Posts Tagged ‘fusarium head blight of wheat’

Wheat Scab Situation

Thursday, May 20th, 2010

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Weather was favorable for scab infection in Kent County, DE yesterday if any was flowering at the time. The forecast is not favorable for scab statewide for the rest of the week. This should put us out of the window where we might see scab this season. There may be some secondary tillers with heads that were possibly at risk the last two days which may show symptoms in the next week or so. If there is any scab it will be considerably lower that what appeared last year.

Fusarium Head Blight Forecast and Alert System

Friday, May 14th, 2010

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

The risk of Fusarium head blight or scab is low for the next several days. There is some rainfall in the forecast for Friday and early next week with warmer temperatures, but until now there has not been enough moisture to produce spores for infection. Most of the wheat by next week should be past flowering and therefore not at risk unless it is very late. There are scattered reports of low levels of leaf rust on Delmarva so scouting should continue.

I just became aware that wheat growers can sign up for scab alerts. See the following information:

Producers, crop consultants, grain processors and others can sign up for the alerts by going to the following web site address: http://scabusa.org/fhb_alert.php. The alerts will be sent out to one’s cell phone or email, depending upon the user’s preference. Frequency and timing of alerts will depend upon a given area’s risk for severe scab – which can vary widely, depending on environmental conditions.

The purpose of the alert system, is to give growers and affiliated industry personnel better advanced notice of potential outbreaks and the risk of scab in their area, thus allowing for timely treatment of fields with fungicides. “We are aware that many farmers do not have easy or convenient access to the Internet, but most of them carry a cell phone,” says Dave Van Sanford, USWBSI co-chair. “We wanted a system that would send an alert to their cell phone, prompting them to take an appropriate action – such as going to the USWBSI website, checking with their county agent, chemical dealer or consultant, or simply looking at their crop to check its stage of development. Our hope is that the alerts will lead to some action that will reduce the impact of head scab on the crop.”

The alert system is tied in with the Fusarium Head Blight Risk Assessment Tool hosted by Pennsylvania State University, Kansas State University, Ohio State University and the U.S. Wheat & Barley Scab Initiative. This web site – www.wheatscab.psu.edu/riskTool_2010.html – provides detailed, daily updated information on scab risk in various U.S. small grain production regions. The FHB Assessment Tool is supplemented by commentaries from various state university plant disease specialists regarding environmental conditions and the presence of scab (or lack thereof) in their state. These commentaries provide the content behind the FHB alerts.

Agronomic Crop Diseases

Thursday, April 8th, 2010

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Wheat
Wheat development is later than normal due to the adverse wet weather conditions beginning back in the fall. It is not too early to remind growers, consultants and fieldmen about several resources that are available for monitoring Fusarium head blight (scab). Two websites are available, the first is the scab predictor site http://www.wheatscab.psu.edu/ with the risk map tool and the second is a new site called Scab Smart.

Scab Smart Web Site Can Help With Head Scab Management
The U.S. Wheat and Barley Scab Initiative (UWBSI) has a Web site that provides farmers with information on how to manage Fusarium head blight, commonly known as scab.

Scab Smart is designed to serve as a quick guide to the integrated strategies that result in optimum reduction of scab and its primary associated mycotoxin, deoxynivalenol (DON).

On the site, producers can access information by management strategy or wheat class. Scab Smart’s content will be updated on an ongoing basis as new management information becomes available.

The site can be accessed through this website http://www.scabsmart.org

Stripe Rust and Leaf Rust
On another topic, stripe rust and to a lesser extent leaf rust, are increasing in the South. There have been reports of greater than normal infection levels of stripe rust in Louisiana, Texas and Oklahoma. It is never easy to predict if it will make it to Delmarva. Stripe rust has not been a problem in Delaware since 2006 and 2007. When it has occurred it has had variable effects on wheat depending how mature the crop is when the disease appears. Most of the damage in the past has occurred in the northern parts of the state. When scouting wheat later in the season keep this disease in mind. Alerts will be given if it gets closer to us. Generally applications with a triazole containing fungicide made at flag leaf emergence through heading will provide good control.


Stripe rust on wheat.

Corn
There have been growers with increasing southern root knot nematode populations in field and sweet corn, especially when pickling cucumbers, soybeans, and lima beans have been in a rotation. The best way to reduce root knot nematodes in corn is with an at-planting application of Counter 15G. The data I have seen for seed treatments that might be effective for root knot have not been consistent at this time. They are definitely worth looking at but how effective they will be is still a question in my mind.

Selecting Head Scab Resistant Wheat

Friday, August 28th, 2009

Dave Van Sanford, Wheat Breeder, University of Kentucky and Bill Bruening, Variety Testing Specialist, University of Kentucky

Bob Mulrooney Notes: This is an excellent article from Kentucky Pest News (#1210 Aug 25, 2009) that is very timely for Delaware growers.

Selection of wheat varieties is one of the most critical management decisions Kentucky wheat producers will make. The decision is complicated this fall by the fact that 2009 was a year in which Fusarium head blight (FHB) or head scab, was a problem for KY wheat growers. The real question is “how important is head scab resistance?” Clearly, in a bad head scab year, growers recognize that FHB resistance is very important. After a year or two with little or no head scab, however, farmers tend to underestimate the value of scab resistance. In any given year, how likely is it that head scab will be a serious disease in Kentucky? We know that with our corn‐wheat‐soybean rotation we will always have plenty of inoculum. Although we don’t know if the moisture requirements of the disease will be met when the crop is flowering, it is reasonable to assume that we will always have a chance of seeing FHB in our Kentucky wheat crop. How serious is the disease? In addition to reducing yield and test weight, the thing that sets FHB apart is the toxin (DON or vomitoxin) that is produced by the fungus. Elevated DON levels can result in serious discounts or even rejection of loads at the elevator or mill. For this reason alone,we need to take head scab very seriously.

Resistant Varieties
The best known and most widely studied genetic resistance comes from Sumai 3, a Chinese spring wheat variety. Pioneer Brand 25R18 is an example of an older soft red winter wheat variety that has Sumai 3 resistance. This is Type II resistance, or resistance to spread of the fungus in the head which means that under heavy FHB pressure, there might be many heads that are infected, but the severity of infection on each head will be low. In addition to the Sumai 3 resistance source, there are numerous adapted SRW varieties with varying levels of scab resistance. Truman and Bess are two varieties released by the University of Missouri which have good scab resistance that is not derived from Sumai 3. Due to the heavy scab pressure throughout Kentucky in 2009, we had a good opportunity to rate scab symptoms on all 88 entries in the state variety trial (Table 1). Keep in mind that these ratings are based on chaff symptoms observed between flowering and physiological maturity. These symptoms often provide a good indication of kernel damage that is likely to occur, but the relationship is not perfect.

Combining Resistance with Fungicides
When we define FHB resistance, our targets include a low level of infection, plump kernels with no yield or test weight reduction and low DON levels in the grain. In a year like 2009 under heavy scab pressure, it takes a combination of good genetic resistance and a well‐timed fungicide application to hit these targets. In Table 2 we present two years of data from our inoculated scab nursery at Princeton, KY where varieties and breeding lines were evaluated with and without a fungicide application. Scab is a difficult disease for farmers, millers and researchers. It takes several years of testing and retesting to really get to know the scab profile of a variety. For this reason, the data in Tables 1 and 2 should be studied very carefully before deciding which wheat varieties to plant this fall. It is also important to apply the other risk management strategies that we have discussed in previous variety selection articles. In particular it is important to remember that wheat growers can minimize their risks by planting several varieties with good yield and test weight potential that complement one another for disease resistance and maturity. Choosing varieties of differing maturities makes sense for a number of reasons, but it is especially important when considering head scab. In those years when head scab is problematic, if the early flowering varieties are hit hard, then the later flowering types often face less scab pressure, and vice versa. A final suggestion is to avoid planting varieties that appear to be very susceptible to head scab. If a variety completely lacks genetic resistance, a fungicide application will not be sufficient to prevent yield loss and elevated toxin levels during an epidemic scab year.

 

Table 1. Scab Ratings (1=excellent; 9=poor) Based on Chaff Symptoms; Each Value Represents the Average of Ratings at 6 Variety Trial Locations in Kentucky, 2009

Variety

Head Scab

AgriPro Branson

6.6

AgriPro COKER9511

3.9

AgriPro COKER Oakes

5.5

AgriPro W1104

4.5

AgriPro W1377

5.4

AgriPro W1566

6.1

ARMOR 3602

6.4

ARMOR ARX 6202

6.3

ARMOR ARX 840

6.8

ARMOR GOLD

7.0

ARMOR RENEGADE

5.0

Beck113

5.3

Beck122

5.7

Bess

4.0

Clark

5.7

Cumberland

6.0

Delta Grow1600

5.8

Delta Grow4500

6.2

Delta Grow5200

5.8

Delta King 9108

5.9

Delta King 9577

7.1

Dixie 907

5.9

Dixie 940

5.9

Dixie 989

6.4

Dyna-Gro 9911

5.3

Dyna-Gro 9922

5.3

Dyna-Gro Shirley

6.0

Dyna-Gro V9710

6.5

Dyna-Gro V9723

5.6

Dyna-Gro V9812

6.6

EXCEL 163

6.9

EXCEL 234

4.2

EXCEL 341

5.6

Exsegen Anna

6.4

Exsegen Candace

6.2

Exsegen Dinah

4.8

Exsegen Lois

5.6

Exsegen Lydia

6.5

Jamestown

6.3

KAS 5003

6.0

KAS 5058

4.9

KAS 7700

5.9

KY 00C-2059-24

5.7

KY 00C-2109-01

7.3

KY 00C-2175-10

6.0

KY 00C-2567-01

6.5

KY 00C-2697-04

5.9

KY 97C-0321-02-01

6.9

KY 97C-0508-01-01 A-1

5.6

KY 97C-0519-04-07

6.1

KY 97C-0540-01-03

5.7

KY 97C-0574-01-04

5.4

Merl

7.1

Milton

5.7

Pembroke

5.1

Pioneer variety 25R63

5.0

Pioneer variety 25R78

7.1

Pioneer variety 26R15

5.5

Pioneer variety 26R22

6.4

Pioneer variety XW07B

7.1

Pioneer variety XW07X

3.5

PROG ENY 117

5.5

PROG ENY 119

5.5

PROG ENY 130

5.3

PROG ENY 136

6.8

PROG ENY 166

6.3

PROG ENY 185

5.9

Red Ruby

6.2

SC 1298

5.8

SC 1318

6.7

SC 1325

5.6

SC 1328B

5.4

SC 1339

7.0

SC 1348

6.0

SS 520

8.0

SS 5205

6.4

SS 548

7.0

SS 8302

4.9

SS 8309

4.4

SS 8404

5.9

SS 8641

7.6

SS MPV-57

6.0

Steyer Geary

6.5

Steyer Jordan

5.4

Steyer Nofziger

6.2

Truman

2.6

USG 3350

6.0

VA 04W-90

5.7

Average

5.9

Table 2. Two Year Comparison of Wheat Varieties and Breeding Lines Treated vs. Untreated with Prosario Fungicide in Princeton Inoculated Scab Nursery, 2008-09 (DON data not available at press time)

Entry

Fungicide Treated

Untreated

Yield
(bu/A)

Test Wt
(lb/bu)

Scabby Seed (%)

Yield
(bu/A)

Test Wt
(lb/bu)

Scabby Seed (%)

AgriPro Branson

77.2

51.3

5.4

60.3

48.1

9.6

AgriPro COKER 9511

75.2

57.9

1.9

67.9

57.0

2.8

AgriPro W1377

69.7

55.8

4.5

56.1

52.2

7.5

Bess

78.8

56.9

2.4

61.9

54.6

5.9

Clark

62.5

54.2

2.7

53.5

51.0

6.7

Cumberland

74.2

52.0

5.6

56.9

47.8

14.9

Delta Grow 1600

70.3

51.5

7.5

50.4

48.5

9.9

Delta King 9577

61.8

49.6

7.2

45.7

45.7

16.6

KY97C-0508-01-01A-1

76.6

53.5

4.2

53.3

49.7

10.7

KY97C-0540-01-03

59.9

51.9

4.8

53.9

50.4

13.8

KY97C-0574-01-04

67.0

53.2

5.2

41.1

47.8

14.9

MO 011126

63.8

54.5

3.8

51.1

50.8

7.7

Pembroke

77.2

54.3

4.1

53.6

50.9

5.6

Pioneer variety 26R15

80.2

51.6

7.0

69.0

49.9

8.3

Pioneer variety 26R22

62.2

50.0

4.8

45.1

44.8

17.0

SS 520

63.0

52.1

5.2

50.4

47.3

12.7

SS 8302

70.1

54.3

2.9

63.8

51.9

8.0

SS 8309

77.2

53.4

3.5

58.5

49.6

8.5

SS 8404

67.0

54.0

3.8

54.0

49.6

11.5

SS MPV-57

65.2

51.6

5.7

57.0

47.2

14.5

Truman

82.5

56.0

3.0

72.9

54.5

3.8

Wheat Disease Update – July 3, 2009

Thursday, July 2nd, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Scab
There have been reports of wheat being rejected at the elevator for excessive vomitoxin (DON) levels in the grain due to head scab infection. The following was written by Dr. Arv Gybauskas from the Univ. of Maryland about blending good grain with contaminated grain. “The question arises can you blend the infected seed lots with clean seed to avoid a complete loss of the harvested seed. Blending to dilute DON levels is very tricky. In the EU it is even illegal once the grain has left the farm and is tested by an elevator or mill. The problem is DON is not uniformly distributed in the seed and without testing and complete mixing of truck-loads of seed you could still end up with a load that could be rejected. In that case you would even have lost the good seed. A better solution, although not an easy one nor is it a guarantee to make the seed marketable, is to further clean out the seed and have it tested again.

To avoid getting into this jam next time, it will take a complete management program that includes rotation, selection of varieties that have some resistance and only recommended fungicides applied when needed. We will present data and more details on these choices as we finalize the results from research trials this season.”

Grain Testing for Vomitoxin (DON)
The Delaware Department of Agriculture is conducting testing for DON in grower submitted samples. Growers should submit a 2 lb sample in a plastic zip-lock bag to the DDA in Dover (2320 S. Dupont Highway, Dover DE 19901). The sample should be clearly labeled with your name, billing address and telephone number. The costs are:

Vomitoxin test = $40/sample (DDA will provide a certificate that certifies the testing procedure). If the grower or their insurance company requires a USDA/FIGIS grade certificate, they will need to locate a laboratory that has that certification.

Grain grade factors (e.g. moisture, test weight, damage) = $15/sample

The link below describes the exact ELISA test that DDA will be conducting: http://www.neogen.com/FoodSafety/pdf/ProdInfo/Page_24.pdf.

Any questions please call the DDA Seed Lab at (302) 698-4590.

How to Get a Good Representative Sample for Testing
The reliability of testing is greatly influenced by the sampling procedure. To achieve a more accurate DON level estimate, it is critical that the collected grain sample be representative of an entire truckload or bin of grain. Grain and other particles separate based on particle size and density as it flows into a truck or bin. Typically, the smaller, denser material is near the center and the larger, lighter material is near the outside of the container. Therefore, it is expected that there will be a variation in the concentration of affected kernels in various portions of a truckload. In addition, since DON levels can vary greatly between kernels of similar size and density, it is important to take several samples from various locations within the load. Probe samples should not be taken from the center or outer portions of a load because these areas do not reflect a cross section of the load. The samples also must represent spatially distinct areas of the load. The probe should collect the sample from as much of the entire depth of the truck as possible. Four to five probes per truck are recommended. To obtain an accurate sample from an end gate grain stream, samples from the entire width and depth of the grain stream should be collected, not just the first and last portion of the load. A Pelican sampler or other sampling device aids in proper sample collection. At least four samples of the entire grain stream should be collected at intervals to represent spatially different portions of the load. Information from NDSU fact sheet “DON (Vomitoxin) in Wheat: Questions and Answers” http://www.ag.ndsu.edu/pubs/plantsci/pests/pp1302.pdf.

Wheat Disease Update – June 12, 2009

Friday, June 12th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Wheat is rapidly turning but scab is widespread in the state. We did not dodge the bullet unfortunately. Levels of scab really vary depending on the flowering time of the wheat and whether it corresponded with favorable weather for infection. We can expect lower yields and test weights were scab is heavy.

The first symptoms of Fusarium head blight include a tan or brown discoloration at the base of a floret within the spikelets of the head. As the infection progresses, the diseased spikelets become light tan or bleached in appearance. The infection may be limited to one spikelet, but if the fungus invades the rachis the entire head may develop symptoms of the disease. The base of the infected spikelets and portions of the rachis often develop a dark brown color. When weather conditions have been favorable for pathogen reproduction, the fungus may produce small orange clusters of spores or black reproductive structures called perithecia on the surface of the glumes. Infected kernels are often shriveled, white, and chalky in appearance. In some cases, the diseased kernels may develop a red or pink discoloration.

fusariumgrain 

Grain produced in heads damaged by Fusarium head blight is often shriveled, white, and chalky in appearance.

Fusarium graminearum is known to produce two important mycotoxins, deoxynivalenol (DON) and zearalenone, which can contaminate the diseased grain. The mycotoxin DON can cause reduced feed intake and lower weight gain in animals at levels as low as 1-3 ppm, especially in swine. Vomiting and feed refusal can occur when levels of DON exceed 10 ppm. Humans are also sensitive to DON, and the FDA has recommended that DON levels not exceed 1 ppm in human food. Ruminant animals, including dairy cows and beef cattle, are less sensitive to the toxin. The fungal toxin zearalenone has estrogenic properties and produces many reproductive disorders in animals. Swine are the most sensitive to the toxin, but cattle and sheep may also be affected. Zearalenone concentrations of 1-5 ppm can result in negative effects in animals and humans. Producers concerned about these mycotoxins should have grain tested prior to feeding to animals. Contact the state or local extension office for more information about testing for mycotoxins.

When high levels of Fusarium head blight are present in fields, precautions can be taken to reduce mycotoxin contaminations of the grain. The mycotoxin contamination is often highest in the severely diseased kernels. Adjusting the combine to blow out the small, shriveled kernels can help reduce mycotoxin levels. Harvested grain should be dried to 13.5 percent moisture as soon as possible to limit continued fungal growth. Grain suspected to have been damaged by Fusarium head blight should be tested for DON and zearalenone at a private agricultural lab or grain elevator. Do not mix contaminated grain with good grain prior to a mycotoxin analysis. The mixing will result in more contaminated grain, which may be difficult to sell.

Edited from Penn State fact sheet on Head Blight authored by Eric DeWolf. http://www.wheatscab.psu.edu/PDF/Fusarium_Head_Blight_.pdf

Leaf rust is present in varying amounts. In my estimation it has arrived too late to impact yield, but it can be seen on unsprayed wheat that is still green. Tan spot turned out to be the most prevalent foliage disease this year.

Corn and Wheat Disease Update – June 5, 2009

Friday, June 5th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Corn
No need for me to tell you how bad the weather has been so far for corn. Stands are still being reduced by excessively wet soils and the Pythium and Fusarium damping-off that is occurring as a result of the wet soils. Fungicide treated seed, good drainage and some warm temperatures would help considerably in getting the plants out of the ground and growing.

Wheat
Fusarium head blight or scab is being seen in some fields in Kent and Sussex counties. The occurrence and severity so far has been variable but, in general, I think we dodged a bullet this time. Our wheat for the most part was already in flower before the most favorable weather came for scab (Figure 1).

fusarium head blight 

Figure 1. Fusarium head blight or scab.

Take-all was diagnosed this week as well from two fields. Take-all is characterized by patches in the field that can vary in size but the wheat is generally stunted and the heads bleach out prematurely. Infected plants can be easily pulled out of the ground due to the extensive root rot that occurs. The other symptom is the dark streaking at the base of the stem (lowest node under the leaf sheaths), see Figure 2. Take-all can be controlled by rotating out of wheat for a year. However planting wheat followed by double crop soybeans followed by wheat is not an effective rotation for take-all control. Manganese levels also interact with take-all. Be sure that soil levels of manganese are adequate for the crop and check pH so that the managanese is available. High pH makes manganese unavailable.

takeall

Figure 2. Take-all symptoms on the lower nodes. Note lack of roots as well.

Tan spot (Figure 3) has been present for almost three weeks in wheat. This foliar disease can look like Septoria (Stagnospora) leaf and glume blotch. It is caused by the fungus Pyrenophora tritici-repentis.

 tanspot

Figure 3. Tan spot symptoms on wheat.

It has been widespread on Delmarva this season because of the amount of rainfall that we have had. It is too late for any control, but this disease is favored by wet, warm weather. Most of the spots are in the lower canopy and may reach the flag leaf before the plants begin to dry down. Applications of foliar fungicides at heading or earlier have been providing good control of this disease. At present most of the infection is in the lower canopy and the effect on yield should be minimal if the disease does not move up to the flag leaf or the leaf below the flag leaf.

Agronomic Crop Disease Update – May 22, 2009

Friday, May 22nd, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Corn
Pythium seedling damping-off as well as Fusarium seedling blight have been diagnosed from several fields that were very wet and the corn took from 10-14 days to emerge. The cool wet weather contributed to the widespread damping-off problem we are seeing. The amount of disease experienced depended on when the corn was planted in relation to the rains. With the warmer temperatures and more normal soil moisture, there should be no problems replanting with treated seed. No additional soil fungicide treatments should be needed if soil moisture is normal at replanting.

Barley
After evaluating the variety trials in all three counties I can report that there are low levels of the spot blotch form of net blotch, scald, and powdery mildew on susceptible varieties. ‘Thoroughbred’ varies in the amount of powdery mildew infection but it has been high overall. Fusarium head blight or scab was also seen on two barley varieties, Nomini and FS 950. The incidence was fairly low (3-5%) and the severity was low as well, maybe only 10-15% of the head was infected. Head scab in barley is a rare occurrence on Delmarva.

 Fusarium head blight on barley

Fusarium head blight on barley.

Wheat
If this weather continues we may have missed a potential scab problem in wheat. So far scab has not been seen. Low levels of powdery mildew and tan spot were seen while evaluating the wheat variety trial.

Agronomic Crop Disease Update

Friday, May 15th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Soybean Rust Update
Rust is developing very slowly despite excessive rainfall in some of the Gulf Coast states. Florida is remaining mostly dry. Rains have delayed some of the sentinel plot planting in LA and MS. There have been no new detections on kudzu since the last report. Those interested in following soybean rust can visit the ipmPIPE website at www.sbrusa.net.

Wheat Head Scab
The good news is that the current forecast for head scab is low for the next 72 hours. For wheat that was flowering from May 7 through May 10 the risk that scab could develop was 56-63%.

Avoid Spray Drift
Most applicators are aware that Quadris and Quilt can be very phytotoxic to certain apple varieties. Be sure that spray drift does not come in contact with apple trees or phytotoxicity can occur. With all the wheat that was recently sprayed we have had several cases of phytoxicity reported.

Soybean Cyst Nematode
It is still not too late to check for soybean cyst nematode especially if susceptible soybeans are going to be planted. Soil test bags with the submission form can be purchased at the Extension offices. If you have a fax machine and need results quickly, test results can be sent via fax if you provide the number on the Nematode Assay Information Sheet. This information sheet can be found on the web at the Plant Clinic Website http://ag.udel.edu/extension/pdc/index.htm.

Fusarium Head Blight or Head Scab of Wheat

Friday, May 8th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Wheat in most of Delaware is approaching heading or heads have emerged and could be flowering by the weekend depending on temperature. The risk of head scab or Fusarium head blight has increased with the recent wet weather pattern, which might continue into next week. Growers need to carefully evaluate the need for fungicides that could help suppress development of the disease. In the past we have not had good fungicide options but now that we have several fungicides with the capability to suppress the disease this option should be considered if the risk is high enough and it is economically sound. If the current conditions persist, large areas of Delaware could be at risk for scab infection. The new risk management tool is located at the Fusarium head blight website http://www.wheatscab.psu.edu. It can be useful once heading begins and the risk of scab increases as flowering approaches. The new version that is running now has the ability to give a 24-72 hour forecast looking at the previous several days as well as the weather forecast for the next several days. Those buttons are at the top left side of the forecast page.

Fungicide applications at heading but before flowering have not been very effective and are not recommended for scab suppression. The final decision to spray must be made as close to flowering as possible.

Fungicides must be applied at the correct time to control Fusarium head blight. 

First choice of products for scab suppression is Prosaro at 6.5 fl oz/A or Proline at 3 oz/A tank mixed with Folicur at 3 oz/A, second choice is Proline at 5.7 oz/A or Caramba at 14 oz/A, third choice is Folicur at 4 oz/A. Note Folicur is the weakest product for scab suppression and at best will only produce a slight reduction in disease. Folicur should only be selected if none of the other recommended products is available. No other products are registered for application at flowering and strobilurin-containing fungicides that are not registered for scab suppression may even increase vomitoxin in the finished grain. Use only recommended products when the risk warrants their use and apply as close to initial flowering as possible to be effective against scab.

Below are some suggestions that can help to evaluate the risk of disease:

Previous Crop: The fungus that causes head scab survives in the residues of many grass crops. The fungus is also a pathogen of corn and the most severe disease often occurs when wheat is planted in fields with large amounts of corn residue left on the soil surface. Planting wheat into wheat residues also increases the risk of scab, but this residue tends to break down more quickly diminishing the risk of disease relative to corn residue.

Resistant Varieties: All but a few wheat varieties that we grow are susceptible to head scab and the few that have some resistance do not provide enough resistance to protect the crop from a severe outbreak of the disease.

Weather Conditions: The infection of the wheat takes place at flowering or during the early stages of the grain filling period. This time period clearly influences the amount of disease present. However, the weeks preceding flowering are also important. Frequent rainfall and extended periods of high relative humidity prior to flowering favors the reproduction of the fungus that causes head scab. In fact, some of the worst epidemics of scab occur when conditions are favorable for reproduction of the fungus prior to flowering followed by a few days that are conducive for infection during the flowering or early stages of grain fill.