Crop development (growth stage estimations)
With below-average temperatures during May, the wheat crop is still behind in development compared to the historical average. Our estimated development for wheat around Kansas ranges from near physiological maturity in the far southeast corner of Kansas, to heading and flowering in the far northwest corner of the state (Figure 1). This ranges from one to three weeks behind, depending on planting date, although these differences are not as apparent when comparing with the 5-yr average percent wheat headed as reported by the USDA (Figure 2). Late-sown fields, such as fields planted after soybeans and after all the rain received during October, are the furthest behind in development. The late development of the crop can induce heat stress during grain fill, potentially decreasing grain yield. Maximum daily temperatures above approximately 81 F during grain filling can start negatively impacting wheat yields.
Figure 1. Estimated wheat growth stage based on accumulated temperatures since January 1, 2019.
Figure 2. Percent winter wheat headed (current versus 5-yr average, upper panel) and comparison between percent wheat headed in 2019 versus the 5-yr average as reported by the USDA on June 3, 2019 (lower panel). Figures created by Leonardo Bastos, K-State Research and Extension.
Parts of central Kansas received as much as 30 inches of rainfall since April 1 (Figure 2, upper panel), and as much as 60 inches of precipitation since September 1 (Figure 3, lower panel). This excessive amount of rainfall caused flooded fields in a large portion of the state, ranging from Dickinson/Marion counties down to Sumner county, and as far west as Barton county. These waterlogged conditions are causing several wheat fields to drown out and die prematurely (Figure 4). The actual affected area within each field varies from field-to-field depending on position on the landscape, drainage potential of the field, soil texture, etc. In the extreme cases, more than 80% of the field have prematurely died due to waterlogged conditions (Figure 4).
Figure 3. Cumulative precipitation between April 1 and June 10, 2019 (upper panel), and cumulative precipitation for the winter wheat growing season (September 1, 2018 to June 10, 2019, lower panel).
Figure 4. Wheat fields prematurely dying due to waterlogged conditions. Upper photo is a wheat field in southern Dickinson County in which the areas with some slope, such as the field corners and around the drainage tiles, are still green; but flat areas have drowned out. Photo taken by Jenny Sherbert, Agronomy Department Coordinator with Agri Trails Coop in Hope, KS. Lower photo is a wheat field in Sedgwick County also showing sections of the field dying prematurely due to waterlogging. Photo taken by Jeffrey Seiler, K-State Agricultural Agent.
Wheat that was in later stages of kernel development when saturated soil conditions prematurely killed the crop, such as into the soft dough stage or later, will likely see reduced test weight and an increase in shriveled or shrunken grains. For wheat that was further behind, such as fields that were just starting grain fill or not yet at grain filling, the injury will likely be greater and range from moderate damage to complete loss. Due to excessive moisture conditions, the USDA report slightly increased the percent of acres under poor or very poor conditions in Kansas, Oklahoma, Nebraska, and Missouri in the June 3, 2019 report (Figure 5). It will be interesting to see how these acres that prematurely died will be reflected in future USDA reports.
Figure 5. Winter wheat crop condition report from USDA Crop Progress Report released on 3 June 2019 (Figure created by Leonardo Bastos, K-State Research and Extension).
Beyond the incidence of stripe and leaf rusts (covered in detail in previous eUpdate articles), head scab is occurring in several fields in central Kansas (Figure 6) due to the cool, wet weather during the critical flowering time (Figure 3). Field conditions were too wet for farmers spray against this disease, which increased the incidence and severity of the disease. Still, even in sprayed fields, the control is far from optimum. Fields planted to more susceptible varieties are showing greater incidence and severity of the disease, but even fields planted to varieties such as Everest, Zenda, or WB4269, which have greater tolerance to the disease, are showing signs of the disease. This disease has several implications: i) yield loss per se, due to blighted or sterile florets and poor grain fill; ii) poor grain quality, as the affected kernels will have low test weight and chalky/tombstone appearance; iii) marketing, storage and utilization concerns, as this fungus can lead to accumulation of vomitoxin (DON) that can lead to discounts in the elevator; and iv) problems with seed germination if saving seed for a next crop.
Figure 6. Symptoms of head scab in a susceptible variety near Belleville (Republic County), KS. Photo taken on June 5, 2019 by Romulo Lollato, K-State Extension Wheat Specialist.
Romulo Lollato, Extension Wheat Specialist
Erick DeWolf, Extension Wheat Pathologist
Mary Knapp, Weather Data Library
Ignacio Ciampitti, Cropping Systems Specialist
Leonardo Bastos, Post-doctoral researcher, Dr. Ciampitti’s Lab