ISSUE 1 May 4, 2006
FUNGICIDE SEED TREATMENTS MAY BENEFIT SOYBEANS
Soybean seeds and seedlings are susceptible to a number of pathogens lurking in the soil, waiting for the right conditions. These pathogens include Pythium, Phytophthora, Rhizoctonia and Fusarium species. In North Dakota, soil conditions can turn wet and cold overnight. Under these cool (less than 60 F) and wet soils, the soybean seeds will germinate and emerge very slowly, making them more susceptible to attack by seed and seedling pathogens.
Fungicide seed treatments might be a valuable tool to use to protect soybean seeds and seedlings against diseases. Research conducted in multiple years and locations in North Dakota, shows that there may be an overall benefit using seed treatments on soybeans.
The biggest benefits were observed in years and locations where soil conditions turned wet and cool after planting. In years and locations where "big" benefits were not observed, the seed treatments generally paid for themselves. Averaged over all 14 environments in the study, the net return with the use of seed treatments ranged from $10 to $20 per acre compared with untreated soybeans, depending on the product used.
Under certain soil types, management practices and field histories, the probability of getting a benefit from a seed treatment probably increases. These conditions include:
* Heavy clay or poorly drained soils
* No-tillage or reduced-tillage
* Early planting
* Tight crop rotations
* Disease history of the field
When choosing a fungicide seed treatment, choose a product that contains either mefenoxam or metalaxyl. These chemicals protect against Pythium and Phytophthora. The product also should contain at least one other chemical, such as fludioxonil, azoxystrobin or others, that will protect against Fusarium and Rhizoctonia."
In general, most "newer" seed treatment products are safe on nitrogen-fixing Bradyrhizobium found in inoculants, but some products and formulations may be better than others.
For more information about specific seed treatment products, check the 2006 North Dakota Field Crop Fungicide Guide available through the NDSU Extension Service, as well as the NDSU Extension Plant Pathology Web site at http://www.ag.ndsu.nodak.edu/extplantpath/. Always read and follow manufacturers’ label directions.
Extension Plant Pathologist
NDSU PLANT DIAGNOSTIC LAB WEEKLY REPORT
SEED HEALTH TESTING UPDATE
Seed health testing in the Plant Diagnostic Lab is winding down, with a few last minute submissions. The most common tests performed this past winter include screening for potato bacterial ring rot, culturing for Aschochyta on pulse crops, and determining foliar bacterial disease potential on dry bean seed (using the Dome method).
The lab has performed significantly more seed health tests this past winter compared to the last two years.
NEW DATABASE SYSTEM
The NDSU Plant Diagnostic Lab has adopted a new method for managing information for samples submitted to the lab and for creating invoices and managing other aspects of billing. Extension personnel can have limited access to the database system as submitters, and they are encouraged to submit sample information using the system. Use of the new system, known as the Plant Diagnostic Information System (PDIS), should improve turnaround time for samples submitted by extension personnel, particularly if e-mail is the chosen form for receiving the diagnostic reports. At present, the general public does not have access to using PDIS to submit sample information. So, sample information can still be received in the "old fashioned" way by hand writing information onto a lab information request form. These forms are available at your local county extension office or at the lab’s website, http://www.ag.ndsu.nodak.edu/diaglab, as a downloadable pdf file. In general, there is a routine diagnostic fee of $15 for North Dakota residents (an additional charge may apply, depending on testing needs), and $25 for non-residents. Although not required, consider consulting with your local county extension agent, whenever possible and practical, before submitting a sample to the NDSU Plant Diagnostic Lab. Contact the diagnostic lab if you have any questions.
(see more Plant Diagnostic Lab articles in Horticulture section)
NDSU Plant Diagnostic Lab
SECTION 18 GRANTED FOR TEBUCONAZOLE FUNGICIDE FOR WHEAT AND BARLEY
The US Environmental Protection Agency recently granted a specific exemption (Section 18) for use of four fungicides on wheat and barley in North Dakota for Fusarium head blight suppression. The products (and their manufacturer) are: Folicur 3.6F (Bayer CropScience), Orius 3.6F (MANA), TebuStar 3.6L (Albaugh) and Embrace 3.6L (Agriliance). The active ingredient in all four products is tebuconazole and all are recommended to be used at the 4 fl oz. per acre rate for Fusarium head blight.
Tebuconazole may be applied up through the beginning of flowering (Feekes 10.51) in wheat and up through full head emergence (Feekes 10.5) in barley. The pre-harvest interval for these products is 30 days. Each label states that the lowest rate of a spray surfactant should be tank-mixed with the products, as well. NDSU data shows that tebuconazole has always performed better in controlling Fusarium head blight when an appropriate adjuvant is added, than if no adjuvant is applied. NDSU data also has shown that the full label rate of 4 fl oz/acre consistently performs better than reduced rates of tebuconazole in reducing Fusarium head blight, no matter what the adjuvant added.
CEREAL DISEASE REPORTS FROM OTHER STATES MAY 2, 2006
North Dakota’s small grains are still being planted, but some spring wheat is up and most winter wheat fields look great. Other than potential seedling diseases, most disease issues are still some weeks away, but some, such as the rusts, are being observed in other states, and have the potential to move northward.
The Cereal Disease Laboratory in St. Paul, MN has published four Cereal Rust Bulletins already this year. Report No. 4, dated May 2, 2006, indicated that wheat leaf rust (Puccinia triticina) is widespread throughout the southern US. Susceptible winter wheat cultivars, such as Jagelene and Jagger, showed 80% leaf rust severities in nurseries in Texas. However, only very low levels of rust were reported in commercial wheat fields in Texas and Oklahoma, because of dry conditions in those areas. A few plants were seen with leaf rust in Kansas on April 21, as reported to the Cereal Disease Lab, but rust was hard to find in Kansas by May 1.
Last year, wheat stripe rust (Puccinia striiformis f. sp. tritici) was fairly common, but not severe, in southwestern ND wheat fields. Conditions in southern plains states had been favorable in 2005 for development, and stripe rust spores moved northward into our western counties. This year, wheat stripe rust infection in the southern Great Plains and southeastern states is at a much lower level than last year at this time, so we may see little stripe rust in ND, if conditions remain unfavorable for stripe rust development to our south. On April 26, an observation was made of stripe rust on lower leaves on winter wheat at St. Paul, but this stripe rust was thought to be an overwintering infection.
A May 2 report to the Cereal Disease Lab from Drs. Bob Hunger and Tom Royer of Oklahoma State University indicated that wheat in many areas is already in the milk stage in parts of that state. Wheat streak mosaic virus has been observed in the panhandle area of Oklahoma, and barley yellow dwarf virus symptoms are very common in areas near Stillwater, OK, indicating a potential for aphid populations to move into our wheat and barley later in the season.
The Cereal Rust Bulletin also reported low levels of oat crown rust observed in Texas and Georgia. Buckthorn, the alternate host for oat crown rust, has just leafed out in our area now.
WHEAT LEAF RUST REACTIONS IN SPRING WHEAT 2005
Hard red spring wheat cultivars were evaluated at three locations in 2005 for wheat leaf rust reactions, by Dr. Jack Rasmussen and Mr. Jim Jordahl of the NDSU Plant Pathology Department. Many spring wheats commonly grown in ND still have good levels of resistance to wheat leaf rust, but several others are quite susceptible to the prevalent races found in the state.
The chart below illustrates the leaf rust reactions of a number of named cultivars that were evaluted in 2005 at Prosper, Carrington and Langdon. Values are averages over the three locations.
Extension Plant Pathologist