Evaluating the efficacy of methoxyfenozide on Louisiana, Texas and the mid-southern soybean looper populations

The soybean looper, Chrysodeixis includens (Walker), is a defoliating insect pest of soybean in the Mid-South and Texas. In 2008, Louisiana producers reported unsatisfactory control of soybean loopers in soybean with methoxyfenozide. In 2009 and 2010, field collections from Louisiana, Missouri, Mississippi and Texas were exposed to discriminating concentrations (0.020 to 5.000 ai ìg/ml) of methoxyfenozide in diet incorporation bioassays. All field colonies were compared to a reference strain LC50 of 0.007 ìg/ml for 2009 and 0.008 ìg/ml for 2010. Louisiana populations exhibited LC50’s of 0.079 ìg/ml and 0.122 ìg/ml for 2009 and 2010, respectively, which were the highest values among all field collections during three years. The Missouri collections demonstrated the lowest LC50’s with 0.025 ìg/ml in 2009 and 0.011 ìg/ml in 2010. In general, results of these discriminating concentration tests indicated that all field collections showed elevated LC50’s compared to the reference colony. Additional field experiments were conducted to evaluate the efficacy of foliar insecticides against Louisiana soybean loopers. Significant differences among treatments for defoliation area were determined between lepidopteran specific and broad spectrum insecticides. For the 2009-10 experiment chlorantraniliprole had the lowest defoliation 3,7,14,21 and 28 days after treatment (DAT) (0.20, 0.20, 0.50, 0.57, 0.97 cm2) while lambda-cyhalothrin had the highest (1.12, 2.38, 2.06, 2.79, 2.25 cm2). In 2011, defoliation and days to 100% mortality were evaluated at two locations for R3 and R5 development stages. Chlorantraniliprole provided the lowest days to mortality (2.3) at R3 and (1.0) at R5 while oxadiazine resulted in the highest (5.7 and 6.0)

Determining the Influence of Imidacloprid and Glufosinate Ammonium on the Population Dynamics of Twospotted Spider Mite Populations in Louisiana Cotton

Twospotted spider mites, Tetranychus urticae, is an important agricultural pest of many field crops worldwide. This study investigated the impacts of imidacloprid seed treatments on populations of twospotted spider mites while also investigating if exogenous applications of jasmonic acid can offset any hormone modulating effects caused by seed treatments. Imidacloprid seed treatments significantly increased cumulative adult mite days in 2013 but not 2015 or 2016 in the field. Applications of 10 millimolar jasmonic acid did not reduce mite severity or injury in all field trials. Imidacloprid seed treatments significantly increased all spider mite life stages in the laboratory while applications of jasmonic acid significantly reduced all mite life stages on neonicotinoid treated and non-treated cotton. Seed treatments do not affect the host preference of twospotted spider mites compared to non-treated however, jasmonic acid applications reduced the host suitability of seedling cotton to only adult mites. Additionally, leaf dip bioassays were conducted to evaluate resistance levels to abamectin in 12 populations of T. urticae collected from the Midsouth. Louisiana populations were highly resistant with corresponding LC50 values of 0.082 and 0.184 ppm and resistance ratios of 630 and 1415-fold. One population from Mississippi was slightly resistant with an LC50 value of 0.0021 ppm and a resistance ratio of 11.1 compared with a susceptible control population. Finally, greenhouse and field applied foliar spray tests and leaf dip bioassays were conducted to examine the susceptibility of T. urticae to glufosinate ammonium in cotton. Leaf dip bioassay results indicated that T. urticae were highly susceptible to concentrations of formulated glufosinate ammonium. The LC50 value was determined to be 10.31 ppm. Field applied glufosinate ammonium at 1.61 and 3.14 L ha−1 provided 48.86 and 80.22 percent control while fenpyroximate provided 89.62 percent control 5 days after application in 2015. Greenhouse applications resulted in 55.43 percent control 14 days after application with 0.73 L ha−1 while 1.61 L ha−1 resulted in 72.86 percent control and 3.14 L ha−1 resulted in 91.85 percent control of T. urticae populations. Data generated from these studies provide useful information on integrated pest management of twospotted spider mites in Midsouth cotton

Microscopic description of Gamow-Teller transitions in middle pf--shell nuclei by a realistic shell model calculation

GT transitions in $N=28\sim 30$ nuclei are studied in terms of a large-scale realistic shell-model calculation, by using Towner's microscopic parameters. $B({\rm GT})$ values to low-lying final states are reproduced with a reasonable accuracy. Several gross properties with respect to the GT transitions are investigated with this set of the wavefunctions and the operator. While the calculated total GT$^-$ strengths show no apparent disagreement with the measured ones, the calculated total GT$^+$ strengths are somewhat larger than those obtained from charge-exchange experiments. Concerning the Ikeda sum-rule, the proportionality of $S_{\rm GT}$ to $(N-Z)$ persists to an excellent approximation, with a quenching factor of 0.68. For the relative GT$^-$ strengths among possible isospin components, the lowest isospin component gathers greater fraction than expected by the squared CG coefficients of the isospin coupling. It turns out that these relative strengths are insensitive to the size of model space. Systematics of the summed $B({\rm GT})$ values are discussed for each isospin component.Comment: IOP-LaTeX 23 pages, to appear in J. Phys. G., 5 Postscript figures available upon reques

Microscopic description of nuclei in the middle of the pf-shell by a shell model calculation with G-matrix interaction

Energy levels and electromagnetic properties of with $N=28\sim 30$ nuclides are studied in terms of a large-scale shell model calculation, which contains no newly adjusted parameters. The Kuo-Brown $G$-matrix interaction is shown to reproduce energy levels of 205 low-lying states of these nuclei. We evaluate effective charges by incorporating the core-polarization effects caused by the coupling to GQR's. We then compute E2 moments and transition probabilities. The M1 moments and transition rates are calculated by quoting the effective $g$-factors of Towner, which are obtained by taking into account the meson-exchange and the core-polarization mechanisms. By this microscopic calculation most of the E2 properties and the magnetic moments are reproduced. Although there are agreements and disagreements in the M1 transition rates, the general tendency is reproduced. The $(e,e')$ and $(p,p')$ excitation from the ground state to some low-lying $2^+$ states is also discussed.Comment: 63 pages (LaTeX, to be published in Nucl. Phys. A

Pest population dynamics are related to a continental overwintering gradient

Overwintering success is an important determinant of arthropod populations that must be considered as climate change continues to influence the spatiotemporal population dynamics of agricultural pests. Using a long-term monitoring database and biologically relevant overwintering zones, we modeled the annual and seasonal population dynamics of a common pest, Helicoverpa zea (Boddie), based on three overwintering suitability zones throughout North America using four decades of soil temperatures: the southern range (able to persist through winter), transitional zone (uncertain overwintering survivorship), and northern limits (unable to survive winter). Our model indicates H. zea population dynamics are hierarchically structured with continental-level effects that are partitioned into three geographic zones. Seasonal populations were initially detected in the southern range, where they experienced multiple large population peaks. All three zones experienced a final peak between late July (southern range) and mid-August to mid-September (transitional zone and northern limits). The southern range expanded by 3% since 1981 and is projected to increase by twofold by 2099 but the areas of other zones are expected to decrease in the future. These changes suggest larger populations may persist at higher latitudes in the future due to reduced low-temperature lethal events during winter. Because H. zea is a highly migratory pest, predicting when populations accumulate in one region can inform synchronous or lagged population development in other regions. We show the value of combining long-term datasets, remotely sensed data, and laboratory findings to inform forecasting of insect pests

Technology-based approaches to managing cotton bollworm in Bt Cotton

The bollworm (Helicoverpa zea), also known as the corn earworm, is considered the most economicallydamaging caterpillar pest in Texas and Mid-southern U.S. cotton production. The use of Bt expressing cottonvarieties has allowed for successful control of lepidopteran pests such as the tobacco budworm (Chlorideavirescens) for over two decades and led to the complete eradication of pink bollworm (Pectinophoragossypiella) in the U.S. Despite successfully introducing Bt cotton varieties for these pests, injury frombollworm can still be observed in all Bt cotton varieties, though injury is reduced, especially when multiple Bt toxins are expressed.Chase Floyd (University of Missouri); David Kerns (Texas A and M); Whitney Crow, Don Cook, Tyler Towles, Jeff Gore, Angus Catchot and Fred Musser (Mississippi State University); Ben Thrash, Nick Bateman, Gus Lorenz and Glenn Studebaker (University of Arkansas); Sebe Brown and Scott Stewart (University of Tennessee)