By Pierce A. Paul
After being slowed down by cold temperatures over the last 7-10 days, the wheat crop is now heading-out or flowering in some parts of the state – do not be deceived by the fact that plants still look short in some fields. Heading and flowering will continue over the next few weeks. These are very important growth stages from the standpoint of disease management, since it is critical to maintain the health of the heads and the leaves during grain fill to enhance yield.
- Examine primary tillers at multiple locations in the field – remove them if it makes it easier for you to examine;
- Identify the flag leaf, which is the uppermost (last) leaf, and look at the position of the head in the leaf sheath of the flag leaf;
- If the flag leaf is fully emerged and the head is still encased and swollen in the leaf sheath, then you are still at Feekes 10, the boot stage;
- If the first few spikelets are out of the leaf sheath then you are at Feekes 10.1;
- If about 25% of the head is out of the leaf sheath then you are at Feekes 10.2;
- If about 50% of the head is out of the leaf sheath then you are at Feekes 10.3;
- If about 75% of the head is out of the leaf sheath then you are at Feekes 10.4; and
- If the head is fully emerged (the entire head is out of the leaf sheath) then you are at Feekes 10.5;
- Once the heads are completely out, it may take another 3-5 days, and sometimes longer if it’s cool, for it begin to flower.
This stage is marked by the extrusion of anthers from the spikelets; the reason for which this process is also referred to as anthesis. The identification of this growth stage is very important for the management of Fusarium head blight (head scab) with fungicides.
10. Closely examine the heads (also called the spike) of primary tillers at multiple locations in the field for the presence of anthers – often seen as a yellowish (or other color) part of the flower hanging from the spikelet;
11. If no anthers are seen, then your wheat may still be at the heading growth stage, Feekes10.5;
12. If the first few anthers are seen hanging from florets/spikelets in the central portion of the spike, your wheat is at Feekes 10.5.1 - early flowering or early anthesis;
13. If anthers are seen hanging from florets/spikelets in the central and top portions of the spike, your wheat is at Feekes 10.5.2 - mid-flowering or mid-anthesis;
14. If anthers are seen hanging from florets/spikelets along the entire length of the spike, your wheat is at Feekes 10.5.3 - late-flowering or late-anthesis;
Note: When trying to identify flowering growth stages, based your assessment on the presence of fresh (brightly colored) anthers, since dried, discolored, and spent anthers may remain hanging from the spikes well after Feekes 10.5.3. This can be misleading. Fungicides are most effective against head scab and vomitoxin when applied during Flowering.
Head scab and vomitoxin become our biggest concerns at this time of the wheat season. For wheat flowering today, May 8, the risk of scab is low across most of the state (the map is green), but moderate in parts of the west (yellow areas close to the Indiana border). The risk is also moderate-high in the northeast corner if the state, but the wheat in that region is not yet flowering. Several fields across Southern and Central Ohio will reach anthesis during this week. The risk will likely remain low if it stays cold, in spite of the rains, but continue to keep your eyes on the weather and the scab forecasting and alert systems over the next few weeks, and be prepared to apply a fungicide (Prosaro or Caramba at full label-recommended rates) at flowering if the risk increases.