Thrips are major agricultural pests throughout much of the United States. More information is needed about sampling methods, management practices, and insecticide susceptibility to help better control this pest. A two year survey was conducted to determine the species present in southeast Virginia and the population characteristics of those species. Thrips were monitored using yellow sticky traps. Tobacco thrips, Frankliniella fusca, were the most abundant species. In general thrips populations began to build up beginning in April, peaked in August, and then started to decline. Differences in this trend were observed between species. A study was conducted in seedling soybean to evaluate the within-plant location of thrips, whether a plant subsample could be used for thrips monitoring, and to determine the thrips species complex present. Soybean thrips, Neohydatothrips variabilis, were the most prominent species present. The greatest density of thrips larvae was located in the terminal bud of the seedling and suggests that immature thrips aggregate. Neither of the proposed subsamples of plant material explained the variability in immature thrips numbers and at this time we recommend whole-plant sampling for obtaining the most accurate estimate of thrips populations in seedling soybean. Tobacco thrips, F. fusca, as well as a complex of other thrips species attack cotton and peanut seedlings and can cause significant yield loss to these crops in the mid-Atlantic U.S. Experiments were conducted in these two crops to assess the efficacy of a novel diamide insecticide cyantraniliprole applied as a liquid in-furrow at planting and post-plant emergence broadcast spray treatment to control thrips. In both cropping systems cyantraniliprole significantly reduced the number of immature thrips and reduced thrips feeding injury to the plants. In several instances cyantraniliprole treatments resulted in increased yield as compared to the non-insecticide treated control and yields which were statistically similar to those obtained with standard thrips control insecticides. Laboratory bioassays were conducted to evaluate the toxicity (LC50 values) of cyantraniliprole and two conventional insecticides against F. fusca adults. Results of these assays were inconclusive. At times F. fusca adults were susceptible to the insecticides, but the results could not be replicated consistently. / Master of Science

Remediation of chlorinated ethene contaminated sites presents a problem for the environmental industry. Many innovative technologies exist to remove these chemicals from the subsurface; however, most of these technologies require extensive time and incur significant cost. A technology called bioremediation utilizes microorganisms to break down contaminants such as perchloroethene (PCE), trichloroethene (TCE), dichloroethene (DCE), and vinyl chloride (VC) to non-toxic compounds in a process called reductive dechlorination. Microorganisms that are capable of dechlorination usually require reducing conditions as well as bioavailable hydrogen and carbon sources. Emulsified vegetable oil has emerged as a cost-effective source of degradable organic matter to facilitate reductive dechlorination in the subsurface. Through Æ Ã -oxidation, microorganisms can break down the long chain fatty acids in vegetable oil into smaller fatty acids such as acetate, propionate, and butyrate. The fermentation of the oil provides reduced conditions as well as a slow release of hydrogen and carbon into the subsurface. This study consisted of an evaluation the effectiveness of emulsified vegetable oil in stimulating reductive dechlorination using sixteen laboratory microcosms constructed from soil and groundwater from an aquifer contaminated with TCE located at the Naval Weapons Station in Charleston, South Carolina. Each microcosm was monitored for chloroethenes, volatile fatty acids, long chain fatty acids, and total carbon on a weekly basis. Results show successful fermentation of fatty acids and reduced conditions favorable for dechlorination. / Master of Science

In-storage losses of seed vigor, i.e., aging, that occur between harvest and planting may leave soybeans essentially worthless as seed. Peroxidation of lipids, with resultant loss of membrane integrity, is theorized to be a primary event in seed aging. Lipid antioxidants might have the potential to protect dry seed by neutralizing free radicals, which propagate lipid peroxidation and other destructive events. Seed were treated with antioxidants in dimethyl sulfoxide (DMSO) to investigate possible protective effects of antioxidants during storage and thus also provide evidence for the lipid peroxidation model of seed aging. The toxicity of DMSO to soybean seed was found to be minimal at treatment times of 15 min or less. Seed were treated for 15 min with 0, 5, 25, and 50 mM solutions in DMSO of propyl gallate (PG), butylated hydroxyanisore (BHA), butylated hydroxy toluene (BHT), and tert-butylhydroquinone (TBHQ). Germination, seed leakage, seedling vigor, and phospholipids in the embryonic axis were monitored following storage at 40 C for up to 90 days. / Master of Science

Soybean looper and corn earworm are economically damaging pests in Mississippi soybeans. Chemical control plays a large role in the control of these pests. Some producers have started applying an automatic co-application of insecticide and fungicide at the R3 growth stage. Insect growth regulators are a commonly used insecticide for this management strategy. The purpose of this research was to evaluate the impact of insect growth regulators on soybean looper and corn earworm mortality when applied with an automatic fungicide application at the R3 growth stage in soybean. Insecticide treatments included methoxyfenozide, diflubenzuron, and novaluron. These insect growth regulators showed very little control and mortality, especially when compared to chlorantraniliprole, which has become an industry standard for control of lepidopteran pest control of in soybean. The automatic application of an insect growth regulator insecticide with a fungicide at the R3 growth was not viable for economic insect management strategies.

Trypsin and alpha-chymotrypsin were immobilized on nylon pellets or porous glass by covalent methods to change molecular properties and functional characteristics of soybean proteins. The amount of trypsin immobilized on nylon pellets using the glutaraldehyde method was high when the pellets were treated with methanolic solution and 6 - 8% glutaraldehyde as well as high concentrations of soluble trypsin. Immobilized trypsin and chymotrypsin had uniform pKm and were stable at high temperatures. The optimum pH for activity of immobilized enzymes could be changed by using different supports and different methods of immobilization. A multi-enzyme system with immobilized trypsin and chymotrypsin was designed to produce an efficient hydrolysis and various desirable products of hydrolysis. Controlled hydrolysis of soybean proteins by immobilized enzyme(s) increased water holding capacity, oil holding capacity, and relative viscosity, and improved emulsifying and foaming characteristics. Hydrolysis by immobilized protease(.s) increased solubility, relative viscosity and foaming ability of partially purified fractions. Succinylated soybean proteins had high oil holding capacity, viscosity, emulsifying ability, emulsion stability, and foaming ability. The order in which succinylation and hydrolysis by immobilized enzymes were done, conferred on soybean proteins various functional properties. Evaluation of the molecular size of modified soybean proteins with sodium dodecyl sulfate (SDS) indicated that immobilized trypsin and chymotrypsin preferentially hydrolyzed specific protein components, and that succinylation enhanced hydrolysis, expanded protein molecules, and dissociated subunits. Measurement of molecular size and charge of the modified soybean proteins without SDS showed that immobilized trypsin hydrolyzed the intermediate subunits relatively fast, and succinylation separated the intermediate subunits. Succinylation increased the average molecular charge of soybean proteins, while hydrolysis decreased their average molecular size and their average molecular charge. The ratio of the average molecular weight to the average molecular charge could explain various functional properties. When the ratio was less than 5.0 x 10⁵, the modified soybean proteins had high soluble amino groups, high foaming ability, low water holding capacity and low foam stability. When the ratio was 9.0 x 10⁵, oil holding capacity, emulsifying ability, and emulsion stability were maximum. Relative viscosity was high at a constant value of 2.5 x 10⁵. / Ph. D.

Soybean, Glycine max (L.) Merr., fruits 10-25 mm long contained nine fractions having cytokinin-like activity detectable by the Amaranthus bioassay. These fractions were derived from purification of extracts from 15 g of immature fruits. The fractions were purified by polyvinylpyrrolidone (PVP), paper, Sephadex LH-20 and high performance liquid chromatography. The fractions separated on the basis of polarity into polar, moderately polar and relatively non-polar groups, compared to zeatin. The polar fraction was the single most bioactive fraction and the active substance was tentatively identified as a zeatin glucoside or zeatin riboside glucoside. The moderately polar fraction contained bioactive substances that co-eluted with zeatin and zeatin riboside in four chromatographic procedures. The relatively non-polar fraction contained two bioactive components, one chromatographically resembling 2iPA, and the second less polar. A conjugated cytokinin was released from the original aqueous phase by alkaline phosphatase hydrolysis. This substance co-eluted with zeatin riboside on Sephadex LH-20. Further purification and analysis by multiple ion monitoring GC-MS did not yield conclusive identification of the cytokinins. Based on bioassay, the biological estimates of cytokinin-like substances present in the extracts were below the detection limit of the GC-MS. Obtaining sufficiently large samples of soybean fruits at the proper stage of physiological interest complicated definitive structural identification based on the purification and identification techniques used. / Ph. D.

Clomazone is a recently introduced herbicide for the selective control of grass and broadleaf weeds in soybeans. Field studies were conducted in full-season no-till soybeans to determine the efficacy of clomazone as a preplant and preemergence herbicide. Clomazone applied preemergence provided large crabgrass (Digitaria sanguinalis L.) control equivalent to that of oryzalin applied preplant or preemergence and provided better control of several broadleaf weeds. Control from preplant applications of clomazone was not adequate. Preemergence and preplant incorporated applications of clomazone were compared in conventionally-tilled soybeans. Clomazone efficacy at two depths of incorporation was also investigated. Clomazone applied preemergence generally provided control of large crabgrass and several broadleaf weed species equivalent to preplant incorporated applications. The addition of imazaquin or chlorimuron plus linuron improved smooth pigweed (Amaranthus hybridus L.) control over that provided by clomazone alone. These combinations generally did not improve large crabgrass, jimsonweed (Datura stramonium L.), and common lambsquarters (Chenopodium album L.) control over that of clomazone alone. Shallow incorporation (4 cm) of clomazone provided better weed control than deep incorporations (8 cm). Studies were conducted to evaluate efficacy and to quantify volatilization of three clomazone formulations (emulsifiable concentrate, wettable powder, and a microencapsulated formulation) following soil application. Samples were collected at the first, second, and tenth day after clomazone application. The three clomazone formulations provided control of large crabgrass. Clomazone volatilization was greatest 24 h after application from the emulsifiable concentrate and wettable powder formulations and declined at the second and tenth day after application. Volatilization from the microencapsulated formulation was lower than the other two formulations at all sampling times. Clomazone volatilization was greater from preemergence than preplant incorporated applications. Differential selectivity studies were initiated to determine the absorption, translocation, and metabolism of clomazone in tolerant soybean and smooth pigweed and susceptible redroot pigweed and livid amaranth exposed to foliar and root applied clomazone. Redroot pigweed and livid amaranth absorbed more clomazone through the roots than soybean and smooth pigweed. Absorption of foliar-applied clomazone was limited in all species. Of the clomazone absorbed in all species, most was translocated to the leaf tissue. Two metabolites of clomazone were found. One was determined to be a GS-clomazone conjugate. Differences in clomazone metabolism among species examined were not found. Growth and physiological responses of a normal hybrid ('DeKalb XL67'), a dwarf mutant, and an albino mutant of corn (Zea mays L.) to clomazone and interactions of gibberellin with clomazone on normal corn were examined. The dwarf mutant displayed greater tolerance to clomazone than normal corn. Growth measurements suggested that gibberellin was antagonistic with clomazone. / Ph. D.

With the adoption of the Xtend® technology growers began to report reduced control levels of weedy grasses when applying tank-mixes of glyphosate and dicamba. Therefore, research was conducted at the Delta Research and Extension Center in Stoneville, MS from 2019 to 2021 to examine influence of herbicide mixtures with dicamba, as well as carrier volume and nozzle type. Results indicated barnyardgrass control 14 and 28 DAT was greatest with glyphosate alone. Control was not different when DGA or BAPMA dicamba or 2,4-D choline were mixed with glyphosate. At 28 DAT, barnyardgrass control was 15 to 18% lower with herbicide mixtures compared with glyphosate alone. Barnyardgrass control with glyphosate plus dicamba was not decreased by drift-reducing nozzles. Carrier volume of > 94 L ha-1 provided greater control of barnyardgrass compared to 47 L ha-1. These results indicate potential of reduced barnyardgrass control with glyphosate plus dicamba.

Potassium (K) deficiency of soybean [Glycine max (Merr.) L.] is common throughout the Mid-Southern region of the United States. Visual symptoms of K deficiency may be absent or subtle during early and mid-reproductive growth stages. Correcting K deficiency in-season is problematic due to limited research. Information regarding soybean yield response to in-season fertilizer K application time is limited to growth stages prior to the onset of R1. Research is also limited on new higher yielding soybean cultivars. The objective of this study was to evaluate influences of in-season K application timing during reproductive growth stages on soybean yield. Field experiments were established in 2019, 2020, and 2021 to evaluate the effect of soybean potassium rate and timing during reproductive growth stages. Four independent experiments were established to: (1) determine the effect of applying K fertilizer to sufficient soils at different times in-season on yield and plant K status on two different soil textures, (2) determine the effects of K timing, K rate, and dicamba rate on yield and plant stress, and (3) determine the effects of K timing and desiccation on yield and plant stress. Results indicate that potassium application rate and timing during soybean reproductive growth stages do not increase yield on soils with adequate K present. Soybean trifoliate leaf tissue K analysis and petiole sap K analysis had no response during reproductive growth stages when K fertilization occurred on soils with ample K. Potassium fertilization did not aid soybean recovery after dicamba injury.

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