DISEASES OF CULTIVATED PLANTS 601 



the study of the sugar cane diseases, the study of these will be taken 

 up as time permits. 



Summary. During the past season the sugar planters of Loui- 

 siana have had considerable trouble in obtaining good stands of cane. 

 The investigations of the experiment station have shown the trouble 

 to be due primarily to several fungous diseases. These diseases have 

 been much more severe this year than in previous years on account 

 of the very dry spring. The dry weather reduced the vitality of 

 the cane and made it more susceptible to the diseases. The diseases 

 present in the state are the red rot, the rind disease, the pineapple 

 disease, and the root rot. The red rot, rind disease, and root rot 

 are widely distributed over the state, but the pineapple disease is at 

 present only known in one parish. (La. E. S. B. 120.) 



COTTON DISEASES. 



Root-Knot, Root-Galls, Root Nematodes. Only a few cases of 

 root-knot of cotton in this state have been brought to my attention, 

 yet I am loath to believe that it is not quite common, especially on 

 thin sandy soil and worn out lands. Cotton growers are probably 

 more ignorant of the presence of this disease in their fields than 

 any other. This is likely the true explanation of the lack of satis- 

 factory information on the distribution of this trouble throughout 

 the state. Mr. Orton, of the Department of Agriculture, has found 

 that root-knot of cotton is often associated with wilt. Root-knot so 

 weakens the root system that it affords easy or favorable conditions 

 for the entrance of the wilt fungus. Many weeds and cultivated 

 plants are subject to this trouble. One of our best soil renovators, 

 the cowpea, is very susceptible. It is bad economy to follow diseased 

 cowpeas with cotton. 



Root-knot is a disease that attacks the roots or underground 

 parts of the cotton plants. All cotton plants suffering from root-knot 

 are dwarfed. When the roots are badly diseased, the plant suffers a 

 lack of food and water, wilts and finally dies. A plant may not 

 show any striking symptoms but on examining the roots the cause 

 of the disease can be easily determined. They are covered with 

 warts, galls or excrescences of various sizes and shapes, and some- 

 times are as large as an inch in diameter. When the affected roots 

 begin to die they send out new roots so that before long the root 

 system becomes bushy and tangled. 



This root affection is due to a microscopic worm about 1/60 

 to 1/20 of an inch long. It burrows into the root, thus setting up an 

 irritation which later produces these wart-like excrescences or knots. 

 If these knots are numerous the nutrition of the plant is interfered 

 with. It becomes enfeebled and finally dies. 



No treatment of diseased roots with poisons, is practicable since 

 the amount necessary to kill the worm would also seriously injure 

 the root. Carbon bisulphide, arsenic and kerosene emulsions have 

 been tried without success. Alkaline fertilizers such as kainit, 

 potash, and lime have been mentioned as good checking agents. 

 Allowing the land to go fallow for two seasons has resulted in almost 

 ridding the soil of the worm.__This method is expensive and un- 



