Tobacco budworm (TBW), Heliothis virescens (F.), larvae were highly susceptible to feeding on Bt cotton leaves or flower buds with 100% and 96% mortality occurring within 4 days, respectively, compared to an average mortality of 95% for cabbage looper (CL), Trichoplusia ni (Hübner), and 57% for beet armyworm (BAW), Spodoptera exigua (Hübner), after 14 days feeding on Bt leaves. Larval weights, of CL and BAW after 7, 10, or 14 days of feeding on Bt leaves were lower compared with those feeding on non-Bt cotton leaves. BAW, CL, and TBW larvae consumed significantly less Bt leaf area per feeding day compared with DPL 5415.

Season-long protection from pink bollworm (PBW), Pectinophora gossypiella (Saunders), damage has been outstanding each year, since 1996, in NuCOTN 33B7 (Bt) commercial cotton plantings in Arizona. Cotton is a perennial plant and whether or not the insect toxic protein was expressed in overwintered Bt cotton was unknown. This could be a consideration in Arizona Bt resistance monitoring in the field since occasional overwintered volunteer cotton plants may occur. In 2002 we studied Cry1Ac levels in overwintered volunteer Bt cotton plants and determined their effects on PBW and tobacco budworm (TBW), Heliothis virescens F., larval mortalities. No TBW larvae survived three-day feeding periods on Bt leaves compared with < 3% TBW larval mortality feeding on DPL 5415 leaves. PBW larval mortality after three-day feeding on flower buds or seven-day feeding on Bt cotton bolls exceeded 98% compared with 40 to 41 % mortality feeding in DPL 5415 fruiting forms. Cry1Ac toxic protein in leaves, flower buds or cotton bolls of overwintered Bt cotton was not significantly different compared with 2002 seeded cotton.

The focus of our 2002 field study was to answer a fundamental question in insect control. Once spraying has begun for a particular pest, when should it stop? In this case, we are faced with the question of when to discontinue sprays for Lygus hesperus in cotton. Cotton is susceptible to Lygus any time there are productive squares on the plant. This study developed a series of worst-case scenarios in which to provide information on timing of the latest possible sprays of economic benefit. By late planting (30 May) varieties from three different maturity groups, we were able to examine Lygus control dynamics just prior to, at, and after cutout — initiation of cut-out was defined as NAWF = 5. We found large differences in yield among the four Lygus chemical termination (LT) treatments. The earliest termination (LT1, 2 weeks prior to cut-out) suffered the largest losses to Lygus, ca. 20–50% of the maximum yield. Conversely, extending Lygus chemical control 1–3 weeks after cut-out (LT3 & LT4) provided no yield benefit whatsoever, regardless of the variety examined. Maximum yields and maximum profits were gained in the LT2, where Lygus controls were continued up to 1 week prior to cutout. Given that there was only 1 week separating the LT1 and LT2 timings, it is clear that timing is absolutely critical. The timing used in this study corresponds with previously established threshold guidelines; treat when there are at least 15 total Lygus with at least 4 nymphs per 100 sweeps. Levels far exceeded this threshold late in the season, yet additional chemical controls after cut-out provided no additional yield or control benefits. Further, we have confirmed that nymphs are the life stage of major concern with, by far, the most capacity to reduce yields. Nymphal reductions were well-correlated with yield enhancement. The best timing (LT2) achieved ca. 93% reduction in nymphal densities during the critical 3- week period around cut-out. In contrast, adult numbers were reduced by only 16% during the same period. These results establish an upper bound for treatment of Lygus, no later than 1 week prior to cut-out; however, more work is necessary to identify if earlier cessation is possible under more normal planting conditions.

We summarize information on the performance of Bt cotton against pink bollworm (PBW), Pectinophora gossypiella, in Arizona following six years of use of this new technology. Monitoring of PBW susceptibility to Bt toxin Cry1Ac was conducted annually since 1997 by collecting insects from ten to 17 cotton fields, culturing strains in the laboratory, and measuring susceptibility to Cry1Ac in diet-incorporation bioassays. Based on survival in discriminating concentration bioassays of 10 μg Cry1Ac/ml of insect diet, resistant PBW were detected in low frequencies at 10 out of 17 Arizona locations sampled in 2001 and ranged from 0.0 to 4.0%. Though significantly more abundant than in the previous three seasons, resistant PBW were statistically less abundant in 2001 than they were in 1997. One collection from Paloma, AZ, had 4.0% survivors (uncorrected, actual survival) in bioassays of 10 μg/ml and samples from Coolidge, Maricopa, and Parker Arizona yielded • 1.0% survivors of this concentration. Susceptibility of a limited numbers of 2001 collections of PBW from California, New Mexico and Texas is also reported. Bioassays of 2002 collections are underway at the time of this writing. In a parallel effort, field efficacy of Bt cotton against PBW was documented at five to 39 Arizona locations per year since 1995 by collecting cotton bolls at seasons’ end and counting PBW and exit holes. In 39 pairs of adjacent Bt and non-Bt fields evaluated in 2001 by the Arizona Cotton Research and Protection Council, mean end-of-season pink bollworm infestation levels were > 15% for non-Bt fields and were < 0.15% in adjacent Bt fields. Thus, field observations indicated that performance of Bt cotton continued to be excellent throughout Arizona in the 2002 season.

Whiteflies and Lygus bugs continue to be key pests of Arizona cotton. Some of our most popular and time-tested chemicals are still providing efficacy toward Lygus or whiteflies when used in a timely manner. However, promising new chemicals may also become available in the near future. Through research, growers can be kept updated on options for successful IPM. An experiment was conducted in order to expand our knowledge of currently available compounds and upcoming advances in insecticide development. In this experiment, 11 different compounds were tested for efficacy and duration of activity against whiteflies, Lygus, or both. Although none were active on Lygus adults, some chemicals were very effective on all stages of nymphs. Orthene® or Vydate® continue to show good results against Lygus but did not yield as high as one new compound. The best performing insecticide against Lygus was flonicamid, a novel chemistry under development by FMC. This insecticide had the best control over Lygus nymphs, was the highest yielding treatment, and required one less spray than other top performing compounds. Among newer chemistries for Lygus control is fipronil (Regent® by BASF), which performed slightly better than Vydate but not quite as effective as Orthene. Another higher-yielding regime included the use of novaluron, a novel insect growth regulator (IGR) scheduled for registration in 2005 (Diamond® by Crompton Corporation). This IGR was tested against whiteflies and Lygus bugs, but in light of yield data, Lygus efficacy should be examined more closely. None of the neonicotinoids were effective against Lygus, but several proved to be promising for whitefly control. Of the neonicotinoids tested and sprayed on threshold, dinotefuran (under development by Valent) showed good activity. The performance of spiromesifin (Oberon®, a new chemistry by Bayer) was similar to dinotefuran but needing one less spray. Intruder® out-performed all whitefly treatments, requiring only two sprays to control whiteflies season-long. Both Intruder or currently used IGRs (Knack® and Courier®) proved to be very effective against whiteflies. All insecticides in this test underwent very rigorous testing under extreme Lygus and whitefly pressures.

The integrated control concept emphasizes the importance of both chemical and biological control for pest suppression in an agricultural system. A two-year field study was conducted to evaluate the selectivity of acetamiprid for controlling sweetpotato whitefly, Bemisia tabaci, in cotton compared with a proven selective regime based on insect growth regulators (IGRs) of pyriproxyfen and buprofezin. Acetamiprid was highly effective in controlling all stages of B. tabaci compared to our untreated control and generally produced lower pest densities than the IGR regime. However, six of 14 taxa of arthropod predator were significantly depressed with the use of acetamiprid compared to our untreated control, including common species such as Geocoris punctipes, Orius tristicolor, Chrysoperla carnea, Collops vittatus, Hippodamia convergens, and Drapetis nr. divergens. Compared to other independent and concurrent studies using mixtures of broad-spectrum insecticides at the same research site, acetamiprid depressed fewer populations of predator taxa in our study, but for those taxa affected, reductions from acetamiprid were larger in many cases. In contrast, only one species was significantly reduced in the IGR regime compared with the untreated control. Predator:prey ratios were generally depressed with the use of acetamiprid compared with both the IGR and untreated control regimes. Parasitism by aphelinid parasitoids was unaffected or depressed slightly in all insecticide regimes compared with the control. Although highly efficacious for whitefly control, our results suggest that acetamiprid is a poor substitute for IGRs currently used in an integrated control program for B. tabaci in cotton.

Lygus hesperus (Knight) has been the number one pest of Arizona cotton since 1998. With advances in the selective management of Arizona cotton’s other two key pests (i.e., Bemisia tabaci and Pectinophora gossypiella), there has been less opportunity for collateral control of this yield-limiting pest. There has also been a new premium placed on locating less disruptive, even selective, control methods that are compatible with existing selective technologies. Our laboratory routinely screens candidate compounds for efficacy against Lygus hesperus under desert conditions. Promising leads are further developed and evaluated in the field for efficacy, spectrum of activity and safety for beneficial arthropods. Our recent findings have identified three compounds with potential for delivering economic control of Lygus hesperus with greater safety for beneficial arthropods than current standards of control. At the same time, our work has importantly identified many compounds that are ineffective against our Lygus, despite reported success against a related species, the tarnished plant bug, Lygus lineolaris (e.g., acetamiprid, imidacloprid, indoxacarb, pyrethroids, thiamethoxam). Flonicamid, a pyridine carboxamide, is under development by FMC in the U.S. This aphicide has shown excellent results in controlling our Lygus in cotton. Novaluron, a chitin inhibitor under development by Uniroyal (as Diamond®) in the U.S., has rate sensitive activity against Lygus in cotton. Metaflumizone (BAS320I), under development by BASF in the U.S., is a semi-carbazone chemistry with significant efficacy against Lygus hesperus. These three or potentially other new leads in insecticide discovery may play an important role in transitioning Arizona cotton growers away from neuro-toxic, broad-spectrum, and disruptive organophosphates and carbamates currently used to control Lygus in cotton. The potential benefits to natural enemy conservation should help stabilize insect pest management in Arizona cotton, thus minimizing the chances of secondary pest outbreaks and costly pest resurgences. Until selective alternatives are found and registered, acephate (e.g., Orthene 97 by Valent USA) and oxamyl (Vydate C-LV by DuPont) remain our standard recommendations for Lygus control in Arizona cotton.

When a product performs better or worse than expectations, there are many biological, ecological, and operational factors that must be examined. Genetic resistance to the pesticide itself is often a concern. The control interval depends on the ecological impact of biotic (e.g., presence and function of natural enemies) and abiotic (e.g., frequency and severity of storms) factors. Timing, rates, and application methods used are also key factors affecting product performance. A four-year study to evaluate pyriproxyfen (Knack®) field performance in Arizona was initiated in 2004, after levels of whitefly susceptibility in statewide surveys were observed to be decreasing. Grower sites in Maricopa, Buckeye, Wellton, and Marana were used. We controlled for major operational factors by using a common timing, rate, and aerial application for each Knack spray. Resistance bio-assays were conducted on progeny of field-collected adults, pre- and post-spray. New eggs were marked in-field prior to spraying and examined in the field and lab in order to isolate Knack-associated mortality caused by direct toxicity as well as by ecological factors (e.g., bioresidual). Nymphal bioassays were used to evaluate metamorphosis inhibition. Population trends were estimated using standard sampling methods. Appropriate check plots were compared to the Knack treatment. Study results suggest Knack field performance and pyriproxyfen resistance has not changed significantly among the years or locations examined to date. In 2005, many struggled to gain control over whitefly populations. This work indicated that Knack performance and resistance parameters were within the range expected for the last several years. However, operational and ecological barriers to the performance of Knack and other chemistry were in play. Late planted conditions, lush winter vegetation capable of hosting whiteflies, poor growing conditions, and an extended period of extreme immigration pressure were all factors that diminished the impact of Knack and other products in 2005. In contrast, the winter preceding 2006 was among the driest on record followed by a very active monsoon season in central Arizona. High winds and dust movement, and a very active natural enemy community helped to continually lower whitefly populations. The result was a whitefly season characterized as light, with overall foliar insecticide usage setting a 28-yr record low for Arizona cotton. Barring all other operational and ecological factors at work, control intervals should have been similar each year. Yet, observed intervals have been different (e.g., 2005 vs. 2006) and point to the importance of these external factors in assessing product performance. Work will continue in 2007 to identify factors that contribute to whitefly outbreak conditions. These data will be key to understanding any performance changes, either due to operational or ecological factors mentioned above or due to innate changes in whitefly susceptibility. This will be important in advising growers about the risk factors associated with whitefly outbreaks and should lead to recommendations for minimizing these risks.

In the Western U.S., Lygus spp. (Hemiptera: Miridae) can cause major losses to cotton, vegetables, seed crops, and a variety of other crops. However, the economic impact of this pest remains largely undocumented in most crops. Two major data sources were used to quantify the economic impact of Lygus in lowdesert upland cotton production in Arizona: a statewide Pesticide Use Reporting (“1080”) database and an annual “Cotton Insect Losses” (CIL) survey of cotton Pest Control Advisors (PCAs). Both data sources include information on the target pest for insecticide applications, making it possible to single out Lygus control efforts. PUR data, based on information submitted by applicators to the Arizona Department of Agriculture, provides quantitative information on a high proportion of Lygus applications in cotton, but is incomplete, since not all types of applications require reporting. These data are complemented by information from the CIL survey to provide a more complete picture, based on direct responses from PCAs about their pest management practices. While the 1080 database is very useful in documenting a high proportion of Lygus insecticide use in cotton, by definition, these data on their own cannot provide good estimates of statewide behaviors with respect to Lygus management. In contrast, this is exactly what the Cotton Insect Losses survey is designed to do. As indicated by 1080 data and CIL data from 2001 to 2005, Lygus is the most important pest in Arizona cotton most years, based on application*acres of all foliar insecticides. Other key pests by this measure are sweetpotato whitefly, Bemisia tabaci Genn., and to a lesser extent pink bollworm, Pectinophora gossypiella (Saunders). Whitefly is the most important Lygus co-target, when applications are aimed at controlling more than one pest. The most commonly used foliar materials against Lygus in Arizona cotton are acephate, endosulfan and oxamyl, and they are typically used at about 90% of maximum label rates. About 80% of Lygus applications occur between mid-July and late-August. Average spray intensity (based on average sprays per acre) was calculated independently using the CIL and 1080 data sets and compared. For every year except for 2004, the CIL data estimates a somewhat higher insecticide use against Lygus . Several reasons for this discrepancy were identified, including less than 100% pesticide use reporting on 1080s; differences in the insecticides included in the estimates (top three active ingredients only for 1080 estimate, all insecticides for CIL estimate); and differences between how the two datasets apportion a single spray event among multiple pest targets. The intensity of Lygus management varies by county, based on 1080 data and county-level information on cotton acreages. Pinal county, which has the most cotton acres, shows the highest sprays / acre of the top three active ingredients to control Lygus . Analysis of 2005 1080 data at the section level indicates a relationship between the proportion of sections where cotton is grown in a Township - Range and spray intensity for Lygus control. Growers in Township - Ranges with a low proportion of cotton sections (10–15%) tend to make more sprays per field to control Lygus . However, Township – Ranges with the lowest and highest proportions of cotton sections (<10% and >90%) tend to show trends of lower spray requirements for Lygus control. These data suggest the possibility that landscape factors can influence Lygus populations at the local level, although more research in this area is needed. Lygus is perhaps the most significant economic pest of Arizona cotton. Cotton Insect Losses survey data indicate that a high proportion of cotton insect pest management efforts are directed toward Lygus control. Up to 40% of foliar insecticide sprays target Lygus , for about one third of the foliar insecticide budget for growers most years. Despite these control efforts and associated costs, Lygus are consistently listed in the CIL by survey respondents as the most damaging insect pest of cotton, accounting for more than 50% of insect-related yield loss most years. These two different and complementary data sets provide important baseline information on the current status and economic impact of Lygus in Arizona cotton, which will be useful for measuring changes in Lygus impact and control practices over time. A number of factors could potentially impact these practices in the future including (1) the introduction of new selective chemistry for Lygus control; (2) the introduction of transgenic control options for Lygus ; and (3) landscape-level changes that can have area-wide impact on Lygus management in cotton and other crops. These data underscore the need for continued research to develop effective, selective tools for improved Lygus management in cotton, and to integrate these into effective IPM programs. Data documenting a pest’s economic impact provides a rationale for funding to support critical IPM research and education. There is a need to similarly document the economics of Lygus management in other crops including vegetables, seed crops, and alfalfa, and the impact of landscape-level factors on Lygus management in a variety of crops.

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