Role of Slash 



Volatile odors produced by the newly felled trees, perhaps accompanied by other 

 conditions resulting from silvicultural operations, appear to be what attracts weevils 

 to thinned areas. ^ Though adult weevils feed on foliage of crop trees in the thinned 

 areas, the thinning slash does not appear to be utilized by Magdalis either as larvae 

 or adults. This was repeatedly confirmed by carefully examining boles, limbs, shoots, 

 and foliage of newly cut trees as well as of trees in all stages of deterioration from 

 early spring to late fall over the 4-year study period. 



The fact that Magdalis gentilis did not utilize thinning slash appears to be a 

 unique behavior; other Magdalis species feed in or on slash, on other dead or dying 

 material, or on weakened trees. In Ontario, Canada, adults of M. perforatus Horn 

 oviposit in recently dead branches and larvae feed in the pith, sapwood, and inner bark 

 of fresh slash from thinnings and prunings of young red pine, Pinus resinosa Ait., and 

 Scots pine, Pinus sylvestris L. (Martin 1962, 1964). Upon emergence from the slash, 

 adults feed on new shoots of standing trees. Magdalis austera Fall, M. lecontei Horn, 

 and M. auneiformis Horn breed in dead and dying broken branches, twigs or dead outer 

 wood (Craighead 1950) as well as feed beneath the bark and into the wood of living 

 shoots, killing small branches and terminal twigs (Keen 1952). However, as far as 

 observed, they do no appreciable amount of damage (Doane and others 1936). Adults of 

 the blue pine weevil, M. frontalis Gyll., feed on young shoots (Bukzeeva 1965) and 

 mine the buds (Karaman 1963) of weakened young pine. Larvae of the red elm bark weevil, 

 M. armiaollis (Say) often occur in immense numbers under the bark of dying or recently 

 dead elms (Hoffman 1939). Red elm bark weevil adults are reported to have been at- 

 tracted to and to have infested white elm, Ulrms ameriaana L, , which were cut as trap 

 logs in Manitoba and Saskatchewan (Hildahl and Wong 1965). 



^In another study, R. F. Schmitz (Research Entomologist, Forestry Sciences Labor- 

 atory, Moscow, Idaho) and I found that volatile material from foliage of ponderosa 

 pine, Pinus ponderosa Laws., appeared to be primarily responsible for attracting the 

 weevil, Magdalis leoontei Horn. In July 1966, we dissected two ponderosa pines each 

 into three components: bole sections, nonfoliated portions of limbs, and foliage. We 

 placed each component into saran-covered cages, and set the cages, along with empty 

 cages, about 100 feet apart in a ponderosa pine thinning area. In early August, we 

 collected eight and 24 times as many weevils from the cages containing foliage as we ^ 

 did respectively from cages containing nonfoliated limbs and bole sections. No weevils 

 were attracted to empty cages. 



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