48 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



Species Hosts and distribution 



Phymatodes hardyi (V. D.) . . Douglas-fir, true firs. Pacific Coast States. 



hirtellus (Lee.) Ponderosa and Jeffrey pines. California and 



Oregon. 



vulneratus (Lee.) Bigleaf maple and ash. Pacific Coast States. 



Poliaenus oregonus (Lee.) . . True firs, Douglas-fir, and hemlock. Western 



States. 

 Saperda populnea (L.) Poplar. North America. 



TWIG MOTHS AND TIP MOTHS 



The caterpillars of a large group of moths bore into and feed 

 on the fresh, tender bark, and cambium layers of growing ter- 

 minal and lateral shoots. Their feeding causes the deformation or 

 death of these parts, causing the tree to be many-branched and 

 poorly shaped, and sometimes kills it. Such damage is particularly 

 serious in young plantations or cut-over lands where a second crop 

 of straight, vigorous trees which will produce sound lumber in the 

 shortest possible length of time is desired. Older trees are also 

 attacked by these moths, but the injury to them is much less con- 

 spicuous and of little significance. 



Damage of this type is caused principally by the caterpillars of 

 moths belonging to the genera Dioryctria of the family Pyralidae 

 and Rhyacionia, Petrova, Eucosma, and Laspeyresia of the family 

 Olethreutidae. 



The control of cambium-feeding twig and tip moths is very 

 difficult, and as yet no completely satisfactory methods have been 

 evolved. Spraying with an oil solution of DDT in May, when the 

 eggs are hatching, has given good results, but the time of applica- 

 tion is such an important consideration that the method should be 

 used only with the advice of an expert. The use of other sprays is 

 still in the experimental stage. Hand picking of the infested tips 

 offers some hope of control on small valuable plantations that are 

 isolated from sources of reinf estation. 



TWIG MOTHS 



While in the caterpillar stage the twig moths, belonging to the 

 genus Dioryctria, bore into the cambium of trunk, branches, and 

 twigs, or into the fresh green cones of pines, Douglas-fir, true firs, 

 and spruce. The entrance to the tunnel is usually indicated by 

 webbed larval castings. If the tree offers resistance to attack, a co- 

 pious flow of pitch forms a resinous mass at the entrance. The 

 damage results in serious injury or death of the parts affected or 

 may even kill the tree. 



The ponderosa twig moth (Dioryctria ponderosae Dyar) causes 

 considerable injury in the plantations of the Nebraska National 

 Forest, where it attacks ponderosa, Scotch, Austrian, jack, and 

 Norway or red pines. Most of the trees attacked are under 8 inches 

 in diameter, and the bole and tops are frequently girdled by the 

 larval tunnels. Damage to Scotch and Austrian pines is particu- 

 larly serious. This insect is probably distributed through most of 

 the Western States, having been recorded from Nebraska, Mon- 

 tana, and northern California. 



The adults are blackish-gray moths with a wing expanse of 



