This study was undertaken to determine the biology and ecology of Chirothrips falsus Priesner and its relationship to the typically poor seed set of black grama. The work was conducted on native range, principally at the University Ranch near Las Cruces, and on irrigated plots at the Middle Rio Grande Branch Station near Los Lunas. Tests showed that seed yields can be significantly increased by thrips control. SD 4402 (Telodrin) gave the best control and the greatest increase in seed yield, although dieldrin and Guthion gave good control and substantial seed increases. The granulated systemics, di-syston and phosphamidon, were significantly inferior to dieldrin spray for thrips control and the resulting seed increase of black and blue grama. A series of three spray applications of Bidrin at weekly intervals, begun shortly before the grass began to bloom, reduced thrips numbers and increased seed yields more effectively than similar schedules begun one and two weeks earlier.