Cause: Fusarium graminearum, Fusarium pseudograminearum, Fusarium culmorum
Symptoms:
· Tan to brown discoloration at the base of the head
· Diseased spikelets (partial bleaching of the head) or entire head turns white
· Under moist conditions, pink/orange color is seen (produced by fungal spores and hyphae) on the surface of the glumes
· Infected kernels are shriveled, white, and chalky in appearance (‘tombstones’)
Outcomes of disease: Low yields, low test weights and low seed germination; Toxin contained in kernels us called deoxynivalenol (DON), also known as vomitoxin. The threshold level for human food is 1 ppm and feed is 2 ppm. There are higher tolerances for contaminated grain as livestock feed. There is a zero tolerance for DON in malt barley.
Often confused with:
· Take-all, caused by Gaeumannomyces graminis var. tritici, also causes bleached heads. Take-all does not cause partial bleaching of the heads. The characteristic take-all symptom is a shiny black discoloration of the base of the plant and stem. The plants pull out of the ground easily.
· Fusarium crown rot, common root rot, and physiological responses or drought may also cause bleached heads.
· Insect damage to stems (e.g. from stem maggots) may also cause individual heads to bleach. Pulling on these usually results in their breaking off at the point of damage.
Life cycle of the pathogen:
Scab is initially introduced into a field through infected seed or wind-borne inoculum. The causal agents can overwinter on crop stubble such as wheat, barley, and corn, and spread rapidly by rain splash and wind. The head, and in particular the open female flower during anthesis, 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 higher evening dew periods.
Management Approaches
Cultural Management Practices
· Plant healthy, high germ seed
· Use a seed treatment fungicide when planting seed with low levels of Fusarium –Use scab-tolerant varieties (see the most recent variety trial data for scab tolerant varieties adapted to your area)
· Crop rotation to a broadleaf crop
· Withhold irrigation during flowering, which can extend up to 7-10 days
· Incorporate cereal straw or corn stubble to accelerate degradation and inoculum destruction.
Fungicide Program
Apply a fungicide to the crop at flowering if:
· If planting into fields with:
· A history of scab
· A high crop residue of wheat, barley, or corn that resides on the soil surface
· Weather or irrigation schedule is predicted to be wet during flowering
· Foliar spray must be applied at the first sign of anthers extruding from the head to protect the flowers for 7-10 days
Product list for Fusarium Head Scab:
|
Product |
Product rate/acre |
Application timing |
|
Tebuconazole -Folicure -Orius -TebuStar |
4 fl oz |
Up to Feekes 10.5 (late heading emergence) plant stage One application per season, MT Sec. 18 Be aware of the pre-harvest interval (see label) |
|
Propiconazole - Tilt - PropiMax
|
2-4 fl oz |
Feekes 8 (emerging flag leaf); 24(c) label allows application to flowering, Feekes 10.5 Do not apply more than 4 oz/season |
|
Prothioconazole - Proline - Prosaro (not yet labeled in U.S.) |
4.3-5.7 fl oz |
Barley Feekes 10.3-10.5; Wheat Feekes 10.4-10.5; Maxiumum 9.37 fl oz/a per year |
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
Categories: Small grains, Diseases, Fusarium head scab
Date: 2/6/08
