NEW HAMPSHIRE COLLEGE 

 , AND EXPERIMENT STATION. 



(Extension Press Bulletin No. 34.) 



THE ELM LEAF-BEETLE. 

 By W. C. O'Kane. 



In many sections in southern New 

 Hampshire the Elm Leaf-beetle has worked 

 considerable injury in recent years. 

 Whether this pest is likely to increase 

 further is problematical. It is possible 

 that the insect has reached its maximum. 

 Meanwhile, in some sections where the 

 pest is badly injuring the foliage of the 

 elm, it is highly advisable to take meas- 

 ures to protect these valuable shade trees 

 wherever feasible. 



The work of the elm leaf-beetle is easily 

 recognized. In the spring, as soon as the 

 elm leaves are expanded, the adult beetles 

 appear and eat round or oval holes in the 

 foliage. These adults are small, rather 

 dull-colored insects, about one fourth of 

 an inch long. The general color is greenish 

 yellow. There is an obscure dark stripe 

 down each side of the back and incon- 

 spicuous dark markings just back of the 

 head. These beetles have spent the winter 

 in such shelter as crevices in the bark of 

 the trees, or in any other convenient place. 

 Frequently large numbers hibernate in 

 attics of houses and are noticed when 

 they become active in the spring and go 

 to windows in order to get out. 



THE LIFE ROUND. 



While they are feeding the beetles are 

 laying eggs on the under side of the leaves. 

 The eggs are orange in color, shaped like 

 a tiny small-necked bottle, and are laid 

 in clusters containing twenty or more. 

 They can easily be seen with the naked 

 eye. 



In the course of a few days the eggs 

 hatch and small grubs feed on the leaves, 

 gnawing off the surface but not eating 

 clear through. The grubs are dull yel- 



lowish in color with a dark stripe down each 

 side of the back. When full grown they 

 are about half an inch in length. As they 

 grow, the grubs almost completely destroy 

 the surface of the leaves, so that the 

 foliage turns brown and dies. 



After they have reached full growth the 

 grubs descend the trees, find shelter in 

 crevices in the bark or collect in large 

 numbers around the base of the tree, and 

 change to a resting stage called the pupa. 

 The pupa has neither legs nor wings. 

 The color is bright yellow. 



From the pupa in another week or ten 

 days emerges an adult beetle like the one 

 which first appeared on the tree. These 

 adults again seek the leaves and lay eggs 

 as did the first lot. By the time this 

 second generation appears the tree has 

 had opportunity to produce a new lot of 

 leaves. From these eggs a second lot of 

 grubs hatch and the injury goes on as 

 before. The beetles resulting from this 

 second lot of grubs are the ones that hide 

 away to spend the winter. 



THE MEANS OF CONTROL. 



The only effective means of control is 

 to apply a poison spray to the leaves of the 

 trees. The best material to use is arse- 

 nate of lead at the rate of five pounds to 

 fifty gallons of water. The spray must 

 be applied so as to coat the outermost and 

 highest leaves on the tree because it is at 

 these points that the beetles lay their eggs. 

 The time to spray is just as soon in the 

 spring as the leaves are well unfolded, 

 while the adults are feeding and egg- 

 laying. If the infestation is severe it may 

 be necessary to apply a second spray at 

 the time that the grubs are hatching, 

 which usually will be about the middle to 

 the latter part of June, in New Hampshire. 



If the first generation is effectively 

 checked there will be little damage from 

 the second generation. 



Frequently in New Hampshire the 

 numbers of the second generation are 

 greatly reduced from natural causes. 

 The more serious injury is that done by 

 the first generation. 



Approved : 

 J. C. KENDALL, 



Director of Extension Work. 

 Durham, N. H., April, 1913. 



