The susceptibility of cotton to spring emergence of pink bollworm (PBW) was evaluated for a variety of planting dates in Pinal Maricopa, LaPaz and Yuma counties using historical climate records and heat-unit-based models that predict PBW emergence and cotton development. Early planted cotton proved most susceptible to the PBW emergence, however, cotton type (shoe vs. long staple) and springtime weather conditions both played an important role in overall susceptibility.

Field experiments conducted in 1989 comparing effects of planting date and irrigation termination date on pink bollworm in both in- season and overwintering infestations indicated different responses depending upon the location and type of cotton. Tests were located at: Yuma Agricultural Center; Marana Agricultural Center; and Maricopa Agricultural Center. Infestations at Yuma ranged from 0% at early flowering to 80% infested bolls prior to harvest. Marana had equally high infestations at the end of the season, while Maricopa had the lowest infestations ranging from 2% to 5% for Pima and 3 %-17% for Upland. Planting date or species of cotton did not affect early infestation. Data comparing plots for overwintering infestations are still being evaluated. Continuous insecticide treatments were made at all locations after squaring began.

Cotton cultivars and germ plasm lines were screened for resistance to pink bollworm. Sixteen advanced strains were selected for resistance to pink bollworm and/or high yield potential. In a regional early maturing germ plasm lines test, only the short- season check had less seed damage caused by pink bollworm than did the long-season check. Five lines yielded more lint than both checks. In a Pima test, Pima S-6 nectariless had 14% less seed damage than Pima S-6. Seven pink-bollworm-resistant germ plasm lines will be released in the near future.

Ethephon applied at rates of 0.50 or 0.75 lb AI/acre removed early-season squares and delayed initiation of pink bollworm, Pectinophora gossvpiella (Saunders) infestations and reduced the number of infested bolls on early-season fruiting branches, without affecting yield except for ethephon at 0.751b AI /acre at one location. Higher rates of application reduced yields. In most cases, ethephon treatments delayed flowering but plants compensated for removal of early- season squares and equalled or surpassed accumulated flowering of untreated control plants later in the season.

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The susceptibility of cotton to spring emergence of pink bollworm (PBW) was evaluated for a variety of planting dates in Pinal, Maricopa, LaPaz and Yuma counties using historical climate records and heat - unit -based models that predict PBW emergence and cotton development. Early planted cotton proved most susceptible to the PBW emergence, however, springtime weather conditions also played an important role in determining overall susceptibility. Growers wishing to incorporate planting date as one aspect of PBW management should keep abreast of early season weather conditions.

Cotton fields treated with Gossyplure pheromone for pink bollworm, Pectinophora gossypiella (Saunders), management were surveyed to evaluate the effectiveness of the pheromone treatments. Fields were randomly chosen within four separate areas of the Parker Valley and Palo Verde Valley and sampled weekly for presence of pink bollworm (PBW ) larvae. No differences were found in cotton yields between fields treated with pheromone and non- treated fields.

Development and reproduction of pink bollworm were studied in relation to four cotton cultivars. Larval developmental times were shortest on pima cotton and longest on a resistant okra-leaf variety (WC-12NL). Prepupal and pupal developmental times were generally unaffected by cultivar. Larval establishment and survival did not differ significantly among cultivars. Female moths laid fewer eggs on pima bolls early in the season and fewer eggs on the okra-leaf cultivar on a season -long basis in comparison with two conventional upland cultivars. Fecundity of adults from the four cultivars varied little but was generally highest in adults from larvae reared on pima cotton. Results have implications for predicting pink bollworm phenology and population development in different cultivars.

Different planting and termination dates of Pima S-6 and Upland (Deltapine 90) cotton (Gossypium barbadense L. and hirsutum L. respectively) were tested for their effects on pink bollworm (Pectinophora gossypiella) infestations. Tests were conducted during 1989 and 1990 cotton seasons at the University of Arizona Yuma Valley Agricultural Experiment Station. Planting dates indicated little effect on early season infestations of pink bollworm for either cotton. However. irrigation termination had the greatest effect on late season infestations. In 1989. heat unit (degree day 12.8/30° C. lower and upper thresholds) accumulations were several days earlier than 1990, due to a very warm year. Pheromone trap counts indicated higher populations in 1989 than 1990; however. infestations in the field were similar between the years. Infestations dramatically increased during July through September, indicating that a longer cotton season with actively growing fruit, results in a continued population increase. The termination dates affected the amount of fruiting structures left in the field and thereby affected infestations of overwintering larvae in the field. Termination date had a dramatic effect on the % bolls infested with overwintering larvae and the density of overwintering larvae /m.

Responses of five field -collected populations of the pink bollworm. Pectinophora gossypiella (Saunders). from Arizona and southern California. were compared with those of a standard. susceptible -laboratory strain. Field strains showed less than twofold difference in response to azinphosmethyl at LD₅₀ but had variable levels (1.3- to 18.3-fold) of response to permethrin. Strains from Yuma and Phoenix (Arizona) and Westmoreland (California) had highest levels of resistance to permethrin.