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



pith, where they overwinter. Pupation occurs late the following 

 spring, and the new adults emerge by boring through the outer 

 bark to attack new trees. In older established forests damage is 

 restricted to the very young trees and usually is not important. 

 Control by burning the infested trees and by spraying living trees 

 has been undertaken only for the protection of planted areas. 



The pine reproduction weevil (Cylindrocopturus eatoni Buch.) 

 (4-6) (fig. 16) probably is the most destructive species of this 

 genus. During the period from 1938 to 1942 this weevil killed be- 

 tween 70 and 90 percent of the small ponderosa and Jeffrey pines 

 planted in 1932-34 on one brushfield plantation in northeastern 

 California. Since then it has made serious inroads into other plan- 

 tations. The adults are extremely active insects. Soon after 

 emergence late in May and in June they begin feeding by making 

 noticeable punctures on the surface of the needles, and later they 

 make similar punctures in the thin bark of the stems and 

 branches. Eggs are deposited in punctures in the outer bark dur- 

 ing June and early in July. The larvae start feeding in the cortex 

 and, as they develop, extend their mines through the inner bark 

 along the surface of the sapwood. This mining of the subcortical 

 area usually causes the trees to die late in the summer or early in 

 the fall. When mature, the larvae bore into the wood, and in small 

 trees enter the pith, where they rest in their burrows from Sep- 

 tember until the following spring. Pupation occurs late in April 

 and in May, and the new adults emerge in June. Airplane spraying 

 with DDT in oil proved effective on one large brushfield plantation 

 in northern California in 1947. Some individual pines appear to be 

 capable of resisting the weevil, and recent studies conducted at 

 the Institute of Forest Genetics in California indicate that certain 

 hybrid pines that are resistant to weevil attack can be developed. 



The Douglas-fir twig weevil (Cylindrocopturus furnissi Buch.) 

 (54) (fig. 17), similar to C. eatoni, attacks and kills scattered 

 small branches on open-grown Douglas-fir reproduction. These 

 attacks may deform and retard the growth of the trees. Some trees 

 less than 5 feet high may be killed outright ; but by the time Doug- 

 las-firs have attained a height of 15 to 20 feet, they are no longer 

 subject to appreciable damage. Adults emerge from the middle of 

 June to the first week in August. After feeding for about 1 month, 

 they deposit eggs in small punctures on stems and branches. The 

 small larvae bore down to the surface of the wood, where they 

 extend their feeding galleries. On approaching maturity, the lar- 

 vae frequently bore through the wood into the pith. Larvae of 

 all sizes overwinter, and pupation takes place the following spring, 

 chiefly during May and June. There is one main generation and 

 possibly a partial second each year. Natural control is obtained 

 through host resistance, competition for food, and abundant para- 

 sitism. Artificial control has not been attempted. 



There are many other described and undescribed species of 

 Cylindrocopturus only two of which have been definitely asso- 

 ciated with western forest trees. 



