CONTROL OF BOOT-KNOT. 47 



ever, as a means of combating nematodes it is not recommended by 

 Prof. Selby. The strength of the sokition used there was about 1 to 

 1^ parts commercial formaldehyde to 400 of water, which is less than 

 that found to be really effective against tliis nematode. 



The treatment of living plants in the greenhouse to destroy root- 

 knot is fraught ^vith considerable difficulty. Means that will destroy 

 the nematodes are mostly injurious to the plants containing them. 

 Thus, steaming or drying and freezing the soil can not be thought of, 

 as these processes are fatal to the plants. So, too, the use of carbon 

 bisulphid has in a similar way proved not feasible. It is still possible, 

 however, that certain plants less susceptible to this chemical, if per- 

 fectly dormant and rather dry, might escape without serious injury 

 when enough of it was used to kill the nematodes present. This must 

 be determined by experiment. Under certain conditions the use of 

 the formaldehyde solution has been found efficacious with some kinds 

 of roses. Many plants are killed outright by the treatment, but roses, 

 at least some sorts, are less susceptible to injury. The first experi- 

 ments in this line were performed in February, 1902, in the green- 

 houses of Mr. Loose, a florist of Alexandria, Va., under the direction 

 of Mr. A. F. Woods, of the Bureau of Plant Industry. The writer 

 cooperated in so far that he examined the roots for nematodes after 

 the experiment. The following extracts from Mr. Loose's report of 

 the experiment indicate the methods used: 



In the early part of February a bed of Bridesmaids, 150 feet long and 3 feet wide, 

 4 inches soil, was thoroughly saturated, using 50 gallons of the 1 per cent mixture. 

 The plants did not seem to suffer from the application, and one week later we were 

 able to see young healthy roots making their appearance, while the old fibrous roots 

 were entirely decayed. We then treated in the same manner Bride, Kaiserine, 

 Chatanays, Nephetos, Beauty, Liberty, and Meteor with equal success as to freeing 

 the soil of the pest. 



Some strong-growing varieties, however, such as Beauties, Chatanays, and Kaiser- 

 ine, suffered and lost much of their foliage. Even some of the soft growth wilted 

 during the sunny part of the day. My experience in this treatment is that care 

 should be taken to harden the plants by lower temperatiire and keeping the beds 

 dry, being careful, however, to give the plant a good watering 12 hours before apply- 

 ing the mixture. * * * The cut of roses on February 10, at the time when we 

 applied the remedy, had dwindled down to 250 a day. It remained practically sta- 

 tionary during the four following weeks. We were able, however, to notice that the 

 foliage was regaining its normal color and the plants were stiirting strong growths. By 

 April 1 our cut had increased to 500 daily, mostly prime stock, and by the middle of 

 April it had resumed its normal cut of 1,000. 



As a matter of experiment we left a few plants untreated at the ends of some of the 

 benches, and to-day. May 10, they are practically worthless, showing effectually that 

 the spring weather had nothing to do with the improvement. The roots of the un- 

 treated plants looked like a ball of fern roots used for orchid potting, full of galls and 

 matted, plants making a weakly growth, foliage pale, and flowers insignificant. On 

 the contrary, the plants treated last February have healthy strong roots, making fine 

 growth and the foliage of the very best color. 

 91294°— Bui. 217—11 i 



