35 



gas mains. Such trees have but little reserve vitality and are 

 easy victims to damage by the beetle. The weakened condition 

 of trees defoliated by the elm-leaf beetle invites or favors attack 

 by other insects, notably borers, bark beetles and the elm-bark 

 louse. 



Natural Enemies. 



Several species of predaceous beetles are known to attack this 

 insect. In Massachusetts two species of soldier bugs (Podisus 

 serieventris and P. placidus) are its most common enemies. 

 These beneficial little bugs frequent the infested trees and prey 

 upon the larvae and pupae.* 



Remedies. 



In combating the elm-leaf beetle the chief reliance should be 

 placed upon the use of arsenical insecticides, and of these the most 

 satisfactory is arsenate of lead, which should be used at the rate 

 of 5 to 10 lbs. (actual arsenate of lead) to 150 gallons of water. 

 Its preparation and application are discussed on another page. 



The first spraying should be in May or early in June while the 

 beetles are feeding. This treatment, as has been shown by Mr. 

 C. L. Marlatt, is very efficacious, since by destroying the mature 

 beetles, egg-laying and the consequent development of larva? are 

 prevented. Later, when the larvae have appeared and the main 

 body of the foliage has developed, a second application should be 

 made. This, if thorough, may suffice for the season, although in 

 some cases a third spraying may be necessary for the second 

 brood. In all cases the insecticide should be used in liberal 

 quantities. 



With rough barked trees many of the larvae pupate in the 

 crevices on the trunk and even far up in the tree, hence scraping 

 the bark is advisable. This will cause the larvae to descend to the 

 ground to pupate, where they will be found massed in great 

 numbers at the base of the trees, under or along the bottom 

 rails of fences nearby, and in other convenient spots. In this 

 stage they may be destroyed by kerosene emulsion applied to the 

 trunks and to the ground beneath the trees. 



Spraying Outfits. For use in parks or cities where large num- 

 bers of trees are to be sprayed, a power-spraying outfit will be 

 found the most satisfactory. This consists of a small engine with 

 suitable pump, mounted on a substantial one-horse truck which 

 also carries the spraying tank and supplies. There are several 



* At Squantum, July 12, a third species of predaceous bug (Stiretrus anchor- 

 ago) was found feeding upon the larvse of the elm-leaf beetle. 



