August, 1945 



Carter: Wetwood of Elms 



441 



1943, but two trees injected with copper 

 sulfate and two injected with silver nitrate 

 wilted in 1944. Two of the three trees 

 injected with 8-hydroxvquinolin sulfate 

 did not wilt in 1942, 1943 or 1944, but 

 the third tree wilted in 1942 and again in 

 1943. 



These tests might be interpreted as 

 indicating that mercuric chloride, copper 

 sulfate, silver nitrate, and 8-hydroxyquin- 

 olin sulfate may be of value in controlling 

 wilt. However, it must be borne in mind 

 that of 284 trees in Hinsdale that wilted, 

 1939—1943, only 73 wilted in more than 

 1 year. Also, the wetwood organism was 

 isolated repeatedly, 1942—1944, from the 

 wetwood-af^ected trunk wood of the trees 

 which had received injections in 1941 and 

 1942, indicating that the organism was 

 not killed throughout the affected wood 

 by any of the materials injected. Later 

 experiments indicated that most of the 

 material injected went into the younger 

 sapwood, especially the current-season 

 wood, and not into the heartwood or older 

 sapwood. 



Injections of mercuric chloride and 

 copper sulfate made in August, 1941, 

 caused the cambium to die back 0.5 to 1.5 

 inches around many of the injection holes. 

 Most of these injured areas callused over 

 in 1942. Cambial injury following the in- 

 jections made in 1942 was negligible, 

 since care was taken to prevent the solu- 

 tions from coming in contact with the 

 cambium around the injection holes. 



Miscellaneous Experiments 



Injections of Toxic and Stimula- 

 tory Materials. — An experiment was 

 started on July 29, 1942, to determine 

 whether materials toxic to the wetwood 

 organism, as determined by bactericidal 

 tests, would inhibit or kill bacteria in wet- 

 wood-affected trunk wood and subsequent- 

 ly reduce the pressure in the trunk. Also, 

 materials known to stimulate fermentation 

 were injected into other trees to see if pres- 

 sure could be increased. The toxic materials 

 injected were mercuric chloride, 1 : 500, 

 copper sulfate, 1 : 200, silver nitrate, 

 I 1 : 500, 8-hydroxyquinolin sulfate, 1 : 200 

 and Elgetol, 1 : 40. The stimulatory mate- 

 rials injected were 5 per cent dextrose and 

 nutrient broth plus 1 per cent dextrose. 

 Sterile distilled water was injected as a 



check material. Each material was inject- 

 ed into a single tree. 



A one-half inch hole was bored through 

 the heartwood of each tree to be treated, 

 to about 1 inch from the cambium on the 

 opposite side. A gaugecock was installed 

 in each hole. All injections were made 

 with a hand syringe, fig. 23. After the 

 solutions were injected, the gaugecocks 

 were closed to keep these solutions in the 

 trees. Pressures registered immediately be- 

 fore and immediately after the injections 

 were made and during the remainder of 

 the growing season of 1942 and the season 

 of 1943 are shown in table 5. 



Following the injection of each mate- 

 rial, including distilled water, pressure 

 temporarily increased. However, the 

 pressure in most trees had returned to 

 approximately the initial point within 9 

 hours after the injections were made. 

 Trunk pressures increased during August 

 and September of 1942 in all trees except 

 the one which was injected with 5 per 

 cent dextrose. Pressure readings obtained 

 from each tree followed the normal pres- 

 sure curve from June to mid October of 

 1943. Failure of the toxic materials to 

 reduce pressure suggested that these 

 materials either had not become distribut- 

 ed throughout the bacteria-infected wood, 

 that through some chemical change they 

 were not toxic to the bacteria after being 

 injected into the wood or that the quantity 

 of materials was not sufficient to produce 

 the desired result. 



Distribution of Malachite Green 

 in Elms. — Malachite green was used to 

 study the distribution of materials injected 

 into elms. These tests were made August 

 31, 1943, on 8-year-old American elm 

 trees growing in our experimental nurs- 

 ery. Methods of supplying the dye were 

 ( 1 ) through a hole bored under dye in 

 the trunk, dye being held against the trunk 

 in a cuplike container that kept the hole 

 submerged while it was being bored and 

 for 10 minutes afterwards; (2) by the 

 hand syringe method, fig. 23 ; (3) by cut- 

 ting the tree and immersing the cut trunk 

 base in the dye; (4) by cutting the leader 

 and immersing the cut end in the dye; 

 and (5) by cutting a branch and immers- 

 ing the cut end in the dye. Two trees were 

 subjected to each method of treatment. 



Penetration of malachite green through 

 a hole in the trunk submerged below the 



