The recent, historical rainfall events absolutely will negatively impact the wheat crop.
Low-lying field areas, such as terrace channels and old plow furrows, already had seen premature death of the crop due to saturated soil conditions. Low-lying areas of fields have started to turn white due to saturated soil conditions. Damage from flooding will be the most immediately observable impact of the recent rain, but saturated soil conditions will negatively impact yield even in areas that are not flooded.
The amount of damage from flooding depends on the amount of time the crop was under water and the growth stage of the crop. Wheat that was covered by standing water more than 24 hours is the greatest concern. Wheat in the later stages of kernel development, such as into the soft dough stage or later, likely will see reduced test weight and an increase in shriveled or shrunken grains. For wheat that is further behind, such as fields just starting grain fill or not yet at grain filling, the injury likely will be greater and range from moderate damage to a complete loss.
Lodging and excessive moisture also can worsen the incidence and severity of many fungal diseases. Damp conditions, coupled with the cool temperatures, are near perfect for stripe rust development, so there is a chance it could cause serious yield losses for fields that escaped from the flooding.
All of these issues are going to require a field-by-field observation to determine the extent of damage. We know the crop as a whole is negatively impacted, but the impacts are farm-specific. There is really nothing a producer can do at this point other than sit and wait. There are not any products or spray applications we recommend at this time to assist in recovery from flooding or lodging.
Producers should continue to monitor fields for pests such as true armyworms. Infestations occur more frequently around waterways, areas of lush growth or areas with lodged plants. Since armyworms tend to feed at night, it is easier to scout after dusk when activity is higher. Damage ranges from ragged leaf margins to head clipping (usually younger secondary tillers). Current treatment threshold is 4-5 per linear foot of row. If wheat is past the soft dough stage, control is not warranted unless obvious head clipping is continued. It is typically not economical to spray if only awn feeding is occurring past soft dough.
In addition to true armyworms being found in wheat, we also have found wheat head armyworms. The wheat head armyworm can feed on the wheat kernel, which can reduce grain yield and increase price discounts. Insect damaged kernels (IDK) is the grain grading factor. The wheat head armyworm typically feed at night and usually worse at the field margins. Scouting after dusk and sampling farther into the field will give a better estimation of the infestation. If chemical control is warranted for either armyworm, be aware of any pre-harvest interval listed on the product label.
Due to a potential delayed wheat harvest and abundance of moisture, some fields may start to become overwhelmed with summer annual weeds. Some harvest aids labeled for wheat include Ally XP, 2,4-D, dicamba, glyphosate and Aim. Paraquat is not labeled and if used can result in condemned wheat. It is important to follow labeled directions for proper application timing and rates.
Bushong is Oklahoma Cooperative Extension Service northwest area agronomy specialist.