i86 Diseases of Greenhouse Crops 



to brownish white slime that is not sticky oozes out. 

 In soft and rapidly growing plants, the whole pith 

 is often converted into a watery slime. In toma- 

 toes and eggplants the disease seldom attacks the 

 fruit but is confined to the vegetative parts. 



Southern wilt attacks not only the tomato and 

 eggplant, but it also causes a serious disease on po- 

 tato, tobacco, peanut, nasturtium, ragweed, impa- 

 tience, and verbena, in the open. 



The Organism. Fseudomonas solanacearutn is a 

 medium-sized rod, with rounded ends and motile 

 by means of polar flagella. Pseudo-zoogloese are 

 common in old cultures. No spores are formed; on 

 agar-agar, colonies are white, then dirty white, after- 

 wards becoming brown with age. The organism 

 does not liquefy gelatine and produces no gas. 



Control. All diseased plants should be carefully 

 pulled out and destroyed by fire. The house should 

 be given all the ventilation possible and water with- 

 held for a while. Syringing of the plants should 

 cease until the disease subsides. In watering care 

 should be taken not to splash soil particles on the 

 plant. All insect pests whether sucking or biting 

 should be controlled, as these usually help to spread 

 the disease. This trouble is likely to be prevalent 

 in greenhouses in the Southern states. 



Damping Off. See Pythium. 



Late Blight 



Caused by Phytophthora infestans (Mont.) 

 De By. 



