Cotton Growing in Arizona 273 



time the cowpeas are coming into full bloom. A more practical 

 method is to plant the cowpeas at the time the cotton is planted, as 

 this avoids the necessity of special irrigation to bring up the cowpeas. 

 It is claimed that the planting of cowpeas in this way has a beneficial 

 effect upon the growing cotton. In handling the cowpeas in this man- 

 ner, it has been customary to plant two rows of cotton and the third 

 row of cowpeas. We do not have accurate or conclusive information 

 regarding the benefit of planting cowpeas with cotton. There is con- 

 siderable evidence to prove that a legume crop may have beneficial 

 effects upon a companion crop, but whether it will pay in the case of 

 cotton remains to be proven. If cotton is planted in this manner, it 

 should be considered an experiment and an accurate comparison should 

 be made with the common methods of planting. 



ANGULAR LEAF SPOT 



Fortunately there are not many cotton diseases of serious conse- 

 quence in Arizona at the present time. Probably the disease that has 

 caused heaviest losses is one that farmers have observed but little, 

 even though it may be present to a considerable degree. This is a 

 disease called Angular Leaf Spot or Black Arm Disease of cotton. 

 This disease attacks the plant in all stages of its growth, appearing on 

 the younger plants as small dark angular spots on the leaves. Later 

 the disease attacks the stems and fruit, showing as darkened, shrunken 

 spots. Control measures are still in the experimental stage, but there 

 is evidence that control, at least in the seedling stage, can be effected 

 by careful treatment of the seed before planting. If treatment of 

 seed to control this disease is attempted, the following is recommended. 



bichloride oe mercury treatment for angular leaf spot 



Dissolve one ounce of bichloride of mercury in a small quan- 

 tity of hot water, then mix into seven and one-half gallons of water. 

 Dip the seed into this solution, stirring to make sure that it is thor- 

 oughly wet and allow to soak for one hour. Spread the seed out and 

 dry thoroughly before putting into sacks. 



Do not dip more than three lots of seed into the same solution, as 

 each lot of seed weakens the solution. 



Bichloride of mercury is a poison, and the solution should be 

 destroyed in order that people or animals may not drink it by mistake. 



Bichloride of mercury corrodes metal and solutions of it must not 

 be placed in metal utensils. Wooden or earthenware vessels should be 

 used. 



