August, 1945 



Carter: Wetwood of Elms 



439 



tered and autoclaved sap from wetwood- 

 affected elms. For these tests a sample of 

 sap was divided into four portions. One 

 portion was untreated, one was autoclaved 

 at 15 pounds for 20 minutes, one was 

 passed through a Berkefeld filter and one 

 was filtered and then autoclaved. The un- 

 treated sap had a pH of 7.40, the auto- 

 claved sap a pH of 8.09, the filtered sap 

 a pH of 6.26 and the filtered and auto- 

 claved sap a pH of 6.33. Autoclaving 

 resulted in an increase in the pH of both 

 the unfiltered sap and the filtered sap. 

 When samples of unfiltered and filtered 

 sap were autoclaved, a brown, fluffy pre- 

 cipitate was formed, \\hich settled to the 

 bottom of the container upon standing. 

 The formation of this precipitate may 

 have accounted for the differences in the 

 pH readings obtained before and after 

 autoclaving. 



Sap collected from the diseased tis- 

 sues of a wetwood-affected tree is alkaline. 

 Supposedly it is, or contains, the products 

 of the long-continued fermentation of fer- 

 mentable materials present in the tree. In 

 the laboratory, nutrient broth plus dex- 

 trose eventually becomes strongly acid 

 (p. 422) as the result of fermentation by 

 Erivinia nimipressuralis. The difference in 

 pH between fermented sap and fermented 

 medium appears inconsistent. However, 

 Conner, Peterson & Riker (1937) have 

 shown that the crown gall bacterium, 

 Phytomonas tumefaciciis, brings about an 

 acid condition when it is grown with glu- 

 cose as the main source of energy but an 

 alkaline condition when grown in a medi- 

 um that does not contain glucose. The 

 wetwood organism likewise brings about 

 an alkaline condition when it is grown in 

 nutrient broth without dextrose. It would 

 seem, therefore, that fermentation as it 

 occurs in the tree goes on when no sugar 

 or only traces of sugar are present. The 

 validity of this assumption is further em- 

 phasized by our failure to obtain tests for 

 reducing sugars in any of the sap samples, 

 or in any of the leach samples (p. 437) 

 until after they had been autoclaved. 



Control Studies 



Control studies, which were started in 

 1940, included injection of chemicals into 

 trunk wood, fertilization, and installation 

 of trunk drains. The chemicals injected 



were Helioue, mercuric chloride, copper 

 sulfate, silver nitrate, and 8-hydroxyquin- 

 olin sulfate. The fertilizers used were 

 10-8-6 commercial fertilizer and urea. 



Helione Injections and Feeding 

 in 1940. — Twenty elms, 3 to 10 inches 

 d. b. h., were selected for this experiment. 

 Nine of these trees had wilted in 1939 

 and all 20 in July, 1940. The 20 trees 

 were treated. as follows: (1) Eight trees 

 were injected with Helione — 2 trees 

 with a 1 : 200 dilution, 2 with a 1 : 500 

 dilution, 2 with a 1 : 750 dilution and 2 

 with a 1:1,000 dilution — and each re- 

 ceived 250 ml. of solution. (2) Eight trees 

 were injected with Helione in the same 

 manner as in (1) but were also fed 10-8-6 

 fertilizer. (3) Four trees were fed 10-8-6 

 fertilizer but were not injected with 

 Helione. 



Helione injections were made during 

 August and September, 1940. Fertilizer 

 was applied during September and Octo- 

 ber by the punch bar meth(xl in amounts 

 of 25, 35 and 40 pounds to 3 — i--, 6- and 

 8-inch trees, respectively. 



Subsequent to treatment, seven of the 

 eight trees injected with Helione, but 

 given no fertilizer, wilted in 1 or more 

 years: three in 1941, two in 1942 and 

 three in 1944. One of the three trees 

 that wilted in 1944 had wilted in 1941 

 also. None of the eight trees injected with 

 Helione and given fertilizer wilted in 

 1941, but five of them wilted in 1942 

 and one of these five wilted also in 1943 

 and 1944. Wilt occurred in all four of 

 the trees which were given no injections 

 but were given fertilizer, two in 1941, 

 one in 1942 and one each year, 1941—1944. 

 Only one of the eight injected trees and 

 three of the eight trees that were injected 

 and fed did not wilt during the 4 years 

 following treatment. Under the conditions 

 of this experiment, injecting with Helione, 

 feeding with 10-8-6 fertilizer or combin- 

 ing both treatments did not appear to be 

 effective in preventing wilt. 



Urea Feeding in 1941-42.— Urea 

 was fed by the punchbar method to 10 

 elms, 3 to 5 inches d. b. h. Five of these 

 trees were fed 15 pounds of urea each 

 and five were fed 25 pounds of urea each. 

 Each tree received half of its dosage of 

 urea in October, 1941, and the other half 

 in April, 1942. Previous to treatment, 

 eight of the 10 trees had wilted in 1941, 



