:: , i :, ANNUAL REPORT, 1932 / 17 



eggplant occurred at a soil temperature range ol 77°-95° F., and most infection at 

 77°. No infection occurred at soil temperatures of 55.4° and 95° F. 



When aluminum sulfate was used to acidify the soil, no infection occurred at pH 

 values below 5.0; and when inoculated sulfur was used, there was slight infection 

 at pH 4.0-4.2. Aluminum sulfate gave more consistent control of wilt at the low 

 values than sulfur. 



Results of field applications of aluminum sulfate and sulfur were disappointing 

 and revealed no justification for artificial soil acidification in the field as a means 

 of control. The culture of eggplant on naturally acid sod land offers the best 

 means of controlling wilt. The investigation is concluded with this report. 



Control of Greenhouse Vegetable Diseases. (K. F. (iuba, Waltham.) 



Tomato leaj-mold. Extensive tests reveal the lack of immunity among any 

 varieties of tomatoes to attack by Cladosporium fulvum Cke., but some varieties 

 show a mild resistance as expressed in slight spore production, belated infection, 

 and yellow spots, in contrast to a rich growth of the fungus on foliage of susceptible 

 varieties. The varieties Maincrop, Up-to-Date, Norduke, and Norton were most 

 resistant. Maincrop and Up-to-Date produce small, smooth tomatoes and set 

 heavily; Norduke and Norton produce large, rough tomatoes and set verj' poorly 

 under glass. Reciprocal crosses of these varieties have been obtained for future 

 study. Riverside X Up-to-Date, Stonnors M. P. X Up-to-Date, Maincrop X 

 Up-to-Date, and E. S. 1 X Up-to-Date, crosses made by Dr. W. F. Bewley of 

 Fuigland for resistance to Cladosporium, are similar to Maincrop and Up-to-Date 

 in cropping characters and resistance. Of these four hybrids, Stonnors M. P. 

 X Up-to-Date and Maincrop X Up-to-Date were most resistant. These hybrids 

 have been crossed further with Norton and Norduke in the hope of developing 

 a suitable greenhouse tomato which is, at least, less troubled by the disease 

 than the standard varieties now being grown. 



A paper dealing with the relation of environment to the development and control 

 of tomato leaf-mold under glass is in preparation. 



Effect of hydrocyanic acid gas on cucumber plants sprayed with copper fungicides. 

 Cucumber plants were always injured when gas followed copper fungicides con- 

 taining calcium hydroxide, sodium hydroxide, or sodium carbonate. Even when 

 the alkali compound was reduced to produce neutral mixtures, injury resulted 

 after gas. Injury occurred regardless of whether the gas was evolved from Cyano- 

 gas or from sodium cyanide, or whether chemical hydrated lime, milk of lime, or 

 lime water was used in the preparation of Bordeaux. 



Injury was always correlated with water soluble copper which increased with 

 the amount of alkali present in the spray. 



Residues of Bordeaux on glass acted upon by gas yielded soluble copper and 

 hydrocyanic acid gas, and these occurred in a fairly constant ratio. The toxic 

 salt is presumably calcium cuprocyanide CaCu2(CN)45H20. 



If spraying greenhouse cucumbers with Bordeaux is warranted, fumigation 

 with hydrocyanic acid gas should precede the copper treatment, or cyanide fumiga- 

 tion should be abandoned in favor of tobacco fumigants. The investigation is 

 concluded with this report. 



Control of the root-knot uonatodc in greenlionses with carbon disidfldc emulsion. 

 This investigation has been completed and the results published in Bulletin 292. 



Eradication of Nematodes in Greenhouse Soils by the Use of Chemicals. 

 (L. H. Jones.) In further experiments, using a mixture of liquid orthodichloro- 

 benzene adsorbed in diatomaceous earth and calcium cyanide, nematodes were 

 eradicated from soil in six-inch flower pots that was heavily inoculated with large 



