ISSUE 9 June 28, 2001
SCLEROTINIA RISK MAP FOR CANOLA
The map is now up and running, with the map being posted late in the day on Mondays and Thursdays. There seem to be some questions that emerged on interpretation of the risk map.
We had lots of rain a week ago, but the Risk Map doesn’t show high risk. Why? This is answered in some of the explanations published with the Map:
"The germination of sclerotinia sclerotia requires about 10 days of moist soil above field capacity. When they germinate, sclerotia produce the spore bearing structures called apothecia that release spores, which attack canola and cause stem rot. Spores are released by the apothecia at about the same time as canola comes into flower."
We have had saturated soils for over 10 days yet the Risk Map shows only moderate risk. Why? Information published with the map states " Local weather, soil and crop conditions may result in a more favourable condition for germination of the sclerotinia sclerotia than is indicated on the regional risk forecast map." Growers should keep in mind that if they are in a localized area that is much wetter than much of the surrounding area, their risk may be greater than that shown for the region.Art Lamey
As of June 26, Dr. Jim Miller, USDA Cereal Rust Pathologist, found trace levels of wheat leaf rust on Agassiz winter wheat and Thatcher spring wheat at Casselton in variety plots. Jerry Schneider, NDSU IPM Scout, found leaf rust in a commercial, half-headed spring wheat field in Emmons Co., with 16% incidence and trace severity. Leaf rust spores have been detected in spore traps being monitored by Dr. Len Francl, NDSU Plant Pathology Dept. These spores started appearing in the traps around June 23-24.
Dr. Mike Peel, NDSU Extension Agronomist, found fairly high levels of stripe rust on June 22 on a soft red winter wheat cultivar called Foster in a variety plot at Lisbon. On June 25, Dr. Jim Miller found a trace amount of stripe rust on this same soft red winter wheat cultivar in plots at Casselton, and also found a fair amount of stripe rust on Norstar winter wheat at Casselton, with incidence at 5% and severity from trace to 40%. Stripe rust has not been observed in any commercial wheat fields, winter or spring, at this time. Recent warm to hot temperatures should help shut the stripe rust down.
CORRECTION TO FUNGICIDE TABLE IN CROP AND PEST REPORT No. 8.
In last week’s Crop and Pest Report, I published a table of foliar fungicides registered for small grains in ND. I neglected to distinguish which ones were registered only for wheat. Those registered just for wheat include: Benlate, Quadris, Flint, and Stratego, plus the 24 (c) label for Tilt allows heading application to wheat only, and not barley.
ENVIRONMENT AND SMALL GRAIN FUNGICIDES
A lot of wheat and barley is in the early heading stage or beyond now. The heat over the past weekend really pushed the crop. Decisions for fungicide use are being made, and all indications from the disease forecasting model and from weather forecasts, indicate that disease potential could be high. The disease forecasting models show many recent days have been favorable for tan spot infection. Successful use of his model also depends on field scouting to confirm presence of disease.
Dr. Francl’s spore traps are also picking up Fusarium scab spores in low to high numbers now, depending on sampler location. The weather forecast for much of the state says chance of scattered showers or thunderstorms for the next week. With these indicators, and the potential high yields in many locations, I think that use of fungicides should be considered and evaluations per individual farmer’s fields be made.
Conditions that favor disease are: saturated soils, high humidities, high dew points, low solar radiation, and temperatures below 900F. On the other hand, dry soils, high temperatures, dry and sunny days, and windy conditions will make infections much less likely.
IPM SURVEY RESULTS
The IPM field scouts have started to pick up higher incidences of tan spot in some areas, as well as some spot and net blotch in barley. Jerry Scneider has detected symptoms of Septoria now in a few fields in south central ND. A few cases of loose smut also are being detected in headed wheat. The following are some updated maps of survey detections, with survey results through 6/22.
Spot Blotch in Barley
TEXAS KARNAL BUNT OUTBREAK - IMPLICATIONS FOR SPRING WHEAT
Sites of detection and quarantine: Karnal bunt (KB) disease was detected several weeks ago in Texas wheat, in the central counties of San Saba and McCulloch, and also in fields in north central Texas in Archer, Throckmorton and Young counties. Grain in Baylor county is regulated, as well, because of possible movement of infected grain. These more northern counties in Texas were new locations for detection of this disease. The original U.S. outbreak of KB was in Arizona in 1996 and the disease had not been detected in U.S. wheat beyond some areas in Texas, Arizona, and California since 1997. Inspectors have found KB in approximately 30-40% of fields tested in regulated areas of Arizona and Texas, and in about 6% of fields tested in regulated areas of California. Areas now known to have KB disease in 2001 are under USDA quarantine. Custom harvesters operating in Texas have had to disinfect their combine, trucks and other harvesting equipment prior to moving into another state.
The disease: Karnal bunt is caused by the smut fungus, Tilletia indica, which infects kernels of wheat and triticale. The disease can cause yield losses and impart a fishy odor to the grain, but is not harmful to humans or livestock. More information can be obtained about the fungus and the disease from an excellent web site:
Impact: The biggest damage this disease can do to U.S. wheat is cause loss of markets. The fungus is a quarantined pest for most of the grain-importing countries of the world, and detection of this pest in northern spring wheat would be devastating to our exports. The disease and the fungus have NOT been found in ND, as determined by NDSU field surveys and by annual cooperative surveys of harvested grain conducted by the ND Dept. of Agriculture and the USDA/APHIS. The chances of this disease becoming established in ND are remote, but precautions to prevent its introduction are still necessary.
Among those precautions are the appropriate cleaning of combines, trucks, seed handlers, and other machinery before their entry into ND from affected areas. The USDA has a very stringent cleaning protocol for machinery from quarantined areas. ND producers should ask for information from custom harvesters about where they have been operating and get assurances that machinery has been appropriately cleaned. If the operators have come from regulated areas, they should have an APHIS issued certificate indicating their equipment has been cleaned and disinfected.
Kansas and Colorado are also now recommending a voluntary cleaning protocol for Karnal bunt, a protocol they would like to see followed by all custom combiners coming into their states from other areas. This voluntary cleaning protocol for Karnal bunt recommends some general, precautionary measures using low-pressure, high-volume water for cleaning interstate combines. The protocol is:
Voluntary Cleaning Protocol for Karnal Bunt
1. Do preliminary cleaning before leaving the old field. Clean off feeder house and reel, open trap doors, then run the machine until loose grain is out.
2. Select an area for cleaning with access to a water hydrant.
3. Remove the header and clean it separately.
4. Park on pavement where waste grain can be swept up and disposed of properly. Combine can be tilted to help drain horizontal augers.
5. Open all access doors, traps, and elevators and remove sieves.
6. Run machine until loose grain is all out.
7. Use a garden hose and nozzle to dislodge debris. Start at front and clean in direction that grain flows through machine.
8. If possible, remove the concaves and wash the cylinder area, or flush the concaves in place.
9. Clean grain tank and unloading augers.
10. Run machine again to shake any remaining grain loose.
11. Clean debris and grain out that collects on undercarriage.
12. Dispose of waste grain, weed seeds, and debris in landfill or bury it deeply.
Note: These above measures are not as stringent as the protocol used by USDA for cleaning combines from quarantine areas. Also, cleaning a combine can be hazardous; proper eye protection and avoidance of moving parts are necessary.
POTATO BLIGHT HOTLINE
Late blight has not yet been detected in our growing region. Non-irrigated sites have not yet reached the late blight severity threshold value of 15, but all irrigated sites have. Growers and field scouts are urged to continue scouting fields for the presence of late bight symptoms, and a reward is out for the first three late blight samples confirmed by NDSU’s Potato Pathology lab.
SUGARBEET BACTERIAL LEAFSPOT
Leaves of sugarbeets were examined on June 26 for Cercospora leaf spot, but no evidence of Cercospora was found. The leaves did have considerable bacterial leafspot, which can be confused with Cercospora. Cercospora leaf spots are distinguished by the black fruiting bodies present in the light greyish colored spots, while bacterial leaf spot produces irregular-shaped to circular spots with very dark to almost black borders, and no black fruiting bodies in the center of the spot. Cercospora may show up the first week of July, as rows close.
Extension Plant Pathologist