Effects of herbicide-induced habitat alterations on blackbird damage to sunflower

In August 1992, we treated cattail-dominated wetlands in four 23-km² blocks with aerially-applied glyphosate herbicide (5.3 1 ha⁻¹). Four other blocks of wetlands were left untreated (reference). We assessed the effects of cattail (Typha spp.) reduction on roosting blackbird (Icterinae) numbers and sunflower damage within the blocks. Blackbird numbers did not differ between posttreatment years (P = 0.453) or between treated and reference wetlands (P = 0.469), averaging 6227 ± 4185 (SE) birds per block. Sunflower damage within blocks was similar between posttreatment years (P = 0.250) and did not vary (P = 0.460) between treatments ( ). However, positive linear relationships were detected between blackbird numbers (y) and hectares of live cattails (x) [(y = 442.2 x)] (P = 0.006) and between blackbird numbers (x) and kilograms of sunflower lost per hectare per year (y) [(y = 0.003 x)] (P = 0.0001). Cattail reduction appears to discourage roosting blackbirds and, thus, may reduce sunflower damage in adjacent fields.     

Assessing compensation for insect damage in mixed plantings of resistant and susceptible potatoes

Plant mixtures have been proposed for pesticidal transgenic potatoes as a means to reduce selection intensity favoring resistant insect genotypes. Colorado potato beetle,Leptinotarsa decemlineata (Say), defoliation was simulated in mixed plantings of susceptible and resistant potato “mimics” to evaluate yield compensation. Various mixtures of susceptible and resistant potato were planted at two densities and two locations in eastern North Carolina. Resistant plants were undamaged throughout the season whereas susceptible plants were completely defoliated by hand either during early or late bloom. The ability of non-defoliated plants to compensate for neighboring defoliated plants was investigated through single-plant and smallplot field experiments for 2 years. Yield compensation for defoliated plants by neighboring non-defoliated plants was not evident in our studies. Yield of two potato plants, positioned on either side of a defoliated plant, was not different from yield of two potato plants positioned on either side of a non-defoliated potato plant. Compensation in mixtures of resistant and susceptible potato was not evident using several non-linear regression analyses. A negative linear relationship existed between yield and an increasing percent of susceptible plants in the mixture for all planting densities, at each location, every year.     

Red-winged blackbird (Agelaius phoeniceus L). feeding response to oil and anthocyanin levels in sunflower meal

Bird damage to sunflowers might be reduced by the development of resistant cultivars. Neagra de Cluj may be one such cultivar, with high levels of anthocyanin (a possibly aversive flavour) in achene hulls, but low oil yield. Four experiments were designed to assess the importance of oil content and anthocyanin concentration in feeding preferences expressed by red-winged blackbirds (Agelaius phoeniceus L.). Differences in oil concentration of 15% (w/w) were reliably discriminated in two-choice tests: higher concentrations were preferred. Conversely, all anthocyanin concentrations (0·5, 1·0, 2·5 and 5·0% [w/w]) were avoided, and two-choice tests suggested that higher concentrations (2·5 and 5·0%) were relatively more aversive. Both anthocyanin concentration and oil content could influence Neagra de Cluj resistance to bird depredation. Of these two characteristics, oil may be relatively more important.     

Characterization of by-products of sunflower culture – commercial applications for stalks and heads

The by-products of sunflower production were characterized. The sunflower heads contain a strong smelling essential oil (EO) (0.2%) and pectins (22%). The galacturonic acid (GA.A.) content of the pectins depends on the extraction conditions (water-soluble pectins: 67%, soluble in ammonium oxalate/oxalic acid: 74%, in hydrochloric acid: 33%). They are all slightly methylated (degree of methylation (DM) <20%). The stalks may be readily separated into two parts: fiber (external part, 90%) and the pith (internal part, 10%). The mechanical properties of paper pulp obtained by thermomechanical treatment in a twin-screw extruder of the whole stalks or depithed stems were investigated. The pulps had high values of ring crush test (RCT) and concora medium test (CMT), which make them suitable for the manufacture of cardboard. Low-density materials can be also shaped with ground pith. The role of water-soluble substances in the cohesion of these materials is discussed. Its mechanical properties, which are comparable to those of polystyrene, were determined. They may find application in the packaging and packing industries.     

Use of glyphosate for managing invasive cattail (Typha spp.) to disperse blackbird (Icteridae) roosts

Hybrid cattail (Typha × glauca Godr.) has become the dominant emergent vegetation in many wetlands of central North America’s Prairie Pothole Region (PPR). Hybrid cattail, an invasive species, can outcompete native emergents and form a dense canopy that alters the original physiognomy and ecological processes of the wetland. Blackbirds (Icteridae), which number in the millions in late summer in the PPR, use cattails for reproduction, loafing and roosting. Ripening crops, especially sunflower, planted near wetland roost sites can sustain considerable economic damage from blackbirds. Producers of sunflower in North Dakota and South Dakota can obtain assistance from the U.S. Department of Agriculture’s Wildlife Services unit to prevent blackbird damage. Beginning in 1991, Wildlife Services began aerially spraying cattails with glyphosate herbicide to reduce roosting substrate and lessen the severity of localized sunflower damage. As the program enters its 20th year, we review published research aimed at assessing the ecological effects and efficacy of glyphosate use in wetlands. Additionally, we incorporate unpublished data gathered to enhance the program’s environmental safety and efficacy.     

Deposition and redistribution of fungicides applied by air and chemigation for control of late blight in commercial potato fields

The fungicides metiram, mancozeb, metiram + triphenyltin hydroxide, propamocarb hydrochloride + chlorothalonil, dimethomorph + mancozeb, cymoxanil + mancozeb, and chlorothalonil were applied by aircraft and through center-pivot irrigation systems (chemigation) to replicated plots in commercial fields of ‘Russet Burbank’ potato. Fungicide deposition and redistribution were indirectly determined by inoculation of excised leaves withPhytophthora infestans and directly by chlorothalonil residue analysis from upper, middle, and lower crop canopies. The effectiveness of two surfactants added with fungicide and applied by aircraft, an increased water volume rate used by aircraft, and a reduced water volume used with chemigation was also determined. The addition of synthetic latex and siliconepolyether surfactants did not increase efficacy of metiram or mancozeb in controlling late blight when applied by aircraft. The protectant fungicides metiram, mancozeb, and chlorothalonil were not significantly different from dimethomorph + mancozeb, cymoxanil + mancozeb, and propamocarb hydrochloride + chlorothalonil in late blight control when applied by aircraft. However, cymoxanil + mancozeb had limited efficacy when applied by chemigation. Fungicide deposition through the canopy differed when air applications were made before or after canopy closure (row closure). Fungicides applied by aircraft prior to row closure protected the entire canopy; whereas, fungicide application after row closure initially protected the top and middle canopies, and subsequent applications and redistribution of the fungicides were needed for adequate protection throughout the canopy. The fungicides and fungicide mixtures tested were evenly deposited throughout the potato canopy with each chemigation application. Severity of late blight did not differ on leaves treated with mancozeb or chlorothalonil applied by aircraft at water volumes of 47 L/ha and 94 I/ha and then inoculated withP. infestans, nor did severity of late blight differ on inoculated leaves previously treated with chlorothalonil by chemigation at water volumes of 15,145 and 50, 571 L/ha.     

Application strategies for an anthraquinone-based repellent to protect oilseed sunflower crops from pest blackbirds

Non-lethal alternatives are needed to manage the damage caused by wild birds to oilseed sunflower crops (Helianthus annuus Linnaeus). We evaluated field residues and experimental applications of an anthraquinone-based repellent (active ingredient 50% 9,10-anthraquinone) to minimize red-winged blackbird (Agelaius phoeniceus Linnaeus) depredation of oilseed sunflower. Chemical residues from experimental applications of the anthraquinone-based repellent (4.7 l/ha and 9.4 l/ha; low, high) in a ripening oilseed sunflower field were 481 ppm and 978 ppm anthraquinone at the beginning of blackbird damage, and 385 ppm and 952 ppm anthraquinone at the end of blackbird damage, respectively. Prior to harvest, we observed 402 ppm and 462 ppm anthraquinone in the oil, and 27 ppm and 165 ppm anthraquinone in the pomace from crushed sunflower achenes previously sprayed with the low and high applications, respectively. For the purpose of developing application strategies useful for avian repellents, we subsequently investigated blackbird feeding response to oilseed sunflower treated with the anthraquinone-based repellent and either a registered insecticide or a registered fungicide popularly used for ripening sunflower. We observed a positive concentration–response relationship among blackbirds exposed to anthraquinone and the insecticide (a.i. 8.4% esfenvalerate), or anthraquinone and the fungicide (a.i. 23.6% pyraclostrobin). Blackbirds reliably discriminated between untreated sunflower and that treated with 1810 ppm anthraquinone and 0.1% of the insecticide or 1700 ppm anthraquinone and 0.14% of the fungicide during our preference experiments. Given that ripening achenes are inverted from conventional pesticide applications throughout much of the period associated with blackbird depredation, we also evaluated blackbird repellency of the anthraquinone-based repellent applied to involucral bracts (i.e., the back of sunflower heads) of oilseed sunflower. Blackbirds did not discriminate between untreated involucral bracts and those treated with foliar applications comparable to 4.7 l/ha or 9.4 l/ha; blackbirds consumed more achenes from untreated sunflower heads than from those treated with 18.7 l/ha of the anthraquinone-based repellent. Supplemental repellent efficacy studies should investigate blackbird response to anthraquinone-based repellents (e.g., ≥4.7 l/ha) within 10–100 ha sunflower fields and include independent field replicates with predicted bird damage, repellent application strategies developed for protection of ripening crops, pre- and at-harvest repellent residues, and bird damage and crop yield measurements.     

Double-stocking for overcoming damage to conifer seedlings by pocket gophers

A 5-yr study was conducted on national forests in Idaho and Oregon to evaluate how doubling the seedling stocking rate of lodgepole pine (Pinus contorta) would relate to 5-year survival and the uniformity of distribution of seedlings in the presence of northern pocket gopher (Thomomys talpoides) damage. Either 4 or 8 seedlings were planted in 40-m² subplots (1000 or 2000 seedlings/ha) and monitored for gopher damage. We found that the number of seedlings attacked by gophers, and consequently, the number of seedlings surviving for 5 years, were directly proportional to the stocking rate, but the consistency of seedling distribution within each site (as measured by the proportion of 40-m² subplots with ≥ 2 surviving seedlings) did not double with stocking rate. In some situations, increasing the stocking rate should be considered as a method for overcoming pocket gopher damage.     

Modelling density thresholds for managing mouse damage to maturing wheat

Predator-prey theory suggests that pest damage that occurs over a period of time is related to the initial pest density and their functional and numerical responses to the resource. Estimating the relationship between damage and initial density is therefore fundamental to determining the threshold density (D_T), above which the economic benefits of control exceed the economic costs of control. A manipulative experiment was conducted to parameterize a model of D_T for managing yield loss (YL) caused by mice (Mus domesticus L.) from the milky stage to harvest, by assessing the relationship between YL and initial mouse density at the milky stage (D_I). This relationship subsumed the functional and numerical response of mice to maturing wheat crops. The experiment was conducted in a typical wheat field and D_I was manipulated by releasing a known number of mice into an experimental crop enclosed by a mouse proofed fence. The estimated relationship was asymptotic exponential: YL increased almost linearly with D_I until apparent competition between mice occurred at densities in excess of about 500 mice ha⁻¹; and apparent competition limited further increases in YL at densities in excess of 2133 mice ha⁻¹. D_T varied depending on the effectiveness of the control method in reducing D_I and the cost of control as a percentage of the farm-gate value of wheat. D_T was 89 mice ha⁻¹ for triggering aerial baiting if this method was effective in reducing D_I by 41% and if the cost of baiting was 7.54% of farm-gate value of wheat. Grain growers will be able to use D_I immediately to make informed, timely decisions for managing mouse damage to wheat crops. Mouse densities should be monitored well before the milky stage so that D_I can be forecast by the trend of monitored densities. If the forecast D_I exceeds D_T, management should be implemented at least a week before the milky stage (allowing a week for control such as baiting to take effect). However, if the forecast D_I is much higher than D_T so that even after control the reduced D_I would still be higher than D_T, then additional control may be applied so that the final control applied a week before the milky stage would reduce D_I below D_T.     

The potential of nitric oxide for reducing oxidative damage induced by drought stress in two turfgrass species,creeping bentgrass and tall fescue

Drought stress is a major factor‐limiting grass growth. The production of reactive oxygen species (ROS) increases under stress conditions and causes cell oxidative damage. This study investigated the effect of sodium nitroprusside [a nitric oxide (NO) donor] treatment on drought stress in two turfgrass species, creeping bentgrass and tall fescue. Physiological characteristics such as relative water content (RWC), ion leakage, chlorophyll and proline content, and activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) were evaluated after 40 d drought stress and in the recovery stage. Results showed that nitric oxide (NO) treatment, especially 150 μm , could maintain significantly higher RWC and reduce ion leakage under drought stress conditions in both species. Furthermore, both turfgrass species showed higher chlorophyll and proline content after drought stress period when sprayed with NO, while chlorophyll and proline content of control plants declined. Drought stress significantly reduced SOD and APX activity, while NO treatment induced higher SOD and APX activity under drought conditions. After recovery, leaf RWC returned to the control level; however, NO‐sprayed plants showed higher RWC compared to controls. Both turfgrass species exhibited lower chlorophyll content at the recovery stage when exposed to severe drought stress, and NO application increased chlorophyll content compared to controls. No significant differences were found between NO treatment and control plants for proline and SOD activity, but APX activity of NO‐sprayed plants was higher than in the control plants. These results suggest that foliar application of NO may alleviate drought stress in turfgrass by maintaining membrane stability and inducing antioxidant enzyme activity.     

Evaluation of seed treatment insecticides for management of the rice water weevil,Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), in commercial rice fields in Louisiana

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor^® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx^® Rice, Syngenta^® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside^®, Valent^® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.     

A new method for assessing land leveling to produce high quality consolidated paddy fields

The quality of leveling of 0.3-ha consolidated paddy fields in Japan was investigated. The leveling of normal consolidated plots was accurate to within 7 cm from a horizontal plane, with an average standard deviation of about 18 mm for the points measured throughout the plot. The investigated paddy fields had inclinations ranging from horizontal to quite steep; the average inclination was 0.56‰ (1/1,718). The traditional assessment method is based on a horizontal plane. Because it is difficult to use this method to assess the leveling conditions of paddy fields that have an inclined surface, a new assessment method that accurately evaluates the sloped plane of a paddy field is proposed. The new method assesses the leveling conditions within a field by means of a "state index" that considers both the inclination and the surface roughness. Using this state index not only allowed the conditions to be effectively evaluated, but also helped reduce the extra workload needed to level the field to the farmers' requirements after the initial consolidation. Electronic Publication     

Wise use of paddy rice fields to partially compensate for the loss of natural wetlands

This paper reviews the scientific information related to climate change impacts on wetlands and functions of human-made wetlands such as paddy rice field and treatment wetland are described to partially compensate for the loss of natural wetlands. Wetlands are among the world’s most productive environments and are cradles of biological diversity, providing the water and primary productivity upon which countless species of plants and animals depend for survival. Considerable evidence suggests that some global warming is occurring, which has important implications for wetland system as well as human life and wildlife. Direct effects of climate change on wetlands are likely to be accentuated by human induced changes that will increase stress to wetland ecosystems. The Ramsar Classification System for Wetland Type provides three broad categories: marine/coastal wetlands, inland wetlands, and human-made wetlands. Human-made wetlands are as important as natural wetlands, and the largest human-made wetland is a paddy rice field (130,000,000 ha) taking about 18% of total global wetland, which is second only to natural fresh wetlands. Paddy rice fields provide not only rice production for food, but also diverse multi-functionalities such as flood control, groundwater recharge, soil erosion control, water quality purification, air purification and cooling, wildlife habitat, amenity and social benefits. The economic value of multi-functionalities estimated by contingent valuation method (CVM) and travel cost method was in the range of U$ 9.75–11.46 billion, which is greater than the value of rice production itself in Korea. Unfortunately, there is an indication of decreased area in paddy rice field in Korea after 1990 showing about 20% decrease in 15 years. Another human-made wetland type is a constructed wetland for water purification, and thousands hectares of wetlands are scheduled to be constructed for reservoir water quality improvement in next 5 years in Korea, and their application is expected to be more common in near future. There is a growing consensus that wetlands are critically important ecosystems that provide globally significant social, economic and environmental benefits. Wise use of human-made wetlands is as important as conservation of natural wetlands, which can be a viable element to overall climate change mitigation and can partially compensate for the loss of natural wetlands.     

Efficacy and environmental fate of copper sulphate applied to Australian rice fields for control of the aquatic snail Isidorella newcombi

Copper sulphate pentahydrate (CuSO₄·5H₂O) is widely used for controlling Isidorella newcombi, an aquatic snail that causes substantial damage to rice crops in southeastern Australia. We conducted field trials on a Birganbigil clay loam soil that demonstrate high levels of efficacy against adult I. newcombi (95% mortality at 6.38 kg ha⁻¹ CuSO₄·5H₂O (1.14 mg Cu L⁻¹)). Dissolved copper fell below the detection limit (0.02 mg Cu L⁻¹) between 7 and 20 d after spraying at application rates up to 2.16 mg Cu L⁻¹ (12 kg ha⁻¹ CuSO₄·5H₂O). Total copper concentrations in the water column fell below the detection limit (0.007 mg Cu L⁻¹) 7–12 d after spraying at initially applied concentrations of 0.52–1.12 mg Cu L⁻¹, but remained detectable (0.01–0.02 mg Cu L⁻¹) until 30 days after spraying (the conclusion of monitoring) when applied at higher initial concentrations (1.18–2.16 mg Cu L⁻¹). There was a strong positive correlation (r² = 0.90, P < 0.001) between copper application rate and copper concentrations in surface sediments 30 d after spraying. Bioassays with immature snails using three different test soils beneath irrigation water showed that underlying soil type strongly influenced the response of snails to applied copper, with significant (P < 0.05) differences between LC₉₀ values which ranged from 0.41 to 1.04 mg applied Cu L⁻¹. Laboratory studies showed that dissolved copper concentrations remained significantly higher (P < 0.05) in the water column above the soil that had the most deleterious effect on copper toxicity. Dissolved organic carbon concentrations were significantly (P < 0.05) higher in both this soil and in the overlying water in the corresponding bioassay system, and correlated more closely with LC₉₀ values than other water chemistry parameters such as total hardness. Our results support the ongoing use of a variable copper application rate of 6–12 kg ha⁻¹ CuSO₄·5H₂O to allow for site-specific variations in efficacy, and suggest that variations in the release of dissolved organic carbon compounds from flooded soils may be a key factor moderating copper toxicity to I. newcombi in rice fields.     

闽西北稻区双季稻改再生稻避蚊减害技术研究

通过对再生稻受稻瘿蚊危害轻的现象的研究，明确了在稻瘿蚊重发区双季稻改再生稻可以有效地控制稻瘿蚊成灾；再生稻避蚊减害的原因是因为再生芽易受害期短和可能与再生稻的株型结构特点有关；不同播期的再生稻避蚊减害效果不一样。3月20日前播种的避蚊减害效果好；及时烤田是再生稻避蚊减害的关键技术之一。     

Predicting pre-harvest sprouting susceptibility in barley: Looking for “sensitivity windows” to temperature throughout grain filling in various commercial cultivars

Pre-harvest sprouting (PHS) is common in cereals that lack grain dormancy if maturing grain is exposed to rain. This phenomenon leads to immediate loss of seed viability, and since the malting process requires germination, its occurrence is highly undesirable in malting barley crops. Dormancy release rate is genetically and environmentally controlled. We evaluated the effect of temperature during grain filling on the dormancy release pattern (and then on the PHS susceptibility) of grains from five malting barley (Hordeum vulgare L.) cultivars widely sown in Argentina, with the aim of predicting PHS susceptibility of a barley crop from easy-to-gather data. Barley cultivars (Quilmes Ayelén, Q. Palomar, Q. Painé, B1215 and Scarlett) were sown on different dates over a 3-year period for generating variability in the thermal environment during grain filling. The period from pollination to physiological maturity (PM) was adjusted to a thermal time (TT) scale, which was then arbitrarily divided into 50 °C d intervals. Mean air temperature within each interval and for the whole filling period was calculated for the different sowing dates. Dormancy release pattern was followed by determining a weighed germination index (GI) throughout grain filling and maturation. We sought a linear relationship between temperature during grain filling and GI at some moment after PM. For all barley cultivars, except B1215, a significant (p < 0.001) and positive correlation was found between the GI of grains with 10–20% moisture content (fresh basis) and mean temperature within TT intervals located at the last stages of seed development. Then, simply temperature-based models for predicting crop PHS susceptibility were generated for each barley cultivar. Moreover, we intended a single, universal prediction model constructed with data from all cultivars. Two general forms were proposed, but the relationships were slightly less tight when each barley cultivar model was used. A preliminary validation for each cultivar model was done for three genotypes with independent data from four sites of the major barley production area in Argentina. When comparing experimental and field data regressions we did not find significant differences in slope for any cultivar (p > 0.25). However, most of the observed GIs were higher than predicted. This upwards displacement of GI–temperature relationship suggests the role of other environmental factors (i.e. water and soil N availability, day length), differing among tested locations. We are currently evaluating and quantifying the effect of these factors with the aim of improving PHS susceptibility prediction in malting barley crops.