UNL CropWatch Sept. 3, 2010: Plant Fungicide-Treated Wheat Seed to Avoid Disease Problems

UNL CropWatch Sept. 3, 2010: Plant Fungicide-Treated Wheat Seed to Avoid Disease Problems

Photo: Loose smut Photo: Common bunt  Photo: Black point
 Figure 1. Loose smut  Figure 2. Common bunt Figure 3. Black point

Photo: Fusarium head blight

Figure 4. Fusarium head blight (scab)

Photo: Fusarium head blight

Figure 5. Scabby grain

Photo: Black chaff

Figure 6. Black chaff

Sept. 3, 2010

Wet weather during the 2010 wheat growing season favored development of many wheat diseases including seed-transmitted diseases. These diseases lower both yield and grain quality. Some can cause up to 100% economic loss the following year due to rejection of contaminated grain at the elevator and several can cause damping off and seedling blights during or after emergence in the fall. Damping off and seedling blights also can be caused by fungi that are not seed-transmitted but live in the soil.

The Diseases

Seed-transmitted diseases include loose smut (Figure 1), common bunt or stinking smut (Figure 2), and seedling blights resulting from seed infected by fungi that cause black point (Figure 3) and Fusarium head blight or scab (Figures 4 and 5). Seed can also harbor fungi that cause tan spot and Septoria leaf and glume blotches, which increases inoculum for these diseases. Black chaff (Figure 5), a bacterial disease, also is seed transmitted. However, fungicide seed treatments do not control black chaff. For information on how to manage black chaff, see NebGuide G1672, Black Chaff of Wheat.

Why it's Important to Treat Seed

Fungicide seed treatments control seed-transmitted diseases caused by fungi. Soilborne fungi that cause damping off and root and crown rots also are effectively controlled by treating seed with fungicide. Thus, a good stand establishment and healthy and vigorous seedlings result, which optimizes the chances of obtaining high yields. If systemic fungicides are used to treat seed, additional protection from fall season foliar diseases is provided. It is important to note that treating seed infected by the Fusarium head blight (scab) fungus controls damping off and seedling blights in the fall; it has no effect on development of scab the following growing season. For information on how to manage scab, see Extension Circular EC1896, Fusarium Head Blight of Wheat.

Treating Seed

It is best to buy certified treated seed or utilize a commercial seed conditioner to clean and treat seed. Seed treated on-farm should be cleaned before treatment. Thorough coverage maximizes effectiveness of the seed treatment. A partial list of seed treatment fungicides is given in Table 1.

Due to the many seed-transmitted diseases that affected wheat grain this year, including loose smut, common bunt, scab, and black point, it is highly recommended that certified seed treated with a systemic fungicide be planted for next season’s crop. If farmer-saved or bin-run seed must be used, it should be cleaned thoroughly and treated with a systemic fungicide before planting.

Stephen Wegulo
Extension Plant Pathologist, Lincoln
 

 

Table 1. Partial list of fungicide treatments for wheat seed.

Fungicide

Active Ingredient

Mode of Action

Rate per 100 lbs*

Allegiance FL

metalaxyl

Systemic

0.10-0.375 fl oz

Captan 400

captan

Contact

1.5-4.0 fl oz

Captan 400-C

captan

Contact

1.5-4.0 fl oz

Charter

triticonazole

Systemic

3.1 fl oz

Charter PB

Triticonazole+thiram

Systemic + Contact

5.5 fl oz

CruiserMaxx Cereals

difenoconazole + mefenoxam + thiamethoxam

Systemic

5.0 fl oz

Dithane DF Rainshield

mancozeb

Contact

2.3-3.5 fl oz

Dithane M45

mancozeb

Contact

2.2-3.3 fl oz

Dividend Extreme

difenoconazole + mefenoxam

Systemic

1.5-2.0 fl oz

Dividend XL RTA

difenoconazole + mefenoxam

Systemic

5.0 fl oz

Grain Guard

mancozeb

Contact

2.0 oz

Incentive RTA

difeconazole + mefenoxam

Systemic

2.5-10.0 fl oz

LSP

thiabendazole

Systemic

2.0-4.0 fl oz

Mankocide

mancozeb + copper hydroxide

Contact

4.0 fl oz

Penncozeb

mancozeb

Contact

2.3-3.5 fl oz

Prevail

carboxin + PCNB + metalaxyl

Systemic

1.5-3.0 fl oz

Proceed

prothioconazole + tebuconazole + metalaxyl

Systemic

5.0-7.5 fl oz

Raxil MD

tebuconazole + metalaxyl

Systemic

5.0-6.5 fl oz

Raxil MD W

imidacloprid + tebuconazole + metalaxyl

Systemic

5.0 fl oz

Raxil MD Extra

tebuconazole + metalaxyl + imazalil

Systemic

5.0 fl oz

Raxil MD Extra W

imidacloprid + tebuconazole + metalaxyl + imazalil

Systemic

3.5-4.6 fl oz

*Rates may have been updated on the label.  Use the rate on the current label.

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Nebraska-Lincoln Extension is implied.