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PROTECTING SHADE TREES FROM INSECTS 



R. A. ST. GEORGE 



Many kinds of insects attack shade 

 trees. Some of the worst infest the 

 trunk or the branches or the leaves. 

 Some merely mar the appearance of 

 the part attacked. Others cause severe 

 injury. But of all of them it can be said 

 that they have specific habits whereby 

 they and their damage can be iden- 

 tified, assessed, and used to determine 

 the need for applying control meas- 

 ures. It is convenient to separate the 

 more important insect enemies of 

 shade trees into two groups, those that 

 attack weakened and dying trees and 

 those that infest the more healthy ones. 



THE FIRST GROUP includes many 

 species of bark-infesting and wood- 

 boring beetles. They can detect trees 

 that have reached a decadent stage 

 long before a man can see the changes 

 associated with decadence. 



The ambrosia beetles frequently are 

 among the first insects to attack weak- 

 ened trees. Their presence can be de- 

 tected by the strings or piles of white, 

 powdery frass that they push to the 

 bark surface as they extend their tun- 

 nels deep into the wood. It is a posi- 

 tive indication that the tree is dying. 

 If the infestation is confined to a small 

 area on one side of the trunk, the tree 

 might be saved by taking measures to 

 revitalize it fertilizing and watering, 

 and by applying a protective chemical 

 spray to the stem of the tree. But if 

 the attack extends entirely around the 

 trunk, the processes of decadence are 

 likely to have progressed so far that 

 the tree will die, and the expenditure 

 of large sums of money to save it is 

 questionable. Often it is more practical 

 to dispose of such a tree than to try to 

 save it. 



Certain of the roundheaded beetles 

 attack dying trees. The females of some 

 species of the roundheaded beetle make 

 slits or pits in the bark and deposit their 

 eggs in them. After the larvae have 



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worked beneath the bark and into the 

 wood their presence can be detected 

 by the noise they make while cutting 

 their tunnels and also by the coarse, 

 shredded wood fibers that are pushed 

 to the bark surface. 



Many bark beetles attack weakened 

 trees. They work between the bark and 

 the wood. They make small shot holes 

 in the bark and push their granular 

 borings to the surface. Their color, 

 which is similar to that of the bark, 

 helps one to distinguish between the 

 bark borers and wood borers. Certain 

 species, known as turpentine beetles, 

 are much larger than the rest of the 

 bark beetles and confine their attacks 

 to the bases of trees. A large, reddish 

 pitch tube is formed at each point of 

 entry. In the eastern and southern sec- 

 tions of the country, their attacks are 

 mostly unsuccessful, but in the western 

 pine regions turpentine beetles can 

 sometimes kill slow-growing and in- 

 jured trees and cause considerable con- 

 cern to owners of mountain homes. 



The obvious way to combat these in- 

 sects is to keep the trees healthy to 

 remove the factors responsible for the 

 weakening of shade trees. Among the 

 factors causing the most damage are 

 prolonged droughts; earth fills; sun- 

 scald and whipping of the stems, due 

 to severe thinnings around trees left 

 for natural shade; mechanical injury 

 to the trunks and roots of trees made by 

 heavy equipment while cutting roads 

 and grading the soil around new 

 homes; poor drainage; transplanting 

 at the wrong time of year; and not 

 using due caution in handling the 

 trees or caring for them sufficiently 

 until they are well established. 



THE SECOND GROUP includes those 

 insects that attack healthy trees. All 

 parts of the tree are subject to infesta- 

 tion. 



The stem borers include many kinds 



