Do Beneficial Insect Habitats Also Provide Quality Brood Habitat for Northern Bobwhite?

Strips of fallow vegetation along cropland borders are an effective strategy for providing northern bobwhite (Colinus virginianus) habitat. However, a limitation of fallow borders is the lack of nectar-producing vegetation needed to sustain many beneficial insect populations. Planted borders that contain mixes of prairie flowers and grasses may harbor more diverse arthropod communities, but the relative value of these borders as bobwhite brood habitat compared to fallow borders is unknown. Vegetation composition likely has the largest influence on a field border’s structural characteristics, which consequently may impact bobwhite foraging efficiency. Thus, actively planting field borders may not yield the vegetative composition and structure needed to provide quality brood habitat. We used groups of 6 human-imprinted bobwhite chicks as a bioassay for comparing 4 different field border treatments (planted native warm season grasses (NWSG) and prairie flowers, planted prairie flowers only, fallow vegetation, or mowed vegetation) as brood habitat from June to August 2009 and 2010. All field border treatments (0.33 ha each) were established around 9 organic crop fields. Groups of chicks were led through borders for 30-min foraging trials and immediately euthanized at the end of each trial. Their crops and gizzards were dissected in the laboratory, and eaten arthropods were measured, counted, and identified to taxonomic family. We used allometric equations to estimate the live weight of all arthropods consumed, and to calculate a mean foraging rate (grams of arthropods consumed/ chick/30 min) for each field border treatment. We used a modified leaf blower-vacuum to sample arthropod prey availability and diversity in each field border treatment. Sampled arthropods were counted and identified to taxomomic family. We also calculated a Shannon-Weiner diversity index for each field border treatment. Foraging rate did not differ among border treatments in 2009 or 2010. Similarly, mean arthropod densities and diversity calculated from blower-vac samples did not differ among treatments in 2009 or 2010. Chick foraging rate was relatively high and arthropod prey was abundant even in mowed field borders. We suspect the amount of arthropod prey foods is likely not a limiting factor for bobwhite chicks in uncultivated habitats, rather, vegetative structure that facilitates movement, supports a suitable thermal micro-climate, and provides protection from predators is most important for bobwhite broods. Our results suggest that field borders planted for promoting beneficial insects provide bobwhite brood habitat equivalent to fallow borders. However, beneficial insect habitats are expensive, and require additional time and funding to insure successful establishment. The cost of establishing planted NWSG and prairie flowers and planted prairie flowers only borders in our study was ~ $1,928 and$1,773/ha, respectively. Fallow borders are likely the most cost-effective option for landowners/managers whose primary interest is providing bobwhite habitat

Effects of Preplant and Postplant Rotary Hoe Use on Weed Control, Soybean Pod Position, and Soybean Yield

Demand for organic food products has consistently increased for more than 20 yr. The largest obstacle to organic soybean production in the southeastern United States is weed management. Current organic soybean production relies on mechanical weed control, including multiple postplant rotary hoe uses. Although postplant rotary hoe use is effective at the weed germination stage, its efficacy is severely compromised by delays due to weather. Preplant rotary hoeing is also a practice that has been utilized for weed control but the effectiveness of this practice to reduce the need for multiple postplant rotary hoeing for organic soybean production in the southeastern United States has not been investigated. Preplant rotary hoe treatments included a weekly rotary hoeing 4 wk before planting, 2 wk before planting, and none. Postplant rotary hoe treatments consisted of zero, one, two, three, and four postplant rotary hoe uses. Weed control was increased with preplant rotary hoeing at Plymouth in 2006 and 2007 but this effect disappeared with the first postplant rotary hoeing. Multiple postplant rotary hoe uses decreased soybean plant populations, decreased soybean canopy height, lowered soybean pod position, and decreased soybean yield. Plant mapping revealed that the percentage of total nodes and pods below 30 cm was increased by increased frequency of postplant rotary hoe use

Beneficial insect borders provide northern bobwhite brood habitat.

Strips of fallow vegetation along cropland borders are an effective strategy for providing brood habitat for declining populations of upland game birds (Order: Galliformes), including northern bobwhite (Colinus virginianus), but fallow borders lack nectar-producing vegetation needed to sustain many beneficial insect populations (e.g., crop pest predators, parasitoids, and pollinator species). Planted borders that contain mixes of prairie flowers and grasses are designed to harbor more diverse arthropod communities, but the relative value of these borders as brood habitat is unknown. We used groups of six human-imprinted northern bobwhite chicks as a bioassay for comparing four different border treatments (planted native grass and prairie flowers, planted prairie flowers only, fallow vegetation, or mowed vegetation) as northern bobwhite brood habitat from June-August 2009 and 2010. All field border treatments were established around nine organic crop fields. Groups of chicks were led through borders for 30-min foraging trials and immediately euthanized, and eaten arthropods in crops and gizzards were measured to calculate a foraging rate for each border treatment. We estimated arthropod prey availability within each border treatment using a modified blower-vac to sample arthropods at the vegetation strata where chicks foraged. Foraging rate did not differ among border treatments in 2009 or 2010. Total arthropod prey densities calculated from blower-vac samples did not differ among border treatments in 2009 or 2010. Our results showed plant communities established to attract beneficial insects should maximize the biodiversity potential of field border establishment by providing habitat for beneficial insects and young upland game birds

Beneficial insects move from flowering plants to nearby crops

Marking studies demonstrated that lady beetles, lacewings, syrphid flies and parasitic wasps fed on nectar or pollen provided by borders of flowering plants around farms; many insects moved 250 feet into adjacent field crops. Studies using the elemental marker rubidium also showed that syrphid flies, parasitic wasps and lacewings fed on flowering cover crops in orchards and that some moved 6 feet high in the tree canopy and 100 feet away from the treated area. The use of nectar or pollen by beneficial insects helps them survive and reproduce. Therefore, planting flowering plants and perennial grasses around farms may lead to better biological control of pests in nearby crops

Estimated least-square mean (± standard error) foraging rates for northern bobwhite chicks within field border treatments.

<p>Foraging rates were collected in North Carolina in 2009 and 2010. Foraging rates are reported as g of arthropods consumed/chick/30 min. Least-square mean estimates and SE were derived from MIXED models.</p

Creating Predictive Weed Emergence Models Using Repeat Photography and Image Analysis

Weed emergence models have the potential to be important tools for automating weed control actions; however, producing the necessary data (e.g., seedling counts) is time consuming and tedious. If similar weed emergence models could be created by deriving emergence data from images rather than physical counts, the amount of generated data could be increased to create more robust models. In this research, repeat RGB images taken throughout the emergence period of Raphanus raphanistrum L. and Senna obtusifolia (L.) Irwin and Barneby underwent pixel-based spectral classification. Relative cumulative pixels generated by the weed of interest over time were used to model emergence patterns. The models that were derived from cumulative pixel data were validated with the relative emergence of true seedling counts. The cumulative pixel model for R. raphanistrum and S. obtusifolia accounted for 92% of the variation in relative emergence of true counts. The results demonstrate that a simple image analysis approach based on time-dependent changes in weed cover can be used to generate weed emergence predictive models equivalent to those produced based on seedling counts. This process will help researchers working on weed emergence models, providing a new low-cost and technologically simple tool for data collection

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As plant litter decomposes, its mass exponentially decreases until it reaches a non-zero asymptote. However, decomposition rates vary considerably among litter types as a function of their overall quality (i.e., carbon:nitrogen (C:N) ratio and litter chemistry). We investigated the effects of hairy vetch (HV: Vicia villosa Roth):cereal rye (RYE: Secale cereale L.) biomass proportions with or without broadcasted poultry manure on overall litter quality before and during decomposition. As HV biomass proportions increased from 0 to 100%, the relative susceptibility of HV:RYE mixtures to microbial decomposition increased due to: (i) decrease in the initial C:N ratio (87:1 to 10:1 in 2012 and 67:1 to 9:1 in 2013), (ii) increase in the non-structural labile carbohydrates (33 to 61% across years), and (iii) decrease in the structural holo-cellulose (59 to 33% across years) and lignin (8 to 6% across years) fractions. Broadcasted poultry manure decreased the overall initial quality of HV-dominated litters and increased the overall initial quality of RYE-dominated litters. Across all HV:RYE biomass proportions with or without poultry manure, chemical changes during litter decay were related to proportional mass loss. Therefore, the relative decrease in carbohydrates and the concomitant increase in holo-cellulose and lignin fractions were more pronounced for fast decomposing litter types, i.e., litters dominated by HV rather than RYE. While our results suggest possible convergence of litter C:N ratios, initial differences in litter chemistry neither converged nor diverged. Therefore, we conclude that the initial chemistry of litter before decomposition exerts a strong control on its chemical composition throughout the decay continuum.</div