10 BULLETIN '787, TJ. S. DEPAETMENT OE AGRICULTURE. 



small, naturally pruned dead branches are seen and many trees are 

 thinned out naturally as the others increase in size. Few root sprouts 

 appear. Infested plantations are very irregular in outline; broken 

 tops, trees of irregular size, and many root sprouts and suckers are 

 characteristic indications of borer damage. 



CONDITIONS UNDER WHICH LOCUST CAN BE GROWN. 



From the history of the foregoing tracts it is evident that black 

 locust can be grown profitably under circumstances that require little 

 care, or, in fact, better results are obtained without too much atten- 

 tion. After comparing all the data available it seems that provision 

 for sufficient shade during the period of groioth subject to borer 

 attack is all that is necessary in order that this tree lasij be grown 

 successfully. 



This can be achieved by some system of close and mixed plant- 

 ing. Experiments of such a character should be tried. In nature it 

 is accomplished by close reproduction coming up around the seed 

 tree, by root, sprouts from older trees, or often by the mixture of 

 other plants growing with the locusts. Weeds and vines often form 

 the needed shade, as illustrated by trees in old fence rows. It is ver^f 

 essential that this shade be present after the trees reach 1| to 2 

 inches in diameter, and that it be continued until they attain 5 or 6 

 inches. After this time thinning and pruning can be done with 

 little or no subsequent injury by the borers. 



Close planting or thick growth of these trees also is necessar}^ to 

 produce ' straight, unbranched boles. Trees in the open are always 

 much branched and rather crooked, but those grown in forests are 

 tall, straight, and naturally pruned while the branches are quite 

 small. 



That difference in site or locality is not the influencing factor in 

 the gTowing of uninjured trees is evident from the fact that in every 

 locality examined it was possible to find examples of borer-free and 

 destroyed trees growing 100 yards apart. It is also evident that 

 goldenrod is not necessarily associated with greater damage by the 

 borer, for in the same abandoned field, massed with this plant, were 

 found plots of trees absolutely free from injury and near-by isolated 

 trees badly infested. Again, localities where no goldenrod is growing 

 may have borer-infested trees, the adults feeding on other composites, 

 as illustrated by example 7. 



The idea has been advanced that the borers are more abundant 

 in some localities than in others and that this will account for the 

 difference in infestation. This difference can not be sustained, as the 

 beetles are present everywhere within the natural range of this tree. 

 Side by side we find stands of badly infested trees and trees contain- 

 ing no borers. It is rather to be believed that in localities where locust 



