ground. We did this to insure that the stump surface would 
not already be infected, on the assumption that the pathogen 
is confined to the roots and root collar of live pine trees. 
Eight different chemicals were tried: urea, ammate, ammonium 
fluoride, creosote, pentachlorophenol, Borateem, borax, and 
borax with ethyl alicohol. Ethyl alcohol was added to one bo- 
rax suspension to lower its freezing point for use in very 
cold weather. Each chemical was applied to cut surfaces of 
20 stumps immediately after felling trees; 20 stumps were left 
untreated to serve as controls. 
Approximately 1 hour after chemicals were applied, sur- 
faces of all stumps were inoculated by atomizing them with a 
suspension of F. annosus conidia in distilled water. 
After an incubation period of 3 months we sawed off sec-— 
tions about 2 inches thick from the tops of the stumps, en- 
closing each section in a polyethylene bag, and incubating at 
room temperature. In about a week the sections were examined 
under a microscope for signs of the fungus. Then the sec- 
tions were split and small chips of wood removed aseptically 
from the split surfaces and placed in sterile malt-agar | 
slants. After incubation at room temperature for 6 or 7 days, 
the slants were inspected for colonies of F. annosus. 
RESULTS AND DISCUSSION 
Ninety-five percent of the control stumps became infect- 
ed (table 1). Urea was the only material that gave absolute 
protection. All the others gave partial protection with cre- 
osote and pentachlorophenol being the least effective. 
The various chemicals differ in the way they prevent or 
reduce stump colonization by F. annosus. Urea, ammate, and 
ammonium fluoride--compounds high in nitrogen--stimulate the 
growth of other fungi (e.g., Peniophora gigantea (Fr.) Massee 
and Trichoderma spp.) that are antagonistic to F. annosus. 
The borate compounds, borax and Borateem, are toxic to the 
fungus spores, while creosote and pentachlorophenol act as a 
barrier to spore germination. 
Based on British experience, creosote has, until recent- 
ly, been recommended for control of F. annosus in this coun- 
try but our results indicate that other materials are more ef- 
fective. We recommend agricultural grade urea containing 45 
percent nitrogen, or one of the borate compounds because they 
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