ISSUE 7 JUNE 17, 1999
SMALL GRAIN DISEASE SURVEY UPDATE
The small grain disease survey began in earnest last week. Seventy -two fields in 17 counties were examined for leaf diseases and insects. Growth stage of winter wheats ranged from late boot to flowering, while growth stages of the spring wheats ranged from two leaf to early boot.
Southwest and west central districts: Amy Dukart found low levels of tan spot in most fields, with some higher incidences in McKenzie and Dunn county wheat fields. On June 14, she found trace amounts of wheat leaf rust and barley leaf rust in Sioux county.
North central district: Wheat fields surveyed by Brittany Sund in McLean Co. commonly had tan spot infections on bottom leaves, with some spots also evident on the mid-leaves of the crop. Severities were low.
Central district: Jerry Schneider found leaf rust in 1/3 of the spring wheat fields surveyed and in 2/3 of winter wheat fields surveyed. Tan spot also was common in these fields, but generally at low severity levels. Barley fields surveyed had a few leaf spots on lower leaves.
Southeast and east central districts: Jerry Ries found leaf rust in 58% of the spring wheat fields and in 2/3 of the winter wheat fields surveyed. Generally, only a few pustules were found on lower leaves, but occasional pustules were found on the mid-leaves. In these eastern counties, tan spot or Septoria also were common but not severe.
Incidence and severity of leaf rust in the eastern counties was a little higher in spring wheats than in the winter wheats. Two of the winter wheat fields surveyed were the variety Arapahoe, which has moderate resistance to leaf rust. Identity of the spring wheat fields was unknown, but in 1998, NDSU scientists rated McNeal, 2375, ACBarrie, Ingot, Forge, Majestic, and Trenton has having higher leaf rust severity scores than other varities such as Russ, Keene, Gunner, and Sharp.
Grain aphids were found in 50% of the wheat fields surveyed in the southeast and east central counties. One field had 88% of the tillers infested with aphids. Scattered plants in these fields also showed symptoms characteristic of barley yellow dwarf virus, which is vectored by grain aphids. Early appearance of aphids and barley yellow dwarf may mean potential problems for late planted fields. Also, one field in Traill and one in McLean county had high populations of grasshoppers.
The Kansas Plant Disease Survey Report, June 11, 1999, reports that foliar diseases are taking a toll in their 1999 winter wheat crop, and farmers may expect lower yields than normal because of above normal levels of diseases. Among diseases affecting the hard red winter wheat crop are leaf rust, speckled leaf blotch (= Septoria), and even a few outbreaks of scab in the northeast. Earlier reports had indicated that barley yellow dwarf also was severe in some areas of that state. In contrast, the hard winter wheat quality tour during the week of May 3 reported finding very low levels of diseases. The subsequent rapid development of diseases in the southern winter wheat area reminds us to be ever vigilant for our spring crop.
The USDA Cereal Disease Labs latest map of leaf rust severities in wheat fields, as of June 7, 1999:
Fig 1 Leaf Rust severities in wheat fields of June 7, 1999
FOLIAR FUNGICIDE DECISIONS FOR WHEAT, ND 1999
Each year North Dakota wheat producers struggle with the decision on whether to use foliar fungicides to protect their crop against tan spot, Septoria (Stagonospora) leaf diseases, leaf rust, and Fusarium head scab. Fortunately, improved information to help producers make this decision is becoming available. Last weeks Crop and Pest Report gave the web site address and toll free number for accessing research-based economic threshold and predictive model data for tan spot, Septoria, and head scab on spring wheat:
Current information on this web page indicates that from June 10 through June 13 we had relatively few favorable infection periods for tan spot or Septoria at most locations monitored, although in areas of very high rainfalls, such as in Mohall, ND or Warren, MN, recurring favorable infections periods have occurred. The data also indicate Fusarium spore detections at low to none during the June 10-13 period.
The above information does not take into account the possibility of rust infection periods. Wheat leaf rust requires only 6-8 hours of dew and moderate temperatures of 60-80 F for infection to occur. Producers should be regularly monitoring their crops that are in vulnerable stages, and making fungicide decisions based on five factors:
a) yield potential of crop (some of the early crops look like they have great yield potential)
b) field history (stubble of wheat and/or corn and disease history)
c) price of wheat (the lower the price, the more marginal the return)
d) presence of disease on lower leaves or leaves below flag; and
e) wet, humid weather conditions that may favor disease (check the disease forecasting information available on the web page indicated above).
SUMMARY OF 1999 GREENHOUSE FUNGICIDE PPLICATION TRIALS NOW AVAILABLE
A four page summary of the NDSU greenhouse studies on improving fungicide application for wheat/barley head scab control is now available through the NDSU Ag. Communication Distribution Center (701-231-7883 or email Sharon Lane at email@example.com).
The report is Extension Report 56, and titled "Improved Fungicide Spraying for Wheat and Barley Head Scab Control". The report describes some of the optimum spray parameters for various nozzles, when tested on hard red spring wheat, durum, and barley. Summary recommendations for 1999 are given.Marcia McMullen
QUADRIS USE ON CANOLA FOR SCLEROTINIA STEM ROT
General information was provided on the registration of Quadris for canola in Crop and Pest Report No. 2. Quadris should be applied at 10-25% bloom, or when there are approximately 10-18 open flowers on the main stem. Keep in mind that the label rate for Sclerotinia is 9.2 fl oz/A for light to moderate disease pressure and 15.4 fl oz/A for heavy disease pressure. Both rates performed well last summer in Kent McKays trial at Newberg under moderately heavy pressure. Similar results were obtained in trials across western Canada. This years canola crop is ranging from bolting in some areas to barely emerged to not planted, depending on location and weather.
I have had some reports of early planted canola that is very thick and bolting. Since these fields should have a good yield potential, they might be candidates for a fungicide, unless the weather turns dry. Due to the cost of Quadris and the soft price of canola this year, I had suggested that a yield potential of 2,000 lb/A was needed to justify using a fungicide. I am sticking to that figure, even though 1,500 lb/A is the figure that has been used in Canada; however the Canadian figure is based on better canola prices and lower fungicide prices.
There was a disturbing question the other day. What about using rates of Quadris lower than 9.2 fl oz/A? Dont even think of it! The 6.2 fl oz rate is registered only for early season blackleg control. The 6.2 fl oz rate was in Kent McKays trial last summer, and also in trials across western Canada. Based on what data we have at the moment, this rate cannot be relied on for Sclerotinia control and should not be considered. Too low a rate doesnt save money, it wastes money.
SCLEROTINIA STEM ROT OF CANOLA PUBLICATION AVAILABLE
An extension publication entitled Sclerotinia Stem Rot of Canola Biology and Management was published recently. Prepared jointly with Dr. Dick Meronuck, extension plant pathologist, University of Minnesota, this publication provides basic information on the symptoms, biology and management of Sclerotinia stem rot of canola. Now that a fungicide is registered for use on canola, decisions regarding the use of a fungicide are discussed in the publication. The publication includes a Sclerotinia Stem Rot Checklist, prepared by the Canola Council of Canada, and reproduced by permission. The checklist provides a series of questions and a point system to help determine whether or not it may be economic to use a fungicide. Single copies of the Sclerotinia publication have been distributed to key counties in northwest Minnesota and in North Dakota, Research Extension Centers in North Dakota, the Northwest Experiment Station in Crookston, the Minnesota Canola Council and the Northern Canola Growers Association.
Copies may be ordered from:
Distribution Center, NDSU Extension Service
Morrill Hall, P.O. Box 5655
North Dakota State University
Fargo, ND 58105-5655
Voice: (701) 231-7882
FAX: (701) 231-7044
Information on ordering is also available on the Web at:
SCLEROTINIA RISK MAP FOR CANOLA
The Canola Council of Canada maintains an excellent Web site which is full of canola production and protection information found by clicking on the title "The Growers Manual". It includes an excellent section on Sclerotinia stem rot and its management. The Sclerotinia Stem Rot checklist, mentioned in the previous article, is part of the Sclerotinia information in The Growers Manual.
By clicking on "Weather and Forecasts", one can access the Sclerotinia Risk Map. The risk map is posted twice a week on Mondays and Thursdays, with the first posted on June 14 and the second on June 17. Actually, there are three maps: one shows the risk of Sclerotinia, one shows the degree of soil saturation (important for Sclerotinia) and one shows the stage of crop development across Manitoba, Saskatchewan and Alberta. The map does not extend south of the Canadian border, but can be useful for producers that are in the northern-most tier of counties. The Web site, called The Canola Connection, is located at:
MORE POTATO LATE BLIGHT HOT LINES
Last week I gave listed the number for the North Dakota late blight hot line, available nationally. Below is a listing of potato late blight hot lines, all available throughout the US:
North Dakota: 1-888-482-7286.
The Idaho and North Dakota numbers are new.
Extension Plant Pathologist
PLANT DIAGNOSTIC LAB REPORT
It seems to be the year for rust on woody species. Last week, the big question was on buckthorn rust and this week, its ash rust. Puccinia sparganioides, the fungus that causes ash rust, can cause very dramatic symptoms and in some parts of the country is very destructive on ash. Like rust on buckthorn, P. sparganioides produces five spore stages and requires two different host species to complete its life cycle. There are two spore stages that occur on the ash, in the spring and the summer; and three different spore stages, one of which is the overwintering spore, that occur on the alternate hosts, prairie cordgrass and inland saltgrass. Both of these grasses, cordgrass (Spartina pectinata) and inland saltgrass (Distichlis spicata) are common throughout North Dakota and western Minnesota.
Despite the spectacular symptoms, ash rust is not usually economically destructive on ash in North Dakota. Infection begins in the upper leaf surface of the ash as yellow to yellow-orange spots. As the disease progresses, clusters of a second spore stage form on the undersides of leaves and on stems. These appear as bright orange spots and may cause a swelling and distortion of leaves and stems. To reiterate, damage is not usually severe enough to warrant treatment, however on young trees, it can be enough of a stress factor that the tree becomes more susceptible to other diseases, insects, or environmental injury. Fungicides that are available if application becomes necessary include myclobutanil (Systhane WSP or Eagle), propaconazole (Banner Maxx), chlorophenoxy dimethyl butanone (Bayleton 25 and Strike 25), and chlorothalonil (Manicure and Daconil Weather Stik).