Crop & Pest Report
Small Grain Diseases (5/24/12)
Scattered rains across the state over the weekend and through last night (May 22) will increase the risk of tan spot infection in those areas seeing the most rain. Dew points averaged over 50 degrees in many areas on 5/22, indicating more favorable environment for fungal infection.
The small grain disease forecasting site (www.ag.ndsu.nodak.edu/cropdisease) indicates some risk of infection for tan spot in the last few days, as indicated in the table example for Carrington, ND, given below. Please check the site for disease risk at the nearest NDAWN location to you, as the week and crops progress.
A trace level of stripe rust was observed in “Mayville” spring wheat by a private company agronomist near Grand Forks this week. This stripe rust infection is confirmed but surprising, considering the heat and relatively dry conditions in most areas up to now. This disease has been common in KS and NE, but has not been reported in ND up until now. (see information below on rust development in KS and NE).
Marcia McMullen
Extension Plant Pathologist – Cereal Diseases
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Fusarium Head Blight (FHB = Scab) Forecasting (5/24/12)
Winter wheat is rapidly developing in North Dakota and some may be entering heading stage. Many winter wheat cultivars have considerable susceptibility to leaf diseases, leaf rust, and also Fusarium head blight.
As growers consider application of fungicides to flowering winter wheat for management of these diseases, they can estimate the risk of leaf infections at the NDSU Small Grain Disease Forecasting site, as indicated above. This site also has information on risk of Fusarium head blight (FHB) infections associated with weather at the NDAWN weather stations: the flowering growth stage must be chosen.
A broader use of additional weather information is used in the national Fusarium head blight forecasting system, found at www.wheatscab.psu.edu. At this site, the user first clicks on spring wheat, then on cultivar susceptibility level, and then on the state of ND on the map. As of Wednesday, May 23, the FHB risk for ND is very low across the whole state!
Marcia McMullen
Extension Plant Pathologist – Cereal Diseases
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NDSU Potato Blightline to Operate in 2012 (5/24/12)
The Plant Pathology Department at North Dakota State University will again be providing the potato Blightline service at no charge to the potato industry of North Dakota and western Minnesota in 2012.
Based on the amount of late blight found in 2011, there is a good chance that late blight will be present in 2012 if conditions are favorable. The NDSU Blightline is the first place to go to get the most recent blight updates and management information.
This will be the eighteenth year that this service has been provided by NDSU and sponsored by Syngenta Crop Protection. The hotline uses local weather data collected from weather stations throughout our area to forecast the occurrence and spread of late blight in fifteen non-irrigated and twelve irrigated production areas in ND and western MN. The data is processed by the North Dakota Agricultural Weather Network (NDAWN) and analyzed by a computer program (WISDOM) to forecast when conditions are favorable for late blight to occur.
The forecast information is used by plant pathologists Gary Secor and Neil Gudmestad to make late blight management and fungicide recommendations. The recommendations are made Monday, Wednesday and Friday of each week during the growing season. The first late blight hotline will be Friday June 1st, and it is anticipated that the Blightline will continue through mid-September depending on disease pressure. The Blightline will also be used to confirm reported late blight sightings and serve as clearing house for national late blight information. In addition to late blight forecasting, the hotline also provides cumulative P-values for early blight disease forecasting and management recommendations. Finally, it serves to alert growers of other disease and insect news, as well as posting messages of general interest such as potato field day dates.
The hotline recommendations can be accessed by phone or website. The toll free phone number is 888.482.7286
The NDAWN website for potato disease forecasting contains colored maps of ND to pictorially illustrate the late blight severity values (both two day and seasonal), favorable day values and P-day values for early blight throughout ND. That site is: www.ndawn.ndsu.nodak.edu Go to applications and then click the potatoes drop down box.
Current and archival information on late blight and other potato diseases, and research trial data, can also be found at http://www.ndsu.edu/potato_pathology
You can also connect to the latest blight hotline news and message update reminders by text messaging type BLIGHTND to 97063, or on Twitter follow @SyngentaSpuds.
Growers and scouts are encouraged to send suspect late blight samples to us for positive identification. Late blight is a community disease and proper identification and prompt notification is important. Leaf samples should be placed in a slightly inflated zip-lock plastic bag without a wet towel and sent to:
NOTE new mailing address: Gary Secor, NDSU Dept 7660, PO Box 6050, Fargo, ND 58108. Our phone number is 701.231.8362 and email address is gary.secor@ndsu.edu. We wish you a successful potato year.
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Southern Plains Wheat Disease Reports (5/24/12)
Wheat has progressed rapidly in Kansas, being in the milk to soft dough stage at Hutchinson, KS (central part of state), as reported by Bob Bowden, USDA-ARS pathologist.
The warm, dry weather there has slowed stripe rust development, but leaf rust continues to be severe in winter wheat cultivars such as Jagalene, Jagger, and Overley. Leaves were dying from leaf rust and maturity at this location. In NE, Stephen Wegulo, Extension Plant Pathologist, reports that stripe rust is the most widespread disease on winter wheat flag leaves, but dry and hot weather has slowed its development. He is now reporting wheat leaf rust in central Nebraska, as well.
Marcia McMullen
Extension Plant Pathologist – Cereal Diseases
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Root Rots (5/24/12)
I have received questions about the potential for root rot development under dry and warm conditions. Although recent rains have occurred and more rain is in the forecast for some of the state, so there is great variability in soil conditions locally and statewide.
In general, root rots are much less problematic in dry conditions than in wet conditions. Some root rot pathogens are not impacted much by dry conditions, while others all but disappear.
Pathogens in the near-fungal group ‘oomycetes’ are inhibited by dry conditions. They have swimming spores that need water to move, to cause infection and for disease to develop or for an epidemic to spread. This group includes pathogens that cause downy mildew on sunflower, phytophthora on soybeans, pythium on many crops, late blight on potatoes, aphanomyces on sugar beets, and other less common diseases.
Root rot pathogens that are true-fungi, such as Fusarium and Rhizoctonia, are less dependent on moisture to cause problems. For the most part they need some moisture to get going, but soils do not need to be saturated for long periods of time to have problems. Also, warm temperatures are not necessarily inhibitive for disease development. For example, Rhizoctonia in sugar beet is minimally active until the soil temperatures reach the mid-60’s oF or greater.
When assessing root rots in dry years another thing to consider is the damage potential. If roots rot pathogens cause infections early in the plants growth stage and the weather becomes very dry, the compromised roots are going to have a much harder time collecting moisture than if the soil was wet. As a result, yield loss can occur from root rots in dry years; but this all depends on the development of the infections earlier in the season.
Sam Markell
Extension Plant Pathologist
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Managing Rhizoctonia Solani in sugarbeet (5/17/12)
Rhizoctonia root rot is the worst production problem faced by sugarbeet growers in North Dakota and Minnesota. Rhizoctonia root rot has become more widespread and severe over the past decade with the increased use of soybean, edible beans, and corn in rotation with sugarbeet, along with wet field conditions.
Rhizoctonia root rot is caused by a fungus, Rhizoctonia solani, which can cause infection in wet as well as in dry fields when the soil temperature is above 65 F. The disease is more severe in warm and wet fields with a history of the problem. To further compound the problem, a very severe form of the fungal pathogen is becoming widespread in southern Minnesota and the Red River Valley. R. solani also causes seedling damping-off and crown rot. The best way to manage R. solani is to plant early in cool soils using a partially Rhizoctonia resistant variety and timely applications of effective fungicides.
Seedling damping-off occurs just after planting in warm and wet soils. This disease is not very common since planting is typically done when soils are still very cold (45 to 55 F) in North Dakota and Minnesota. Quadris and Headline fungicides applied in-furrow are effective at controlling damping-off. Research is on-going to find effective seed treatments that will control damping-off. Crown rot was a major problem when conventional varieties were used and tillage practices to manage weeds resulted in throwing of infected soil into crown of plants. After a flooding rainfall, infected soil may get into crown of plants causing infection. Crown rot could be controlled by a foliar application of Quadris before infection takes place. The widespread use of Roundup Ready sugarbeet does not require tillage for effective weed control and therefore very little crown rot occurs. In the annual sugarbeet survey, growers have reported over the past three years that root rot has become their number one problem. Quadris and Proline provide effective control of crown rot when applied just before the average daily soil temperature at the 4 inch depth reaches 65 F. The fungal pathogen which causes root rot is present in the soil. As such, fungicides should be targeted to the hypocotyl/crown area and into the soil since the fungicides when applied to leaves do not translocate downwards to the root. Ideally, fungicide to target R. solani should be applied just before a rain so that it gets down to the roots and the soil around the roots to provide protection. There is no data available on how effective fungicides are at controlling R. solani when applied in a band or broadcast in dry and warm conditions, or how severe the disease will be in dry field conditions. Greenhouse research shows that disease severity is significantly lower in soils at 25, and 50%, compared to 75 and 100% moisture holding capacity. It is possible that fungicides used with higher water volumes of 15 to 20 GPA will be more effective at controlling R. solani than lower (10 GPA) water volumes, and that band applications may be more effective than broadcast application since the fungicide is more likely to reach the root and soil to provide protection. Research conducted in years when there were prolonged periods of favorable conditions (warm and wet) for R. solani infection and development, research data indicated that two post applications of fungicides resulted in better R. solani control and higher yields than one application.
Currently, average daily soil temperature in sugarbeet production areas is at the threshold of 65 F. Fields with a history of root rot should be treated. However, the top one to two inches of soil in many areas is very dry. Fungicide application in the evening should help in getting the fungicide into the soil and close to roots. Rainfall will be required to move the fungicide to protect roots. Hopefully, there will be rainfall soon.
Mohamed Khan, Extension Sugarbeet Specialist
NDSU & University of Minnesota
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NDSU Small Grain Disease Forecasting Site Activated (5/17/12)
The NDSU small grain disease forecasting site has been activated for the season.
The web address is: http://www.agndsu.nodak.edu/cropdisease/ . Information about the risk of wheat tan spot, Septoria blotch, and wheat leaf rust are available, based on weather data provided by each of the NDAWN weather sites. A user of this site choses which growth stage their crop is in or approaching. Information about the risk of Fusarium head blight infection also is available, when the flowering growth stage is chosen. Currently, as winter wheat is approaching flag leaf stage in some areas, risk of any of the fungal diseases above is low, based on the dry weather that has occurred in recent days. According to NDAWN data, the average dew point over the past week has been below 40 degrees across the state. We usually see fungal disease infections when dew points are in the 50+ degree range.
Marcia McMullen
Extension Plant Pathologist, Cereal Crops
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NDSU 2011 Cereal Fungicide Results Available On-Line (5/17/12)
A compilation of the 2011 NDSU seed treatment and foliar fungicide results on cereals is available now on-line.
It can be found in the new publications column of the NDSU Extension Plant Pathology website: http://www.ag.ndsu.edu/extplanpath/. The compilation contains trial results from across the NDSU research extension centers and off-station sties, results on seed treatment of spring wheat and foliar fungicide applications on spring wheat, winter wheat, durum wheat, barley, and corn.
Marcia McMullen
Extension Plant Pathologist, Cereal Crops
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No wheat rust found in ND yet (5/17/12)
Extension Plant Pathologists from Kansas and Nebraska continue to report the occurrence of stripe rust in their states, but have indicated in very recent reports that dry weather during the past week has slowed the development of this disease, and also pushed the maturity of their winter wheat crops ahead by 2-3 weeks from normal.
Leaf rust is severe in susceptible winter wheat varieties in south central Kansas, but the first confirmation of leaf rust in Nebraska was on May 1. Current levels of wheat leaf rust in Nebraska are low. It is too soon to know the impact of these rust diseases on ND wheat, but as of May 15, no rust has been reported on winter or spring wheat in the state. Generally, first detections in ND are the first part of June, but it is an early year. Also, wheat rust pathogens need at least 6 hours of dew for infection to occur.
Marcia McMullen
Extension Plant Pathologist, Cereal Crops
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Wheat Disease Updates from Southern Plain States (5/10/12)
Extension Plant Pathologists from Kansas and Nebraska are reporting some low to moderate levels of disease in winter wheat fields in those two states.
In a 5/4/2012 report from Kansas, Erick De Wolf reported that stripe rust appeared to be slowed down by high temperatures last week in Kansas, but cooler temperatures this week may allow some increase in stripe rust development. Wheat leaf rust increased in the past two weeks in KS, especially in susceptible varieties in central and northeast KS. Wheat in KS is in past flowering and in grain fill stages now.
In a 5/7/2012 report from Nebraska, Stephen Wegulo reported that a survey of wheat fields in the Nebraska Panhandle showed some stripe rust in the southern panhandle, but wheat in the northern Panhandle appeared free of stripe rust. Dr. Wegulo also reported symptoms of barley yellow dwarf virus were seen in all the fields they surveyed in south central and southeast Nebraska, but incidence levels varied per field.
Stripe
rust and leaf rust are monitored and mapped by the USDA Cereal Disease Lab in
St. Paul. These maps are found under the
heading “2012 Rust Observation Maps” at the following web site: http://www.ars.usda.gov/Main/docs.htm?docid=9757
. A link to the latest Cereal Rust
Bulletin (# 4, May 7, 2012) also is found at the same web location, as well as
information on rusts of barley, oats, and rye.
Observations in states to our immediate south provide us clues to risk
of these rust diseases occurring in our small grain crops, as more rust spore
production in those states indicates greater potential movement into our state
on prevailing southern winds. No rust has been observed yet in ND on the
very young spring and winter wheat crops.
Marcia McMullen
Extension Plant Pathologist, Cereal Crops/IPM Coordinator
NDSU Crop & Pest Report - May 24, 2012
