Seven commercial ultra narrow row (UNR) cotton fields were monitored on a weekly basis in Maricopa County, AZ in 1999. Varieties of Delta Pine and Sure Grow were planted from April 15 to June 1 and reached cut-out after accumulating 1913 to 2327 heat units after planting. Average yield for UNR cotton was 2.1 bales per acre which was 0.4 bales per acre lower than the five year average for cotton planted on conventional row spacings. Fiber quality from gin records for 801 bales had average micronaire readings of 4.54 and grades of 11 and 21 for 74% of bales. Discounts for extraneous matter (bark, grass, and cracked seed) was 5.4% and average strength (34.8) and staple lengths (27.12) were in acceptable ranges. Total cash costs ranged from $450 to $705.

A field trial was established during the 2001 growing season as part of the statewide Upland Cotton Variety Testing Program. This trial was located in Thatcher with Dennis Layton Farms as the cooperator. The location was one of eleven around the state. Seven Upland cotton varieties to be evaluated at this location were entered by various cooperating seed companies. A new variety from FiberMax produced the highest yield and also possessed the highest quality fiber making it the variety that would have produced the highest gross income to the producer.

Twelve varieties were tested including three New Mexico Acalas and one Acala from Buttonwillow Research in California, six Roundup Ready varieties, five of which also contained the Bt gene, along with a couple of other varieties were planted including FiberMax 989, which has been the highest yielding variety in the trial for two of the past three years. The highest yielding variety in the trial was FiberMax 989R, the Roundup Ready version of FM 989, with a yield over 950 pounds of lint per acre. 1517-95 and SureGrow 521RR followed in yield. Yields were considerably lower than seen in the previous year’s study (1). Several Roundup Ready varieties were included in this study. Plant mapping data and HVI data are also included in this report.

Twelve varieties were tested including three New Mexico (NM) Acalas and one Acala from ButtonWillow Research in California, six Roundup Ready varieties, five of which also contained the Bt gene, along with a couple of other varieties were planted including FiberMax 989R, the Roundup Ready version of FM 989, which was the highest yielding variety in the trial for two of the past three years. The highest yielding variety in the trial was SureGrow 215BR, the stacked (Bt/Roundup Ready version of SG 125), with a yield near 925 pounds of lint per acre. FM 989R and DP 436BR followed SG 215BR in yield with yields not significantly different from the leader. Yields were slightly lower than seen in the previous year’s study (1). Plant mapping data and fiber quality (HVI) data are also included in this report along with lint value estimates and crop value per acre.

Six New Mexico and California Acala cotton varieties were tested along with three upland varieties with good quality and excellent yield potential in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was DP 655BR with a yield of 1367 pounds of lint per acre. The next highest variety was Fiber Max 989. This latter variety, while not officially classified as an Acala, produced the longest fiber in the study. Yield and other agronomic data as well as fiber quality data are contained in this paper.

Pink bollworm (PBW), Pectinophora gossypiella (Saunders), diapause larval exit from immature green bolls and larval and pupal mortality after exiting bolls, were studied at Phoenix, AZ in the insectary. Diapause larvae exited immature bolls sporadically during January, February, and early March. Thereafter, exit from the bolls was more consistent and highest numbers emerged in late April, May or early June. Larval and pupal mortality were high during January to early February and March, decreased in mid-March through early June, and increased again in mid-June to early August. Larvae remained in immature bolls as long as 319 days after harvest. Moth emergence was significantly correlated to accumulated heat units (12.8 and 30.6°C lower and upper developmental thresholds).

Fifteen lines from 3 different cotton families were compared. Each family had a conventional, non-transgenic standard, as well as 4 other transgenic lines. In some cases, near isogenic lines were available that theoretically only vary from their sibling lines in the presence or absence of one or more transgenes. Each Bt line was evaluated for this trait’s efficacy in controlling pink bollworm under high pressure, artificial infestations. Various agronomic properties were measured including yield, micronaire, ginning properties, and fiber quality. Heat tolerance, a key goal for Arizona adapted varieties, was also evaluated using a flower rating system. The Cry1Ac gene performed flawlessly in preventing PBW larval development when expressed alone (Bollgard®) or in combination with Cry2Ab (Bollgard II®) (i.e., 100% effective, 0 large larvae from 30185 PBW entry holes). In all cases where large larvae were found in Bollgard or Bollgard II plots, the plants bearing the infested bolls were not expressing the Cry1Ac toxin. Thus, those few times when larvae were found, it was due to contaminants in the seed supply. The novel Cry2Ab only expressing plants, produced for non-commercial testing purposes, were also very effective in controlling PBW large larval development; however, control was less than the Cry1Ac-expressing lines (99.622%, 3 large larvae from 4436 entry holes). The ramifications of this are discussed. In terms of agronomic performance, the transgenic lines performed similarly within families and usually not different from the conventional standards. In some cases, statistically different results were found; however, in all but a few cases, performance parameters were superior in the transgenic lines when compared to the conventional standard. Even so, there are instances where characteristics of the transgenic line were inferior to the conventional standard, especially in some fiber properties. Heat tolerance was again similar throughout 2 of the cotton families (SG125 and DP50). However, for the DP5415 family, 3 of the 4 transgenic lines outperformed the conventional standard. More testing under more environmental conditions is warranted before firm conclusions are drawn.

Evaluations of the non-target effects of transgenic cotton, modified to express the insecticidal proteins of Bacillus thuringiensis (Bt), have been underway in Arizona since 1999. Here we provide a preliminary report of replicated field studies conducted from 1999 to 2001 to examine comparative affects of Bt cotton on natural enemy abundance, overall arthropod diversity, and natural enemy function. Analyses completed to date indicate that natural enemy abundance and overall arthropod diversity are affected by use of additional insecticides for other pests, but not directly by transgenic cottons in comparison with non-transgenic cottons. Further studies suggest that natural enemy function, measured as rates of predation and parasitism on two key pests (Pectinophora gossypiella (Saunders) and Bemisia tabaci (Gennadius)) of cotton in the western U.S., is unaffected in Bt cotton. Our preliminary results suggest that use of transgenic cotton may not have any unintended effects and represents an extremely selective pest control method that could facilitate the broader use of biological control and IPM in an agricultural system long dominated by the use of broad-spectrum insecticides.

Studies were conducted to follow seasonal susceptibility of feral pink bollworm (PBW), Pectinophora gossypiella (Saunders) larvae to NuCOTN 33B (Bt) and Deltapine (DPL) 5414 in furrow and furrow plus supplementary drip-irrigated cotton field plots. Laboratory bioassays of laboratory - reared PBW larvae to flower buds and bolls and cabbage looper (CL), Trichoplusia ni (Hübner), larval mortality feeding on DPL 5415 and Bt cottons leaves were also conducted. Cry1Ac insect toxic protein contents in the different plant tissue were determined by Enzyme Linked ImmunoSorbent Assay (ELISA) throughout the season to compare in relation to PBW and CL mortality data. Irrigation type had no effect on PBW or CL larval mortality parameters measured. DPL 5415 bolls had 0.15 feral live larvae per boll and no dead larvae per boll compared with no live and 0.12 dead feral larvae per Bt boll. Whole plant samples showed 0.5 to 8.6% live larvae boll infestations compared to no live PBW life stages and no exit holes for Bt bolls. No PBW larvae survived on day four following bioassay infestation of one-third grown Bt flower buds with PBW neonate larvae as compared to 90% larval survival on DPL 5415 flower buds. Immature bolls harvested in the field and artificially infested with PBW larvae in the laboratory showed averages of 3 to 52% live larvae per boll, all in fourth instar of development, for DPL 5415 bolls compared to no live larvae, no development beyond the first instar, and no exit holes for Bt bolls. Cry1Ac protein level in flower buds were 0.11 to 0.16 ppm and 0.14, 0.11 and 0.05 ppm, in each case, per wet weight gram of boll tissue in bolls during the season. For CL leaf bioassays, larval mortalities after 7 days feeding on Bt leaves were variable ranging from 82 to 94% from node 8 on 61 and 82 days after planting (DAP) to 32, 38 and 7% on leaves from node 16 on 82, 117, and 159 DAP, respectively, and 28 and 6% on leaves from node 24 on 117 and 159 DAP. Cry1Ac amounts were 0.96 and 0.85 ppm (wet wgt per g of Bt leaf tissue), from leaves from node 8 (61 and 82 DAP), 0.53, 0.50 and 0.22 ppm (node 16, 82, 117, and 159 DAP) and 0.44 and 0.18 ppm (node 24, 117 and 159 DAP). Numbers of cotton bolls, lint and seed per acre were significantly greater from plots that were furrow plus drip irrigated as compared to furrow irrigated alone. DPL 5415 and Bt cotton yields were not significantly different.

Genetically modified cotton expressing the Cry1Ac toxin has been used in Arizona since 1996 with exceptionally positive results in terms of economic returns to growers and reductions in insecticide use in cotton. Since 1995, average insecticide use in Arizona cotton has declined from greater than six applications per acre to less than two in 2000. Bt cotton has contributed greatly to these savings to growers, as have insect growth regulators used for whitefly control. Collections of pink bollworm, Pectinophora gossypiella, made in 1997 and subsequently exposed to Cry1Ac in the laboratory from 1998 to 2000, yielded a laboratory strain with susceptibility to Cry1Ac reduced 1,000 to 3,000- fold, relative to highly susceptible field populations. Unparalleled measures have been taken to detect and manage this resistance. In this report we summarize results of statewide monitoring of pink bollworm susceptibility to Cry1Ac conducted from 1997 to 2000, and results of field evaluations of the effectiveness of Bt cotton from 1995 to 2001. Susceptibility of Arizona pink bollworm to Cry1Ac, increased from 1997 to 2000. Mean corrected mortality in 1μg/ml Cry1Ac assays was 57.4% in 1997, 90.6% in 1998, 97.9% in 1999 and 97.4% in 2000. Mean corrected mortality in bioassays of 10 μg/ml also increased: it was 94.1% in 1997, 99.9% in 1998, 100% in 1999 and 100 % in 2000. Field performance of Bt cotton in 2000 continued to be excellent at 39 locations throughout Arizona cotton at which paired Bt and non-Bt fields were evaluated. Whereas non-Bt cotton fields had mean infestations of over 15% infested bolls, Bt cotton fields averaged less than 0.15% infested bolls. Thus, after six years of intensive use of Bt cotton in Arizona, pink bollworm populations show no signs of being resistant to Bollgard cotton. Indeed, for reasons that are not understood at this time, they have been found to be significantly more susceptible to the Bt toxin in Bollgard cotton at the end of the 2000 season than they were in 1997.