ISSUE 5 June 11, 2009
NDSU IPM SURVEY BEGINS
NDSU IPM Field Scouts were trained on survey procedures for diseases and insects of five major crops, on June 3rd at the Carrington Research Extension Center. The field scouts will be recording the incidence and severity of major disease and insect pests in wheat, barley, soybean, canola, and sunflower across all counties of North Dakota. The information they gather is used by extension specialists and county agents to alert producers of any immediate management needs. The data also is used to verify that our field crops donít have pests of export concern ( this effort supported in part by the ND Dept. of Agriculture). Information the scouts gather is shared each week in the NDSU Crop and Pest Report, and maps of pest occurrences are posted on the NDSU IPM web page.
The 2009 field scouts are:
surveying in the northeast region of the state (coordinated by Lionel Olson, Area Extension Agronomist, Langdon REC);
Dixie Dennis, surveying in the southwest and west central regions (coordinated by Roger Ashley, Area Extension Agronomist, Dickinson REC);
Kyle Gerner, surveying in the east central and southeast regions (coordinated by Marcia McMullen, Sam Markell, and Jan Knodel, NDSU Extension Plant Pathology and Entomology);
Chelsey Johnson, surveying in the north central and northwest regions (coordinated by Jeremy Pederson, Area Extension Agronomist, Minot, North Central REC);
Taylor Mattson, surveying in the central and south central regions (coordinated by Greg Endres, Area Extension Agronomist, Carrrington REC).
This year, the scouts are starting about a week later than most years, because of the lateness of the growing season.
NDSU IPM SURVEY RESULTS, JUNE 9
In the first partial week of scouting, the NDSU IPM scouts surveyed 38 wheat fields. Of these fields, 9 were winter wheat, most in the late jointing to early flag leaf emergence stage. The remainder of the fields were spring wheat, ranging from 1 Ĺ leaf to tillering growth stages. Most fields looked very good for stand and tiller development.
Symptoms of tan spot infection were observed in 30 of the 38 fields, with the average severity across all fields of 4.2%. The highest severities of tan spot were observed in winter wheat, up to 35% in one field planted into wheat stubble.
Other observations made by the scouts included light levels of wheat streak mosaic virus in four winter wheat fields and in one spring wheat field. No wheat leaf rust was observed in North Dakota surveys. However, wheat leaf rust was observed last week in susceptible winter wheat cultivars in Nebraska and south central South Dakota.
NDSU DISEASE FORECASTING SITE INDICATES RECENT RAINS FAVORABLE FOR TAN SPOT INFECTION
The NDSU wheat disease forecasting site that provides information on the risk of tan spot, Septoria blotch, leaf rust and Fusarium head blight, is available at:
The recent rains across the state have resulted in favorable conditions for wheat tan spot infection at almost every NDAWN site. However, the temperatures have been too cold to favor the other three diseases on this forecasting site. Tan spot predictions are obtained with a 3-step process:
1) choose the nearest NDAWN station and highlight this site;
2) click on the leaf stage of the crop;
3) click on get forecast.
NDSU Ext. Plant Pathologist
EARLY SPORE STAGES OF SUNFLOWER RUST FOUND IN NORTH DAKOTA AND MINNESOTA
In the last week, the pycnial and aecial stages of sunflower rust has been found on volunteer or wild sunflowers in North Dakota and Northern Minnesota. Kyle Schepp and Kent McKay (Vision Research) and Mike Hutter (Northern Ag Management) have identified early sunflower spore stages on volunteers in north central ND and Northwest North Dakota, respectively, Jack Rasmussen (NDSU Plant Pathology) identified pycnia on wilds in the eastern part of ND, and Craig Hanson (BASF) and Charla Hollingsworth (U MN Crookston) have found pycnia in NW MN. Pycnia are found on the upper side of leaves and usually appear as orange, relatively non-structures pustules, often with a yellow halo (Figure 1). Pycnia give rise to aecia, which are found as clusters of small yellow-orange cups on the underside of leaves or cotyledons opposite the pycnia (Figures 2 and 3). They produce a spore (aeciospore) that will reinfect sunflowers and produce the typical dusty-brown uredia pustules that we are most familiar with (Figure 4).
|Fig. 1. Pycnia
on volunteer sunflower
(Photo B. Harveson)
|Fig. 2. Aecia on
(Photo S. Markell)
Fig. 3. Aecia on
|Fig. 4. Uredia on
(Photo S. Markell)
Although this is the second consecutive year that early sunflower rust spore stages have been found, their occurrence is believed to be rare. However, when aecia are found, economically significant epidemics of rust are more likely because inoculum is abundant early, and new races may emerge that overcome resistant hybrids. Last year, epidemics of rust were frequent in commercial fields where aecia were identified in late June and early July. In one field in Northwest ND (aecia were identified in late June) the untreated strip of the field yielded approximately 200 lb/A, while the field area treated with two applications of fungicides averaged approximately 1400 lb/A.
Although the fire alarm shouldnít be pulled yet, this occurrence should be a warning sign that an early epidemic of rust is possible in some areas, and serious thought should be put into a few actions.
First. Due to environmental conditions last fall and this spring, weed control has suffered. In fields that had sunflowers last year, it is very important to control the volunteers. This is particularly true if the field borders (or is near) this years flowers. Rust spores have little trouble traveling from field to field and beyond, so if environmental conditions are appropriate, an epidemic in a commercial field that sits next to infected volunteers is likely.
Second. Since wild sunflower are equally likely to have rust, if possible, wild populations should be destroyed.
Third. Scouting sunflower fields for rust should began relatively soon after the crop is up. There is approximately two weeks between initial infection and symptom development so you likely can wait until a few weeks after emergence. Rust is most likely to cause economic damage when it is found early. Fortunately, it is a very controllable disease, but early control is the best control. In a future article I will have information about fungicides and timings that may help decision making about fungicide application.
Fourth. Donít panic. Rust needs dew periods to develop, so windy dry nights will limit infection. Last year we had some very severe rust, but many fields had very little infection, effectively escaping the epidemic. Further, if the disease shows up relatively late in commercial fields, little if any yield loss will occur.
Extension Plant Pathologist
University of Minnesota-Crookston