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• 2121. [Article] The effect of physical and chemical agents on the storage characteristics of raw vegetables and fruits

  This investigation was concerned with the reduction of waste in raw vegetables and fruits between the times of harvest and consumption. Reduction of spoilage in produce was attempted by means of chemical ...

  Citation × Citation Citation Abstract Copy Title: The effect of physical and chemical agents on the storage characteristics of raw vegetables and fruits Author: Lorant, George John, App, Jean This investigation was concerned with the reduction of waste in raw vegetables and fruits between the times of harvest and consumption. Reduction of spoilage in produce was attempted by means of chemical and. physical agents as well as a combination of both. The first phase of the work consisted of an evaluation of a number of chemical compounds with respect to their effectiveness in reducing post-harvest spoilage. The second part dealt with an evaluation of several transparent films applied to raw produce as wrappers and their effect on the keeping quality of the plant material until consumed. Finally combinations of surface disinfection and overwrapping were evaluated for effectiveness against raw produce spoilage. 1. Disinfection Approximately 26 compounds were tested as aqueous dips using 3 concentrations of each on 7 major vegetables and 2 fruits. The following types of compounds were studied. 1. Quaternary ammonium compounds (chlorides, bromides and pyridinium derivatives) 2. Chlorine liberators (organic and inorganic) 3. Phenols (simple and poly-phenols) 4. Quinones and hydroquinones 5. Salts of fatty acids 6. SO₂ liberators 7. Benzoates The chemical treatments were evaluated for each produce by comparison with untreated controls using duplicate tests with triplicate samples for each chemical and concentration. Promising treatments were found for all but one produce (strawberries). The treatments showing promise for each of Pascal celery and Emperor grapes were further tested on a larger scale uaing commercial size units of produce as test samples and long term cold storage. Three chemical treatments for each product were judged satisfactory enough to warrant further testing by means of field trials. The chemicals found most promising for celery were Onyxide, Cetab and Decco while Roccal, Dowicide C and Phygon were selected for grapes. A field test of the three above mentioned treatments for Pascal celery was completed. One thousand bunches per chemical were tested under commercial conditions of dipping and storing. An equal number of untreated bunches was also tested. Half-lots of each treatment were evaluated on each bunch for 11 subjective characteristics and standard mold and bacterial counts of each crate of celery were made after 8 and 14 weeks of storage. On the basis of a statistical analysis of the results, 0.1% Decco of pH=5 can be recommended for the reduction of general rot development in cold storage Pascal celery. Onyxide and Cetab significantly reduce the development of mold but commercial application cannot be recommended because the amount of visible stalk injury was significantly increased over that shown by corresponding untreated or Decco treated celery. 2. Prepackaging The following films were compared for their merit in prolonging the salable life of raw produce. Pliofilm 75FF, Pliofilm 75N2, Pliofilm 75P6A, Cellophane 300LSAT, Cellophane 300MSAT-86, Lumarith P-912, Dupont Acetate 100CA48, Polythene and Kodapak II-130. Wrapping techniques were also evaluated using the followng variations; Complete seals, tent-flap closures, single hole punctures, multiple punctures and windo bags. The following products were studied: celery, tomatoes, carrots, lettuce, cauliflower, chopped salad mix, spinach, strawberries, raspberries, blackberries, and boysenberries. Harvested produce was packaged both before and after the removal of field heat. Behavior of the pre-packaged products in both 33°F storage and subsequent 8O°F storage was studied. Cold storage was extended as long as 120 days while subsequent holding at room temperature varied widely from produce to produce. Observations were made at regular intervals for each product. Several hundred uniform samples were evaluated for most products using duplicates of each treatment for every observation period. Evaluation of most samples included weightloss, C0₂ (and sometimes O₂) of the container atmosphere, mold and decay development, flavor, color, odor, wilting and shriveling. The following conclusions were drawn: All films and wrapping methods affect produce quality. For each produce, treatments could be singled out which were superior to unwrapped controls. However any particular film and type of seal found to be superior for one produce was often not acceptable for another fruit or vegetable. Among the factors found to be critical for the proper choice of treatment were type of produce, produce temperature when packed, length of storage, and temperature of storage. A. Cold Storage For most products, the partially sealed, low permeability MSAT containers and the completely sealed Polythene wraps scored highst for overall product quality. These treatments prevented the accumulation of undesirable CO₂ while at the same time protecting the produce against weightloss and consequent wilting. For some produce, especially berries, wilting was not apparent even in high permeability films such as acetates. B. Warm Storage For produce with high respiration rates (spinach, and berries) only acetate films were acceptable as wraps. The partially sealed low permeability films maintained good quality in warm storage but the high humidity within the package was conducive to micro-organism activity. Thus, in many cases samples disinfected prior to packaging in those films improved the warm storage quality. Disinfection also improved the quality of tomatoes and chopped salad mix in acetate wraps. Of the high permeability films, no significant difference was found among the Dupont acetate, Lumarith and Kodapak II. The type of seal also did not affect the characteristics of these wraps. The low permeability films differed principally in the amount of CO₂, retained by the container during storage. The Pliofilms retained the highest C0₂, levels followed by LSAT and then MSAT Cellophane. The sealed polyethylene, the single puncture and tent flap MSAT wraps exhibited similarity, especially with respect to C0₂ accumulation. The multiple puncture low permeability wraps showed characteristics between acetates and the last mentioned group. Correlation between CO₂ accumulation and off-flavor formation could be determined for most products. Higher CO₂ levels were tolerated at short storage intervals without off- flavor formation by most products but the rate of change in CO₂ tolerance varied from produce to produce. Correlation between % weightioss and degree of wilting could also be expressed as a function of the pre-packaging treatments used. Storage infection was eliminated by all films independent of the type of seal used. It should be emphasized that only a study of the resuits and relationships discussed under each product can serve as a basis for future work and commercial application of the methods presented in this work. Title: The effect of physical and chemical agents on the storage characteristics of raw vegetables and fruits Author: Lorant, George John, App, Jean This investigation was concerned with the reduction of waste in raw vegetables and fruits between the times of harvest and consumption. Reduction of spoilage in produce was attempted by means of chemical and. physical agents as well as a combination of both. The first phase of the work consisted of an evaluation of a number of chemical compounds with respect to their effectiveness in reducing post-harvest spoilage. The second part dealt with an evaluation of several transparent films applied to raw produce as wrappers and their effect on the keeping quality of the plant material until consumed. Finally combinations of surface disinfection and overwrapping were evaluated for effectiveness against raw produce spoilage. 1. Disinfection Approximately 26 compounds were tested as aqueous dips using 3 concentrations of each on 7 major vegetables and 2 fruits. The following types of compounds were studied. 1. Quaternary ammonium compounds (chlorides, bromides and pyridinium derivatives) 2. Chlorine liberators (organic and inorganic) 3. Phenols (simple and poly-phenols) 4. Quinones and hydroquinones 5. Salts of fatty acids 6. SO₂ liberators 7. Benzoates The chemical treatments were evaluated for each produce by comparison with untreated controls using duplicate tests with triplicate samples for each chemical and concentration. Promising treatments were found for all but one produce (strawberries). The treatments showing promise for each of Pascal celery and Emperor grapes were further tested on a larger scale uaing commercial size units of produce as test samples and long term cold storage. Three chemical treatments for each product were judged satisfactory enough to warrant further testing by means of field trials. The chemicals found most promising for celery were Onyxide, Cetab and Decco while Roccal, Dowicide C and Phygon were selected for grapes. A field test of the three above mentioned treatments for Pascal celery was completed. One thousand bunches per chemical were tested under commercial conditions of dipping and storing. An equal number of untreated bunches was also tested. Half-lots of each treatment were evaluated on each bunch for 11 subjective characteristics and standard mold and bacterial counts of each crate of celery were made after 8 and 14 weeks of storage. On the basis of a statistical analysis of the results, 0.1% Decco of pH=5 can be recommended for the reduction of general rot development in cold storage Pascal celery. Onyxide and Cetab significantly reduce the development of mold but commercial application cannot be recommended because the amount of visible stalk injury was significantly increased over that shown by corresponding untreated or Decco treated celery. 2. Prepackaging The following films were compared for their merit in prolonging the salable life of raw produce. Pliofilm 75FF, Pliofilm 75N2, Pliofilm 75P6A, Cellophane 300LSAT, Cellophane 300MSAT-86, Lumarith P-912, Dupont Acetate 100CA48, Polythene and Kodapak II-130. Wrapping techniques were also evaluated using the followng variations; Complete seals, tent-flap closures, single hole punctures, multiple punctures and windo bags. The following products were studied: celery, tomatoes, carrots, lettuce, cauliflower, chopped salad mix, spinach, strawberries, raspberries, blackberries, and boysenberries. Harvested produce was packaged both before and after the removal of field heat. Behavior of the pre-packaged products in both 33°F storage and subsequent 8O°F storage was studied. Cold storage was extended as long as 120 days while subsequent holding at room temperature varied widely from produce to produce. Observations were made at regular intervals for each product. Several hundred uniform samples were evaluated for most products using duplicates of each treatment for every observation period. Evaluation of most samples included weightloss, C0₂ (and sometimes O₂) of the container atmosphere, mold and decay development, flavor, color, odor, wilting and shriveling. The following conclusions were drawn: All films and wrapping methods affect produce quality. For each produce, treatments could be singled out which were superior to unwrapped controls. However any particular film and type of seal found to be superior for one produce was often not acceptable for another fruit or vegetable. Among the factors found to be critical for the proper choice of treatment were type of produce, produce temperature when packed, length of storage, and temperature of storage. A. Cold Storage For most products, the partially sealed, low permeability MSAT containers and the completely sealed Polythene wraps scored highst for overall product quality. These treatments prevented the accumulation of undesirable CO₂ while at the same time protecting the produce against weightloss and consequent wilting. For some produce, especially berries, wilting was not apparent even in high permeability films such as acetates. B. Warm Storage For produce with high respiration rates (spinach, and berries) only acetate films were acceptable as wraps. The partially sealed low permeability films maintained good quality in warm storage but the high humidity within the package was conducive to micro-organism activity. Thus, in many cases samples disinfected prior to packaging in those films improved the warm storage quality. Disinfection also improved the quality of tomatoes and chopped salad mix in acetate wraps. Of the high permeability films, no significant difference was found among the Dupont acetate, Lumarith and Kodapak II. The type of seal also did not affect the characteristics of these wraps. The low permeability films differed principally in the amount of CO₂, retained by the container during storage. The Pliofilms retained the highest C0₂, levels followed by LSAT and then MSAT Cellophane. The sealed polyethylene, the single puncture and tent flap MSAT wraps exhibited similarity, especially with respect to C0₂ accumulation. The multiple puncture low permeability wraps showed characteristics between acetates and the last mentioned group. Correlation between CO₂ accumulation and off-flavor formation could be determined for most products. Higher CO₂ levels were tolerated at short storage intervals without off- flavor formation by most products but the rate of change in CO₂ tolerance varied from produce to produce. Correlation between % weightioss and degree of wilting could also be expressed as a function of the pre-packaging treatments used. Storage infection was eliminated by all films independent of the type of seal used. It should be emphasized that only a study of the resuits and relationships discussed under each product can serve as a basis for future work and commercial application of the methods presented in this work. Close

• 2122. [Article] The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients

  Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition ...

  Citation × Citation Citation Abstract Copy Title: The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients Author: Lemein, Todd Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition from invasive species. Vegetation has been demonstrated to reduce wave energy, increase sedimentation, and decrease erosion in tidal environments under a range of conditions. Similarities and differences between the morphology of vegetation species may play an important role in understanding the mechanism between vegetation, sedimentation, and wave energy. Diversity of species within vegetation communities has been shown to reduce the success of biological invasions from invasive species as well as increase the ability of the community to adapt to environmental changes such as inundation period (period of time vegetation is submerged partially or fully by water). The species present along coastal marshes and specifically at the interface between vegetated marsh and unvegetated mudflat provide an opportunity to better understand the interactions between vegetation and its physical setting. In this dissertation I focus on the species and vegetation communities that are present at this interface of the terrestrial and aquatic boundary to better understand how plant communities may be characterized, how they respond to disturbance, how they are distributed, and how they may influence the physical environment in which they grow. In Chapter two, I explore the ability to use image analysis and the lateral obstruction of vegetation to describe a species density, height and diameter and evaluate the tradeoffs in using image analysis over more traditional methods. In Chapter three, I evaluate the response of an emergent vegetation species, threesquare bulrush (Schoenoplectus pungens), to different depths of complete burial as could be expected from extreme storms, hurricanes, tsunamis, or restoration efforts involving sediment amendment. Chapter four describes the distribution of coastal marsh communities of the Laurentian Great Lakes along an elevational gradient beginning at the terrestrial and aquatic boundary, identifying patterns of wetland distribution, species composition, and exotic plant invasion. In Chapter five, I conclude the dissertation with an evaluation of the effects of two morphologically distinct species of emergent marsh vegetation, threesquare bulrush and Lyngbye’s sedge (Carex lyngbyei), on the sedimentation rate and variability in Tillamook Bay, OR and compare the results to the current understanding of vegetation-sediment feedback. In Chapter two, I found that for morphologically simple species, such as S. pungens, image analysis of lateral obstruction can be used to determine important morphological characteristics of a stand of vegetation including the mean stem height, density, and mean diameter. The method provides a description of the vertical variation in morphologic structure, providing a rapid analytic tool for exploring the effects of vegetation on wave and sediment interaction. However, I note that more morphologically complex species, such as sedges and grasses may not be as easily described using image analysis. In Chapter three, I determined that aboveground biomass of S. pungens would return to pre-disturbance levels following burial by up to 40 cm of mineral sediment after two years. Vegetation was observed to survive burials depths of up to 80 cm, although initially at much lower density. The aboveground height of stems were statistically similar to unburied controls after two years, which is important for the continuation of ecosystem services such as wave attenuation. The results suggest that S. pungens is capable of returning to pre-disturbance levels of biomass following large natural sedimentation events such as extreme storms, hurricanes, or tsunamis, and that burying portions of marshes with sediment as a restoration tool is not likely to harm the buried vegetation. In Chapter four I refine and describe 21 coastal vegetation communities in the Laurentian Great Lakes and the ecological gradients along which they are distributed. Latitude, agricultural intensity, site geomorphology, substrate, and water depth were found to be the significant variables that determined community distribution. Additionally, we observed an expansion of invasive plant species near areas of high anthropogenic activity such as farms and urban centers. In Chapter five, I found that there were species-specific differences in sedimentation rate and variability in Tillamook Bay, OR. Schoenoplectus pungens was found to retain more sediment than C. lyngbyei. Sedimentation rate was observed to be variable by location within the estuary. Two patterns of sediment accumulation were observed. The first occurred along vegetation gradients, with increased sedimentation farther into vegetation beds. In the second pattern, sediment accumulation was observed to be greatest at the marsh/mudflat boundary where vegetation was dense and then decreased with increasing depth into the vegetation. In conclusion, this dissertation explores the interaction of emergent wetland vegetation with environmental factors. Image analysis provides a new tool for rapid characterization of vegetation structure, a burial experiment documents Schoenoplectus pungens’ tolerance to sand burial, a field study at Tillamook, OR documents the relationship between sediment accumulation and emergent vegetation beds, and a wetland classification is developed for coastal wetlands along the Great Lakes, which includes plant communities dominated by S. pungens. Title: The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients Author: Lemein, Todd Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition from invasive species. Vegetation has been demonstrated to reduce wave energy, increase sedimentation, and decrease erosion in tidal environments under a range of conditions. Similarities and differences between the morphology of vegetation species may play an important role in understanding the mechanism between vegetation, sedimentation, and wave energy. Diversity of species within vegetation communities has been shown to reduce the success of biological invasions from invasive species as well as increase the ability of the community to adapt to environmental changes such as inundation period (period of time vegetation is submerged partially or fully by water). The species present along coastal marshes and specifically at the interface between vegetated marsh and unvegetated mudflat provide an opportunity to better understand the interactions between vegetation and its physical setting. In this dissertation I focus on the species and vegetation communities that are present at this interface of the terrestrial and aquatic boundary to better understand how plant communities may be characterized, how they respond to disturbance, how they are distributed, and how they may influence the physical environment in which they grow. In Chapter two, I explore the ability to use image analysis and the lateral obstruction of vegetation to describe a species density, height and diameter and evaluate the tradeoffs in using image analysis over more traditional methods. In Chapter three, I evaluate the response of an emergent vegetation species, threesquare bulrush (Schoenoplectus pungens), to different depths of complete burial as could be expected from extreme storms, hurricanes, tsunamis, or restoration efforts involving sediment amendment. Chapter four describes the distribution of coastal marsh communities of the Laurentian Great Lakes along an elevational gradient beginning at the terrestrial and aquatic boundary, identifying patterns of wetland distribution, species composition, and exotic plant invasion. In Chapter five, I conclude the dissertation with an evaluation of the effects of two morphologically distinct species of emergent marsh vegetation, threesquare bulrush and Lyngbye’s sedge (Carex lyngbyei), on the sedimentation rate and variability in Tillamook Bay, OR and compare the results to the current understanding of vegetation-sediment feedback. In Chapter two, I found that for morphologically simple species, such as S. pungens, image analysis of lateral obstruction can be used to determine important morphological characteristics of a stand of vegetation including the mean stem height, density, and mean diameter. The method provides a description of the vertical variation in morphologic structure, providing a rapid analytic tool for exploring the effects of vegetation on wave and sediment interaction. However, I note that more morphologically complex species, such as sedges and grasses may not be as easily described using image analysis. In Chapter three, I determined that aboveground biomass of S. pungens would return to pre-disturbance levels following burial by up to 40 cm of mineral sediment after two years. Vegetation was observed to survive burials depths of up to 80 cm, although initially at much lower density. The aboveground height of stems were statistically similar to unburied controls after two years, which is important for the continuation of ecosystem services such as wave attenuation. The results suggest that S. pungens is capable of returning to pre-disturbance levels of biomass following large natural sedimentation events such as extreme storms, hurricanes, or tsunamis, and that burying portions of marshes with sediment as a restoration tool is not likely to harm the buried vegetation. In Chapter four I refine and describe 21 coastal vegetation communities in the Laurentian Great Lakes and the ecological gradients along which they are distributed. Latitude, agricultural intensity, site geomorphology, substrate, and water depth were found to be the significant variables that determined community distribution. Additionally, we observed an expansion of invasive plant species near areas of high anthropogenic activity such as farms and urban centers. In Chapter five, I found that there were species-specific differences in sedimentation rate and variability in Tillamook Bay, OR. Schoenoplectus pungens was found to retain more sediment than C. lyngbyei. Sedimentation rate was observed to be variable by location within the estuary. Two patterns of sediment accumulation were observed. The first occurred along vegetation gradients, with increased sedimentation farther into vegetation beds. In the second pattern, sediment accumulation was observed to be greatest at the marsh/mudflat boundary where vegetation was dense and then decreased with increasing depth into the vegetation. In conclusion, this dissertation explores the interaction of emergent wetland vegetation with environmental factors. Image analysis provides a new tool for rapid characterization of vegetation structure, a burial experiment documents Schoenoplectus pungens’ tolerance to sand burial, a field study at Tillamook, OR documents the relationship between sediment accumulation and emergent vegetation beds, and a wetland classification is developed for coastal wetlands along the Great Lakes, which includes plant communities dominated by S. pungens. Close

• 2123. [Article] Cultural controls for suppressing Phytophthora cinnamomi root rot of blueberry

  Phytophthora cinnamomi is a soilborne pathogen that causes root rot disease of highbush blueberry (Vaccinium corymbosum L.). When new installations of susceptible blueberry cultivars are infected with ...

  Citation × Citation Citation Abstract Copy Title: Cultural controls for suppressing Phytophthora cinnamomi root rot of blueberry Author: Yeo, John R. Phytophthora cinnamomi is a soilborne pathogen that causes root rot disease of highbush blueberry (Vaccinium corymbosum L.). When new installations of susceptible blueberry cultivars are infected with P. cinnamomi, plants often fail to grow significant new tissue, greatly reducing yields over the life of the planting. Chemical fungicides are available for disease suppression including mefenoxam and phosphonate compounds. However these tools are not available for organically certified growers. Initially, this research focused on non-chemical control strategies for blueberry root rot disease, including cultivar selection, soil amendments (gypsum and a variety of organic materials) via a series of trials in the greenhouse. Based on the findings of the greenhouse experiments, a field trial was conducted to evaluate a combination of cultural factors in a two year field experiment. Pre-plant gypsum incorporation into soil was evaluated as a control strategy in the field experiment in combination with other cultural practices that were hypothesized to affect disease including mulch type (geotextile weedmat or sawdust), and drip irrigation line placement. Eighteen highbush blueberry cultivars and advanced breeding selections were evaluated for susceptibility or resistance in three greenhouse experiments. Cultivars varied widely in susceptibility, with 'Duke,' 'Draper,' 'Bluetta,' 'Blue Ribbon,' 'Cargo,' 'Last Call,' 'Top Shelf,' and 'Ventura' exhibiting high levels of susceptibility to the disease. More resistant cultivars included 'Legacy,' 'Liberty,' 'Aurora,' 'Overtime,' 'Reka,' and 'Clockwork'. By selecting cultivars with superior resistance, growers may avoid yield losses associated with the disease, enhancing production profitability. Although choosing a disease resistant cultivar is likely the most effective control strategy for blueberry, other cultural disease control practices are needed when susceptible cultivars are grown to fill market demands. Fungicides can control disease in conventional plantings, but cannot be applied within certified organic production systems. Gypsum and organic amendments sometimes provide suppression of Phytophthora root rot in crops other than blueberry. Three greenhouse trials were conducted to evaluate organic soil amendments (peat, sawdust, dairy solids compost, yard debris compost, and composted municipal biosolids blended with douglas-fir bark) incorporated at 20% v/v into soil, and gypsum (CaSO₄) incorporated at 5% (v/v) for disease suppression in factorial combination. Trials were conducted with a disease susceptible cultivar ('Draper'), and soil moisture was maintained near saturation, favoring disease development. Organic amendments did not suppress disease in any of the experiments. Gypsum was effective in disease suppression in one of the three experiments. Gypsum provides a source of soluble calcium, and previous reported studies have demonstrated a mechanism for calcium-mediated suppression of P. cinnamomi. An additional greenhouse study was conducted to determine the relationship between gypsum application rate, soluble calcium in soil solution, and disease suppression. Soluble Ca in soil solution reached a plateau concentration of ~454 mg Ca L⁻¹ soil solution at gypsum application rates equal to or above 16 meq gypsum 100g⁻¹ soil. Higher gypsum application rates did not increase soil solution Ca, or provide additional disease suppression. Rates of gypsum required for disease suppression increase soil electrical conductivity (EC) beyond current recommended salinity guidelines for blueberries (> 2.0 mS/cm). The effects of salinity on plant growth were evaluated in a six month greenhouse experiment, using gypsum (CaSO₄) or potassium sulfate (K₂SO₄) salts to increase EC. Treatment EC levels ranged from 0.3 to 2.6 mS/cm, in ten increments. The maximum EC value chosen for this experiment approximates the maximum value for gypsum solubility in soil solution. Aboveground plant biomass declined more rapidly when EC was supplied by potassium sulfate than it did with gypsum. Root biomass declined when EC was supplied by potassium sulfate, but it was not affected by gypsum rate. Leaf cation concentrations responded strongly to increasing rates of potassium sulfate application. Leaf K increased dramatically, accompanied by declines in leaf Ca and Mg concentration. In contrast, leaf cation concentrations were much more stable when EC was adjusted by gypsum addition. Under the conditions of this greenhouse experiment, the increase in EC accompanying gypsum application had only minor effects on plant growth and nutrient uptake, suggesting that gypsum application is a viable option for trial in the field. A two year field trial was conducted to evaluate cultural practices for efficacy in suppressing P. cinnamomi root rot disease. Pre-plant gypsum incorporation into soil was evaluated as a control strategy in combination with other cultural practices that were hypothesized to affect disease: mulch type (geotextile weed mat vs. sawdust), and drip irrigation line placement. Disease suppression over two growing seasons was evaluated with the highly susceptible cultivar 'Draper' grown on a site with clay loam soil. P. cinnamomi inoculum was mixed into soil before planting. Experimental design was a 2x2x2 factorial with 2 mulch types (geotextile weed mat or douglas-fir sawdust), 2 drip line placements (narrow or wide placement relative to plant row), and 2 gypsum rates (0 and + gypsum). Gypsum was incorporated into planting beds in a 30-cm band at an application rate of 22,420 kg ha⁻¹ in-band equivalent to 2,242 kg ha⁻¹ on a whole-field basis. Drip irrigation treatments consisted of two drip lines placed either adjacent to the plant crown or 20-cm on either side of the crown (wide placement). A fungicide treatment was included to provide an assessment of the efficacy of cultural disease control vs. a chemical alternative. The fungicide treatment was mulched with sawdust and irrigated with drip lines adjacent to plants, and did not receive gypsum application. Mulch type had no significant effect on plant biomass after two years, but plants grown under sawdust had slightly higher biomass and less root infection. Soluble Ca, as measured by mini-lysimeters placed in the rootzone, was increased by gypsum application, especially with wide placement of drip irrigation lines. The disease suppressive effect of gypsum amendment depended on irrigation line placement. Soluble Ca movement in soil was associated with water movement away from drip emitters. When drip irrigation lines were placed adjacent to the plant crown, soluble Ca was moved away from the plant with the wetting front. With wide drip line placement , soluble Ca was moved toward the roots. Plants grown with wide drip line placement and gypsum addition had the lowest root infection incidence and highest plant biomass, likely as the result of more soluble Ca in the rootzone. Despite significant increases in plant biomass with gypsum and widely-placed irrigation lines, plants treated with conventional fungicide had approximately twice as much biomass after two growing seasons. An integrated control program is required for cultural suppression of blueberry root rot disease. Organic production using highly susceptible cultivars in the presence of P. cinnamomi is difficult, and may not produce equivalent yields to conventional production. Improved plant performance in the presence of P. cinnamomi was observed in these trials using cultivar resistance, gypsum, and widely-spaced drip irrigation lines. Other cultural practices, such as careful irrigation scheduling, and appropriate rate and timing of N fertilizer application are also important for disease suppression. In the future, greater P. cinnamomi disease suppression should be possible by using the disease suppressive cultural practices identified in this research in combination with a disease-resistant cultivar. Title: Cultural controls for suppressing Phytophthora cinnamomi root rot of blueberry Author: Yeo, John R. Phytophthora cinnamomi is a soilborne pathogen that causes root rot disease of highbush blueberry (Vaccinium corymbosum L.). When new installations of susceptible blueberry cultivars are infected with P. cinnamomi, plants often fail to grow significant new tissue, greatly reducing yields over the life of the planting. Chemical fungicides are available for disease suppression including mefenoxam and phosphonate compounds. However these tools are not available for organically certified growers. Initially, this research focused on non-chemical control strategies for blueberry root rot disease, including cultivar selection, soil amendments (gypsum and a variety of organic materials) via a series of trials in the greenhouse. Based on the findings of the greenhouse experiments, a field trial was conducted to evaluate a combination of cultural factors in a two year field experiment. Pre-plant gypsum incorporation into soil was evaluated as a control strategy in the field experiment in combination with other cultural practices that were hypothesized to affect disease including mulch type (geotextile weedmat or sawdust), and drip irrigation line placement. Eighteen highbush blueberry cultivars and advanced breeding selections were evaluated for susceptibility or resistance in three greenhouse experiments. Cultivars varied widely in susceptibility, with 'Duke,' 'Draper,' 'Bluetta,' 'Blue Ribbon,' 'Cargo,' 'Last Call,' 'Top Shelf,' and 'Ventura' exhibiting high levels of susceptibility to the disease. More resistant cultivars included 'Legacy,' 'Liberty,' 'Aurora,' 'Overtime,' 'Reka,' and 'Clockwork'. By selecting cultivars with superior resistance, growers may avoid yield losses associated with the disease, enhancing production profitability. Although choosing a disease resistant cultivar is likely the most effective control strategy for blueberry, other cultural disease control practices are needed when susceptible cultivars are grown to fill market demands. Fungicides can control disease in conventional plantings, but cannot be applied within certified organic production systems. Gypsum and organic amendments sometimes provide suppression of Phytophthora root rot in crops other than blueberry. Three greenhouse trials were conducted to evaluate organic soil amendments (peat, sawdust, dairy solids compost, yard debris compost, and composted municipal biosolids blended with douglas-fir bark) incorporated at 20% v/v into soil, and gypsum (CaSO₄) incorporated at 5% (v/v) for disease suppression in factorial combination. Trials were conducted with a disease susceptible cultivar ('Draper'), and soil moisture was maintained near saturation, favoring disease development. Organic amendments did not suppress disease in any of the experiments. Gypsum was effective in disease suppression in one of the three experiments. Gypsum provides a source of soluble calcium, and previous reported studies have demonstrated a mechanism for calcium-mediated suppression of P. cinnamomi. An additional greenhouse study was conducted to determine the relationship between gypsum application rate, soluble calcium in soil solution, and disease suppression. Soluble Ca in soil solution reached a plateau concentration of ~454 mg Ca L⁻¹ soil solution at gypsum application rates equal to or above 16 meq gypsum 100g⁻¹ soil. Higher gypsum application rates did not increase soil solution Ca, or provide additional disease suppression. Rates of gypsum required for disease suppression increase soil electrical conductivity (EC) beyond current recommended salinity guidelines for blueberries (> 2.0 mS/cm). The effects of salinity on plant growth were evaluated in a six month greenhouse experiment, using gypsum (CaSO₄) or potassium sulfate (K₂SO₄) salts to increase EC. Treatment EC levels ranged from 0.3 to 2.6 mS/cm, in ten increments. The maximum EC value chosen for this experiment approximates the maximum value for gypsum solubility in soil solution. Aboveground plant biomass declined more rapidly when EC was supplied by potassium sulfate than it did with gypsum. Root biomass declined when EC was supplied by potassium sulfate, but it was not affected by gypsum rate. Leaf cation concentrations responded strongly to increasing rates of potassium sulfate application. Leaf K increased dramatically, accompanied by declines in leaf Ca and Mg concentration. In contrast, leaf cation concentrations were much more stable when EC was adjusted by gypsum addition. Under the conditions of this greenhouse experiment, the increase in EC accompanying gypsum application had only minor effects on plant growth and nutrient uptake, suggesting that gypsum application is a viable option for trial in the field. A two year field trial was conducted to evaluate cultural practices for efficacy in suppressing P. cinnamomi root rot disease. Pre-plant gypsum incorporation into soil was evaluated as a control strategy in combination with other cultural practices that were hypothesized to affect disease: mulch type (geotextile weed mat vs. sawdust), and drip irrigation line placement. Disease suppression over two growing seasons was evaluated with the highly susceptible cultivar 'Draper' grown on a site with clay loam soil. P. cinnamomi inoculum was mixed into soil before planting. Experimental design was a 2x2x2 factorial with 2 mulch types (geotextile weed mat or douglas-fir sawdust), 2 drip line placements (narrow or wide placement relative to plant row), and 2 gypsum rates (0 and + gypsum). Gypsum was incorporated into planting beds in a 30-cm band at an application rate of 22,420 kg ha⁻¹ in-band equivalent to 2,242 kg ha⁻¹ on a whole-field basis. Drip irrigation treatments consisted of two drip lines placed either adjacent to the plant crown or 20-cm on either side of the crown (wide placement). A fungicide treatment was included to provide an assessment of the efficacy of cultural disease control vs. a chemical alternative. The fungicide treatment was mulched with sawdust and irrigated with drip lines adjacent to plants, and did not receive gypsum application. Mulch type had no significant effect on plant biomass after two years, but plants grown under sawdust had slightly higher biomass and less root infection. Soluble Ca, as measured by mini-lysimeters placed in the rootzone, was increased by gypsum application, especially with wide placement of drip irrigation lines. The disease suppressive effect of gypsum amendment depended on irrigation line placement. Soluble Ca movement in soil was associated with water movement away from drip emitters. When drip irrigation lines were placed adjacent to the plant crown, soluble Ca was moved away from the plant with the wetting front. With wide drip line placement , soluble Ca was moved toward the roots. Plants grown with wide drip line placement and gypsum addition had the lowest root infection incidence and highest plant biomass, likely as the result of more soluble Ca in the rootzone. Despite significant increases in plant biomass with gypsum and widely-placed irrigation lines, plants treated with conventional fungicide had approximately twice as much biomass after two growing seasons. An integrated control program is required for cultural suppression of blueberry root rot disease. Organic production using highly susceptible cultivars in the presence of P. cinnamomi is difficult, and may not produce equivalent yields to conventional production. Improved plant performance in the presence of P. cinnamomi was observed in these trials using cultivar resistance, gypsum, and widely-spaced drip irrigation lines. Other cultural practices, such as careful irrigation scheduling, and appropriate rate and timing of N fertilizer application are also important for disease suppression. In the future, greater P. cinnamomi disease suppression should be possible by using the disease suppressive cultural practices identified in this research in combination with a disease-resistant cultivar. Close

• 2124. [Article] Comparative wintering ecology of two subspecies of sandhill crane : informing conservation planning in the Sacramento-San Joaquin River Delta region of California

  California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being ...

  Citation × Citation Citation Abstract Copy Title: Comparative wintering ecology of two subspecies of sandhill crane : informing conservation planning in the Sacramento-San Joaquin River Delta region of California Author: Ivey, Gary L. California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being compromised by urban expansion, other developments, and conversions to incompatible crop types. Greater (G. c. tabida) and lesser sandhill cranes (G. c. canadensis) both have special conservation status in California; the greater is listed as threatened and the lesser as a bird species of conservation concern by the state. However, basic information about their wintering ecology has been lacking to design biologically sound conservation strategies to maintain their wintering habitats. My study of sandhill cranes focused on one major Central Valley wintering region, the Sacramento-San Joaquin River Delta (Delta). I compared daily movements and winter site fidelity between the two sandhill crane subspecies, evaluated the timing of crane arrival and departure from the region, assessed foraging habitat choices, measured abundance and distribution in the Delta, documented the characteristics of roost sites, and developed habitat conservation models and decision tools for managers to facilitate habitat conservation and management. Both crane subspecies showed strong fidelity to my Delta study area. Foraging flights from roost sites were shorter for greaters than lesser (1.2 ± 0.4 km vs. 3.1 ± 0.1 km, respectively) and consequently, mean size of 95% fixed kernel winter home ranges was an order of magnitude smaller for greaters (1.9 ± 0.4 km² vs.21.9 ± 1.9 km², respectively). The strong site fidelity of greaters to roost complexes within landscapes in the Delta indicates that conservation planning targeted at maintaining and managing for adequate food resources around traditional roost sites can be effective for meeting sandhill crane habitat needs, while the scale of conservation differs by subspecies. I recommend that conservation planning actions consider all habitats within 5 km of a crane roost as a sandhill crane conservation "ecosystem unit." This radius encompasses 95% and 69% of the flights from roosts to foraging location (commuting flights) made by greaters and lessers, respectively. For lessers, a conservation radius of 10 km would encompass 90% of the commuting flights. Management, mitigation, acquisition, easement, planning, and farm subsidy programs intended to benefit cranes will be most effective when applied at these scales. Within these radii, conservation and management of wintering habitats should include creating both new roost and feeding areas to ensure high chances of successful use. Sandhill cranes used major crops and habitat types available in the landscapes surrounding their roost sites and focused most of their foraging in grain crops. They generally avoided dry corn stubble, selected dry rice stubble early in the season, and rarely used dry wild rice stubble. Tilled fields were also usually avoided but were occasionally used shortly after tillage. Mulched corn ranked high in comparison to other corn treatments while mulched rice use was used similarly to dry rice stubble. Both subspecies often highly favored cropland habitats when they were initially flooded. Cranes were attracted to new plantings of pasture and winter wheat. One important difference between the subspecies was that lessers used alfalfa which was generally avoided by greaters. Dry corn stubble was avoided while dry rice stubble was favored early in winter. If wildlife managers want to encourage winter field use by cranes they could provide incentives for favorable practices such as production of grain crops, reduction or delaying tillage and flooding of grain fields, provision of irrigations to some crop types, and increasing the practice of mulching of corn stubble. Of the 69 crane night roosts I identified, 35 were flooded cropland sites and 34 were wetland sites. I found that both larger individual roost sites and larger complexes of roost sites supported larger peak numbers of cranes. Water depth used by roosting cranes averaged 10 cm (range 3-21 cm, mode 7 cm) and was similar between subspecies. Roosting cranes avoided sites that were regularly hunted or had high densities (i.e., > 1 blind/5 ha) of hunting blinds. Roost site design and management should consider providing and maintaining large roost complexes (100 - 1000 ha) ideally in close proximity (< 5 km) to other roost sites, with large individual sites (> 5 ha) of mostly level topography, dominated by shallow water (5-10 cm depths). The fact that cranes readily use undisturbed flooded cropland sites makes this a viable option for creation of roost habitat. Because hunting disturbance can limit crane use of roost sites I suggest these two uses should not be considered compatible. However, if the management objective of an area includes waterfowl hunting, limiting hunting at low blind densities (i.e., < 1 blind/60 ha) and restricting hunting to early morning may be viable options for creating a crane-compatible waterfowl hunt program. Radio-marked sandhill cranes arrived in the Delta beginning 3 October, most arrived in mid-October, and the last radio-marked sandhill crane arrived on 10 December. Departure dates ranged from 15 January to 13 March. Mean arrival and departure dates were similar between subspecies. From mid-December through early-February in 2007-2008, the Delta population ranged from 20,000 to 27,000 sandhill cranes. Abundance varied at the main roost sites during winter, likely because sandhill cranes responded to changes in water and foraging habitat conditions. Sandhill cranes used an area of approximately 1,500 km² for foraging. Estimated peak abundance in the Delta was more than half the total number counted on recent Pacific Flyway midwinter surveys, indicating the Delta region is a key area for efforts in conservation and recovery of wintering sandhill cranes in California. Based on arrival dates, flooding of sandhill crane roost sites should be staggered with some sites flooded in early September and most sites flooded by early October. Maintaining flooding of at least some roost sites through mid-March would provide essential roosting habitat until most birds have departed the Delta region on spring migration. Not all 5-km radius ecosystem units are equal in their value to greater sandhill cranes, and the relative foraging value of a particular parcel within an ecosystem unit depends on the numbers of cranes using the focal roost site, the habitat choices they make, and the probability that they will fly to a particular parcel. Additionally, some ecosystem units overlap, and in these overlap zones, the probability of crane use is higher, because of additive effects. To provide a tool to allow managers to further refine management plans, I developed a model which allows more specific focus of crane conservation, mitigation and habitat management, using what my study revealed about greater sandhill cranes. This model considers the abundance of greaters at individual roost sites and the probability that they would fly to a given location. Sites closer to roosts had a higher probability of crane use. I calculated the probability that greaters would fly to a parcel within concentric 1-km intervals as a product of the proportion of commuting flights of individuals that reached that interval, and the proportion of all commuting flights that reached that interval. Within crane ecosystem units, it is important to protect the existing habitat from further loss and optimize foraging conditions for cranes. I provide a decision matrix to assist with plans to enhance existing crane landscapes, create new crane habitat areas or mitigate habitat losses. This matrix provides a framework for decision-making regarding enhancing sandhill crane foraging and roost site habitats. Wildlife managers could employ a variety of tools to conserve and manage crane habitats, including fee title acquisitions, private conservation easements, and specific cropland management actions to maintain crane-compatible conditions and high food values for cranes (possibly including providing unharvested food plots). My study has demonstrated that most cranes use a relatively small landscape surrounding their traditional roost sites and that they favor certain crops and post-harvest crop management practices for foraging. However, we need a better understanding of the actual carrying capacity for cranes in these crane management zones to ensure that managers can maintain these sites for cranes in the future. Title: Comparative wintering ecology of two subspecies of sandhill crane : informing conservation planning in the Sacramento-San Joaquin River Delta region of California Author: Ivey, Gary L. California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being compromised by urban expansion, other developments, and conversions to incompatible crop types. Greater (G. c. tabida) and lesser sandhill cranes (G. c. canadensis) both have special conservation status in California; the greater is listed as threatened and the lesser as a bird species of conservation concern by the state. However, basic information about their wintering ecology has been lacking to design biologically sound conservation strategies to maintain their wintering habitats. My study of sandhill cranes focused on one major Central Valley wintering region, the Sacramento-San Joaquin River Delta (Delta). I compared daily movements and winter site fidelity between the two sandhill crane subspecies, evaluated the timing of crane arrival and departure from the region, assessed foraging habitat choices, measured abundance and distribution in the Delta, documented the characteristics of roost sites, and developed habitat conservation models and decision tools for managers to facilitate habitat conservation and management. Both crane subspecies showed strong fidelity to my Delta study area. Foraging flights from roost sites were shorter for greaters than lesser (1.2 ± 0.4 km vs. 3.1 ± 0.1 km, respectively) and consequently, mean size of 95% fixed kernel winter home ranges was an order of magnitude smaller for greaters (1.9 ± 0.4 km² vs.21.9 ± 1.9 km², respectively). The strong site fidelity of greaters to roost complexes within landscapes in the Delta indicates that conservation planning targeted at maintaining and managing for adequate food resources around traditional roost sites can be effective for meeting sandhill crane habitat needs, while the scale of conservation differs by subspecies. I recommend that conservation planning actions consider all habitats within 5 km of a crane roost as a sandhill crane conservation "ecosystem unit." This radius encompasses 95% and 69% of the flights from roosts to foraging location (commuting flights) made by greaters and lessers, respectively. For lessers, a conservation radius of 10 km would encompass 90% of the commuting flights. Management, mitigation, acquisition, easement, planning, and farm subsidy programs intended to benefit cranes will be most effective when applied at these scales. Within these radii, conservation and management of wintering habitats should include creating both new roost and feeding areas to ensure high chances of successful use. Sandhill cranes used major crops and habitat types available in the landscapes surrounding their roost sites and focused most of their foraging in grain crops. They generally avoided dry corn stubble, selected dry rice stubble early in the season, and rarely used dry wild rice stubble. Tilled fields were also usually avoided but were occasionally used shortly after tillage. Mulched corn ranked high in comparison to other corn treatments while mulched rice use was used similarly to dry rice stubble. Both subspecies often highly favored cropland habitats when they were initially flooded. Cranes were attracted to new plantings of pasture and winter wheat. One important difference between the subspecies was that lessers used alfalfa which was generally avoided by greaters. Dry corn stubble was avoided while dry rice stubble was favored early in winter. If wildlife managers want to encourage winter field use by cranes they could provide incentives for favorable practices such as production of grain crops, reduction or delaying tillage and flooding of grain fields, provision of irrigations to some crop types, and increasing the practice of mulching of corn stubble. Of the 69 crane night roosts I identified, 35 were flooded cropland sites and 34 were wetland sites. I found that both larger individual roost sites and larger complexes of roost sites supported larger peak numbers of cranes. Water depth used by roosting cranes averaged 10 cm (range 3-21 cm, mode 7 cm) and was similar between subspecies. Roosting cranes avoided sites that were regularly hunted or had high densities (i.e., > 1 blind/5 ha) of hunting blinds. Roost site design and management should consider providing and maintaining large roost complexes (100 - 1000 ha) ideally in close proximity (< 5 km) to other roost sites, with large individual sites (> 5 ha) of mostly level topography, dominated by shallow water (5-10 cm depths). The fact that cranes readily use undisturbed flooded cropland sites makes this a viable option for creation of roost habitat. Because hunting disturbance can limit crane use of roost sites I suggest these two uses should not be considered compatible. However, if the management objective of an area includes waterfowl hunting, limiting hunting at low blind densities (i.e., < 1 blind/60 ha) and restricting hunting to early morning may be viable options for creating a crane-compatible waterfowl hunt program. Radio-marked sandhill cranes arrived in the Delta beginning 3 October, most arrived in mid-October, and the last radio-marked sandhill crane arrived on 10 December. Departure dates ranged from 15 January to 13 March. Mean arrival and departure dates were similar between subspecies. From mid-December through early-February in 2007-2008, the Delta population ranged from 20,000 to 27,000 sandhill cranes. Abundance varied at the main roost sites during winter, likely because sandhill cranes responded to changes in water and foraging habitat conditions. Sandhill cranes used an area of approximately 1,500 km² for foraging. Estimated peak abundance in the Delta was more than half the total number counted on recent Pacific Flyway midwinter surveys, indicating the Delta region is a key area for efforts in conservation and recovery of wintering sandhill cranes in California. Based on arrival dates, flooding of sandhill crane roost sites should be staggered with some sites flooded in early September and most sites flooded by early October. Maintaining flooding of at least some roost sites through mid-March would provide essential roosting habitat until most birds have departed the Delta region on spring migration. Not all 5-km radius ecosystem units are equal in their value to greater sandhill cranes, and the relative foraging value of a particular parcel within an ecosystem unit depends on the numbers of cranes using the focal roost site, the habitat choices they make, and the probability that they will fly to a particular parcel. Additionally, some ecosystem units overlap, and in these overlap zones, the probability of crane use is higher, because of additive effects. To provide a tool to allow managers to further refine management plans, I developed a model which allows more specific focus of crane conservation, mitigation and habitat management, using what my study revealed about greater sandhill cranes. This model considers the abundance of greaters at individual roost sites and the probability that they would fly to a given location. Sites closer to roosts had a higher probability of crane use. I calculated the probability that greaters would fly to a parcel within concentric 1-km intervals as a product of the proportion of commuting flights of individuals that reached that interval, and the proportion of all commuting flights that reached that interval. Within crane ecosystem units, it is important to protect the existing habitat from further loss and optimize foraging conditions for cranes. I provide a decision matrix to assist with plans to enhance existing crane landscapes, create new crane habitat areas or mitigate habitat losses. This matrix provides a framework for decision-making regarding enhancing sandhill crane foraging and roost site habitats. Wildlife managers could employ a variety of tools to conserve and manage crane habitats, including fee title acquisitions, private conservation easements, and specific cropland management actions to maintain crane-compatible conditions and high food values for cranes (possibly including providing unharvested food plots). My study has demonstrated that most cranes use a relatively small landscape surrounding their traditional roost sites and that they favor certain crops and post-harvest crop management practices for foraging. However, we need a better understanding of the actual carrying capacity for cranes in these crane management zones to ensure that managers can maintain these sites for cranes in the future. Close