A germplasm line of cotton, Gossypium hirsutum L., designated WC-12NL, was grown for 2 seasons in replicated, 0.8 ha plots at two locations and compared with a check cultivar, 'Deltapine 61', for resistance to pink bollworm, Pectinophora gossypiella (Saunders), lint yield, earliness, and fiber properties. The WC-12NL line carries the nectariless and okra-leaf traits and is early maturing, based on sequential harvests of seedcotton, whereas Deltapine 61 is nectaried, with regular leaf shape, and is later in maturity. Cotton bolls at both locations, Brawley, CA and Maricopa, AZ, were checked for pink bollworm eggs. The two cottons were treated with insecticide separately when egg infestations on bolls exceeded the economic threshold (8% at Brawley and 17% at Maricopa). Half of each plot was treated with ethephon ca. 2 weeks after last irrigation. As soon as bolls started to open, seedcotton was harvested once a week.

At Brawley, Deltapine 61 was treated with insecticide nine times in 1986 and seven times in 1987, whereas WC12NL was treated six and four times, respectively, for pink bollworm control. At Maricopa, Deltapine 61 was treated three times both years, and WC-12NL was treated twice in 1986 and once in 1987. Insecticide use was thus reduced from 33 to 67% on WC-12NL. In spite of increased insecticide use, percent seed damage and number of pink bollworm per boll were significantly higher in the Deltapine 61 plots than in the WC-12NL plots both years and at both locations. Lint yield in plots untreated with ethephon, over seasons and locations, was significantly higher for WC-12NL (1,496 kg/ha) than for Deltapine 61 (1,342 kg/ha), but lint yields were not significantly different in ethephontreated plots, 1,375 and 1,332 kg/ha, respectively, for WC-12NL and Deltapine 61. The WC-12NL line was significantly earlier than Deltapine 61 in treated and untreated plots, and over seasons and locations. The fiber of WC-12NL was shorter and weaker than that of Deltapine 61 at both locations in 1986 (1987 fiber data not available). When the fiber samples were classed, however, WC-12NL was not discounted relative to Deltapine 61 and thus its fiber would have received the same price in the marketplace.

Our results are encouraging because they show that pink bollworm resistant traits can be incorporated into a cotton that is competitive in yield potential with a current cultivar. The inferior fiber properties of WC-12NL are disappointing but other pink-bollworm resistant lines having fiber properties equal to cultivars are in an advanced stage of development.