28 MISC. PUBLICATIOX 273, U. S. DEPT. OF AGRICULTURE 



ROOT APHIDS 



Some aphids are root-feeders. One species, Cinara {Lachnus) 

 cuTvipes Patch, was recently found feeding on the roots of small 

 Avhite firs in Oregon. The large carpenter ants {Camponotus her- 

 culemius var. modoc '\Mieeler) were carefully tending them. The 

 ants had gnawed the outer bark and cambium of the fir roots, and 

 colonies of aphids were feeding on the fresh wounds. They were 

 observed Avorking the full length of their beaks into the cambium 

 and feeding on the juices. This same aphid has been found working 

 on the bark of twigs of balsam firs and Cedrus atJantica. 



INSECTS INJURIOUS TO YOUNG TREES (SAPLINGS 



AND POLES) 



Trees in plantations and forests are subject to attack by a great 

 many insect pests' while they are growing from saplings to maturity. 

 After having been at first beset by the root-feeding insects, they 

 are later attacked by another group of injurious insects — those which 

 feed on the rapidly growing terminal shoots, laterals, tips, or buds. 

 This t3^pe of damage seldom results in the death of the young trees, 

 but it often seriously deforms or stunts them. As buds and termi- 

 nals are killed the tree throws out new buds and shoots, which results 

 in much branching. The tree becomes bushy in form, with the main 

 trunk crooked and gnarled, and is often permanently ruined for 

 commercial use. At this stage of the tree's life, leaf-eating and 

 bark-feeding insects also begin to be of importance. 



The control of insects atfecting young trees rarely calls for the 

 application of direct control measures. A certain amount of insect 

 damage is normal in natural forests and is only a part of the natural 

 thinning process. When an epidemic develops as the result of some 

 disturbance of the natural balance, as through the creation of an 

 abundance of slash, windfall, or fire-injured trees, some direct con- 

 trol action may be necessary to protect the younger trees. Usually 

 the indicated remedy is avoidance of the conditions that induce epi- 

 demics or the prompt disposal of breeding material. In plantations, 

 or in the case of trees of special value, some attention to insects may 

 frequently be justified. 



The control of terminal-feeding insects presents an extremely diffi- 

 cult problem. In general little can be done except through spraying, 

 dusting, or hand-picking of damaged shoots and encouraging of 

 parasites. The cambium-feeding insects can usually be controlled 

 by felling and burning the infested material, and leaf -feeding forms 

 can be controlled by spraying or dusting. Special methods adapted to 

 the control of each group will be mentioned under later discussions. 



KEY TO DIAGNOSIS OF INSECT INJURY TO YOUNG TREES 



A. Terminal shoots, laterals, or tips deformed or killed. Trees weakened 

 or stunted but seldom killed (except a few of the smaller seed- 

 lings). 



1. New or old twigs, branches, or succulent shoots killed. Insect 

 tunnels or borings found under the bark. 



a. Point of attack showing a small pitch tube with exu- 

 dation of fine boring dust. Under the bark or in 

 pith are found small egg tunnels of uniform 



