ANNUAL REPORT, 1936 25 



Flood Relief. (The Department.) Following the disastrous flooding of 

 the Connecticut River Valley in March of 1936, an emergency service was 

 established to aid in rehabilitation. Three men were sent into the flooded 

 areas to investigate sanitary conditions and to give advice and service in the 

 elimination or abatement of health hazards. Particular attention was given 

 to water supplies. Private supplies showing evidence of pollution were ster- 

 ilized under the supervision of our field staff and samples were re tested in the 

 laboratory until evidence of pollution had disappeared. Assistance was also 

 given to the State Department of Health in handling water samples taken from 

 municipal supplies. During the emergency 220 bacteriological analyses were 

 made in our laboratory. 



DEPARTMENT OF BOTANY 

 A. Vincent Osmun in Charge 



Control of Greenhouse Vegetable Diseases. (E. F. Guba, Waltham.) 

 Since the previous annual report two more generations (F 3 and F 4 ) of tomato 

 hybrids have been grown for further selections for resistance to Cladosporium 

 leaf mold and for quality. Some seed samples of these tomatoes have been 

 distributed to other experiment station workers in the United States and 

 Canada for trial and report. 



As a between-crop treatment to cleanse the greenhouse interior of fungous 

 spores, the burning of sulfur (4 lbs. to 10,000 cu. ft.) was found to be entirely 

 adequate. Plant life and most insects succumbed to this dosage. Zinc oxide is 

 apparently the only white paint pigment to react with sulfur dioxide to produce 

 a soluble plant poison. The proportion of this pigment which must be present 

 in prepared paint in order to produce sufficient zinc sulfate to cause plant injury 

 remains to be determined. Zinc-coated wires used to trellis plants are also a 

 source of the injurious sulfate. Tinned or stainless steel wires do not react 

 and are recommended as substitutes. Naphthalene vapor and hydrocyanic 

 acid gas, which are sometimes used to eradicate insects between crops, do not 

 react with paint and metal; but in tests at excessively high dosages both lacked 

 fungicidal value when spores of Cladosporium fulvum Cke. were used as an 

 index. 



This fungus is specified in the literature as the cause of a green mold rot of 

 tomato fruits from California and Mexico. Cultural and physiological char- 

 acters of the fungus from rotted California tomatoes arriving at the Boston 

 Terminal Market revealed distinct contrasts to the prevalent Cladosporium 

 leaf mold fungus on tomato foliage under glass. 



It was determined that Cladosporium fulvum Cke. is the cause of a rather 

 prevalent asthma among greenhouse tomato workers in the United States and 

 Canada. According to the writer's experience desensitivity may readily be 

 accomplished by proper treatment with extracts of the fungus. 



Causes and Control of Decay of Winter Squash in Storage. (E. F. 



Guba and C. J. Gilgut, Waltham.) A survey of squash storages in the season 

 of 1935-36 revealed rather wide differences and opinions relative to proper 

 storage temperatures. The merit of low storage temperatures is supported by 

 laboratory cultural studies in which the growth of organisms producing squash 

 rot was completely inhibited at 40° F. and lower. The maintenance of such 

 temperatures in squash storages, however, requires better construction and 



