26 BULLETIN 332, U. S. DEPARTMENT OP AGRICULTURE. 



nearly related to the cotton plant. 1 Neither this weevil nor the true 

 Mexican boll weevil has as yet been observed in the cotton fields 

 of the Salt River Valley. An aphis commonly attacks the young 

 plants, and in 1914 it persisted in large numbers until late in the 

 summer, but it has not been shown that this insect causes serious 

 damage to the crop. Bollworms occur in small numbers, but have 

 not thus far been a source of appreciable damage. The dreaded 

 pink boll worm, which has recently played havoc with the cotton 

 crop of Egypt, has fortunately not yet been observed in the United 

 States, and it is to be hoped that the measures taken by the Federal 

 Horticultural Board will preA^ent its introduction. 



Certain fungous diseases, while rather common, do not appear to 

 be severely injurious. The seedling cotton plants are subject to 

 attack, especially when cold weather occurs after planting, by a 

 species of Rhizoctonia, causing the disorder known as " sore shin." 

 When this disease is very prevalent, some replanting is likely to be 

 necessary, but the plants which survive soon cease to show any effects 

 of the trouble. Small areas, particularly in old fields which have 

 previously been in alfalfa, are subject to a root rot, or wilt, 2 which 

 toward the end of the summer causes the cotton to die rapidly in 

 well-defined spots. The percentage of the total acreage thus affected 

 is small, and the disease does not appear to spread rapidly through 

 the soil or to be a serious factor in production when a suitable rota- 

 tion of crops is followed. 



The cotton seedlings are also subject to a disorder known as leaf- 

 cut, 3 which is apparently a physiological derangement not asso- 

 ciated with a parasitic organism. The symptoms are mutilation of 

 the leaves and sometimes the abortion of the growing point of the 

 stem, resulting in the malformation of the plants most seriously 

 affected. Since the plants are subject to this disorder only while 

 very young, the system of late thinning eliminates its effects by 

 permitting the " chopping " out of the malformed plants. 



CONDITIONS OF SUCCESSFUL EGYPTIAN-COTTON PRODUCTION. 



The experience gained in connection with the establishment of the 

 community growing of Egyptian cotton in the Salt River Valley 

 makes it possible to formulate the conditions which appear to be 

 indispensable to the successful production of this crop in the United 



1 Cook, O. P. A -wild host plant of the boll weevil in Arizona. In Science, n. s., v. 37, 

 no. 946, p. 259-261. 1913. 



Bailey, Vernon. The wild cotton plant (Thurberia thespesioides) in Arizona. In Bui. 

 Torrey Bot. Club, v. 41, no. 5, p. 301-306, 2 fig. 1914. 



Coad, B. R. Relation of the Arizona wild cotton weevil to cotton planting in the arid 

 West. U. S. Dept. Agr. Bui. 233, 12 p., 4 pi. 1915. 



2 The identity of this disease has not yet been established. 



3 Cook, O. F. Leaf-cut, or tomosis, a disorder of cotton seedlings. In U. S. Dept. Agr., 

 Bur. Plant Indus. Circ. 120, p. 29-34, 1 fig. 1913. 



