INSECT INJURY TO COTTON SEEDLINGS ^ 



By B. R. CoAD and R. W. Howe, Entomological Assistants, Southern Field Crop 

 Insect Investigations, Bureau of Entomology 



INTRODUCTION 



The present work deals with leaf mutilation of cotton seedlings 

 {Gossypium spp.) caused b}^ insects. The observations were made in 

 the vicinity of Tallulah, La., during the spring of 191 5. Such injury to 

 cotton seedlings is probably found throughout the entire area of cotton 

 cultivation in the United States. The senior author has noted it in 

 many parts of Texas, both the drier and more humid portions, in Louisi- 

 ana, and in Arizona on irrigated cotton. Since these localities approxi- 

 mate the extremes of rainfall, temperature, and sunshine under which 

 cotton is cultivated, it is reasonable to expect the injury at almost any 

 place. 



CHARACTER OF INJURY 



The injury varies much in appearance and intensity, but all of the 

 examples which have come to the attention of the authors have certain 

 more or less constant characteristics. This is frequently noticed as soon 

 as the seedUngs appear above the ground, although it may not appear 

 until later. The time of the cessation is also variable, but it does not 

 seem to continue after the plants reach a height of 10 to 12 inches and 

 usually stops much earlier. In the vicinity of Tallulah this injury is 

 seen from the first sprouting of the plants until the latter part of May. 



The first appearance is characterized by irregular holes appearing in 

 the cotyledons. These vary from small holes through the leaf or small 

 marginal incisions to almost complete loss of the leaf. Following this 

 the later leaves are attacked in the same manner, with all possible varia- 

 tions in the type and degree of the injury. In some cases the terminal 



bud may be lost. 



LABORATORY STUDIES 



Efforts were made to secure growing plants at the earliest possible 

 date. For this purpose cotton seed was planted in boxes and pots in the 

 laboratory during the very early spring, but lighting facilities were so 

 poor at this season that the plants failed to thrive. The first healthy 

 seedlings which were secured sprouted in the laboratory hotbed March 

 16 from seed planted in the middle of February. Seed planted in another 

 part of this hotbed on March 5 sprouted well a little later. This hotbed 



' The investigations upon which this paper is based were conducted under the direction of Mr. W. D. 

 Hunter, in Charge of Southern Field Crop Insect Investigations. Bureau of Entomology. 



Journal of Agricultural Research, Vol. VI, No. 3 



Dept. of Agriculture, Washington, D. C. Apr. 17, 1916 



de K— 29 



(129) 



