ISSUE 14 August 3, 2000
SMALL GRAIN SURVEY UPDATE
The small grain disease and insect survey is winding down this week
and next. Wheat and barley crops are fast maturing, making disease diagnosis in the field
difficult. Extension IPM scouts from all districts are reporting that the most common flag
leaf diseases on wheat are leaf rust, Septoria and tan spot, with combined
severities ranging from 3% to almost 100%. Severities depend on crop variety, location,
and whether or not fungicides were used. On barley, leaf rust, Septoria, and
spot blotch are evident in some crops. Scab is found in wheat and barley heads in almost all areas of the state, with average head severities ranging from 3% to 80%, again depending on variety, use of fungicide, and location. Other diseases observed to lesser extent include black chaff, glume blotch, barley yellow dwarf, ergot, and loose smut.
Wheat stem maggot was the most common insect problem observed this past week, plus thrips are being detected on green crops. A more complete summary of the survey results will be available in the last Crop and Pest Report for the season.
Root rot infections were very evident this past week in most
counties. The prematurity blight phase of root rot caused plants and heads to turn
prematurely white or bleached. It currently appears that several root invading fungi may
be responsible. Isolations from roots and crowns are being made in the lab, to determine
predominate organisms causing the root rot this year. Results may vary across locations.
Root rot ratings of variety trials are also being taken at several locations to determine
response to the root rot infections this year. Preliminary results indicate variety responses are similar to those listed for HRSW in the ND Crop Production Guide and the NDSU HRSW variety bulletin. However, information on many newer varieties wasnt available before, and this year should give us some good additional information on these varieties.
Fungicide research plots at the ND Research and Extension Centers have recently been evaluated for leaf and head diseases. Data from a seed treatment study at Dickinson also has been taken. Most of the data has not been analyzed yet, because of the amount of data that has been compiled, plus the plots are not harvested yet. Preliminary observations indicate that fungicides have substantially reduced disease levels, noticeable even in the presence of root rot damage. Final reports will be available sometime this fall.
YOUR FUNGICIDE RESULT DATA
I would appreciate learning of any fungicide results from farmers, consultants, dealers, or crop protection company representatives. Some of you have replicated trials or have good check strips along with your treated acres. The more information we have on fungicide use and successes or failures, the better our recommendations can be, plus we use fungicide information to help us get full or special registrations of products.
Extension Plant Pathologist
NEED SUNFLOWER FIELDS WITH DOWNY MILDEW FOR RESEARCH
USDA sunflower pathologist Tom Gulya would like to locate a few fields with uniform downy mildew (preferably greater than 50%) in a 2 acre area within 2 hours of Fargo if possible. He wants to line up growers for fungicide trials yet this year, while he can still observe disease incidence.
If anyone knows of any 2 acre areas with a high incidence of downy
mildew, please contact Tom Gulya. His e-mail is:
DRY BEAN RUST
Dennis Berglund, Centrol, reports that rust is showing up on dry
beans. It is developing rapidly on pinks and is also present on some pintos. As indicated
in Crop and Pest Report No. 7, many commonly grown pinto varieties are resistant to
the rust races currently present in North Dakota. These varieties include: Apache, Burke,
Buster, Chase, Elizabeth, Focus, Frontier, Kodiak, Maverick, Montrose, Remington, UI-320
and Winchester. All pinks and most small reds are susceptible. Some
light red kidneys also are susceptible.
Since the number of rust races present in North Dakota has increased
in recent years, it is essential to monitor not only fields of susceptible varieties, but
all varieties. Susceptible varieties should be sprayed with a rust fungicide once there
are 2-3 pustules per leaf and the lower pods are not yet striping (or fully filled in the
case of other bean classes). If there are one or two "hot spots" in a field, it
should be sprayed. If rust is present in other fields in an area and the crop is in the
flat pod stage or
earlier, it should be sprayed. If rust begins to build up in a variety that is supposed to be resistant, a fungicide might be required. Bravo and maneb are registered for rust. Tilt has a section 18 for dry beans in both North Dakota and Minnesota.
I would also recommend sampling rust if a field of a resistant variety has considerable rust. Collect rust samples, place them loosely in a paper envelope and allow them to air dry before mailing. Submit the sample to Pat Gross for race identification:
Department of Plant Pathology
North Dakota State University
Fargo, ND 58105
Please include information on the variety and class grown, where collected, and name and telephone number (or e-mail address) of the person collecting the sample.
SUNFLOWER RUST WATCH
Although there have been no reports of sunflower rust yet, recent
hot weather would favor rapid buildup of rust. Infection can occur is as little as four
hours of dew at high temperatures. The time for the development of a sporulating pustule
can take as little as 7-8 days at high temperatures night temperatures of 63-72ºF and day
temperatures of 72-82ºF), but twice that long at lower temperatures (night temperatures
of 52ºF and day tempeatures of 63ºF). In addition, more spores are produced
per pustule at high temperatures.
Folicur is available in North Dakota under a section 18. If more than 3% of rust severity (percent of leaf area with rust) occurs on the upper four leaves before or during the bloom stage, an application of Folicur will be economic. Severity can be estimated by using the illustrations in NDSU Extension circular PP-998, Sunflower Rust.
Folicur, available under a section 18, can be used up to 50 days before harvest, which is about ray petal wilt. Once the crop is past ray petal wilt, a fungicide will no longer be economic.
Extension Plant Pathologist
FIRST THE FLOOD, NOW APHANOMYCES ROOT ROT
The flood of June 2000 resulted in thousands of acres of sugarbeet lost to drowning. We received even more rains in subsequent weeks, especially in the East Grand Forks, Hillsboro, and Moorhead factory districts. The wet soils coupled with high temperatures have made field conditions very favorable for the development of Aphanomyces root rot. Consequently, sugarbeet growers are destroying sugarbeet fields that are heavily infected with Aphanomyces root rot.
Extension Sugarbeet Specialist