JACK PINE. 91 
DISEASES.1 
Jack pine stands are usually free of serious fungous diseases, but 
when they reach an age of from 60 to 90 years many of the trees 
become heart-rotted. The fungus that most often causes this con- 
dition is Polyporus schweiniten, but Trametes punt is sometimes re- 
sponsible for it. 
The most common disease in jack pine is the gall-forming rust, 
Cronartium cerebrum (Peck) Hedge. & Long. The injury done to 
young and old trees alike by this fungus is such that, in any system of 
forest management of jack pine, methods for its eradication should 
be considered. ‘‘It causes the death or early suppression of trees of 
tender years and seriously interferes with the development of more 
mature growth.” ! 
The defect known as ‘witches’ broom”’ is frequently present in 
jack pine crowns, especially in open stands on dry, sandy soils. This 
is a bushy growth of fine twigs from an affected point on a terminal 
shoot. The stimulus for this growth is probably furnished, in most 
cases, by some perennial fungus. The ‘‘witches’ broom” precludes 
further development beyond the point of attack, and the increment 
of a badly infected tree falls off rapidly. The damage is not wide- 
spread, however, and in the aggregate is not serious.’ Near the limits 
of its northern range the jack pine is subject to attacks by mistletoe, 
resulting also in the formation of ‘‘ witches’ brooms.”’ 
Several fungous saprophytes attack jack pine wood left in the for- 
est and cause its quick decay. Dead trees usually become unsound 
within 2 or 3 years. 
INSECTS. 
Jack pine is rarely damaged by insects, except where the stand 
has been seriously weakened by fire, especially by fire occurring in 
the summer. According to Dr. A. D. Hopkins, of the Bureau of 
Entomology, United States Department of Agriculture, the living 
jack pine is often attacked and more or less seriously injured at the 
base and on the stems of saplings by bark weevils and bark beetles, 
on the buds and twigs by tip moths, and on the foliage by saw flies. 
The tip moth has attacked most of the jack pine in the plantations 
at Halsey, Nebr., reducing the height growth and causing minor 
crooks. The bark and wood of weakened, dying, and felled trees are 
subject to attack by the common wood-boring insects, which also 
cause pinhole and wormhole defects in the crude products.? 
1 Por a full discussion of the diseases of jack pine, see Bulletin No. 212, U.S. Department of Agriculture, 
“Observation on the Pathology of the Jack Pine,” by James R. Weir, Forest Pathologist. 
2 Any evidence of serious injury to living trees or their products, known or supposed to be caused by 
insects, should be reported to a Federal or State entomologist with a request for advice as to the need of 
adopting measures for prevention or control. 
