14 abstracts: phytopathology 



fern. They include both herbaceous and woody plants and annual, 

 biennial and perennials. The anatomy and development of the parasite 

 is discussed, followed by a comparison between this nematode and the 

 one causing the disease of the sugar beet in Europe, they having been 

 shown to be decidedly distinct as long ago as 1890 by Voigt. It is shown 

 that the chief method of introducing the pest into a new location is by 

 means of live plants, especially nursery stock, and when once introduced, 

 it spreads from place to place in the soil adhering to tools, hoofs of ani- 

 mals, wagons, etc. The presence of the nematode within the roots causes 

 hypertrophy of the tissue resulting in a gall. These galls are usually con- 

 fined to the roots but in some cases were seen to occur on the stems, leaves 

 and fruits where these have come in contact with infested ground. The 

 water-conducting tissues within these galls are very much twisted and 

 dislocated so that when the galls are abundant, the plants are subject 

 to wilting much more easily than the uninfected plants. These fleshy 

 galls also form the center of infection for various parasitic fungi. Con- 

 ditions favoring root knot are high temperature and sandy soil with 

 plenty of moisture altho the soil must not be entirely saturated. This 

 pest is practically inactive at a temperature lower than 10° C, but is 

 able to survive in unprotected soils at — 35° C. The control of root knot 

 is discussed under the following headings: Greenhouses, seed beds, etc.; 

 in the field with no crop present; and in the field occupied by perennial 

 crops. In the first, live steam is most satisfactory altho fresh soil can 

 be used if obtainable nematode free, and formaldehyde, one part of 40 

 per cent solution to 100 parts of water, is successful under certain condi- 

 tions. In the field with perennial crops, practically no treatment is 

 satisfactory except the stimulating of the plants to abundant growth by 

 the use of extra amounts of fertilizers. For exterminating the pest in 

 fields not occupied by perennial crops, rotation methods with non-sus- 

 ceptible crops were the most successful. Those that were most success- 

 ful in the South were the use of Cowpeas {{Vigna unguiculata) , Velvet 

 Bean. (Stizolobium deeringianum) , Florida Beggar weed (Meibomia 

 mollis). Only the non-susceptible varieties of the first can be used, for 

 example, the variety known as Iron. These are grown as summer crops 

 and in the fall rye or oats is sown. Two years of each crop is neces- 

 sary to free the field and in some cases perhaps three would be more 

 successful. There seems to be considerable promise in breeding varieties 

 that are non-susceptible to the trouble. E. A. B. 



