The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

During the past two years we developed an egg sampling plan for the pink bollworm (PBW) to provide a more accurate index of moth (target stage) activity than conventional larval sampling. The plan requires that only the presence or absence of eggs laid on bolls be determined to decide when insecticide treatments are needed. Our objective in 1986 was to determine whether egg sampling vs. conventional treatment criteria (e.g., larval infestations, trap catches of male moths, and /or fixed -spray intervals) provided more optimal timing of insecticide applications in a 640-ac field test. Implementation of the egg sampling method in 8 of the 16 fields resulted in an average 35 percent seasonal reduction in insecticide use when compared to conventional methods. Despite the reduction in insecticide use, PBW larval infestations were not significantly different (P = 0.45) in fields samples for eggs vs. fields sampled for larvae from June to September. Yields were also not significantly different (P = 0.40) between the two sets of fields.

Prep applied to cotton on 15, 23, and 29 September reduced numbers of squares, immature green bolls < 1 inch in diameter, and accelerated mature boll opening. Reduced cotton fruiting forms in Prep- treated plots resulted in reduced boll weevil population development.

No description available.

A nectariless, okra -leaf germplasm line of cotton, Gossvpium hirsutum L., designated WC-12NL, was compared with a nectaried, regular leaf commercial cultivar, 'Deltapine 61' (DPL-61) at two locations, Maricopa, AZ and Brawley, CA. At Maricopa, two and three insecticide applications were required for control of pink bollworm, Pectinophora gossypiella (Saunders), on WC-12NL and DPL-61, respectively. At Brawley, six and nine applications were required. Lint yield of WC-12NL was 30% higher than that of DPL-61 at Maricopa, while at Brawley, lint yields were about equal.

Ninety-nine germplasm lines and a resistant check line of cotton, Gossypium hirsutum L., were infested artificially in the field with eggs of pink bollworm (PBW), Pectinophora gossypiella (Saunders), and evaluated for an antibiosis type of resistance to the insect and also for yield potential. All 99 lines came from crosses of well -adapted cultivars, or the nectariless, or nectariless-okra-leaf versions of those cultivars, with previously identified sources of antibiosis (a type of resistance that affects the growth and development of the insect once inside the boll). Twenty-three of the 99 were selected for low PBW damage or for a combination of high lint yield and low damage.

The development of populations of pink bollworm, Pectinophora gossypiella (Saunders) in 0.003 ha field cages containing 'Deltapine 61' (DPL-61) or a closely related nectariless cultivar 'Deltapine NSL' (DPL-NSL) was studied at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ. Boll infestations were significantly lower in cages of DPL-NSL and total catches of moths in gossyplure-baited Delta traps at the end of the season were lower in these cages. The overall seasonal increases were 15.3- fold for DPL-NSL and 21.4 fold for DPL-61, a highly significant 29% reduction for DPLNSL.

Populations of the western flower thrips, Frankliniella occidentalis (Pergande), were observed in field plots of cotton, Gossypium hirsutum L., Deltapine-61 (DPL-61) and WC-12NL, a nectariless, okra -leaf variety in the DES -56 germplasm line, and in fields of Stoneville-825 (ST-825), DPL-61, and DP -77 in Maricopa, AZ, during June - August 1987. The thrips were collected from plant terminals; square shed was observed on the upper five nodes of plants; and the bractedness (three-bract = normal) of matchhead-size squares was determined from samples of squares picked from the plants and from shed squares beneath the plants. Shed squares were microscopically examined to determine the cause of shedding. Populations of Lygus hesperus Knight were determined from sweep-net samples.

An early -maturing, nectariless, okra-leaf germplasm line of cotton, Gossypium hirsutum L., designated WC-12NL, was compared with a full- season, nectaried, regular -leaf cultivar, 'Deltapine 61' (DPL-61) over two locations, Maricopa, Arizona (AZ) and Brawley, California (CA), and two seasons, 1986 and 1987. Half of each plot was treated with ethephon ( =Prep) when the crop was approximately 60% open. Lint yields were higher in WC-12NL than in DPL-61 at AZ, but not at CA. WC-12NL was earlier maturing than DPL-61, but the difference was greater in untreated than in ethephon-treated plots and at AZ than at CA. From 33 to 67% less insecticide was needed to control pink bollworm, Pectinophora gossypiella (Saunders), on WC-12NL than on DPL-61. Pink bollworm infestations were also significantly lower in bolls of WC-12NL.