Weevil - Red Rot Associations 

In Eastern White Pine 

The presence of red rot (~omes pini) in pruned white 

pine stands has often been attributed to the act of pruning. 

This assumption may well be true for heavily stocked stands 

where thinning has been neglected and pruning scars are slow 

to heal. The question then arises: How do we account for 

the red rot often found in vigorous unpruned white pine 

stands? Evidence collected in connection with a white pine 

log-grade study* at the Pack Demonstration Forest at Warrensburg, N. y., strongly suggests that the white pine weevil was responsible for much of the red rot found in the 

trees examined. 

Such a conclusion is based mainly on these facts : (1) 

Red rot infections were 2s times more frequent in heavily 

weeviled trees (five or more weevil injuries per tree) than 

in trees having fewer injuries. (2) Out of a total of 74 red 

rot infections found in the 97 trees examined, 58 (80 percent) were associated with weevil in jury.%' 

The data (table 1) seem to indicate a clear-cut case t 

against the weevil: weevil injuries appear to be a major 

factor in creating conditions that are favorable for red rot 

infection. However, the question arises as to whether these 

ratio differences are due to the possibility that heavily 

weeviled trees were also genetically more rot-susceptible, 

or whether they are due to the presence of more infection 

points on the heavily weeviled trees. 

The latter reasoning appears more logical. Dead weeviled leaders usually remain attached to the tree for many 

years. . Observations indicate that about 50 years elapse 

before the majority of them are completely overgrown. Red 

rot attacks and follows the pith of these dead leaders to 

the heartwood zone of the host. It then continues its early 

* 

SPONSORED JOINTLY BY THE COLLEGE OF FORESTRY. STATE UN~VERS~TY OF NEW YORK. 

AND THE NORTHEASTERN FOREST EXPERIMENT STATION. U.S. FOREST SERVICE. FOR FURTHER 

DETAILS OF THE STUDY SEE NORTHEAST. FOREST EXPT. STA. FOREST RES. NOTE 67. 1957. ** FOR THE PURPOSES OF THIS REPORT. RED ROT WAS CONSIDERED TO BE 'ASSOCIATED 

WITH WEEVIL INJURY' IF IT WAS FOUND IN OR ADJACENT TO AN OLD WEEVILED LEADER WHEN 

THE LOGS WEWE SAWED INTO,LUMBER. 'WEEVIL INJURY OR ATTACK* REFERS TO ALL WEEVIL 

AN0 WEEVIL- L IKE INJURIES OBSERVED. ALTHOUGH SOME OF THESE MAY HAVE BEEN CAUSED BY 

BIRDS. SQUIRRELS. OR OTHER INSECTS. 
Weevil injuries Trees with Trees without 

per tree red rot red rot 1 Total I 

(number) infections infections 

Number Percent Number Percent Number 

None 0 0 6 100 6 

1-b4 15 33 30 67 45 

5.pr more 34 74 12 26 46 

Total 49 -- 48 - - 97 

activity in the pith zone of the tree. The rapidity with 

which the fungus spreads in the porous pith zone suggests 

that an outside air supply is a vital factor in its development. 

Inspection of the original data from the six unweeviled and rot-free trees does not reveal any startling information. The growth rates of these trees had been slow to 

moderate, which might have resulted in the development of 

slender leaders less susceptible to weevil damage. However, 

these trees, varying in age from 46 to 120 years, were growing on a mixture of sites, and all but one were growing in 

even-aged pure pine stands. 

Only 16 red rot infections out of a total of 74 could 

not be definitely associated with weevil injury. Nine of 

these infections were in butt logs, six being in trees 100 

years of age or older. The presence of small limb stubs and 

punk knots tend to indicate that most of these were branch 

infectiops, although in some cases advanced decay may have 

destroyed the possible evidence of weevil injury. 

Six red rot infections were confined to large knots 

in the logs. It is quite possible that some of these may 

have resulted from weevil injuries in the limbs. 

Losses due to red rot in young and middle-aged white 

pine stands can be blamed to a large extent on weevilinjury. 

Until a practical means of controlling the weevil is developed, these .losses can be minimized by the removal of weeviled trees in thinnings and by the early removal of weeviled leaders during pruning operations. 

--MYRON D. OSTRANDER 

Forest Economist 

Northeastern Forest Experiment Station 

Forest Service, U.S. Dept. Agriculture 

--CLIFFORD H. FOSTER 

Director 

Pack Demonstration Forest 

Warrensburg, N. Y. 

AGR ICULTURE- FOREST SERV ICE-UPPER OARBY