CONTROL OF ROOT-KNOT. 57 



which killed the plants out in some of the plats. The cowpeas in 

 plat 12 showed no nematodes and but few were present in the squashes. 

 Plat 14 had a fair amount of root-knot in the cowpeas and from few 

 to many on the different squash plants. The rest of the plats did 

 not difTer materially from the check plats which were fairly badly 

 affected, in spots very badly. 



The plants growTi on these same plats in 1907 without the addi- 

 tion of the fertilizers again were badly affected except in plat 12, and 

 somewhat in plat 15, wliich remained fairly free, showing a residual 

 effect. 



In the 1907 fertilizer experiments the following results were 

 obtained. The kainit applications were injurious to the germina- 

 tion of the seeds, both the 1,000 as well as the 1,500 pound applica- 

 tion, but naturally the latter more markedly. The amount of root- 

 knot, however, in these plats was slight. Potassium sulphate at 667 

 pounds per acre was not injurious, but at twice that amount it so 

 injured the germination of the cowpeas and beans that they required 

 replanting. Root-knot was fairly abundant and, strangely, more so 

 in the more highly fertilized plat. In both plats the growth of the 

 plants was very vigorous. The sulphate of ammonia at the rate used 

 exerted a ver}^ harmful effect on gennination, requirmg several 

 replantings. The plants that did grow, however, were very vigor- 

 ous, dark green, and rather free from nematodes. The muriate of 

 potash injured the germination of the beans and cowpeas, while the 

 nematodes were fairly abundant. The potassium magnesium car- 

 bonate gave the best and most vigorous plants of all, mthout injury 

 to germination. Root-knot was present in most of the plants, but 

 not abundant. 



Judging from these experiments, it is clear that fertilizers alone 

 can not be depended upon to exterminate root-knot. On the other 

 hand it is also plain that some fertilizers exert a beneficial effect upon 

 the plant and enable it to make a good crop in spite of nematodes. 

 Perhaps they may also increase the resisting power of the plant 

 against the entrance of the nematodes into the roots. The potash 

 fertilizers seem to be most favorable for tliis purpose, so far as the 

 experiments at Monetta and observations elsewhere go. However, 

 it will not be safe to conclude that they will be equally beneficial 

 everywhere. In the sandy, rather potash-free soils of South Caro- 

 lina and Florida the application of potash in amounts not too large 

 seems to be followed by favorable results. 



According to Stift,* Hollrung, in Germany, has sho'WTi that ferti- 

 lizing highly with potash alone is not of much benefit to beets attacked 

 by the sugar-beet nematode. Wimmer has shown that the nema- 



> stilt, 1908. 

 217 



