 volumes and position is illustrated and demonstrated for counting egg 

 clusters of N. sertifer. The pole can also be used to estimate vertical and 

 horizontal coverage, distribution or damage of vegetation or foliage. 



INTRODUCTION 



Field entomologists often have to estimate 

 numbers of insects by examining branches, 

 buds, or twigs. Insect eggs are especially dif- 

 ficult to find and count for population studies or 

 surveys. Several years ago, we investigated 

 ways to estimate numbers of sawfly eggs or egg 

 clusters in a pine plantation. We built a sam- 

 pling pole that delineates known volumes for 

 sampling to estimate population parameters of 

 interest. For instance, it can be used for es- 

 timates of vegetation coverage, vertical and 

 horizontal distribution of vegetation or foliage, 

 and estimates of damage to vegetation caused 

 by defoliation or deer browse. 



We will illustrate the use of the sample pole 

 on an insect problem, but the same procedure 

 can be used for vegetation or damage assess- 



ment. Larvae of the European pine sawfly 

 (Neodiprion sertifer (Geoffroy)) are spring 

 colonial defoliators of Scotch, red, jack, moun- 

 tain, and mugho pines. The economic impact of 

 defoliation is particularly severe in plantations 

 of Christmas trees approaching marketable size. 



Several techniques are available for counting 

 N. sertifer eggs, larvae and cocoons. Lyons 

 (1964) utilized quadrats of various sizes for 

 sampling cocoons and found that the optimal 

 size of the quadrat is related to cocoon density 

 and degree of aggregation, soil type, and method 

 of cocoon extraction. To estimate densities of 

 egg clusters and larval colonies, he used the 

 quadrats and whole trees as sampling units. He 

 concluded that using whole trees generally gave 

 more precise results. Wilson and Gerrard (1971) 

 have proposed a method of estimating the mean 

 number of egg clusters or larval colonies per 



1 



