PEODUCTTON OP AMERICAN EGYPTIAN COTTON. 25 



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 bollworm, which has recently played havoc with the cotton 

 crop of Egypt and of Mexico, was discovered in 1917 at a few 

 localities in Texas, but has not been observed in Arizona and Cali- 

 fornia. It is to be hoped that measures taken by the Federal Horti- 

 cultural Board will prevent its becoming, established in the United 

 States. 



A sucking bug, of the group known as "cotton stainers," has 

 recently caused some damage to cotton in Arizona. 1 



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, oy 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, 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 rotation of crops is 

 followed. ' 



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

 cut, 2 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 v 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 



Bailey, Vernon. The wild' cotton- plant (Thurberia thespesioicltfs) in Arizona. In Bui. 

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



Coad, B. It. 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. 



1 Morrill, A. W. Eighth Ann. Rpt., Arizona Comm. Agriculture -and Horticulture, 191(5, 

 pp. 46-48. 



2 Cook, 0. F. Leaf-cut, or tomosis, a disorder of cotton seedlings. In U. S. Dept. Agr., 

 Bur. Plant Indus. Cir. 120, pp. 29-34, 1 fig. 1913. 



