Carfentrazone-ethyl Pond Dissipation and Efficacy on Floating Plants

Carfentrazone-ethyl (CE) is a reduced risk herbicide that is currently being evaluated for the control of aquatic weeds. Greenhouse trials were conducted to determine efficacy of CE on water hyacinth ( Eichhornia crassipes (Mart.) Solms- Laub.), water lettuce ( Pistia stratiotes L.), salvinia ( Salvinia minima Baker) and landoltia (Landoltia punctata (G. Mey.) Les & D. J. Crawford ) . CE controlled water lettuce, water hyacinth and salvinia at rates less than the maximum proposed use rate of 224 g ha -1 . Water lettuce was the most susceptible to CE with an EC 90 of 26.9 and 33.0 g ha -1 in two separate trials. Water hyacinth EC 90 values were calculated to be 86.2 to 116.3 g ha -1 , and salvinia had a similar susceptibility to water hyacinth with an EC 90 of 79.1 g ha -1 . Landoltia was not adequately controlled at the rates evaluated. In addition, CE was applied to one-half of a 0.08 ha pond located in North Central, Florida to determine dissipation rates in water and hydrosoil when applied at an equivalent rate of 224 g ha -1 . The half-life of CE plus the primary metabolite, CE-chloropropionic acid, was calculated to be 83.0 h from the whole pond, and no residues were detected in water above the limit of quantification (5 μg L -1 ) 168 h after treatment. CE dissipated rapidly from the water column, did not occur in the sediment above the levels of quantification, and in greenhouse studies effectively controlled three species of aquatic weeds at relatively low rates.(PDF contains 6 pages.

Selectivity of Metsulfuron Methyl to Six Common Littoral Species in Florida

Many Central Florida lakes, particularly those in the Kissimmee River watershed, are maintained 0.5 to 1.0 m lower than historic (pre-1960) levels during the summer hurricane season for flood control purposes. These lower water levels have allowed proliferation and formation of dense monotypic populations of pickerelweed ( Pontederia cordata L.) and other broadleaf species that out compete more desirable native grasses (Hulon, pers. comm., 2002). Due to the limited availability of data on the effects of metsulfuron methyl on wetland plants, particularly in Florida, the present study was carried out with the objective of testing its phytotoxicity on six wetland species, to determine the feasibility of its use for primary pickerelweed control

Efficacy and Residue Comparisons between Two Slow-release Formulations of Fluridone

Residue profiles and efficacy of Avast and Sonar, two slow release pellet formulations of fluridone {1-methyl-3-phenyl-5- [3-(trifluoromethyl)phenly]-4(1H)-pyridinone}, were compared in outdoor tanks. Hydrilla (Hydrilla verticillata (L.f.) Royle) and southern naiad (Najas guadalupensis (Sprengel) Magnus) were treated with a split application of 6, 12, 18 and 24 μg/l a.i. fluridone and the concentrations of both formulations compared over a 134-day period. Both pellet formulations exhibited very similar residues over time for each respective treatment, resulted in peak concentrations of fluridone 40 to 50 days after application, and effectively and similarly controlled southern naiad and hydrilla at all rates tested by 92 days after initial application. (PDF contains 3 pages.

ARPN Journal of Agricultural and Biological Science EFFECT OF DIQUAT IN IRRIGATION WATER ON GERMINATION AND VEGETATIVE GROWTH OF RICE

ABSTRACT The effect of different diquat concentrations in irrigation water on rice treated at germinating, young, tillering, and mature stages was evaluated. Diquat phytotoxicity to rice at all stages tested was determined using dry weight and growth inhibition fourteen-days after treatment (14 DAT). Germinating rice seed was the most sensitive to diquat in irrigation water. Concentrations resulting in 10% reduction in seedling dry weight compared to control plants were 0.016 mg L -1 for shoots and, 0.004 mg L -1 for roots, respectively. Concentrations greater than 0.2 mg L -1 inhibited root growth and at 0.4 mg L -1 shoot growth was reduced. Conversely, plants grown in sand and treated at seedling (3-4 leaf), tillering (initial stage) and mature (before seed head setting) vegetative stages were more tolerant to diquat concentrations in irrigation water. Diquat concentrations required to reduce dry weights of rice plants at immature to more mature growth stages by 10% ranged from 1.11 to 2.89 mg L -1 , respectively. Plant growth was inhibited at concentrations greater than 25.0 mg L -1 across all growth stages. Depending upon the application rate, irrigation of newly seeded rice fields with water from diquat treated irrigation canals or ponds should be delayed until plants reach a minimum of 3-4 leaf stage to avoid potential growth inhibition on germinating seeds

Effect of temperature and feeding preference on submerged plants by the island apple snail, Pomacea insularum (d\u27Orbigny, 1839) (Ampullariidae)

Volume: 50Start Page: 248End Page: 25

A New Learning Curve for Department of Defense Acquisition Programs: How to Account for the “Flattening Effect”

Traditional learning curve theory assumes a constant learning rate regardless of the number of units produced; however, a collection of theoretical and empirical evidence indicates that learning rates decrease as more units are produced in some cases. These diminishing learning rates cause traditional learning curves to underestimate required resources, potentially resulting in cost overruns. A diminishing learning rate model, Boone’s Learning Curve (2018), was recently developed to model this phenomenon. This research confirmed that Boone’s Learning Curve is more accurate in modeling observed learning curves using production data of 169 Department of Defense end-items. However, further empirical analysis revealed deficiencies in the theoretical justifications of why and under what conditions Boone’s Learning Curve more accurately models observations. This research also discovered that diminishing learning rates are present but not pervasive in the sampled observations. Additionally, this research explored the theoretical and empirical evidence that may cause learning curves to exhibit diminishing learning rates and be more accurately modeled by Boone’s Learning Curve. Only a limited number of theory-based variables were useful in explaining these phenomena. This research further justifies the necessity of a diminishing learning rate model and proposes a framework to investigate learning curves that exhibit diminishing learning rates