3g MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



Pitch ]Moths 



^^^lile in the caterpillar stage the pitch 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, balsam fir, 

 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 

 even death of the entire tree. 



The ponderosa pitch moth {D lory ct via yonderosae Dyar) causes 

 considerable injur}^ in the plantations of the Nebraska National For- 

 est, where it attacks ponderosa, Scotch, Austrian, jack, and Norwaj^ 

 or red pines. ^lost of the trees attacked are under 8 inches in diam- 

 eter, and the bole and tops are frequentl}^ girdled by the larval ttm- 

 nels. This damage is particularly serious in the case of the two 

 European species, Scotch and Austrian pines. This insect is prob- 

 ably distributed through most of the AVestern States, having been 

 recorded from Nebraska. Montana, and northern California. 



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

 nearly I14 inches. There are two narrow W -shaped bands extending 

 across each forewing; the hind win^s are dusky white. The moths 

 appear from late in July to early in September and deposit eggs 

 singly on the under side of bark scales, on trunk, or branches. The 

 small larvae hatch in from 1 to 4 weeks, depending upon the tem- 

 perature, and spin small hibernacula under bark scales, in which 

 they overwinter. The first evidence of attack appears the following 

 spring in the form of a small quantity of larval castings on the 

 l^ark surface, followed by an exudation of pitch from the entrance 

 hole. The larvae feed in the cambium region and construct irregu- 

 larly shaped galleries beneath the bark. Some of these are rounded 

 cavities with short side galleries, while others extend for several 

 inches around the tree. The mature larvae are about 1 inch in length, 

 usually light brown, though occasionally with a greenish tinge, and 

 the bodies are marked with about six rows of small, dark-brown dots 

 or tubercles. These larvae spin white papery cocoons in the burrows, 

 or sometimes in the dried pitch mass near the surface, in which 

 pupation takes place in Juty. The new adults leave the pupal skins 

 in the cocoons and force their way through exit holes previously pre- 

 pared by the larvae but concealed by flakes of bark or small webs. 

 Control has been attempted by spraying the infested part of the stems 

 Avith orthodichlorobenzene, diluted 1 to 5 with water, to which a 

 small quantity of soap and linseed oil was added. The results were 

 only partially satisfactory. Winter cutting and removal of the 

 most heavily infested trees in the plantations resulted in a consider- 

 able reduction in the infestation. Control measures, however, are 

 still in the experimental stage. 



Dioryctria xantJioeno'bare.9 Dyar is a golden-brown moth about 

 three-fourths of an inch in length, which in the caterpillar stage at- 

 tacks the twigs and cones of ponderosa and knobcone pines and pos- 

 sibly other pines. The caterpillar is pinkish and about 1 inch in 

 length when full grown. It is known in California, Oregon, Wash- 

 ington, and Nebraska. 



