Indiana Plant Diseases, 1921 191 



actly resembling internal brown spot of the Irish potato. Numerous 

 areas of corky brown tissues were scattered throughout the flesh of the 

 roots. Attempts to isolate an organism from the lesions were unsuc- 

 cessful. 



Tobacco. — Angular leaf-spot (14), caused by Bacterium angulatum, 

 was very destructive in Spencer County this year and was worse in 1920, 

 according to the grower who sent in the specimens and who estimated 

 that the crop was damaged to the extent of fifty per cent by this dis- 

 ease in 1920. As a result of this experience the growers harvested 

 earlier in 1921 to avoid the heavy loss due to this disease. The dis- 

 ease was identified by F. D. Fromme. 



Tomato. — Owing perhaps to the excessive rainfall in the spring 

 and late summer, leaf-spot, caused by Septoria lycopersici, was much 

 worse than usual in both market garden and canning crops. The dis- 

 ease was noted at Vincennes as early as June 29, and on early tomatoes 

 in a market garden near Kokomo on July 2. The plants for the latter 

 had been grown in a greenhouse that was also used for a hothouse to- 

 mato crop, and thus were undoubtedly exposed to infection. At this 

 early date, practically no leaf-spot was evident in the canning crop 

 fields in that region. On July 12, the disease was noted in a number 

 of market gardens about Indianapolis and was especially destructive 

 on staked tomatoes under Skinner irrigation and in a greenhouse where 

 overhead watering was practiced. On July 21, leaf-spot was found to 

 be rather worse than was to be expected at this date in a number of can- 

 ning crop fields in Marion County. Late in the season the disease be- 

 came very destructive in the canning crop, as well as the market gar- 

 dens and caused very general premature defoliation. It was observed 

 in severe form near Indianapolis, Greenwood, Whiteland, and Marion 

 in September. 



Considerable evidence was obtained which corroborates the belief 

 that leaf-spot is primarily of plant-bed origin except in cases where 

 crop rotation is not practiced. For instance, leaf-spot lesions were noted 

 on purchased transplants that a grower was setting out on June 1 near 

 Hammond, and later the disease became severe on these plants. At 

 Lafayette no leaf-spot occurred in the plant-beds and none appeared 

 in the fields planted from these beds. Remnant tornato plants are often 

 left to grow during the season in the plant-beds and in two cases ob- 

 served, one near Indianapolis, on July 13, and one in Johnson County 

 on July 16, leaf -spot was present on these old plants. Leaf -spot may 

 also occur on other plants in these beds since Norton (31) in 1917 found 

 that the tomato Septoria would infect eggplant, potato, and horse nettle, 

 and Beach (3) corroborated these results in 1919. Pritchard and Porte 

 (33) in 1921 also report horse nettle susceptible. By means of rem- 

 nant tomato plants and other hosts the volume of infective material 

 in the plant-bed soil may be augmented each summer. It is of primary 

 importance in leaf-spot control that plant-bed rotation and sanitation 

 be practiced. By sanitation is meant the destruction of all remnant 

 tomato plants and susceptible weeds in and near the beds and the pre- 

 caution not to use such soil for eggplants or potatoes. 



The extreme heat of June and July was very favorable to the wilt 



