440 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 4 



one in 1939 and one in both 1939 and 

 1941. 



Subsequent to treatment, only three of 

 the trees wilted, 1942-1944, one in 1942 

 and 1944, one in 1943 and 1944 and one 

 in 1944 only. The tree which wilted in 

 1942 and 1944 had received 25 pounds 

 of urea; the other two had received 15 

 pounds of urea each. 



Drains Installed in 1942. — Drains 

 were installed in 10 affected elms, 4 to 

 6 inches d. b. h, to determine whether 

 provision of an artificial outlet for the ab- 

 normally produced sap and gas in the 

 trunk would prevent wilt. In eight trees 

 the drains were installed on March 24, 

 in one tree on May 13 and in one on June 

 17. Holes were bored into the trunks at 

 an upward slant to within about 1 inch 

 of the cambium on the opposite side. Sec- 

 tions of pipe were then driven into the 

 holes far enough to be firmly held, but an 

 effort was made not to drive them into the 

 wetwood-affected tissue. 



Only three of the trees fitted with 

 drains wilted, 1942-1944. One wilted in 

 1942 and again in 1944, the other two in 

 1943. The tree which wilted in both 1942 

 and 1944 fluxed through cracks immedi- 

 ately above and below the drain, and the 

 bark adjacent to these cracks was killed. 

 In the other two trees, it is possible that 

 cracks in the wood, concealed beneath the 

 bark, permitted seepage of toxic sap into 

 current wood, whence it was distributed 

 to branches and leaves, causing wilt. 



Injections in 1941 and 1942. — In 

 August of 1941, 10 elms affected with 

 wetwood were selected for this experi- 

 ment. All 10 trees were wilting but none 

 of them had wilted in 1939 or 1940. Five 

 of them were injected with mercuric 

 chloride and five with copper sulfate. The 

 five trees injected with copper sulfate were 

 4 to 6 inches d. b. h. and each tree received 

 100 ml. of a 1: 1,000 dilution. The five 

 trees injected with mercuric chloride were 

 3 to 10 inches d. b. h. One 3-inch tree 

 received 50 ml., one 4-inch and two 5-inch 

 trees received 100 ml. each, and one 10- 

 inch tree received 200 ml. of a 1: 1,000 

 dilution. Each injection was made with a 

 hand syringe, fig. 23, through a hole bored 

 in the tree to within 1 inch of the cambium 

 on the opposite side. One to four such 

 holes were bored in each trunk, the num- 

 ber of holes depending upon the size of 



the tree: e. g., one hole in a 3-inch tree, 

 four holes in a 10-inch tree. The total 

 dosage for any tree with more than one 

 hole was divided equally among the 

 several holes. 



From the results of bactericidal tests 

 made in 1942, the amounts of mercuric 

 chloride and copper sulfate injected into 

 these 10 elms in August, 1941, were esti- 

 mated to have been inadequate. The 1942 

 tests were made during February, March 

 and April, and the following concentra- 

 tions of materials were found to kill the 

 wetwood organism : mercuric chloride, 

 1 : 150,000; copper sulfate, 1 : 1,000; silver 

 nitrate, 1 : 50,000 ; and 8-hydroxyquinolin 

 sulfate, 1 : 9,000. On J:he basis of this in- 

 formation, the elms injected in 1941 were 

 reinjected with the same chemicals — 

 mercuric chloride and copper sulfate — in 

 June, 1942. Also, additional elms were 

 selected for injection with silver nitrate 

 and 8-hydroxyquinolin sulfate. 



The amount of material to be injected 

 into each tree was determined in the 

 following manner. First, a wc'od core or 

 boring was obtained with an increment 

 borer, and the diameter of the wood af- 

 fected with wetwood was measured on the 

 core. Then the probable height of the 

 affected wood in the tree was estimated. 

 With these figures, the volume of affected 

 wood was roughly calculated. The amount 

 of chemical injected into each tree was 

 sufficient to give a concentration that 

 would kill the wetwood organism in a 

 volume of water equal to the estimated 

 volume of affected wood. Four elms — 

 three which had wilted in 1940 and 1941 

 and one which had wilted in 1939 and 

 1941 — were injected with a 1 : 500 dilu- 

 tion of silver nitrate ; two of these trees 

 were each given 200 ml., the third was 

 given 300 ml. and the fourth 500 ml. 

 Three elms which had wilted in 19-10 and 

 1941 were injected with a 1 : 200 dilution 

 of 8-hydroxyquinolin sulfate; one of these 

 trees was given 300 ml., the second 800 

 ml. and the third 1,000 ml. After the in- 

 jections were made, the holes were closed 

 with iron set-screws sterilized with 70 

 per cent alcohol. 



The five trees injected with mercuric 

 chloride in 1942 did not wilt in that year, 

 in 1943 or 1944. The five trees injected 

 with copper sulfate and the four injected , 

 with silver nitrate did not wilt in 1942 or' 



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