The Colquitt County area has had rain this week and the area wheat crop is around Feekes stage 10 of development. This has sparked some questions and concerns about fusarium head blight. Below are some questions that I have been getting about this subject and would like to thank Dr. Alfredo Martinez, UGA Plant Pathologist, for the information.
Are weather conditions right for head blight?
The fungi that cause FHB can overwinter on crop stubble such as wheat, barley and corn, and as soilborne inoculum. FHB is introduced into a field through infected seed or wind-borne inoculum. The fungus is spread rapidly by rain splash and wind. The head, and in particular the open female flower during anthesis (pollination), is most susceptible to infection by Fusarium spores. Some infection can occur during kernel development. Moist environmental conditions favor spore (inoculum) production and infection, including rain, irrigation, fog and long evening dew periods. Recent models have suggested that three or more rain or irrigation events from anthesis until 3-5 days post-anthesis and temperatures ranging from 77 to 86 degrees F (25 to 30 degrees C) will result in severe scab if inoculum is present and the variety is susceptible. A good website to monitor conditions for this disease is www.wheatscab.psu.edu .
What about resistant varieties??
Producers are encouraged to select varieties that have some level of FHB resistance. Resistance ratings are available from seed dealers and the annual Statewide Variety testing Georgia 2014 Small Grain Performance Tests – Annual Publication 100-6 (https://www.swvt.uga.edu/2014/sm14/AP100-6-Wht-grain.pdf). Dr. Martinez has a list of varieties
Good Resistance: Dyna-Gro 9171, Jamestown, Pioneer 26R20, SS 8415, SS 8629, USG 3024, TV8525, TV8535, USG 3555
Fair Resistance: AGS 2027, AGS 2035, AGS 2038, AGS 2060, Dyna-Gro Baldwin, LA754, Oglethorpe, Pioneer 26R10, Pioneer 26R61, Roberts, TV8848, TV8861
Poor Resistance: AGS 2026, 26R20, Fleming, SS 8641, USG 3524
Source: 2014-2015 Wheat Production Guide. https://www.caes.uga.edu/commodities/fieldcrops/gagrains/documents/2014-2015WheatProductionGuide.pdf .
What about fungicides?
Control using fungicides can be difficult due to the specific time the fungicides need to be deployed and because selection of fungicides labeled for FHB is limited. Timing of fungicide applications is crucial for the control of FHB. Foliar sprays must be applied at the first sign of anthers extruding from the wheat (anthesis). Triazoles work best when applied right before or at early flowering on the main stem heads. The use of nozzles that provide good coverage of the spike is essential, since fungicide products are ‘locally systemic’ and protect the tissue to which they are applied. The fungicides labeled for FHB disease-suppression only are listed in Table 3. In addition, avoid irrigation during flowering to reduce humidity and therefore to reduce the infection period.
| Fungicide(s)
Table 3: Triazole Fungicides for Fusarium Head Blight |
|||||
| Active ingredient | Product | Rate/A
(fl. oz) |
Head scab | Harvest Restriction | |
| Metconazole 8.6% | Caramba 0.75 SL | 13.5 – 17.0 | G | 30 days | |
| Propiconazole 41.8% | Tilt 3.6 EC | 4.0 | P | Feekes 10.5 | |
| Prothioconazole 41% | Proline 480 SC | 5.0 – 5.7 | G | 30 days | |
| *Tebuconazole 38.7% | Folicur 3.6 F | 4.0 | F | 30 days | |
| Prothioconazole 19%
Tebuconazole 19% |
Prosaro 421 SC | 6.5 – 8.2 | G | 30 days | |
Efficacy categories; P=Poor; F=Fair; G=Good; VG=Very Good; E=Excellent
*A maximum of 4 fl. oz. of tebuconazole-containing products may be applied per acre per crop season.
Table modified from 2015 fungicide table produced by “The North Central Regional Committee on Management of Small Grain Diseases (NCERA-184)” and from the CAES Wheat Production Guide (https://www.caes.uga.edu/commodities/fieldcrops/gagrains/documents/2014-2015WheatProductionGuide.pdf ). This information is provided only as a guide. By law, it is the responsibility of the pesticide applicator to read and follow all current label directions. No endorsement is intended for any products listed, nor is criticism meant for products not listed. The University of Georgia and members or participants in the NCERA-184 committee assume no liability resulting from the use of these products. Always check the label before application for the most current rates and application restrictions.