TOMATO DISEASES 



1975 



The true cause of point rot does not 

 seem to be thoroughly understood. There 

 is evidence to indicate that it is an in- 

 fective disease, the cause of which is dis- 

 tributed by insects. 



It is known that the trouble is more 

 serious in dry weather on light soils 

 where the supply of water is insufficient. 

 This can be corrected either by irriga- 

 tion or by adding organic matter so that 

 the water-holding power is increased. 

 Surface tillage should also be practiced. 

 Experimental work has shown that sub- 

 irrigation is better than surface water- 

 ing, and that where plants are shaded 

 so that transpiration is reduced the 

 amount of rot is considerably lessened. 



Burn or Scald 



A disease of rare occurence character- 

 ized by drying up of leaves. It is an 

 indoor disease attributed to burning 

 from sudden exposure to bright sunshine 

 after cloudy weather, or to lack of water, 

 especially when plants have been accus- 

 tomed to warm, moist air and plenty of 

 water. Plants grown under optimum 

 temperature conditions in properly light- 

 ed and ventilated houses, especially 

 where attention has been paid to their 

 care during cloudy weather, are not like- 

 ly to be affected with this trouble. 



G. E. Stone, 

 Massachusetts Bulletin 138. 



Collar Disease 



Vermicularia sp. 



A peculiar collar disease of fall green- 

 house tomatoes. The symptoms are an 

 abnormal leaf development, after the 

 manner of mosaic disease by artificial 

 inoculation. 



The case under study occured in houses 

 that appeared to be overwatered. The 

 plants set very little fruit and were not 

 profitable. The root system normally de- 

 veloped except in adventitious whorl of 

 roots near the surface. Between these 

 roots and the root crown below, the 

 collar of the plant is surrounded by a 

 development of what appears to be a 

 parasitic fungus, a species of Vermicu- 

 laria. The black masses of the fungus 



are also visible extending down upon the 

 root bases, which are lighter in color. 

 A similar abundance of Vermicularia 

 has been noted on the dead stems of 

 potato tops which have died from fus- 

 arium blight. 



Something can be accomplished by 

 spraying with Bordeaux mixture about 

 the base of the plants. Certainly good 

 will come by withholding excess water. 



A. D. Selby, 

 Ohio Bulletin 214. 



Damping Off. See Root Rot, this sec- 

 tion. 



Downy Mildew, Blight 



Phytophthora infestans 



F. D. Bailey 

 This disease is due to the same cause 

 as the late blight of potato. It has been 

 quite prevalent in certain sections of 

 the Northwest where the potato blight 

 occurred during the season of 1912, and 

 it has caused the loss of a large per- 

 centage of the crop in some cases. (For 

 full account see late blight of potato.) 



Ot^e.n^ii 



Fig. 1, Late Blight of Tomatoes. Caused by 

 the same fungus as the late blight of pota- 

 toes. 



Dry Rot or Dry Weather Rot. See 

 Blossom End Rot, this section. 



Eel Worms. See Root Knot, this sec- 

 tion. 



Fruit Rot. See Blossom End Rot, this 

 section. 



Hollow Stem 



P. H. Rolfs mentions this trouble as 

 occuring in Florida. Plants suffer from 

 this disorder immediately after being set 



