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Frequently
asked questions
What is the risk of having soybean rust in soybean fields in Mississippi in 2005? Risk will be low to medium for early planted soybeans, for later How will we prevent damage from soybean rust if it occurs in 2005? Preventative applications of effective fungicides properly timed will Should I grow soybeans with the threat of soybean rust in 2005? Historical records from other countries indicate the presence of rust, in the first year, results in less damage because of the lower inoculum potential (lower amount of rust spores). Plans should not be altered due to the potential for rust. Rust can be prevented through the use of effective fungicides. What is the origin of soybean rust and how did it spread to Mississippi? Soybean rust was first found in 1902 in Japan and has moved throughout all soybean growing areas of the world by wind blown spores. How long does it require from the time the spore lands on a leaf until it can sporulate again? Generally 9 days, but this varies by the susceptibility of the plant and environmental conditions present at the time the spore lands on the leaf. What is the developmental cycle of soybean rust? Spores are disseminated by wind currents and land on leaves. If environmental conditions are favorable, the spores germinate and directly penetrate the plant tissue. Within 6-7 days a pustule begins to develop and urediospores begin forming and are released in 2-3 days. Pustules can discharge spores for 2-3 weeks thus rapidly spreading this disease to other plants.
Do any soybean varieties have resistance to soybean rust? No commercially available varieties carry resistance to soybean rust. What fungicides will be available for prevention of this disease? Tilt, PropiMax, Bumper, Folicur, Stratego, Laredo, Headline, Quadris, and some possible combinations. What is the estimated cost for control of soybean rust? It is estimated the cost of fungicides will range from a low of $8 to approximately $25 per acre per application. How will producers offset the additional cost for fungicides to maintain profitable soybean production? Fungicide use will typically increase soybean yields even in the absence of rust (a 12 year study in Mississippi indicates a 5.9 bu/A average increase from only 1 application of a fungicide.) How many applications of fungicides will be required to control rust and at what stages of plant growth should these fungicides be applied? The number of applications may range from 0 to 3 and should be applied depending upon if rust is present in the U.S. and what stage the crop is in when rust is discovered. Will combinations of fungicides provide better control of soybean rust? Prevention of soybean rust can be attained with single, or with combinations if timing, rate, and proper coverage are attained. To prevent resistance, different product chemistry must be rotated for each application.
What water volume will be recommended for air and ground application? Air- 5 GPA Ground- 15 GPA Will control be improved by adding crop oil concentrate (COC) if so at what rate? COC and adjuvants may aid in better coverage and canopy penetration. The rate may vary according to the situation. What fungicide combinations and rates will be considered an effective program? Triazole and strobulurin fungicides will provide effective prevention of rust. More details on products and rates will be made available in the near future. Will management of this disease be different when growing Group IV vs. Group V soybean varieties? Yes, early maturity, early planted soybeans should have less risk than later maturity, late planted soybeans. Should I be purchasing fungicide now after new labels are approved in preparation in event there is a shortage for next season? Label approval is still in the process of being obtained for some fungicides. There is still uncertainty regarding if or when soybean rust may appear next season, therefore, 1 application of a strobulurin could be purchased and could be used even if soybean rust did not appear during the 2005 growing season. Studies have shown the advantages of a fungicide application even in the absence of rust. How will the rust prevention fungicide program affect other diseases that normally occur each season on soybeans? Effective prevention of late season soybean diseases will be obtained with the strobulurin fungicides if used at R-3 to R-4 growth stages. While triazole fungicides are very effective for the prevention of rust, they are a poor prevention of most late season diseases.
How does soybean rust over winter and reinfect soybeans the next season? In living tissue of other host plants. It is believed to over winter in southern Florida, southern Texas and the Caribbean. Are seedling soybeans affected by rust and what stages are more susceptible to severe damage? The cotyledons of seedling soybean plants can be infected, but they fall off the plant quickly. Soybeans are most susceptible at bloom (R1) and later stages. Does rotation with non host crops reduce losses from soybean rust? No because it is a wind blown pathogen. Will soybean rust reoccur in the same field where it was found the previous year? The presence of rust in any one field in 2004 has nothing to do with its reoccurrence in the same field or surrounding fields in 2005. Will a cold winter kill the fungus? Cold weather alone will not kill the rust fungus. Rust spores survive no more than 52 days in the absence of a host. How long before a resistant variety can be made available? A resistant variety may not be available before 5 years or longer. Can some fungicides be applied as curative applications after rust is found in a field? Rust control with fungicides is all preventative. Fungicides must be applied before soybean rust becomes established in a field of soybeans. Major losses can be prevented after rust has been located in a particular field (less than 10% infected leaves) with a triazole fungicide.
Will planting date affect rust development and the number of applications of fungicides that will have to be applied? Early planting should reduce losses from rust and the number of applications of fungicides. Will an application of fungicide have to be applied at the R1 stage in 2005, if not how will the timing of the application be determined? Depending on when rust is found in 2005, this will determine if a R1 application is necessary. Early planted sentinel plots will help in determining if a fungicide is necessary. Can a soybean field on a soybean producer's farm serve as a sentinel plot? Yes, if planted much earlier than the remainder of the soybeans to be grown on the farm. However, if planting later the sentinel plots established by the SMART program may provide more advanced information. If fungicides are used in rust prevention will some loss in yield occur? Yes, yield losses are possible, but losses should be minimal if fungicides are applied timely and with good coverage. Will soybean rust have the potential for causing heavy damage every year? It has the potential, but losses will vary from year to year depending on the presence of inoculum, environmental conditions, and if effective fungicides have been used as suggested. How will producers be informed on what, when and how to prevent rust? Information will be provided through county Extension offices, e-mail lists, DTN, Internet sites, publications, meetings, radio, T.V. and all other methods to be determined. What will be the role of field scouting in management of rust? Weekly scouting of sentinel plots will serve as an early alert mechanism, field scouting will insure proper timing of the fungicides and other pest problems that may need management at the same time when fungicide application are being applied. |
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