The Key to Protection 



4*5 



the tip of the abdomen of the wingless 

 female. 



It is thus possible to trap the males 

 and determine with reasonable ac- 

 curacy whether the insect is present 

 in any area. With this knowledge, in- 

 tensive search for egg clusters provides 

 data on where and how abundant the 

 pest is. 



WlTH THE MORE DESTRUCTIVE NA- 

 TIVE insect pests such intensive inspec- 

 tions are not needed. Here the objective 

 is to keep informed as to the areas 

 where the pest is developing in num- 

 bers sufficient to cause important loss. 

 The fact that intensive inspections to 

 locate all infestations are not required 

 does not mean, however, that the task is 

 simple. Restricting surveys to the forest 

 pests, of known importance still re- 

 quires many observations and the use 

 of much technical knowledge. 



THERE ARE MANY DIFFERENT KINDS 

 of important pests, and the habits and 

 method of attack of these are widely 

 varied. The habits of the various tree- 

 killing bark beetles, although similar 

 as to general pattern, cause different 

 symptoms. The fading, browning, and 

 reddening of the foliage of injured 

 trees provide a valuable index of the 

 presence of many forms, such as the 

 deadly western pine beetle. Attacks 

 of the equally destructive Engelmann 

 spruce beetle, however, are not fol- 

 lowed by the browning and reddening 

 of foliage. A group of red-top trees 

 killed by the mountain pine beetle in 

 a lodgepole forest is often the sign of 

 the beginning of an outbreak. Grouped 

 red-top trees killed by the western pine 

 beetle in a ponderosa pine forest in 

 Colorado may indicate the subsidence 

 of an outbreak. Only the trained, ex- 

 perienced entomologist can distin- 

 guish the potential difference between 

 groups of like superficial appearance. 



Many species of insects defoliate 

 trees and here the significance of an 

 infestation may depend on the kind 

 of insect and the type of forest. Where 

 more than one species of insect is 



present, and this frequently occurs, the 

 proportion of each in the mixture may 

 have an important bearing on the 

 potential damage of the infestation. 



IN ALL KINDS OF INSECT INFESTA- 

 TIONS, and especially those where leaf 

 feeders occur, observations on the pres- 

 ence of natural enemies need to be 

 recorded. The presence and abundance 

 of parasites, predators, and disease 

 often have an important relation to the 

 development of the primary pest. 



Illustrations of this nature could be 

 multiplied but would only give added 

 emphasis to the various matters which 

 need to be considered and made part of 

 a survey program to determine the 

 presence and status of forest pests. To 

 secure facts on new and little-known 

 insects and diseases which are or may 

 be injurious to our forests requires an 

 even greater use of specialized infor- 

 mation. The importance of obtaining 

 data on the presence of lesser known 

 species must not be overlooked. No one 

 can forecast when another blight, as 

 destructive as the one which killed the 

 chestnut, may appear. Nor should we 

 fail to be alert to the presence and de- 

 velopment of infestations of species 

 which in themselves may be of only 

 secondary importance, yet when pres- 

 ent with other organisms have a pri- 

 mary place as forest pests. 



THE RELATION BETWEEN BARK BEE- 

 TLES and the Dutch elm disease illus- 

 trates how the combinations of pests 

 change the significance of each. The 

 smaller of two well-known bark beetles 

 native to Europe has been known to be 

 established in the United States since 

 19 10, long before the Dutch elm disease 

 was found here. Although it fed on elm 

 shoots and developed in the branches, 

 it was not of any particular signifi- 

 cance, since it lived in dead and dying 

 branches. When the disease was intro- 

 duced, the habits of living in branches 

 and feeding on young shoots provided 

 a ready means of carrying disease from 

 the infected to healthy trees. The two 

 pests combined make formidable ene- 



