Protecting Shade Trees from Insects 



Trees cut in thinnings made during 

 the fall months should be removed 

 from the property before spring to 

 avoid attracting insects ; if they are cut 

 in summer, they should be disposed of 

 at once. 



The lower part of the trunks should 

 be boxed to protect the bark from 

 mechanical injury while heavy equip- 

 ment is being used about the property. 



Changes in grade level around trees 

 should be avoided wherever possible. 

 If it is necessary to raise the grade 

 more than about 6 inches, injury to 

 the trees can be reduced by installing 

 a system of tiles and a well about the 

 trunk of each of the trees so that air 

 can reach the roots. ( Details are given 

 in Department of Agriculture Farmers' 

 Bulletin No. 1967, Reducing Damage 

 to Trees From Construction Work.) 



Good drainage away from the build- 

 ing and the trees is needed. In trans- 

 planting, one should choose the right 

 time of year to move the particular 

 species. The ball of earth about the 

 roots should be as large as possible. 

 The tree needs plenty of water for a 

 considerable period after it is placed in 

 a new location. 



During a drought, all trees should 

 be watered as much as practical. 



Sometimes it is wise to apply com- 

 mercial fertilizer to the soil around 

 trees to help maintain or improve their 

 vigor. 



Toxic CHEMICALS,, applied to the 

 bark, can often protect trees against 

 insects that attack the main stem and 

 limbs. Such chemical protection is 

 especially desirable where summer 

 homes are built in wooded areas. A 

 chemical like DDT, which acts as a 

 contact insecticide as well as a stom- 

 ach poison, is suitable. It will help to 

 prevent attack even by many of the 

 insects that are attracted to the trunks 

 of weakened trees. 



Applications of DDT in the form of 

 emulsions or wettable powders have 

 prevented attack by many insects that 

 infest the buds and foliage of various 

 kinds of shade trees. However, DDT 



99 



is not a cure-all, and certain insects, 

 such as bagworms, some of the aphids, 

 scales, and the spider mites, are not 

 readily controlled by this chemical. 



Other newer chemicals that have 

 recently appeared on the market and 

 show promise for killing some of these 

 insects and mites are methoxychlor, 

 hexaethyl tetraphosphate, tetraethyl 

 pyrophosphate, and parathion. Meth- 

 oxychlor is reported to be only slightly 

 toxic, while the other chemicals are 

 regarded as being highly toxic to 

 humans and warm-blooded animals, 

 so considerable care must be taken in 

 handling them. Because of this hazard 

 and until further experimentation has 

 been conducted to determine the tol- 

 erance of various plants to these chemi- 

 cals, they are not recommended at this 

 time for general use. 



SEVERAL CONTROLS are now avail- 

 able. Trees that have become infested 

 by insects despite precautionary meas- 

 ures should be examined carefully to 

 determine whether the trees are dying, 

 whether they should be disposed of so 

 as not to menace the remaining trees, 

 or whether they can be saved by the 

 application of a toxic chemical. 



Dying trees in their bark and 

 wood usually contain broods of in- 

 sects that can damage nearby living 

 trees if they are allowed to develop and 

 emerge. 



Bark beetles, usually the most im- 

 portant of these insects, can be de- 

 stroyed either by burning the infested 

 bark or by applying chemicals. It is 

 important that any contemplated con- 

 trol measures be carried out promptly 

 before the insects can mature and 

 emerge, preferably at the first sign of 

 change of color in the foliage. 



All types of bark-boring insects can 

 be killed by felling the trees and 

 thoroughly spraying the bark with a 

 solution composed of one part ortho- 

 dichlorobenzene to six parts of fuel 

 oil. Placing the tree trunks in the sun 

 will help to increase penetration of 

 the spray. The log sections should be 

 turned at least once in order to treat 



