Small-plot Tests Research Articles

Augmented Bowen ratio analysis, II: Ohio comparisons

An experiment conducted over a field of maize in Ohio during the growing season of 2015 provided measurements sufficient to compare among three methods for quantifying net ecosystem exchange of sensible heat, latent heat and carbon dioxide: eddy covariance (EC), the familiar Bowen ratio energy balance (BREB) method and a statistical procedure making use of surface temperature measurements by downward-looking infrared thermometry (the augmented Bowen ratio analysis – ABRA). EC and BREB yield run-by-run estimates of fluxes. The third method (ABRA) gives average values over prescribed ensembles of data. The Ohio observations support the conventional understanding that EC is the preferred methodology provided the site is large enough. Both BREB and ABRA can make use of measurements closer to the surface than EC, and hence are more suited for studies of small test plots. The ABRA method provides results agreeing with conventional BREB and EC in daytime except for periods near dawn and dusk when heat storage can be a substantial contributor in the surface heat energy budget. The unattributed heat storage in the morning found in analysis of observations made elsewhere is substantiated. It is concluded that the apparent heat storage term in the surface heat budget is most influenced by heating of crop biomass and the energy demands of photosynthesis. The comparisons provide clear evidence of the difficulties associated with application of all gradient-based methodologies at night (affecting both BREB and ABRA) when atmospheric stability often prohibits reliable association of fluxes with gradients. CO2 measurements reveal substantial differences among the three different methodologies (ABRA, BREB and EC), with EC appearing to be more robust and therefore preferred if the test area is large enough.

The Use of Canopeo for Seedling Cotton Health Ratings in Small Plot Research

Field experiments were conducted in 2017 and 2018 in west Tennessee to determine if Canopeo, an image analysis tool available as a smartphone app, could be used to supplement current methods to estimate cotton, Gossypium hirsutum L., seedling health in small-plot research tests. A total of six tests, providing a range of cotton seedling health, were used in this analysis. Cotton seedlings in replicated small-plot tests were visually rated for vigor and thrips (Thysanoptera: Thripidae) injury. A photograph of the center two rows of each plot was taken and analyzed to determine green canopy cover using Canopeo. Additionally, above ground biomass samples were collected in three of the tests. Strong correlations were observed between green canopy cover and biomass, green canopy cover and vigor, and thrips injury ratings and biomass. These data suggest that green canopy cover assessment using Canopeo is a useful and non-destructive way to objectively assess treatment effects on plant health in small-plot cotton research trials.

Delineation of Agricultural Drainage Pipe Patterns Using Ground Penetrating Radar Integrated with a Real-Time Kinematic Global Navigation Satellite System

Better methods are needed for mapping agricultural drainage pipe systems. Prior research on small test plots indicates that ground penetrating radar (GPR) is oftentimes capable of detecting buried drainage pipes; however, the feasibility of employing this geophysical technique in larger field areas has not been adequately evaluated. Ground penetrating radar integrated with a Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) may be an effective and efficient means of mapping drain lines within agricultural fields. Therefore, GPR-RTK/GNSS was tested in three agricultural settings; with Site 1 and Site 2 located in Beltsville, MD, USA and Site 3 near Columbus, OH, USA. Soils at the three sites ranged from silty clay loam to loamy sand. A GPR unit with 250 MHz antennas was used to detect drainage pipes, and at Sites 1 and 2, a physical GNSS base station was utilized, while a virtual base station was employed at Site 3. The GPR-RTK/GNSS configurations used in this study delineated a complex rectangular drainage pipe system at Site 1, with one set of drainage pipes oriented southwest-northeast and a second oriented southeast-northwest. At Site 2, a herringbone drain line pattern was outlined, and at Site 3, random drain lines were found. When integrated with RTK/GNSS, spiral or serpentine GPR transects (or spiral/serpentine segments of a GPR transects) were utilized to provide insight on drain line directional trends. Consequently, given suitable field conditions, GPR integrated with RTK/GNSS can be a valuable tool for farmers and drainage contractors needing to map subsurface drainage systems.

Reduction of deoxynivalenol (DON) contamination by improved fungicide use in wheat. Part 1. Dependence on epidemic severity and resistance level in small plot tests with artificial inoculation.

Fungicide control of FHB of wheat generally has poor efficacy and mostly susceptible cultivars are grown. Therefore, the toxin risk is high. We developed a more efficient control by combining an improved resistance with a more precise evaluation of fungicides. Small plot tests (5m2), along with artificial inoculation were used. Visual head symptoms (FHB), kernel infection (FDK) and DON content were evaluated (2009–2012). Fungicide treatments were preventive at the full flowering stage with four isolates of F. graminearum and F. culmorum. The best fungicide decreased DON by 75% (variation between the four years: 60–93%), the least effective gave a 44% reduction (variation: 30–59%). From medium to very high epidemic severity, smaller differences were observed in reduction (64–68%), but the best reduction was seen at medium disease pressure. The medium susceptible GK Bekes reduced DON from 5.86 mg/kg to 2.36–3.46 mg/kg for the fungicides used. The medium resistant GK-Feny varied for fungicides between 0.86–2.58 mg/kg, UTC: 3.90 mg/kg), the most susceptible GK-Kalasz gave 1.07–5.32 mg/kg for fungicides (UTC: 10.01 mg/kg). The cumulative effect of fungicide/variety had a 91% reduction across years. The high reduction is not enough the DON content should also be lower than the 1.25 mg/kg limit. Correlations between traits for fungicides were between r = 0.98–0.99 (p < 0.001), and DON gave the most reliable results. Beside fungicide efficacy, varietal resistance is an important component of effective control of FHB in the field. Susceptible cultivars should be withdrawn from production, but cultivars such as GK Feny can be grown without any serious food safety risk with a single preventive treatment. The fieldwork will be outlined in Part 2.

Reduction of deoxynivalenol (DON) contamination by improved fungicide use in wheat. Part 2. Farm scale tests with different nozzle types and updating the integrated approach

Fungicidal control of Fusarium head blight (FHB) of wheat with fungicides generally has poor efficacy (0–40%). However, small plot trials prove that a 70–90% reduction in toxin contamination is possible. We compared two variants of side-spraying nozzles with the Turbo FloodJet. The new nozzle combination (QJ 90, TT F, XR B) reduced visual FHB scores by 50% as compared to the standard TeeJet XR nozzles. The fungicide choice is decisive, the best product reduced DON by 81%, the least effective only by 31%. Greater genetic resistance is also decisive, the most resistant cultivar showed a 73% reduction in DON across all treatments. The combined effect of the fungicide + cultivar was 98.5% between the UTC and best fungicide/variety combination (GK Feny/PT) across three years. The new combined nozzle was more effective at the better fungicides containing prothioconazole, metconazole and tebuconazole, at the less effective fungicides its effect was only average. Correlations between small plot (Part 1) and farm tests were r = 0.96 (P = 0.001) for FHB, r = 0.91 (P = 0–001) for FDK, and r = 0.75 (P = 0.02) for DON indicating that small plot results forecast field usefulness and reduction in field control was close to the small plot results for all traits. The heart of integrated plant management (IPM) is the combination of variety resistance, the effective fungicide and the side-spraying technology with appropriate nozzle choice. Resistance governs fungicide reduction, nozzle influence, effect of previous crop and tillage. Susceptible cultivars should be withdrawn from production, but cultivars such as GK Feny treated with preventive fungicides at the flowering phase can be grown without any serious food safety risk. With a careful field-specific IPM combination, the reduction can be doubled without significant additional costs.

The moderating effect of water-efficient ground cover vegetation on pedestrian thermal stress

The level of thermal stress experienced by pedestrians in an urban environment is affected by their exchange of energy with their surroundings, and the properties of ground-cover vegetation can have an important influence on this energy exchange − particularly in terms of radiation. Although vegetated surfaces have a low albedo and thus absorb a large part of the solar radiation incident upon them, they can maintain lower temperatures than typical paved surfaces because they are cooled by evapotranspiration. The purpose of this research is to examine the cooling effect of “succulent” surface cover plants that are adapted to arid climates, in comparison to plants such as grass that require substantially more irrigation. The research site, in the Negev desert of southern Israel, consists of several small test plots with different species of succulents and other plants, along with dry ground surfaces. Measurements of surface temperature and albedo provide input for comprehensive pedestrian thermal comfort modeling using the Index of Thermal Stress, assuming an open space scenario with various surface cover treatments. Water requirements of the different plant are examined through an irrigation experiment. Results indicate that although there are thermal differences between the different plant types, these differences are small when compared with non-vegetated surfaces. While the non-succulents are slightly cooler and less stress-inducing than the desert-adapted plants, their water requirements are higher, making them less efficient in terms of the ratio between cooling “benefits” and water “costs”—both of which are expressed in terms of their equivalent energy.

Non-target consequences of insecticides used in apple and pear orchards on Forficula auricularia L. (Dermaptera: Forficulidae)

The common European earwig, Forficula auricularia L. (Dermaptera), is an important generalist predator in apple and pear orchards, regulating populations of several damaging pest species. Large differences in earwig populations in orchards may be the result of pesticide use and timing of pesticide applications. This study investigated the effects of pesticides on nymph, adult female and adult male earwigs in the laboratory and in the field. In the laboratory earwigs exposed to the residues of chlorpyrifos died within 2days. Spinosad was also deemed harmful. Abamectin, chlorantraniliprole and flonicamid were considered earwig safe. Spinosad, spiridoclofen, thiacloprid and methoxyfenozide reduced the growth of nymphs. In a small field plot test on pesticide treated apple trees, earwigs were less sensitive to chlorpyrifos than in laboratory studies and thiacloprid and flonicamid reduced numbers foraging in the trees. The final field test compared growers conventional and earwig compatible spray programs. Whilst earwig numbers increased in orchards with the compatible spray program, populations were significantly negatively affected by the conventional spray programs. The data from this and other studies can be incorporated into future integrated pest management programs in apple and pear orchards to control pests whilst maintaining earwig populations and benefiting from the pest control service they provide.

Performance evaluation of CERES-Wheat model in Guanzhong Plain of Northwest China

Winter wheat (Triticum durum Desf.) is one of the most important food crops in Guanzhong Plain of Northwest China. Irrigation and fertilizer are essential for wheat growth in the region because of inadequate precipitation and unfertile soil in the region. However, in most cases optimal yields are not gained due to unreasonable irrigation and fertilizer applications. A decision-supporting tool is required to facilitate local farmers to evaluate irrigation and fertilizer uses and their impact on yield. In this study, CERES (Crop Estimation through Resource and Environment Synthesis)-Wheat model, a process-based model, was adapted for predicting yield of winter wheat calibrated using plot experiments in the region. Water and nitrogen (N) limitation conditions were included in the experiments conducted in Yangling on small test plots during the growing years of 2009–2010, 2010–2011 and 2011–2012. Results showed that the simulated aboveground biomass, grain yield, leaf area index (LAI), canopy N, cumulative evapotranspiration (ET), water use efficiency (WUE) and nitrogen partial fertilizer productivity (NPFP) deviations from the measured were acceptable with normalized root mean square error (NRMSE) below 21%. LAI rose as N application increased and the synergistic impact of irrigation and N was exerted on LAI. ET and canopy N at maturity increased with irrigation although N application was different for 2010–2011 and 2011–2012. The response of both ET and canopy N to fertilizer N showed the similar trend. Besides, the impact of irrigation on ET was affected by different N applications under low irrigation conditions. WUE and NPFP were exerted a great influence on by N fertilizer and the impact of irrigation on them was not significant. Model sensitivity analysis indicated that the grain yield was very sensitive to field capacity among the factors except for the date-related factors and planting date had a significant influence on grain yield by comparison with the factors related to the date. Therefore, the model can be used for the region to assess and optimize winter wheat yield with respect to irrigation and N applications as well as other influential factors.

Estimation of Soil Material Transportation by Wind Based on in Situ Wind Tunnel Experiments

Abstract 25% and 40% of territory of Hungary is moderate to highly vulnerable to deflation. However, precise estimates about the soil loss and related losses of organic matter and nutrients due to wind erosion are missing in most cases. In order to determine magnitudes of nutrient masses removed at wind velocities that frequently occur in SE Hungary, in-situ experiments using a portable wind tunnel have been conducted on small test plots with an erosional length of 5.6 m and a width of 0.65 m. The wind tunnel experiments have been carried through on a Chernozem which is typical for this region. In order to compare the effects of soil coverage on the masses of blown soil sediment and adsorbed nutrients, two soil surface types have been tested under similar soil moisture und atmospheric conditions: (1) bare soil (dead fallow) and (2) bare soil surface interrupted by a row of maize plants directed downwind along the center line of the test plots. The results of our experiments clearly show that a constant wind velocity of 15 m s-1 (at a height of 0.3 m) lasting over a short time period of 10 minutes can already cause noticeable changes in the composition and size of soil aggregates at the top of the soil surface. Due to the grain size selectivity of the erosive forces the relative share of soil aggregates comprising diameters &gt; 1 mm increased by 5-10% compared with the unaffected soil. Moreover it has shown that short time wind erosion events as simulated in this study can result in erosion rates between 100 and 120 g m-2, where the erosion rates measured for bare soils are only slightly, but not significantly higher than those of the loosely vegetated ones. Soil samples taken from sediment traps mounted in different heights close to the outlet of the wind tunnel point to an enrichment of organic matter (OM) of about 0.6 to 1 % by mass referred to the control samples. From these findings has been calculated that the relocation of organic matter within short term wind erosion events can amount to 4.5 to 5.0 g OM m-2. With the help of portable field wind tunnel experiments we can conclude that our valuable, high quality chernozems are struck by wind erosion mainly in drought periods.

CALIBRATION OF SUGARCANE RESPONSE TO CALCIUM SILICATE ON FLORIDA HISTOSOLS

Silicon is considered a beneficial nutrient for sugarcane (Saccharum spp.) and yield responses to Si applications on Florida organic soils have been well documented. Growers need calibrated Si recommendations to be able to make cost-effective decisions regarding Si applications. The objective of this study was to develop a soil-test Si calibration based on yield responses to Ca silicate on Everglades Histosols. Twelve paired commercial field comparisons and three small-plot tests of Ca silicate application were conducted. Strong responses in t cane ha−1 and t sucrose ha−1 were determined with acetic acid-extractable soil Si <15 g m−3, with some response to approximately 25 g m−3. Recommendations were developed over this range with a maximum Ca silicate rate of 6.7 t ha−1. Optimum leaf Si concentration was determined to be ≥ 6.0 g kg−1, with 0.95 and 0.80 relative yield at 5.0 and 2.5 g kg−1, respectively.

On-farm effects of tillage and crops on soil erosion measured over 10 years in Switzerland

The positive effects of soil conserving farming methods have mostly been demonstrated using small test plots. The present study is aimed at confirming that they also occur on the catchment scale. The impact of crops and soil tillage practises on the extent of soil erosion was determined in 203 crop fields over 10 years in the Swiss Midlands. Soil erosion totalled 1969t or 0.75tha−1yr−1. Most erosion took place in winter wheat fields (33%), which accounted for 22% of the crop area. Second and third most erosion was observed in potato (26%) and fallow (14%) fields. By far the highest mean soil loss was found for potatoes, at 2.87tha−1yr−1. Fallow (1.06tha−1yr−1) and winter wheat (1.05tha−1yr−1) fields were also relatively susceptible to soil erosion. In contrast, values for soil loss below mean were observed for maize (0.44tha−1yr−1), sugar beet (0.27tha−1yr−1), and rape seed (0.39tha−1yr−1). 88% of soil erosion took place on plough tilled land (PT), 9% on non-ploughed land with less than 30% surface residue cover (RT), 1% on mulch-tilled land with more than 30% surface residue cover (MT), and 2% in non-tilled or strip-tilled land with >30% soil cover (NT). At 0.07 and 0.12tha−1yr−1, respectively, the mean soil loss in MT and NT fields was more than an order of magnitude lower than that under PT (1.24tha−1yr−1). Field mappings confirmed the positive effects of the soil conserving soil tillage practises. The risk of soil erosion was significantly influenced by crop rotation. The carry-over effects should be taken into account when studying the effects of cropping methods on soil erosion.

Role of fungicides, application of nozzle types, and the resistance level of wheat varieties in the control of Fusarium head blight and deoxynivalenol.

Fungicide application is a key factor in the control of mycotoxin contamination in the harvested wheat grain. However, the practical results are often disappointing. In 2000-2004, 2006-2008 and 2007 and 2008, three experiments were made to test the efficacy of fungicide control on Fusarium Head Blight (FHB) in wheat and to find ways to improve control of the disease and toxin contamination. In a testing system we have used for 20 years, tebuconazole and tebuconazole + prothioconazole fungicides regularly reduced symptoms by about 80% with a correlating reduction in toxin contamination. Averages across the years normally show a correlation of r = 0.90 or higher. The stability differences (measured by the stability index) between the poorest and the best fungicides are about 10 or more times, differing slightly in mycotoxin accumulation, FHB index (severity) and Fusarium damaged kernels (FDK). The weak fungicides, like carbendazim, were effective only when no epidemic occurred or epidemic severity was at a very low level. Similar fungicide effects were seen on wheat cultivars which varied in FHB resistance. In this study, we found three fold differences in susceptibility to FHB between highly susceptible and moderately resistant cultivars when treated with fungicides. In the moderately resistant cultivars, about 50% of the fungicide treatments lowered the DON level below the regulatory limit. In the most susceptible cultivars, all fungicides failed to reduce mycotoxin levels low enough for grain acceptance, in spite of the fact that disease was significantly reduced. The results correlated well with the results of the large-scale field tests of fungicide application at the time of natural infection. The Turbo FloodJet nozzle reduced FHB incidence and DON contamination when compared to the TeeJet XR nozzle. Overall, the data suggest that significant decreases in FHB incidence and deoxynivalenol contamination in field situations are possible with proper fungicide applications. Additionally, small plot tests can be used to evaluate the quality of the field disease and toxin production.

Testing the reliability of assessment of land management impacts on Scottish upland vegetation

Background: Surveys of land management impacts (e.g. of herbivores) are carried out in the Scottish uplands to meet conservation objectives. The reliability of such assessments has seldom been tested. Aims: To assess the inter-observer reliability of impact assessments. Methods: In the upper Spey valley, central Scottish Highlands, up to 17 observers were asked to assess in 5 m by 5 m plots and 1 ha plots (a) drying and peat loss in blanket bog, (b) browsing of dwarf-shrub heath, (c) grazing and trampling of wind-clipped heath, and (d) trampling and grazing in soligenous mire. Results: Averaged across indicators, complete disagreement between any two observers (high versus low impact) was found to be very unlikely (P < 0.06, and often < 0.001). On the other hand, complete agreement was moderately likely (between P = 0.53 and 0.75). Reliability varied considerably but was greater for large test plots than for small test plots, and for wind-clipped heath and dwarf-shrub heath. Conclusions: Reliability was similar to that experienced in previous studies of land cover mapping, but appeared to be substantially worse than for the estimation of plant cover. However, reliable discrimination between the extremes of high and low impact, as found in the present study, provides adequate precision for the majority of land management planning and monitoring in extensive, open range conditions.

Prevention of Fusarium mycotoxin contamination by breeding and fungicide application to wheat

The two main possibilities for decreasing toxin contamination were investigated in this paper. In the breeding section, we found that for resistance evaluation the ratio of Fusarium-damaged kernels is more important as this has a closer correlation with the deoxynivalenol (DON) content than the extent of Fusarium head blight (FHB). A high variability was found among lines from the non-Fusarium programme. A 50% decrease of DON contamination could be achieved by a simple and consequent resistance control. The tests with the variety candidates proved the same; therefore, the resistance screening for variety registration is an effective means to stop the spreading of highly susceptible genotypes. The resistance breeding programme showed an even larger DON decrease related to regular susceptible control varieties. Fungicide treatments were generally only weakly effective. However, it was shown that the testing methodology was poor, and with the optimal coverage spraying as much as 90% reduction of DON on small plot tests can be achieved. A farm-scale technology was also developed where the DON reduction as a mean for 3 years was higher than 70%, more than double the regular praxis data. To stabilize this efficacy, we need the most powerful fungicides, a nearly horizontal spraying of heads (like Turbo FloodJet nozzles) that receive the necessary coverage and so enough active ingredient to protect heads and the spraying technology should be kept rigorously. A combination of resistance and fungicide application can reduce DON contamination levels to below the European Union limit of 1.25 mg kg−1 for levels which would otherwise be around 8–10 mg kg−1. We think that this will solve most of the problems.

Evaluation of Temephos Formulations Against Aedes taeniorhynchus Larvae

Four commercially available temephos formulations (Abate 4E, Clarke 1% Skeeter Abate [1% SA], Abate 2-BG, and Abate 5-BG) were evaluated against 3rd instars of Aedes taeniorhynchus in laboratory beaker tests and small field test plots. Abate 4E liquid formulation was effective in both the laboratory and plot tests. 1% SA and Abate 5-BG were more effective in the small field test plots than Abate 2-BG.

Field Evaluations of Concentrated Spray Applications of Microencapsulated Sex Pheromone for Codling Moth (Lepidoptera: Tortricidae)

The application of a microencapsulated (MEC) sex pheromone formulation (Checkmate CM-F) for codling moth, Cydia pomonella (L.), in low volume, concentrated sprays was evaluated in a series of small plot and grower trials in apple, Malus domestica Borkhausen, and pear, Pyrus communis L. Preliminary tests found that MEC sprays applied at 172-207 kilopascals in 12-23 liters/ha deposited the highest density of microcapsules per leaf. The addition of a latex sicker did not increase the deposition of microcapsules. Small plot tests in 2004 compared the effectiveness of two low-volume sprayers against a standard high-volume spray (926 liters/ha) applied at 1,379 kilopascals. Moth catches and fruit injury were significantly lower in plots treated with the low-volume sprays compared with plots treated with the standard sprayer. These results suggest that concentrating the MEC formulation increases the deposition of microcapsules and improves its effectiveness. Larger trials were conducted with a low-volume sprayer in 4-ha plots within commercial apple (2005-2006) and pear orchards (2005) paired with similar plots treated with hand-applied pheromone dispensers. Levels of fruit injury were not significantly different between pheromone treatments in any of the three tests. Moth catches, however, were significantly higher in the MEC- versus the dispenser-treated apple plots in 2005. No difference was found in the fruit injury levels in MEC-treated apple orchards in 2005 caused by irrigation method, but moth catches were significantly higher in overhead versus undertree orchards. The advantages and current limitations of using MEC sex pheromone sprays to supplement current grower's management strategies for codling moth is discussed.

Are Bordered Plots Necessary for Corn Performance Tests?

The range of heights and maturities present in a corn hybrid test has the potential to influence the relative importance of border rows, yet many breeding and performance testing programs use unbordered, two-row plots. A series of experiments was conducted at three sites in two years to evaluate the need for border rows in small-plot corn hybrid tests containing hybrids that differ in maturity and height. The six environments provided average grain yields of 77 to 227 bu/acre. Four corn hybrids provided contrasting combinations of relative maturity (RM) and height: 102 RM, medium-short; 110 RM, medium-short; 110 RM, medium-tall; and 116 RM, tall. Hybrids were planted in plots with four rows, 30 ft long, in a randomized complete block experimental design. The outer two rows of each plot functioned both as the border rows for the 4-row, bordered plot treatment and as the plot rows for the 2-row, unbordered plot treatment in a type of split-plot arrangement. Hybrid yield ranks did not change significantly in response to presence or absence of border rows in any of the six environments, supporting the conclusion that bordered plots are not necessary for accurate estimation of yield ranks in corn hybrid performance tests.

EFFICACY STUDIES OF AQUAPRENETM(1.8% AND 2.8% AI) SAND GRANULES AND ALTOSID® XR-G (1.5% AI) SAND GRANULES AGAINST FIRST AND SECOND INSTARS OF OCHLEROTATUS TAENIORHYNCHUS AS A PREFLOOD TREATMENT IN SMALL FIELD PLOTS

An efficacy study was conducted to evaluate sand granule formulations of Aquaprene (1.8% and 2.8% active ingredient [AI]) and Altosid XR-G (1.5% AI) as a preflood application against Ochlerotatus taeniorhynchus larvae in small field test plots. Aquaprene sand granules (2.8% Al) were applied at 2.5 and 5 lb/acre and the 1.8% AI formulation at 4.2 lb/acre. The 1.8% AI formulation was compared with Altosid XR-G sand granules (1.5% AI) applied at 5 lb/acre. Plots were flooded after 7 days, and 1st and 2nd instars were introduced, pupae were collected, and the plots were drained and dried for 9 days. Assessments were made 21 and 35 days posttreatment. Both Aquaprene sand granules formulations exhibited excellent control throughout the 35-day study.

EFFICACY STUDIES OF AQUAPRENE™ (EMULSIFIABLE CONCENTRATE AND WETTABLE POWDER) INSECT GROWTH REGULATOR FORMULATIONS AGAINST THIRD- AND FOURTH-STAGE LARVAE OF OCHLEROTATUS TAENIORHYNCHUS IN SMALL-PLOT FIELD STUDIES

Efficacy studies were conducted with Aquaprene emulsifiable concentrate (EC) (33.6% active ingredient [AI]) and wettable powder (WP) (40% AI) (S)-methoprene insect growth regulator formulations against larval Ochlerotatus taeniorhynchus in small field test plots. Aquaprene EC was applied at 7.18 and 9.57 g/acre. Approximately one thousand 4th-stage larvae were added to each plot before treatment, and 24 h later pupae were collected to determine emergence inhibition. At both applications rates, Aquaprene EC was extremely effective (99%) at significantly reducing adult emergence in the studies. Two application rates ((S)-methoprene at 2.4 and 4.8 g/acre) of the Aquaprene WP also were evaluated against Oc. taeniorhynchus at 1, 3, 7, and 14 days after treatment. Emergence inhibition and statistical analysis showed that significant differences were found between the (S)-methoprene rates of 2.4 and 4.8 g/acre at each posttreatment assessment. The (S)-methoprene rate of 4.8 g/acre was effective in controlling adult emergence for up to 14 days after treatment.

Seagrass recovery in the Delmarva Coastal Bays, USA

Zostera marina (eelgrass) in the coastal bays of the Delmarva Peninsula, USA, declined precipitously in the 1930s due to the pandemic wasting disease and a destructive hurricane in 1933. This resulted in major changes in many of the ecosystem services provided by this seagrass, such as loss of bay scallops ( Argopecten irradians) and disappearance of brant ( Branta bernicla). Natural recovery of Z. marina, possibly deriving from either small remnant stands or undocumented transplant projects after the demise of Z. marina, has been significant in four northern bays, with over 7319 ha reported through 2003 compared to 2129 ha in 1986, an average expansion rate of 305 ha year −1. This rapid spread was likely due to seeds and seed dispersal from recovering beds. However, no recovery had occurred in the southern coastal bays prior to restoration efforts, possibly due to both their distance from potential donor beds, restricted entrances to the bays, and the narrow time period when seeds are available for colonization via rafting reproductive shoots carrying viable seeds. Survival and expansion of small test plots (4 m 2) in these southern coastal bays between 1997 and 2000 demonstrated that propagule supply, rather than water quality, was limiting seagrass recovery in these bays. In 2001, we initiated a large-scale Z. marina restoration effort in the southern coastal bays utilizing seeds, while simultaneously monitoring water quality using spatially and temporally intensive water quality mapping techniques. Between 2001 and 2004, approximately 24 million seeds harvested from natural, dense beds in Chesapeake Bay were broadcast into experimental plots ranging in size from 0.2 to 2 ha in four coastal bays having no seagrass, totaling approximately 46 ha through 2004. Successful germination (estimated at 5–10% of seeds broadcast), growth and expansion of Z. marina in and around these plots over this 3-year test period, as well as water quality data, suggest conditions are appropriate for plant growth. Low-level aerial photographs in 2004 showed 38% of the bottom in 52–0.4 ha plots was covered by vegetation. Increasing Z. marina coverage will have important implications for fisheries and waterfowl but may potentially conflict with aquaculture, which is rapidly expanding in this region. Continued recovery will depend on maintaining good water quality to avoid the macro-algal accumulations and phytoplankton blooms that have characterized other coastal lagoons. The patterns of natural seagrass recovery and the results of restoration efforts we describe here, as well as seagrass recoveries from wasting disease outbreaks, anoxic events, hurricanes, and propeller scarring reported elsewhere, suggest that seeds and seed dispersal play an important role in the recovery and expansion of these beds.