Phenology of fruit development in different maturity types of Upland cotton, Gossypium hirsutum L

Abstract

Fruit development of Upland cotton cultivars in three maturity groups (based on time of boll opening) were evaluated at two planting dates and two planting densities to determine the components contributing to early fruit development as a means for escaping insect damage and hastening crop maturity. Low temperatures delayed fruit development in early-planted cotton and the potential benefit from early planting was partially lost. Short main stem internodes, fruiting at a lower main stem node, and fewer vegetative branches resulted from early planting. Closely spaced plants generally had fewer branches, especially monopodia. One variety responded more favorably to close spacing than the others. The medium-maturing variety was found to flower earlier than the early-maturing variety, suggesting that it might be more likely to escape damage by the boll weevil. The early-maturing variety, derived its earliness from a short boll maturation period. The thermal unit equation-sum of daily maximum temperature (up to 29 C) plus daily minimum temperature (down to 22 C) divided by two, gave a result of 1820 thermal units which provided an excellent estimate of date of first flower. Early boll opening does not always result from early flowering; thus, early maturity is not necessarily indicative of a cultivar's potential for escaping damage by the weevil.