12 



MASS. EXPERIMENT STATION BULLETIN 248 



Table 7. Summary of Control of Infection of Potted Tomato Plants with 



Fungicides. 



Grape Dust 



Hammond's Slug Shot 



Vaporized Sulfur 



Lime-Sulfur 



Solbar 



Copper Sulfate 



Bordeaux mixture. . . . 

 Copper-Lime Dust. . . . 



Semesan 



Uspulun 



Spores Applied in Water 



Times 

 Tested 



Times 



Control 



Favorable 



Times 



Control 



Unfavorable 



Spores Applied Dry 



Times 

 Tested 



Times 



Control 



Favorable 



sulfur, superior and more uniform results were obtained than when the upper 

 leaf surfaces only were protected. In general this was also true of other 

 materials such as Uspulun, copper fungicides, etc., excepting sulfur, when 

 plants were inoculated with a suspension of spores in water. This is ex- 

 plained at least in part by the fact that leaf infection is almost altogether 

 hypophyllous. However, when plants treated in this manner were inoculated 

 with dry spores, vaporized sulfur showed a marked effect, and Grape Dust 

 a somewhat inferior effect. 



The use of spraying and dusting materials in general is not applicable to 

 greenhouse tomato culture, one reason being the undesirable effect of the 

 fungicide upon the plant. Bordeaux mixture leaves a residue. Lime-sulfur 

 is injurious and leaves a residue and sulfur odor. Uspulun is toxic to the 

 foliage at .25 per cent strength, and both Semesan and Uspulun impart a 

 phenol flavor to the tomato fruit. This fact has already been recognized by 

 Triebels (33), Liistner (21) and Jaenicke (17). Solbar leaves a heavy resi- 

 due and sulfur-lime-naphthalene dust imparts a naphthalene flavor to the fruit. 

 Vaporized sulfur and Grape Dust are desirable, but the results suggest that 

 vaporized sulfur would offer the most satisfactory control under the condi- 

 tions prevailing in tomato houses. 



Data in Tables 1 and 7 show that materials toxic to the spores in labora- 

 tory tests gave the most satisfactory control of infection with few exceptions. 

 Those showing this effect when the fungus was applied in water were copper 

 materials, organic mercury compounds, vaporized sulfur, Slug Shot and Grape 

 Dust. In the absence of water, vaporized sulfur gave the same effect, while 

 Solbar, Uspulun, and Grape Dust did not. No control was anticipated with 

 sulfur dusting materials, but potassium sulfide was expected to show some 

 control of foliage infection and did not. Sulfuric acid proved of no value 

 and Schacht's Naphtal-Schwefel, which was the most effective of all dusting 

 materials considered, failed to give control in a single trial. 



The remarkable control of foliage infection of potted plants with vaporized 

 sulfur in contrast to the inconsistent control of spore germination in labora- 

 tory slide tests indicates that conditions existing on foliage are much more 

 favorable for toxicity of vaporized sulfur than on slides in Petri dishes. 

 Under greenhouse cultural conditions tomato foliage is usually bathed in thin 



