Chlorantraniliprole Residual Control and Concentration Determination in Cotton.

Studies were conducted in 2020 and 2021 at the Delta Research and Extension Center in Stoneville, MS, to determine the residual concentrations of chlorantraniliprole in cotton (Gossypium hirsutum, L.) leaves, as well as the concentrations in petals and anthers that developed after the time of application. Foliar applications of chlorantraniliprole were applied at four rates for leaves and two rates for petals and anthers at the second week of bloom. Additional bioassays were conducted to determine mortality of corn earworm (Helicoverpa zea, Boddie) in anthers. For the leaf study, plants were partitioned into three zones consisting of top, middle, and bottom zones. Leaf samples from each zone were analyzed for chemical concentrations at 1, 7, 14, 21, and 28 days after treatment (DAT). Residual concentrations, although variable, persisted through all sampling dates, rates, and zones tested. In this study, chlorantraniliprole remained detectable up to 28 DAT. Results from the cotton flower petal and anther studies detected concentrations of chlorantraniliprole in petals at 4, 7, 10, and 14 DAT, but no concentrations were detected in anthers. Therefore, no mortality of corn earworm was recorded in the anther bioassays. A series of diet-incorporated bioassays were conducted using concentrations previously found in the petal study to determine baseline susceptibilities of corn earworms and predicted mortality. Results from the diet-incorporated bioassays showed similar susceptibility in field and lab colony corn earworms. Concentrations of chlorantraniliprole could provide up to 64% control of corn earworm when feeding occurs on the petals.

Practical resistance to Cry toxins and efficacy of Vip3Aa in Bt cotton against Helicoverpa zea.

BACKGROUND: Crops genetically engineered to make insect-killing proteins from Bacillus thuringiensis (Bt) have revolutionized management of some pests. However, the benefits of such transgenic crops are reduced when pests evolve resistance to Bt toxins. We evaluated resistance to Bt toxins and Bt cotton plants using laboratory bioassays and complementary field trials focusing on Helicoverpa zea, one of the most economically important pests of cotton and other crops in the United States. RESULTS: The data from 235 laboratory bioassays demonstrate resistance to Cry1Ac, Cry1Fa, and Cry2Ab occurred in most of the 95 strains of H. zea derived from Arkansas, Louisiana, Mississippi, Tennessee, and Texas during 2016 to 2021. Complementary field data show efficacy decreased for Bt cotton producing Cry1Ac + Cry1Fa or Cry1Ac + Cry2Ab, but not Cry1Ac + Cry1Fa + Vip3Aa. Moreover, analysis of data paired by field site and year shows higher survival in bioassays was generally associated with lower efficacy of Bt cotton. CONCLUSIONS: The results confirm and extend previous evidence showing widespread practical resistance of H. zea in the United States to the Cry toxins produced by Bt cotton and corn, but not to Vip3Aa. Despite deployment in combination with Cry toxins in Bt crops, Vip3Aa effectively acts as a single toxin against H. zea larvae that are highly resistant to Cry toxins. Furthermore, Vip3Aa adoption is increasing and previous work provided an early warning of field-evolved resistance. Thus, rigorous resistance management measures are needed to preserve the efficacy of Vip3Aa against this highly adaptable pest. © 2022 Society of Chemical Industry.

Tarnished Plant Bug (Heteroptera: Miridae) Behavioral Responses to Chemical Insecticides.

The tarnished plant bug (Lygus lineolaris Palisot de Beauvois) is the dominant insect pest of cotton (Gossypium hirsutum L.) in the Mid-South Cotton Belt. This is partly due to the fact that this pest has developed resistance to most insecticides used for control. Laboratory experiments were conducted during 2014 and 2015 to study the behavioral response of tarnished plant bug nymphs to several classes of insecticides. Twenty third-instar nymphs were placed in individual dishes divided into four quadrants with five green bean pieces in each quadrant (10 treated and 10 untreated green beans in each dish). Dishes were checked at 1, 4, 8, and 24 h. Tarnished plant bug nymphs appeared to avoid green beans treated with IGR, pyrethroid, organophosphate, or carbamate insecticides, while there appeared to be an attraction to green bean pieces treated with sulfoxamine and pyridine carboxamide insecticides. No relationship was observed with neonicotinoid insecticides within 24 h.

Development of Economic Thresholds Toward Bollworm (Lepidoptera: Noctuidae), Management in Bt Cotton, and Assessment of the Benefits From Treating Bt Cotton With Insecticide.

Widespread field-evolved resistance of bollworm [Helicoverpa zea (Boddie)] to Cry1 and Cry2 Bt proteins has threatened the utility of Bt cotton for managing bollworm. Consequently, foliar insecticide applications have been widely adopted to provide necessary additional control. Field experiments were conducted across the Mid-South and in Texas to devise economic thresholds for foliar insecticide applications targeting bollworm in cotton. Bt cotton technologies including TwinLink (TL; Cry1Ab+Cry2Ae), TwinLink Plus (TLP; Cry1Ab+Cry2Ae+Vip3Aa), Bollgard II (BG2; Cry1Ac+Cry2Ab), Bollgard 3 (BG3; Cry1Ac+Cry2Ab+Vip3Aa), WideStrike (WS; Cry1Ac+Cry1F), WideStrike 3 (WS3; Cry1Ac+Cry1F+Vip3Aa), and a non-Bt (NBT) variety were evaluated. Gain threshold, economic injury level, and economic thresholds were determined. A 6% fruiting form injury threshold was selected and compared with preventive treatments utilizing chlorantraniliprole. Additionally, the differences in yield from spraying bollworms was compared among Bt cotton technologies. The 6% fruiting form injury threshold resulted in a 25 and 75% reduction in insecticide applications relative to preventive sprays for WS and BG2, respectively. All Bt technologies tested in the current study exhibited a positive increase in yield from insecticide application. The frequency of yield increase from spraying WS was comparable to that of NBT. Significant yield increases due to insecticide application occurred less frequently in triple-gene Bt cotton. However, their frequencies were close to the dual-gene Bt cotton, except for WS. The results of our study suggest that 6% fruiting form injury is a viable threshold, and incorporating a vetted economic threshold into an Integrated Pest Management program targeting bollworm should improve the sustainability of cotton production.

Quantifying the Impact of Excluding Insecticide Classes From Cotton Integrated Pest Management Programs in the U.S. Mid-South.

Current assessments from the U.S. Environmental Protection Agency suggest that some current insecticides may be lost or severely restricted in the near future. An experiment was conducted from 2014 to 2015 at two locations in Mississippi to determine the impact of losses of insecticide classes on integrated pest management of insect pests in cotton. The treatments included cotton treated with all available classes of insecticides, cotton treated with all classes except neonicotinoids, cotton treated with all classes except pyrethroids, cotton treated with all classes except carbamates and organophosphates, and an untreated control. Plots were scouted weekly and insecticide applications were made with the most efficacious and economical insecticides for each treatment when that treatment reached threshold for a particular insect pest(s). The primary insects at both locations were tobacco thrips and tarnished plant bugs. Thrips pressure was similar at both locations and generally showed that all insecticide treatments provided a similar level of protection compared with the untreated control. At the Stoneville location where tarnished plant bug pressure was greatest, cotton yields and economic returns differed between plots where all classes of insecticides were applied compared with the untreated control and where neonicotinoids were excluded. However, in Starkville where tarnished plant bug pressure was less, there were no differences among treatments. Although yield and economic returns were similar in high tarnished plant bug pressure areas when using all classes compared with managing without pyrethroids or organophosphates, a rotation among all insecticide classes should be beneficial for resistance management in Mid-South cotton production.

Influence of Temperature on the Efficacy of Foliar Insecticide Sprays Against Sugarcane Aphid (Hemiptera: Aphididae) Populations in Grain Sorghum.

The use of foliar insecticide sprays at low temperatures may result in decreased efficacy in grain sorghum, Sorghum bicolor L. Moench, for control of sugarcane aphid, Melanaphis sacchari (Zehntner). Sulfoxaflor and flupyradifurone were evaluated to determine the impact of temperature on their efficacy against sugarcane aphid in grain sorghum. Sorghum was treated at the soft dough growth stage with sulfoxaflor and flupyradifurone, as well as an untreated check. Leaf discs were pulled at various intervals from 0 to 10 d after treatment, placed in water agar plates, infested with aphids, placed in growth chambers at 15.5°C or 29.4°C, and evaluated 48 h after each interval. In 2015, both insecticides resulted in similar levels of sugarcane aphid mortality and efficacy decreased at a similar rate at 15.5°C. At 29.0°C, flupyradifurone resulted in greater mortality of sugarcane aphid than sulfoxaflor as length of time after treatment increased, suggesting that it provides longer residual control than sulfoxaflor. In 2016, both insecticides provided poor control of sugarcane aphid at 15.5°C for all time intervals. At 29.0°C, flupyradifurone provided overall better control than sulfoxaflor. These data suggest that lower temperatures can reduce the efficacy of both sulfoxaflor and flupyradifurone. In addition, flupyradifurone appeared to provide longer residual control and overall better control of sugarcane aphid than sulfoxaflor. If lower temperatures occur when sugarcane aphid populations exceed current thresholds, weather forecast should be considered in pest management decision-making process.

Neonicotinoid Insecticide Resistance in Tobacco Thrips (Thysanoptera: Thripidae) of Mississippi.

Insecticidal efficacy of neonicotinoid insecticides used against tobacco thrips, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae), in cotton, Gossypium hirisutum L. (Malvales: Malvaceae), was evaluated for field populations collected in Mississippi during 2014-2016. Resistance was documented in 16 and 57% of populations to imidacloprid and thiamethoxam, respectively. Resistance levels did not vary by host plant for any neonicotinoid, but resistance levels varied between the two main agricultural areas (Delta and Hills) of Mississippi and among years for some neonicotinoids. In spite of documented resistance, neonicotinoid seed treatments are still used on cotton in the midsouthern United States due to the lack of reliable alternative management strategies. The development of alternative thrips management strategies is critical to the sustainability of cotton production in the midsouthern United States.

A comparison of outcomes between Canada and the United States in patients recovering from hip fracture repair: secondary analysis of the FOCUS trial.

OBJECTIVE: To determine if adjusted mortality, walking ability or return home differed after hip fracture surgery between Canada and the USA. DESIGN: Secondary analysis of the Functional Outcomes in Cardiovascular Patients Undergoing Surgical Hip Fracture Repair (FOCUS) trial data. SETTING: Data were collected from 47 American and Canadian hospitals. PARTICIPANTS: Overall, 2016 subjects with a hip fracture (USA = 1222 (60.6%); Canada = 794 (39.4%)) were randomized to a liberal or restrictive transfusion strategy. Subjects were 50 years and older, with cardiovascular disease and/or risk factors and hemoglobin <100 g/L within 3 days post-surgery. The average age was 82 years and 1527(76%) subjects were females. INTERVENTION: Demographics, health status and health services data were collected up to 60 days post-surgery and mortality to a median of 3 years post-surgery. MAIN OUTCOMES: Mortality, inability to walk and return home. RESULTS: US subjects had higher adjusted mortality than Canadians at 30 days (odds ratio = 1.78; 95% confidence interval: 1.09-2.90), 60 days (1.53; 1.02-2.29) and up to 3 years (hazard ratio = 1.25; 1.07-1.45). There were no differences in adjusted outcomes for walking ability or return home at 30 or 60 days post-surgery. Median hospital length of stay was longer (P < 0.0001) in Canada (9 days; interquartile range: 5-18 days) than the US (3 days; 2-5 days). US subjects (52.9%) were more likely than Canadians (16.8%) to be discharged to nursing homes for rehabilitation (P < 0.001). CONCLUSIONS: Adjusted survival favored Canadians post hip fracture while walking ability and return home were not different between countries. The reason(s) for mortality differences warrant further investigation.

Tarnished plant bug (Hemiptera: Miridae) thresholds and sampling comparisons for flowering cotton in the midsouthern United States.

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), has become the primary target of foliar insecticides in cotton, Gossypium hirsutum L., throughout the Midsouth over the past several years. This prompted a reevaluation of existing action thresholds for flowering cotton under current production practices and economics. A trial was conducted at 19 locations throughout the Midsouth during 2006 and 2007. Threshold treatments ranged from a weekly automatic insecticide application to a very high threshold of 10 tarnished plant bugs per 1.5 row-m on a black drop cloth. Individually, all locations reached the lowest threshold, and eight locations had a significant yield loss from tarnished plant bugs. Across all locations, lint yield decreased 0.85 to 1.72% for each threshold increase of one tarnished plant bug per 1.5 row-m. Yield loss was most closely correlated to pest density during the latter half of the flowering period. The relationship between plant bug density or damage and yield was similar for drop cloth, sweep net, and dirty square sampling methods, but the correlations among these sampling methods were not high. Incorporating actual insecticide application data from the trial and average production and economic factors for Midsouth cotton, the economic threshold, if monitoring once per week, should be between 1.6 and 2.6 tarnished plant bugs per 1.5 row-m during the flowering period. More frequent monitoring or situations where insecticide applications are more efficacious may alter this threshold.

Tarnished plant bug (Hemiptera: Miridae) thresholds for cotton before bloom in the Midsouth of the United States.

Insecticide applications to control tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), during cotton, Gossypium hirsutum L., bud formation are common throughout the Midsouth of the United States. Cultivation practices and the pest complex have changed since action thresholds were established for this pest. A trial was conducted at 33 locations over 3 yr throughout the Midsouth to evaluate tarnished plant bug damage to cotton during the prebloom period. There was no consistent yield response to action thresholds, but average tarnished plant bug density and average square loss were both significant factors impacting lint yield. Based on the yield responses and application frequency of the various action thresholds, the best economic scenario occurred when tarnished plant bug density during the prebloom period averaged eight per 100 sweeps and square retention averaged 90%. The action thresholds required to achieve these averages are expected to be higher than these levels because pest pressure is not normally constant during the prebloom period. When insecticides are required, an application interval shorter than one week may be needed to obtain satisfactory control.

Allele frequency of resistance to Bacillus thuringiensis Cry1ab corn in Louisiana populations of sugarcane borer (Lepidoptera: Crambidae).

Transgenic Bacillus thuringiensis (Bt) corn, Zea mays L., has been widely used to manage a corn borer complex in the mid-southern region of the United States. The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), has become a dominant cornstalk boring species in some areas of this region, especially in Louisiana. Therefore, management of sugarcane borer resistance to Bt corn is critical to ensure the long-term sustainability of Bt corn for the region. This study screened 280 two-parent family-lines of sugarcane borer from four geographical populations in Louisiana during 2005 to determine whether Bt resistance allele frequency in sugarcane borer is sufficiently low to meet the rare resistance assumption of the current "high dose/refuge" resistance management strategy for Bt corn. These sugarcane borer family-lines were examined for Bt resistance by using novel F2 screening procedures. No major Bt resistance alleles were detected in these four populations. The estimated frequency of major Bt resistance alleles was < 0.0027, with a 95% probability and a detection power of 94%. The estimated minor resistance allele frequency was 0.0063, with a 95% CI of 0.0025-0.0117. During a previous study, a major Bt resistance allele was detected in one individual from 213 family-lines of another Louisiana population of sugarcane borer. Combining these data with the current screen, the frequency of major Bt resistance alleles across the five populations was 0.001, with a 95% credibility interval of 0.0001-0.0028 and a detection power of 95%. Major Bt resistance allele frequencies in Louisiana sugarcane borer populations seem to be low, and they should support the rare resistance allele requirement of the high dose/refuge strategy.