11 



Woodlots and orchards are frequently seen in which the trees are 

 dying from defoliation repeated for several years. 



According to Mr. Surface, this defoliation is the work of the spring 

 cankerworm/ and he has published some notes upon the methods of 

 control. When the advisability of planting any land in these coun- 

 ties with forest trees is contemplated, this factor of insect damage 

 must be considered carefully. Methods of control such as are com- 

 monly used in orchards will not usually be practicable in a forest plan- 

 tation. The presence of this insect does not necessarily prevent for- 

 est planting, but requires, rather, a change in the local planting site 

 or a postponement of planting until the pest has been reduced in num- 

 bers by its natural enemies or other agencies. 



INSECT DAMAGE TO THE LOCUST. 



The locust (Bobinia pseudacacia) , because of its rapid growth, its 

 adaptability to different soil conditions, and its value for posts and 

 pit props, is a valuable tree for forest planting. Injuries by certain 

 insects, however, present a great obstacle to its use. The following 

 observations were made in connection with a cooperative study of 

 insect enemies of the locust by the Bureau of Entomology and the 

 Forest Service in 1905. 



The destructive work of the locust leaf -mining beetle (Odontota dor- 

 salis Thunb.) 6 and the locust borer (Cyllene robinise Forst.) requires 

 special consideration wherever the establishment of forest plantations 

 of locust is desired in this region. 



The locust leaf-mining beetle. Severe injury by the leaf-mining bee- 

 tle gives the trees a blighted, brown appearance by midsummer. The 

 examination of a locust tree early in July reveals blister spots on the 

 leaves, caused by the young, or grub, of the beetle, a small, flattened, 

 whitish worm, which eats the soft tissue between the upper and lower 

 surface. Toward the end of July the beetles begin to emerge from 

 the leaves and feed upon the upper surface. The combined effect of 

 the blisters and the subsequent feeding of the adult insects renders 

 the foliage partially or wholly functionless, according to the severity 

 of the attack. This reduction of the working leaf surface, year by 

 year, weakens the tree, since it is not able to produce sufficient food 

 to maintain its growth. Such a condition alone, or in conjunction 

 with secondary causes, may result in the death of the tree within a 

 few years. A cross section of the stem of a tree attacked for several 

 years shows a steady decrease in the width of the rings of annual 

 growth. During the stages of decline and death the locusts have no 



a Volume III, No. 5, The Monthly Bulletin of the Division of Zoology, Pennsylvania State 

 Department of Agriculture. 



6 See United States Department of Agriculture, Division of Entomology, Bulletin No. 38, 

 new series, 1902, "The Leaf -mining Locust Beetle," F. H. Chittenden. 



