INSECT PESTS 231 



attack tobacco, cotton, beans, peas, Irish potato, oats, cocklebur, dew- 

 berry, evening primrose, crab grass, tomato, vetch and many other plants 

 (77,49). 



Thrips attack peanut plants ~most severely while they are small. The 

 upper surface of the developing leaflets are rasped by the insects and as 

 the leaflets unfold they have a scarred and even deformed appearance. 

 Farmers often refer to damaged peanuts as "possum-eared," a term quite 

 suggestive of the appearance of the leaflets. The plants fail to grow prop- 

 erly. Where infestations are severe, stunting occurs and the damaged 

 peanuts recover slowly and perhaps incompletely. Thrips damage usually 

 disappears or becomes less acute, concurrently with increased rate of 

 growth of the plants, the more rapid growth probably resulting from 

 the nitrogen fixation and favorable climatic conditions. 



Thrips injury has been referred to as "pouts." The peanuts, in farmer 

 language, were said to pout until blooming time when growth became 

 more rapid (115). Another condition caused by potato leaf hopper has 

 also been called "pouts." It is apparent that the term "pouts" is not 

 specific, and should not be used to designate thrips injury ( 133) . 



It has been assumed by many that peanuts grow out of the stunted 

 condition resulting from thrips infestation and little permanent harm re- 

 sults. Recent studies discount this view. As a result of experiments at 

 Beltsville, Maryland, it was concluded (116) that thrips reduced the yield 

 of peanuts as much as 2)7 percent. Substantial increases in yields were 

 reported, in some instances, from control of thrips in Maryland and 

 Virginia (120). The author (7) found that control of thrips on runner 

 peanuts resulted in the setting of fruit earlier than on undusted plants, 

 although most of the early crop was lost in the ground at harvest. It ap- 

 pears that permanent damage may result from thrips infestation resulting 

 in decreased yield of peanuts. 



The degree of damage doubtless varies with the type of peanuts, fer- 

 tility of the soil, and weather conditions as well as with the insect infesta- 

 tion. Apparently, damage is more severe and recovery slower on poor 

 than on fertile soils. Additional research is needed to clarify these points. 



Description of stages. Two forms of F. fusca adults occur (49), one 

 with shorter wings than the other. The relative length of wings varies also 

 with the distention of the abdomen at the time of measuring. It is not 

 clear from the literature whether the original description of the insect 

 (69) was of the short- or long-winged type. In 1905, however, the insect 

 was described (70) under the name Euthrips nicotiannae from long- 

 winged females, These descriptions are given belpw ; 



