424 



sufficient Information, improvements In such equipment have been based largely 

 on an Intuitive feeling rather than sound knowledge.' This work has shown the 

 effects of square area, dynamic pressure, and square orientation angle on both 

 the net lift and resultant forces. The results indicate that the zero square 

 orientation angle (bracts upwind) created the largest resultant forces and the 

 180 degree orientation angle (bracts downwind) the largsst net lift forces. 

 For the latter position, the larger squares produced fewer positive net lift 

 forces than the smaller squares. For design purposes, the horizontal air 

 velocity should be 58 fps or greater. A resultant forces coefficient-Reynolds 

 number relationship was not established due to considerable scatter in the 

 data and the narrow range of Reynolds numbers encountered. 



833. Smith, J. W. ; Scott, W. P.; and Parencia, C. R. 1978. Predator-prey 



ratios for control of Heliothis species on cotton. Proc. 1978 Beltwide 

 Cotton Prod. Res. Conf., pp. 111-113. 

 For many reasons including resistance problems, residues, and the increas- 

 ing cost of insecticides, cotton insect control is in a period of transi- 

 tion from almost total reliance on chemicals to pest population management. 

 But for pest management, knowledge of the crop ecosystem is essential. 

 Within field, this means information about the cotton plants, weeds, soil 

 and its biota, pest species with their associated natural diseases and 

 mortality due to beneficial insects, and the influence of man. Moreover, 

 a multitude of other interacting factors must be understood such as the 

 effect Or other nearby agricultural crops, woods, streams, and weedy un- 

 cultivated areas. The use of beneficial arthropods as a part of cotton 

 pest management has engendered considerable discussion, but practical in- 

 formation is lacking. In view of the lack of necessary information, re- 

 ^archers in USDA are particularly interested in determining the role of 

 entomophagous arthropods in controlling Heliothis spp. in cotton pest 



