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use of 4 additional oat varieties as differential hosts. In the same 
way, 3 more collections of the loose smut were differentiated by 
the use of 3 oat varieties. The differential varieties used were 
susceptible to Races 1 of loose and covered smut; some of them 
gave high infections with the new races, while others were free. 
Soft Rot Disease of the Tris 
The bacterial soft rot disease of iris appeared in the new bearded 
iris beds in the Esplanade during mid-May, and reached epidemic 
proportions in July and August. Abundant moisture, warm tem- 
peratures, and succulent plant growth appeared to be predisposing 
factors to this disease. A total of 1,223 rotted plants from an 
original 3,924 plants were removed from the beds. Many more 
plants would have been lost if salvage operations had not been 
undertaken during late July. [even drying the plants in the green- 
house | 
Infection experiments carried out by Dr. L. Gordon Utter 
indicated that the rot organisms were capable of inducing the 
disease through the foliage, rhizomes, and roots. Generally, it 
ailed to entirely check further rotting. 
was necessary to break the surface of these organs, in a manner 
suggestive of insect injury, to accomplish rotting. 
The rot disease could not be effectively controlled with various 
sprays and sulfur dust which were applied to the base of the 
plants or on the foliage. Further experiments have been under- 
taken to determine the effectiveness of various fertilizers and 
chemicals in controlling the rot. 
Ewvperunents on the Control of Iris Thrips 
The methyl bromide fumigations of iris undertaken in 1941 by 
Dr. L. Gordon Utter, with the cooperation of Dr. Floyd F. Smith 
and Mr. F. S. Blanton, of the Division of Truck Crops and Garden 
Insect Investigations, Bureau of Entomology and Plant Quaran- 
tine, Washington, D. C., were brought to a conclusion. 
The purpose of these investigations was to determine the toler- 
ance of planting divisions of many varieties of bearded and beard- 
less iris, when subjected to methyl bromide fumigations at rates 
of 244 or 3 lbs. per 1000 cu. ft. of space for 2% hours at 68°-76° F. 
