August, 1945 



Carter: Wetwood of Elms 



425 



1942 and 1941 wood. Its 1940 summer 

 wood was white, but its 1940 spring wood 

 and all older wood was dark brown and 

 water-soaked. Isolates of fermenting bac- 

 teria similar to the original inoculum 

 were obtained from the brown 1940 

 spring wood. 



With an increment borer, trunk wood 

 samples for culturing were taken April 

 10, 1943, from the remaining three trees, 

 two inoculated with bacteria and one 

 treated with sterile nutrient broth plus 

 dextrose. Isolates of fermenting bacteria 

 similar to the original inoculum were ob- 

 tained from the two inoculated trees. 

 Bacterial growth was not obtained from 

 the trunk wood of the tree injected with 

 nutrient broth plus dextrose. 



Toxicity Tests for Wilt 



Numerous toxicity tests were conducted 

 to determine why wilting occurs on elms 

 affected with wetwood. These tests were 

 made on cut shoots of both elm and 

 tomato and also on potted elm seedlings. 



Laboratory Tests on Gut Shoots. — 

 Cut shoots of elm and tomato were placed 

 in test tubes, one of each in each tube, 

 containing the solutions to be tested. Ob- 



servations were made on the time required 

 for the shoots to wilt. The materials test- 

 ed and the times required for the elm and 

 tomato shoots to wilt in the various solu- 

 tions are given in table 2. All samples of 

 sap were from elms in Hinsdale affected 

 with wetwood. Neither filtering nor auto- 

 claving, nor both, destroyed the toxicity 

 of the sap. The elm shoots wilted in 1.5 

 to 4.0 hours, the tomato in 8.5 hours. 

 The results indicate that filterable and 

 thermostable toxins were present in the 

 sap. 



Water-soluble materials toxic to elm 

 shoots but not to tomato shoots were 

 obtained from normal elm heartwood 

 when it was soaked and also when it was 

 autoclaved in distilled water. The water 

 in which normal heartwood was autoclaved 

 was much more toxic than that in which 

 it was soaked. It caused elm shoots to 

 wilt in 1.5 hours, while water in which 

 heartwood was soaked caused shoots to 

 wilt in 9.5 hours. 



No apparent correlation existed between 

 the amount of liquid taken in and the 

 number of hours before the shoots wilted. 

 However, the total amount of material 

 taken in may have been influenced by the 

 size of the shoots, injury to tissues when 



Table 2. — Results of toxicity tests with sap from infected wood of wetwood-affected elms; 

 sap tested for toxicity on shoots of elm and tomato. All tests were run for 10 hours. 



Material Tested 



Air 



Tap water 



Sterile distilled water 



Sterile nutrient broth plus 1 per cent dextrose. . 



24-hour culture of isolate 41-173 



24-hour culture of isolate 41-173, autoclaved. . . . 



Filtrate of 24-hour culture of isolate 41-173 



Filtrate of 24-hour culture of isolate 41-173, 



autoclaved 



Sap from diseased elm No. 4-7 



Sap from diseased elm No. 6-7 



Sap from diseased elm No. 42-43 



Sap from diseased elm No. 42-43, autoclaved. . . . 



Filtrate of sap from diseased elm No. 42-43 



Filtrate of sap from diseased elm No. 42-43, 



autoclaved 



Water in which normal elm heartwood was soaked 

 Water in which normal elm heartwood was soaked, 



autoclaved 



Hours Required to 

 Wilt 



Elm 



1.0 



No wilt 

 No wilt 

 No wilt 



1.5 



1.5 

 No wilt 



No wilt 

 4.0 



3.5 

 3.5 

 1.5 

 1.5 



1.5 

 9.5 



1.5 



Tomato 



1.5 

 No wilt 

 No wilt 

 No wilt 

 No wilt 

 No wilt 

 No wilt 



No wilt 

 8.5 

 8.5 

 8.5 

 8.5 

 8.5 



8.5 

 No wilt 



No wilt 



Milli- 

 liters OF 

 Liquid 

 Taken In 



8.0 

 7.6 

 2.1 

 0.2 

 3.3 

 3.5 



2.1 

 4.4 



1.5 

 3.7 

 0.6 

 3.0 



2.2 

 1.8 



2.4 



pH OF 



Liquid 



7.16 

 6.40 

 6.38 

 5.55 

 4.65 

 5.13 



4.96 

 7.06 



15 

 28 

 14 

 35 



6.36 

 5.70 



4.96 



