A NEW FRUIT ROT OF TOMATOES’ 
R. FrRanK POOLE 
(WITH PLATE VII) 
During the summer of 1921 a fungus growth following cracking 
of the fruit was noted on tomatoes in several localities of Burlington 
and other counties in New Jersey (fig. 1). The cracking was obvious 
on both green and ripe fruit of the Stone, Baltimore, and Bonny Best 
varieties, but was especially prominent and severe on the latter. 
The cracking is apparently due to one or more physiological causes. 
An examination showed a very dense fluffy growth of Oidiwm lactis 
Fres. in the open cracks of ripe fruit lying on the ground and those 
hanging on the plant to a height of several inches above the soil. 
This fungus, under field conditions, penetrated the interior of the 
tomato, and reduced the fruit to a soft rotten mass in from two to 
five days. The disease was very common throughout the tomato 
ripening period in the fields under observation. No infection was 
noted on uninjured ripe fruit, cracked green fruit, or other parts of 
the plant. 
CausE.—The rot is due to Oidiwm or Oospora lactis. The fun- 
gus is repeatedly isolated from infected tomatoes. It causes 
rapid decay of ripe fruit at 20° C. ina moist chamber. The mold 
is grayish white, fluffy, and dense (fig. 2). The mycelial growth is 
more important than spore production. If, however, a diseased 
tomato be broken open and spread out in a moist chamber for 
twenty-four hours at 20° C. (fig. 3), the fungus appears very similar 
in growth to the Saccharomyces. In this form the spore production 
is abundant, while the mycelial growth is subdued. These two 
factors of mycelium and spore production may be considered as dis- 
tinguishable characteristics of this fungus from other fruit rot 
organisms. The fungus grows abundantly on a large variety of 
culture media. Its only known method of reproduction is non- 
« Paper no. 60 of the Journal Series, New Jersey Agricultural Experiment Stations, 
Department of Plant Pathology. 
Botanical Gazette, vol. 74] [210 
