October, 1929] WHITE PINE WEEVIL 25 



of adults and the removal of infested leaders. Indirect methods consist 

 of silvicultural practices to reduce the infestation and to assist the tree 

 in recovering from weeviling. This is accomplished by adoption of mixed 

 stands or densely planted stands. Natural or biological control by in- 

 sect parasites and predators is important. 



DIRECT CONTROL METHODS 



Chemical Control 



Chemical control methods for the white pine weevil have not been fully 

 investigated. It is a question whether the cost of such control would be 

 justified in a commercial plantation. 



At present we have no spray material giving full control. Walden 

 (1915) reported that lime-sulphur (1 to 8) was one of the best repellents 

 tried. Lime-sulphur cannot be expected to give complete control but 

 will reduce the infestation if applied early in May. Graham (1916) tried 

 16 different materials including various common spray chemicals. His 

 results indicated that creosote, which slightly injures the tree, and car- 

 bolineum, may be of value. Graham found the above materials more 

 effective than lime-sulphur or arsenate of lead. Experiments by Gra- 

 ham (1916) and MacAloney (1926), confirmed by us, show that trees 

 banded with tanglefoot at the base of the leader show^ a substantial de- 

 crease in weeviling. 



In our investigation oil of pine, oil of pine needles, and pinene, were 

 tried as attrahents. Small muslin bags containing three ounces of bran 

 saturated with the above oils were tied to the middle lateral branches of 

 nine trees scattered throughout a plantation. None of these oils attract- 

 ed any weevils. 



Collection of Weevils. 



Frequent collection of weevils from the leaders may be applicable to 

 small ornamental plantings. In order that this method may be effective 

 weevils should be removed at least once a week during the season. Felt 

 (1914) and Walden (1915) used a large net, 15 inches in diameter, to 

 make collecting more expeditious. The net was held on one side of the 

 leader and the weevils were knocked into it by a sharp blow with a stick 

 on the opposite side. In New Hampshire collection of weevils has not 

 proved to be a iiractical means of control. 



Removal of Infested Leaders. 



The removal of infested leaders just below the farthest point reached 

 by the larvse is a common method of control. It is important that this 

 method be practiced successively for several years in order to be effective. 

 Weevils living for more than one year may be sufficient to cause infesta- 

 tion the following year after the leaders are pruned. A marked decrease 

 maj' not be noticed until the third year. 



