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What is new with rhizomania and curly top management and effects of these viruses on storage
Get PDFRhizomania is a serious yield limiting viral disease in sugarbeet first identified in California, USA in 1984. The disease has since spread to all major production areas in the United States. Rhizomania is caused by Beet necrotic yellow vein virus (BNYVV) and vectored by the plasmodiophorid (a fungal-like organism), Polymyxa betae. The virus survives inside the thick-walled resting spore of the vector in the soil, which can remain viable for many years. As a result, once a field is infested, using crop rotation and non-host crops will not be effective for controlling the disease. In the spring with near saturated soil conditions, the resting spore will germinate to release zoospores when in close proximity to sugarbeet roots. The zoospores will attach to the root and transmit the virus to the sugarbeet root. Therefore, the primary control measure will be to grow a sugarbeet cultivar with high resistance to BNYVV. Cultivars with the Rz1 resistance gene are available, but resistance breaking strains of the virus have been found in CA, CO, ID, MN, and OR. In the disease screening nursery in Kimberly, ID, check cultivars with just the Rz2 gene for resistance frequently exhibit symptoms on 10 to 40% of the plants, while cultivars with just the Rz1 gene tend to have just occasional blinking plants (plants with yellow narrow upright leaves). In the nursery and commercial fields, the Rz1 gene seems to be necessary to maintain an acceptable level of resistance, even if the cultivars contain other sources of resistance. Since resistance breaking strains are known to occur and resistance genes only allow for partial resistance to this disease, it would be wise to grow cultivars with additional sources of resistance to help protect Rz1. If inoculum levels are quite high, resistance in the cultivars may breakdown. Another control measure to consider would be to reduce irrigation frequency, so the soil surface dries between irrigations. Genetic engineering approaches have been studied for rhizomania, so hopefully in the near future cultivars with resistance based on transgenic strategies will become available.
Curly top is another serious yield limiting viral disease for sugarbeet grown in semiarid production areas in the United States. Curly top is vectored by the beet leafhopper and can be caused by a number of Curtovirus species: Beet severe curly top virus (BSCTV; formerly CFH strain), Beet mild curly top virus (BMCTV; formerly Worland strain), and Beet curly top virus (BCTV; formerly Cal/Logan strain). Other Curtovirus species have been documented or at least proposed in recent years and some have been shown to occur on sugarbeet in other countries. A survey of the western United States showed BSCTV, BMCTV, and BCTV were present in sugarbeet (6). However, samples in this survey along with some collected in 2012 in Idaho show a virus different from these three was also present in sugarbeet. This “unknown” virus amplifies with the coat protein primers, but does not amplify with the species specific primers. This “unknown” virus is currently being investigated further at the USDA-ARS laboratory in Kimberly, ID. The curly top virus species are carried between growing seasons by adult female beet leafhoppers that overwinter on weeds in desert areas and poorly managed residential areas. The females lay eggs in the spring, leading to the start of approximately three generations under Idaho conditions. When the winter host plants desiccate in the spring, the beet leafhoppers move into crop areas carrying the curly top viruses. Most commercial sugarbeet cultivars in the western United States carry partial resistance to the curly top viruses, but the low to intermediate resistance carried by the cultivars tends not to be as protective prior to the eight-leaf growth stage. Thus, the earlier plants become infected the higher the yield loss. In-furrow, foliar, and seed-treatment insecticides have been used to supplement this host resistance. Based on studies by the USDA-ARS Kimberly sugarbeet program (1,9), the neonicotinoid seed treatments (Poncho, Cruiser, and NipsIt) were established as being effective at reducing curly top through early season control of the beet leafhopper vector. Root yield increases of 17% or more have been observed for Idaho (based on USDA-NASS statistics) and other states with semiarid production areas through the use of these neonicotinoid seed treatments (1,9). These seed treatments provide at least 59 days of beet leafhopper protection after planting along with early season control of leafminer and aphids (1,3,4,7,9). In 2012, research indicated that some labeled foliar insecticides (Asana® and Mustang®) may be used to potentially extend this coverage period. However, foliar insecticides would not be recommended to replace the seed treatments, because of their short efficacy period. Currently genetic engineering approaches are being developed for curly top, so in the future cultivars with resistance based on transgenic strategies may become available.
In storage, sugarbeet roots have been shown to lose an average of 0.2 to 0.3 pounds of sucrose per ton of roots per day when stored under ambient conditions, but losses can be as high as 0.5 pounds depending on cultivar. Thus, cultivar selection for storage could improve storability and reduce sucrose losses in storage (5). However, pathogen (2,5,7,8), pest (3), and environmental influences (over or under watering, frost, etc.) during the growing season can also negatively impact root storability. In particular, rhizomania (5,8) and curly top (7) have been documented to negatively influence root storability. Also, placing roots infested with Rhizoctonia solani and bacteria such as Leuconostoc into storage piles has been shown to reduce sucrose in neighboring healthy roots (2). Thus, keeping sugarbeet plants healthy and as stress free as possible during the growing season will also reduce losses in storage
Investigation of copper sorption by sugar beet processing lime waste
Get PDFIn the western US, sugar beet processing for sugar recovery generates a lime-based waste product (~250,000 megagrams/yr) that has little liming value in the region’s calcareous soils. This area has recently experienced an increase in dairy production, with dairies utilizing copper-based hoof baths to prevent hoof diseases. A concern exists regarding soil copper accumulation as spent hoof baths may be disposed of in waste ponds with pond waters utilized for irrigation. The objective of this preliminary study was to evaluate the ability of lime waste to sorb copper. Lime waste was mixed with increasing copper-containing solutions (up to 100,000 mg/kg), at various buffered pH values (6, 7, 8, 9), and shaken over various time periods (up to 30 days). Copper sorption phenomenon was quantified using sorption maximum fitting and sorption mechanism was investigated using X-ray absorption spectroscopy. Results showed that sorption onto lime waste increased with decreasing pH, and the maximum copper sorption of ~40,000 mg/kg occurred at pH 6. X-ray absorption spectroscopy indicated that copper hydroxide was the probable species present, although the precipitate existed as small multinuclear precipitates on the surface of the lime waste. Such structures may be precursors for larger surface precipitates that develop over longer incubation times. Findings suggest that sugar beet processing lime waste can viably sorb Cu from liquid waste streams, and thus it may have the ability to remove Cu from spent hoof baths
Interaction of sugar beet host resistance and rhizoctonia solani AG-2-2 IIIB strains
Get PDFRhizoctonia root rot caused by Rhizoctonia solani can cause serious economic losses in sugar beet fields. Preliminary evidence suggests there could be interactions between different strains and resistance sources. Thus, field studies were conducted to determine if nine R. solani AG-2-2 IIIB strains varied for virulence when compared with a non-inoculated check and interacted with five sugar beet lines (four resistant lines and a susceptible check). The studies were arranged in a randomized complete block design with six replications. Roots were evaluated for surface rot and internal fungal and bacterial rot in September. All strains were virulent on the susceptible check, FC901/C817, and had the same ranking (r = 1.0) regardless of disease variable. Line FC709-2 was resistant (response not different from non-inoculated check; P > 0.1042) to all strains, while the strain responses resulted in weak interactions with less resistant lines in 14 of 19 variable-year combinations. Since most commercial sugar beet cultivars contain low to intermediate resistance to Rhizoctonia root rot, the strain used to screen should be considered in order to maintain consistent responses between nurseries and commercial fields
Nutrient losses from an irrigated watershed in southern Idaho
Get PDFWater, sediment and nutrients flowing into and out of the 82,000 ha Twin Falls,ID irrigation tract were measured from 2005 to 2008. Approximately 80% of the water flowing into the watershed was irrigation water diverted from the Snake River. About 40% of the watershed inflow returned to the Snake River. Much of this return flow was water from subsurface drain tiles and tunnels that drain shallow groundwater. Converting from furrow to sprinkler irrigation, improved irrigation management, and constructed sediment ponds have reduced sediment loss from 460 kg/ha in 1971 to <100 kg/ha in 2005. In 2007 and 2008, more sediment and phosphorus entered the watershed than returned to the Snake River. Diverting irrigation water into the watershed removed 6300 Mg of sediment, 21 Mg of dissolved P, and 32 Mg of total P from the Snake River on average each year. However, the watershed contributed almost 900 Mg of nitrate-N annually to the Snake River. Conservation practices have effectively reduced sediment and phosphorus losses from the watershed, emphasis now must shift to reducing nitrate loss from the watershed
Soil phosphorus availability differences between sprinkler and furrow irrigation
Get PDFWater flowing in irrigation furrows detaches and transports soil particles and subsequently nutrients such as phosphorus. To reduce the risk of erosion and offsite phosphorus transport, producers in south-central Idaho have been converting from furrow to sprinkler irrigation. We completed research on soil phosphorus dynamics in furrow versus sprinkler irrigated soils from four paired-fields in the region. Surface soils (0-2.5 inches) were obtained from fields in September following barley harvest. Furrow irrigated soils contained 38 parts per million of plant-available phosphorus (i.e. Olsen-extractable), on average, as compared to 20 parts per million under sprinkler irrigation. These results are important as 20 parts per million extractable phosphorus can be construed as the point where soil phosphorus is considered low to medium in soil testing; extractable phosphorus values over 40 parts per million limit sites to phosphorus application based on crop uptake only. These soils were also analyzed using a sequential extraction technique, and total and amorphous iron were determined to identify inorganic phosphorus pools. Soils under furrow irrigation had greater concentrations of inorganic phosphorus in the soluble/aluminum-bound/iron-bound and occluded phases, and in the amorphous iron phase. Phosphorus concentrations in all other soil phases were similar between the two irrigation practices. Findings suggest that iron redox chemistry plays a large role in phosphorus release under furrow irrigation, even in aridic systems. In terms of soil phosphorus, results support the use of sprinkler irrigation as a best management and conservation practice
Rhizoctonia root rot resistance in commercial sugar beet cultivars in Twin Falls County, ID, 2012
Get PDFRhizoctonia root rot continues to be a concerning problem in sugar beet production areas. To investigate resistance to this disease in 26 commercial sugar beet cultivars, field studies were conducted with three Rhizoctonia solani AG-2-2 IIIB strains. Based on means for the 26 cultivars, surface rot ranged from 0 to 96% depending on the strain-cultivar combination. Both the number of dead plants and root surface area rotted resulted in significant (P < 0.0002) cultivar differences. Based on Spearman’s rank correlation coefficient, there was always a significant relationship (P < 0.0390) when comparing cultivar performance across all three strains regardless of disease variable. The three most resistant cultivars performed well against all strains and variables, but still had half the root surface area rotted. Additional efforts need to be made to get more resistance to this disease problem in commercial sugar beet cultivars
Comparison of atmospheric stability methods for calculating ammonia and methane emission rates with WindTrax
Get PDFInverse dispersion models are useful tools for estimating emissions from animal feeding operations, waste storage ponds, and manure application fields. Atmospheric stability is an important input parameter to such models. The objective of this study was to compare emission rates calculated with a backward Lagrangian stochastic (bLS) inversedispersion model (WindTrax) using three different methods for calculating atmospheric stability: sonic anemometer, gradient Richardson number, and Pasquill-Gifford (P-G) stability class. Ammonia and methane emission data from a compost yard at a 10,000-cow dairy were used for the comparisons. Overall, average emission rates were not significantly different among the stability methods. Emission rates correlated well between the sonic and other methods (r2 > 0.79, p < 0.001). The slopes of the regression lines between the sonic and Richardson methods were 0.95 and 1.0 for CH4 and NH3, respectively. The regression line slopes for the P-G method were about 1.9 for CH4 and 1.6 for NH3, which means emission rates predicted with the P-G method tended to be 50% to 100% greater than rates predicted with sonic anemometer data. Based on this limited data set, using the gradient Richardson method to represent atmospheric stability resulted in emission rates that more closely matched emission rates from the sonic method. Considering the amount of variability inherent in emissions calculations, a three-dimensional sonic anemometer should be used, if possible, to directly provide the necessary data to calculate parameters representing wind properties, rather than inferring values from other stability classification methods
Ft. Collins sugar beet germplasm evaluated for rhizomania and storage rot resistance in Idaho, 2012
Get PDFRhizomania caused by the Beet necrotic yellow vein virus (BNYVV) is a worldwide problem that can lead to loss of tonnage and lower percent sucrose in the field. BNYVV can also reduce the storability of roots. To identify germplasm with resistance to these problems, 18 sugarbeet germplasm lines developed by the USDA-ARS Ft. Collins sugarbeet program and four check cultivars were screened in a field experiment arranged in a randomized complete block design with 6 replications. During the growing season plants were evaluated for foliar rhizomania symptoms. At harvest on 4 October 2012, roots were evaluated for rhizomania symptoms and then placed into an indoor commercial sugarbeet storage building in Paul, ID. Foliar symptoms ranged from 0% for resistant checks to 95% for the susceptible check, indicating good separation of germplasm for BNYVV resistance should have been possible in the field study. BNYVV root ratings ranged from a low of 19 for a resistant check to a high of 32 for one of the susceptible entries at harvest. Fungal growth on the root surface in storage ranged from a low of 12% for an entry with good storability to a high of 71% for the BNYVV susceptible check. Entries 11, 12, and 15 performed well for all variables. Incorporating better resistance to BNYVV and good storability into commercial sugarbeet cultivars should allow for increased yields in the field and improved recovery of sucrose from roots in storage
Feed management practices to reduce manure phosphorus excretion in dairy cattle
Get PDFPhosphorus (P) is an essential mineral that needs to be supplied in sufficient quantities for maintenance and growth and milk production in dairy cattle. However, over 60% of the P consumed can be excreted in faeces with a potential to cause environmental pollution. Concern over higher levels of P in intensively managed livestock systems has led to legislation such as
the Water Framework Directive in the European Union. In this manuscript, several methods of reducing P pollution are discussed. A major source of environmental P pollution has been overfeeding P mainly due to addition of ‘safety margin’ over the animal’s requirement and concerns related to fertility. Matching the animal’s requirement and feeding in groups so that animals at the same physiological status are fed according to their requirement has a potential to reduce P excretion significantly. P can also be reduced by matching available P with the metabolizable energy content of the diet because more P can be incorporated into milk when P is utilized by rumen microbes, which are limited by energy. Plants contain phytate bound P that need to be broken up before they can be absorbed by the animal. Although ruminants can digest phytate, use of phytase enzyme could help either directly by acting on phytate P or improvement of feed digestibility. Pasture management can lead to improved nutrient cycling, particularly if the soil is deficient in P. However, overfertilizing pasture could result is higher runoff of dissolved reactive P. Management practices that leave adequate forage residue on the surface such as rotational grazing will improve infiltration and decrease runoff, reducing nutrient losses
Evaluation of sugar beet germplasm for rhizomania and storage rot resistance in Idaho, 2012
Get PDFRhizomania in the field and fungal root rot in storage can both lead to significant sucrose losses in sugar beet roots. In an effort to reduce these losses, sugarbeet germplasm developed by the USDA-ARS Kimberly sugarbeet program was evaluated for resistance to both these disease problems. Nine sugarbeet lines and four check cultivars were arranged in a randomized complete block design with six replications and grown in a field known to be infested with Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania. The plants were evaluated for foliar symptoms in July, August, and September. Plots were harvested in October, roots were evaluated for rhizomania root symptoms, and roots from each plot were also placed in a commercial indoor storage building (set point 34 F) until 7 February (127 days in storage). Most experimental entries were different from the susceptible check for both rhizomania variables. Based on both foliar and root ratings, the most BNYVV resistant entry, K944-EMS-9, was not significantly different from the commercial resistant checks. When the germplasm were evaluated for rot in storage, the primary fungal growth was an Athelia-like Basidiomycete (Mycologia 104:70-78), but Botrytis sp., Penicillium sp., and Phoma sp. were also frequently present. All Kimberly germplasm performed significantly better than the BNYVV resistant and susceptible checks in storage. These preliminary data would suggest that resistance to BNYVV is different from resistance to storage rot since there were no significant differences observed between commercial checks for root rot in storage. The performance of some of the Kimberly germplasm may help identify genetic backgrounds for additional sources of resistance to both BNYVV and storage rots