14 BULLETIN 418^ U. S. DEPARTMENT OP AGRICULTURE. 



VEGETABLE PARASITES. 



The most harmful of the vegetable parasites is a kind of mistletoe 

 {Razoumofskya cainpylopoda) which is, in some localities, very abund- 

 ant. This plant attaches itself to the little twigs and causes in them, 

 as they develop, swelHngs and deformities ("witches' broom"); both 

 on the mam stem and the twigs. It kills single branches outright, 

 but seldom causes the death of a tree; it may, however, weaken the 

 tree's vitality and impair its value for commercial purposes. A rust 

 called Peridermium Jilamentosum causes, on the twigs, swellings which 

 are quite conspicuous in yellow-pine young growth. Yellow pines, 

 especially in the Blue Mountain region, as well as some of their associ- 

 ates, are often heavily covered with two hohens — Aledoria fremontii, 

 " black moss," and Evernia vulpina. These plants are not fatal, but 

 may injure the host trees by shading their foUage and preventing 

 proper bark shedding and aeration. 



Yellow pine is rather free from fungi which cause decay in the 

 wood. One of its worst enemies among the fungi is Polyporus schwei- 

 nitzii (butt rot or dry brown rot), which gains entrance through basal 

 scars and damages particularly the lower portion of the tree. It is, 

 hke most forms of decay, a disease which affects old, overmature 

 timber, and seems to be particularly abundant on situations where 

 the soil is sterile or thin. It is usually difficult to teU from the outside 

 appearance of a tree whether it is affected with butt rot. Another 

 bad form of decay is Trametes pini (ring-scale fungus, pipe rot, or 

 white-pitted rot), which enters the tree at broken tops or in bad 

 wounds on the stem and rots out the heartwood. The presence of 

 Trametes pini can usually be detected by the thin, unhealthy bark 

 and the "bumpy" stems of seriously affected trees. Fomes laricis 

 (chalky quinine fungus, or sap rot) is a third serious fungous enemy of 

 yellow pine. It causes a red heart rot with felts of white mycehum.^ 

 Its fruiting bodies are generally very large, round, hoof-shaped, with 

 a rough white, chalky surface. 



The amount of decay in yellow-pine timber caused by these fungi 

 is of course very variable; some thrifty stands are abnost free from it, 

 and in others it is very bad. On one tract of very overmature timber 

 in central Oregon a third of the trees had to be long-butted from 4 

 to 6 feet each to get rid of the worthless portion of the first log. The 

 scale of over 2,000,000 feet of logs cut in the Blue Mountains shows 

 that only 0.9 per cent had to be subtracted from the full scale on 

 account of rot. In addition, some worthless trees or portions of 

 trees were left in the woods. This would probably indicate for this 

 particular tract an amount of defect on account of rot equivalent to 

 about 2 per cent of the total stand. 



1 U. S. Department of Agriculture, Forest Service Bulletin (unnumbered), "Forest-tree Diseases Com* 

 mon in California and Nevada," by E. P. Meinecke. 



