THE COTTONWOOD BOREE. 7 



the lower edge sunk into the ground about an inch. The top 

 parts of the screen should be pinned to one another with small 

 brads so as to fit closely about the tree; or they may be held in 

 place by a piece of binding twine wrapped around them. The same 

 screen cone will protect a tree for several years if made large 

 at first; but the screens should be examined during June of each 

 3^ear, being loosened where too tight and repaired where torn. 



REMEDIES. 



When the 10 trees were examined in September, 1914, all eggs 

 and young larvae were removed. (Table I.) Where possible the 

 large larva3 were also removed, and the number of eggs and larvae 

 secured from each tree is noted in the table. The tunnels from which, 

 owing to their depth, the larvae could not be removed were treated 

 with a small quantity of carbon bisulphid injected from an oil can. 

 From the 10 trees treated in this manner only five adults emerged 

 during 1914, whereas from two untreated trees that were screened 

 eight adults, or an average of four beetles to a tree, emerged. How- 

 ever, the treatment with carbon bisulphid is of little benefit, as the 

 larger larvae in tunnels from which they can not be removed have 

 done, at this stage, nearly all the injury of which they are capable. 

 The greatest benefit arising from the careful examination of the tree 

 trunks lies in the removal of the immature borers that are working 

 in the bark. This work is inexpensive and is entirely practicable 

 for shade trees. 



SUMMARY. 



The injury b}' the Cottonwood borer results from the adults ovi- 

 positing in cuttings and very young trees, the young larvae cutting 

 the bark and preventing the sap flow, and the larger larvae tunneling 

 the wood, thus weakening the trees against wind. 



The eggs are deposited in the younger trees principally during 

 July and August. The larvae work in the trees until the second 

 summer after the eggs hatch, when the adults emerge from about 

 the middle of June until the 1st of August. 



Oviposition in shade trees may be prevented by screening the bases 

 of the trees. The young larvae can be removed before they injure 

 the trees severely if the remedial work is done during the first two 

 weeks of September, but removal of the large larvae from deep tun- 

 nels often injures the trees mor-e than would the larvae if allowed to 

 remain and complete their development. 



WASinX'/rON : fiOVKIlNMICNT I'ltlNTINd OKlflCE : iniG 



