TOMATO LEAF-MOLD 3 



son nor Williams stated the temperatures under which the tests were con- 

 ducted and both failed to consider the possible relation of temperature to 

 the activity of sulfur compounds. Parker (27) reported good results with 

 ammoniacal copper carbonate wash. Alvesco mildew powder, a copper and 

 sulfur dust of English manufacture, was recommended by A. M. D. (7), 

 Parker (27) and Dyke (8). 



Hasper (12) compared sulfur, copper salts and Uspulun and reported best 

 results with .5 per cent Uspulun applied at 8 to 10 day intervals. In an 

 anonymous paper (1) from Holland, Uspulun .5 per cent and Solbar 1 per 

 cent were reported to give effective control. Solbar caused foliage burning 

 but Uspulun none. Triebels (33) advised treatments with .5 per cent Uspu- 

 lun beginning with the first appearance of leaf-mold and repeating at 2 to 3 

 week intervals up to the time the fruit becomes large. Since the fruits 

 acquire the taste of phenol at this period, he advised using 1 per cent Solbar 

 for subsequent treatments. HoflPerichter (13) obtained good control with 1 

 per cent Solbar. Baehr (2) compared Bordeaux, Cosan and Solbar and re- 

 ported that Solbar alone gave excellent control, while the other materials 

 were of no account. Jonassen (18) advised spraying every fourteen days 

 with 1 to 1.5 per cent Germinal or LTspulun beginning when the houses are 

 set, and with a 5 per cent solution if the disease is already present. 



Sulfuring of the heating pipes has been recommended for combating 

 Cladosporium by Massey and Rhodes (23) and Parker (27). Manufactured 

 devices for vaporizing sulfur, such as Campbeirs Patent Sulfur Vaporizer 

 and the Rota-Generator, have been recommended for controlling Cladospo- 

 rium by Bewley (6) and A. M. D. (7), but Baehr (2) reported no control 

 with the Rota-Generator. 



As the literature reveals, many materials have been suggested. The recom- 

 mendations concerning the choice are contradictory and inconsistent, and 

 those materials which have been reported of merit are unsupported by ade- 

 quate evidence. It has seemed desirable, therefore, to determine the merits 

 of different fungicides in the control of this disease. 



LABORATORY CONTROL WITH FUNGICIDES 

 Effect of Fungicides on Spore Germination 



The technique employed by Makemson (22) and Williams (38) for deter- 

 mining the effect of fungicides on the germination of Cladosporium spores is 

 contrary to natural .methods of dissemination of the fungus and inoculation 

 of the plants in the greenhouse. Makemson applied spores in water drop 

 suspensions to glass surfaces bearing dry deposits of the fungicide, and 

 spores in drops of the fungicide on clean cover glasses. The results by both 

 methods of study were identical. Williams applied water suspensions of spores 

 to glass surfaces bearing dry deposits of the fungicide. 



Cladosporium spores are capable of germinating in moisture saturated air 

 and in the absence of the water drop. Spores are dispersed in the green- 

 house through the medium of the air and in the dry state, being liberated by 

 disturbing leaves aifected with mold. The common practice of tapping the 

 plants with sticks to assist pollination of the flowers is a means of producing 

 spread and epidemics of disease. Under the usual conditions of growing 

 greenhouse tomatoes water is not a carrier of the inoculum. In determining 

 the merits of fungicides for preventing infection, obviously the logical tech- 

 nique to follow is that of applying dry spores to dry fungicidal deposits and 

 of exposing dry spores to contact with dusts or liquids, drying, and then 



