100 



thoroughly the entire bark surface. 

 Care must be taken in applying this 

 spray to avoid getting it on living trees, 

 shrubs, or flowers, as it will injure or 

 kill them. Precautions must be taken 

 also to keep the spray from coming in 

 contact with the skin and especially 

 from reaching the eyes of the operator. 



Borers that tunnel the main trunks 

 of shade trees are difficult to control. 

 The method usually employed consists 

 of injecting into the burrow some 

 fumigant, such as carbon bisulfide, and 

 then closing the opening with putty or 

 its equivalent, so as to confine the gas. 



If the insect is of the type that works 

 mainly beneath the bark, like the dog- 

 wood borer, a mixture of paradichloro- 

 benzene and cottonseed oil daubed on 

 the parts attacked is often effective in 

 killing the insects. A DDT emulsion 

 sprayed on the bark should be bene- 

 ficial in preventing further attack, and 

 the application of fertilizers and water 

 will increase the vitality while the trees 

 are overcoming the infestation. 



Damage to pine trees caused by tur- 

 pentine beetles can be checked either 

 by cutting out the attacking beetles as 

 soon as the pitch exudations are ob- 

 served or by injecting carbon bisulfide 

 into their galleries. 



Infested terminals of trees attacked 

 by twig borers and twig girdlers should 

 be removed and burned. 



A good control for scale insects and 

 mites consists of applying a dormant- 

 strength miscible oil spray in the spring 

 just before new growth begins. These 

 and other sucking insects, like aphids, 

 that are present on the terminal shoots 

 in summer should be sprayed with a 

 contact insecticide, such as an emulsion 

 of nicotine sulfate, soap, white oil. 



Damage by tip moths can be checked 

 by spraying the terminal growth of 

 pines with a DDT emulsion or wettable 

 powder. For best results, the spray has 

 to be put on as the eggs hatch. 



Many of the leaf feeders are con- 

 trolled with applications of lead ar- 

 senate, which is more effective than 

 DDT in controlling certain insects, 

 such as the bagworm. In general, how- 



Yearboo^ of Agriculture 1949 



ever, DDT is the more valuable ma- 

 terial because it is effective a long time 

 and because it kills insects when they 

 crawl over sprayed surfaces, as well as 

 when they eat it or are touched by it. 



Various kinds of spraying equip- 

 ment are available for applying in- 

 secticides to shade trees. The simple 

 3-gallon type is suitable for spraying 

 a few low trees about a home. Large 

 power sprayers and the new mist blow- 

 ers are used for treating large trees on 

 residential, city, or park areas. 



If an insect outbreak affects the 

 trees over a wide territory, it is best for 

 all concerned to cooperate in planning 

 a control program. United action can 

 reduce the insect population more 

 quickly and more effectively than if 

 each person acts independently. Fur- 

 thermore, where tall trees are con- 

 cerned, community action will make 

 practical the use of high-power spray- 

 ing equipment, such as hydraulic 

 machines or the more modern mist 

 blowers. It is not necessary to go into 

 detail on an important point like this 

 a point that every home owner ap- 

 preciates. He knows how difficult and 

 costly it is to replace trees that have 

 died, how precious are his shade trees, 

 how close his friendship with them can 

 become quite beyond measurement 

 in dollars and cents. But if such a 

 measure is needed, we have one by J. 

 A. Hyslop, formerly of the Depart- 

 ment of Agriculture. He has estimated 

 that the losses due to insects in shade 

 trees total 87 million dollars a year in 

 the United States. Home owners, alone 

 and together, can stop the insects. 



R. A. ST. GEORGE is an entomol- 

 ogist in the Bureau of Entomology 

 and Plant Quarantine, and is sta- 

 tioned at the Agricultural Research 

 Center at Beltsville. He is a graduate 

 of the Massachusetts Agricultural Col- 

 lege and George Washington Univer- 

 sity. He has been associated with the 

 Division of Forest Insect Investiga- 

 tions since 1918 and has specialized in 

 research problems concerning insects 

 that affect forest and shade trees. 



