14 MASS. EXPERIMENT STATION BULLETIN 248 



counts of the prunings were made at intervals during the growth of the crop. 

 The materials used and the tabulated control results are presented in Table 

 8. As the counts show, none of the materials, except possibly Solbar and 

 Uspulun, was effective. The disease became so serious that no leaves free of 

 Cladosporium were found on the later counts in any of the plats. Solbar and 

 Uspulun furnished the better controls early in the growth of the crop but 

 these were so slight as to have no effect upon the yield or later incidence of 

 the disease. All materials excepting Solbar caused injury; Solbar and lime- 

 sulfur left residues on the fruit; and Uspulun, lime-sulfur and potassium 

 sulfide left an objectionable flavor. 



A control experiment with spraying materials was conducted in one of the 

 greenhouses of J. Winthrop Stone in Watertown, Mass. Single rows across 

 the width of the greenhouse were treated with liquid materials selected to 

 offer the best control. The plants were set during the first week in Septem- 

 ber. Treatments were made on October 7, 17 and 31. There was no leaf-mold 

 present when the first treatments were made. On the first application Uspulun 

 was used at .25 per cent strength and caused burning. In subsequent treat- 

 ments its strength was reduced to .20 per cent. New Jersey Dry Mix 1.25 

 per cent was substituted for sulfuric acid .03 per cent in the second treatment 

 on account of injury resulting from the latter. Uspulun, copper sulfate, po- 

 tassium sulfide, lime-sulfur and New Jersey Dry Mix were injurious to the 

 foliage, — the sulfur materials especially so on the sunny side of the rows. 

 Bordeaux mixture, lime-sulfur. New Jersey Dry Mix and Solbar left heavy 

 residues. Foliage counts were made on November 21, December 14- and 

 January 1 (Table 9). Only treated foliage was considered in the counts, 

 except in the count of January 1 when some of the slightly treated and 

 untreated leaves were included with the prunings. This foliage represented 

 the upper rosette of leaves when the final application of October 31 was made 

 and since the leaves were rather small and sheltered at that time coverings 

 of spray were not as good as on the older and more fully developed leaves 

 represented in the counts previous to January 1. The perceptible residues 

 from Bordeaux, Solbar, lime-sulfur and New Jersey Dry Mix permitted dis- 

 carding any foliage not showing residue, but since Uspulun, Semesan, potas- 

 sium sulfide and copper sulfate left no discernible residues no segregation of 

 covered and uncovered leaves was possible. It appears for this reason that the 

 controls of January 1 do not coincide with those previously obtained. 



On this crop, heating was practiced liberally from the time the plants were 

 set. Three lines of heating pipe each 12 feet apart extended lengthwise 

 through the greenhouse above the ground in addition to the piping along the 

 side walls. Since it was evident on October 31 when the final treatments were 

 made that liberal heating was controlling the disease effectively, further treat- 

 ments were discontinued. Infection, therefore, was not severe enough so that 

 the relative efficiency of the materials used could be determined by casual 

 observation. Foliage counts, however, showed a superior effect from Uspulun 

 and Solbar, but the significance of these counts is decreased considerably 

 by the relative lack of disease in the controls. 



Spore toxicity studies showed that naphthalene is fungicidal to the spores 

 of Cladosporium and suggest that the frequent disinfection of the tomato 

 vines with naphthalene dust should offer control. This material was con- 

 sidered regardless of the eft'ect its vapors have upon the quality of the fruit. 

 A compartment of the greenhouse with a bed area of 900 square feet and a 

 volume of 10,000 cubic feet was used. The tomatoes were set early in Feb- 

 ruary, 1926. A sulfur-lime-naphthalene dust containing one part of each in- 



