6 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
Defoliating insects likewise cause extensive losses to standing tim- 
ber, roughly estimated at about 20 million dollars annually for the 
entire country over a period of 25 years. Damage from insect attack 
to felled timber, logs, lumber, poles, ties, and wood in buildings is 
probably in excess of $60,000,000 annually. 
Damage to trees valued for esthetic reasons is extremely difficult to 
estimate. Street and shade trees around homes, in parks, and on 
recreational areas have values far beyond the lumber they contain. 
Various estimates of insect damage to the trees of city parks and 
streets throughout the country, based on the supposed number of such 
trees and a nominal value for each tree are available. A conservative 
selection from these estimates would indicate a monetary loss of about 
$100,000,000.° 
The principal annual losses caused by forest insects are as follows: 
Bark theerles 28 ee ea ee sD FEST 2 cee D2 SSE Tanne Od ve $20, 000, 000 
Defoliators and other losses to standing timber SpE MURS aoe A wr Mit At 20, 000, OOO 
ImsectsS aflectine. LOEESt LOG UCTS ee eee ee ee 60, 000, 000 
Insects ‘alfecting shade: and ornamental trees= ses eee 100, 000, 000 
EFFECT OF INSECTS ON THE COMPOSITION OF GROWING STANDS 
The reproduction of the forest is often influenced and sometimes 
completely changed in character by the activities of insects. Cone 
beetles in the white pines and some of the western yellow pines, certain 
moths in the yellow pines, seed chalcids in Douglas-fir, and nut weevils 
in acorns and hickory nuts destroy at times nearly 100 percent of the 
seed crop. During periods of excessive activity of these insects, the 
reproduction in mixed stands may contain a preponderance of the less 
desirable species. . 
After the seedlings are established, certain insects such as white 
grubs (the larvae of June beetles) may cut off the roots, or the Pales 
weevil may girdle the young plants above ground, and thus again 
alter the proportion of a particular species becoming established. ‘Not 
infrequently after logging operations in the Northeast, white pine 
reproduction 1s completely. destroyed by the Pales weevil. 
During the sapling stage of a stand, when competition is keen among 
individuals or species composing a mixture, modifications of the stand 
by insects become more apparent. The white-pine weevil in the North- 
east frequently determines the final character of the stands seeded 
on old fields or clearings. Malformation of the trees is most severe in 
nearly pure pine. Curiously enough, as the percentage of hardwood 
increases, the weevil damage in the pines decreases—a good argument 
for mixed forests. 
In our mixed coniferous-hardwood forests of the Northeast, de- 
fohators periodically appear and remove high percentages of certain 
conifers. Conifers succumb readily to heavy defoliation, whereas 
hardwoods resist repeated defohations. In these forests fir and spruce 
are largely protected from spruce budworm outbreaks as long as the 
hardwood canopy is dominant. But as the percentage of softwood 
ieeiGe. J. A. LOSSES CAUSED BY INSECTS, MITES. AND TICKS IN THE UNITED 
STATES. U.S. Bur. Ent. and Plant Quar. E—-444, 57 pp. 1938. [Processed.] 
