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Performance of Commercial Cotton Cultivars under Elevated Densities of Tobacco Budworm

USDA-ARS, Crop Science Res. Lab., P.O. Box 5367, Mississippi State, MS 39762.

^* Corresponding author.

The development of improved cultivars is essential for continued economic production of cotton, Gossypium hirsutum L. Information is limited on how different cotton cultivars compare under elevated densities of tobacco budworm, Heliothis virescens (F.), an economically important cotton pest. Seven field tests were conducted between 1988 and 1992 to evaluate cotton cultivars grown under elevated densities of tobacco budworm (TBW). Cultivars were grown under two regimes: (i) artificial elevated infestation, w/TBW, and (ii) elimination of tobacco budworm, w/o TBW. Elevated densities of TBW (w/TBW) significantly reduced yields compared with w/o TBW, but reduction varied among years and tests. The regression equation for lint yield w/TBW on lint yield w/o TBW was Y = –111.0 + 0.6X. Thus, for every 1.0 kg of lint yield increase per hectare due to cultivar improvement, the corresponding increase under artificial TBW infestation was only 0.6 kg. The regression coefficient for lint percentage on lint yield w/o TBW was Y = 30.85 + 0.006X. These data show that cotton breeders have developed high-yielding cultivars, but that progress is still needed in the development of resistance to the tobacco budworm injury. They also show that, as cultivars with higher yield potential were developed, these cultivars were better able to tolerate damage by the tobacco budworm. The parity between yield increase per se and yield under elevated densities of tobacco budworm is not 1.0:1.0, but rather 1.0:0.6. This is a useful and practical level of parity.

Received for publication December 12, 1994.