Economic evaluation of boll weevil (Coleoptera: Curculionidae) management options for early-planted, irrigated cotton in the Texas rolling plains

A full-season, threshold-based insecticide control program, primarily for boll weevils, Anthonomus grandis grandis Boheman, was compared with no insecticide control in irrigated cotton in the northern Texas Rolling Plains from 1993 to 1995. These 2 insecticide-use options were compared in 3 cotton varieties (Paymaster HS-26, TAMCOT HQ95, All-Tex Quickie) and 2 row spacings (76 cm and 102 cm). Cotton was planted in late April-early May each year, which is an earlier planting time than the preferred period of late May-early June. Net returns per hectare were calculated for each treatment and used to determine the most cost-effective chemical and row spacing management option for each cultivar. Of the 29 insecticide applications for thrips, boll weevils, bollworms, Helicoverpa zea (Boddie), and cotton aphids, Aphis gossypii Glover, during the 3-yr study, 23 were for management of boll weevils. Boll weevil damage was lowest in HS-26 in the 76-cm spacing and in Quickie in the 102-cm spacing; these cultivars produced fewer squares and bolls in these 2-row spacings, respectively, than did the other 2 cultivars. Average yield and net income were higher in the 76-cm row spacing than in the 102-cm spacing, and yield and income were higher in HS-26 and HQ95 than in Quickie in both row spacings. Average yields were higher in treated plots, but average net income was higher in untreated cotton. In the 76-cm row spacing, highest net return was obtained from untreated Quickie ($161.10/ha), whereas in the 102-cm row spacing, highest net returns were obtained in treated HS-26 ($174.47/ha) and untreated HQ95 ($167.25/ha). In treated and untreated cotton, the break-even yields were 697 and 514 kg lint per hectare, respectively. In treated plots, yields for HS-26 in both 76- and 102-cm row spacings and for HQ95 in the 76-cm row spacing exceeded the break-even yield. Yields in all untreated plots, except Quickie in the 102-cm row spacing, exceeded the break-even yield. Based on comparisons of net returns between treated and untreated plots of each cultivar, only HS-26 in the 102-cm row spacing responded adequately to a full-season insect control program. In all other comparisons, net returns were numerically higher in untreated plots. Insecticidal control should be tailored to the cultivar and row spacing used.