132 Journal of Agricultural Research voi. vi, no. 3 



This frame was first erected April 26 and on April 30 the first seedlings 

 appeared above the ground. Of the 18 which sprouted this first day, 5 

 showed injur3^ On May i, 9 of the 45 seedlings showing above the 

 ground were injured, while on May 3, 10 out of 50 were injured. On 

 May 4, 16 out of 70 and on May 5, 22 out of 70 were injured. These 

 observations were continued until May 8 and new seedlings were injured 

 practically every day. 



On May 8 a second test of the same sort was started. In this case, 

 however, the cotton row was covered just before sprouting with heavy 

 pasteboard boxes, i foot square and 8 feet long. These boxes were cov- 

 ered with several layers of 8-ounce duck and were only removed from 

 over the plants during the hotter part of the day. Minimum thermom- 

 eters were arranged under the boxes and in the open in the same manner 

 as that just described in the preceding test. In this case considerable 

 differences in the nightly minimum temperatures were noted. It was 

 usually from 3 to 6 degrees warmer under the box than in the open. On 

 May 12 the first seedlings appeared, and of the 39 in sight, 3 showed 

 injury to the leaves. This test was continued six days longer and the 

 injury continued to appear. 



For comparison with the seedlings growing in the garden and hotbed, 



a number of seeds were planted at intervals in pots and crocks containing 



soil sterilized by baking. Part of these were allowed to remain exposed 



in the open, while others were placed in screen, cages. In the hundred 



or more seedlings grown in this manner not a single sign of injury was 



found, whereas the injury was appearing abundantly on plants growing 



in the garden and hotbed at this same time. From this it seemed quite 



evident that the cause of the injury was located in the soil which had 



not been baked. 



FIELD OBSERVATIONS 



As the injury was appearing in the various fields at this same time, 

 efforts were made to learn its extent and to discover any insects which 

 might cause the lesions. In these studies all insects which were known 

 to be leaf feeders were noted and an attempt was made to secure positive 

 samples of their injury to cotton. On April 19 four small lepidopterous 

 larvae were found feeding upon the leaves of cotton seedlings at a plan- 

 tation near Tallulah. The injury which they were producing was 

 apparently identical with that already noted. These larvae belong to 

 the family Liparidae and are commonly known as "tussock moths" 

 (H enter ocampa leucostigma Smith and Abbot) . On this same date three 

 larvae of the same species were found feeding on the seedlings in the 

 hotbed and one was found in the laboratory garden. Following this 

 the field examinations showed a considerable number of these larvae to 

 be present around Tallulah, and associated with them were found several 

 species of cutworms and "measuring worms." All produced nearly the 

 same type of injury to the seedlings. 



