The continued wet weather and harvest delays are increasing the potential for preharvest sprouting. Once the dormancy of the seed is broken and sprouting is initiated the quality of the grain deteriorates, grain elevators will check for this decline in quality using the Hagberg Falling Numbers test. The HRSW that are ranked moderately susceptible to pre-harvest sprouting are listed in Table 1. Understand that the potential for preharvest sprouting increases if you swath the grain or if you leave it stand too long while waiting for the grain to reach 13% moisture, all the while rain and heavy dews are forecasted. Rather, harvest the grain as quickly as possible and as soon as moisture content approaches 15% as HRSW can be readily stored up to three months at that moisture content.

Table 1 - HRSW varieties with a higher risk of preharvest sprouting

Variety Preharvest Sprouting Rating*

Bigg Red 4
Blade 5
Granger 4
Hat Trick 4
Sabin 4
Samson 4
Traverse 4

* 1=best, 9=worst

There are two methods of pre-harvest management for wheat that can speed up harvest. Swathing or windrowing is one method. An application of glyphosate is a second option. Several brands of glyphosate are labeled for preharvest weed control. Research has shown that glyphosate can also quicken the dry down of the wheat crop if conditions for dry down are adverse. The preharvest interval for preharvest glyphosate is seven days and expects only to gain a couple of days at the most. More time can be gained with swathing.

The optimum time for either pre-harvest management tool is right at or just after physiological maturity of the crop. At physiological maturity, the crop has the maximum kernel dry weight and no additional dry matter will be deposited in the grain. The kernel moisture percentage at physiological maturity is relatively high and can vary from 20 to 40%. Research has shown that swathing just before physiological maturity does not harm the grain yield or quality. This practice, however, is not recommended when using glyphosate as a pre-harvest tool.

There are two visual indicators that can be used to determine whether the crop has reached physiological maturity. The first indicator is the loss of green in the kernel and the appearance of a dark layer of cells or pigment strand along the crease of the wheat kernel (Photos 1). Kernels in the same spike will reach physiological maturity at different times with the middle of the head maturing first.

Another visual indicator is the loss of green from the peduncle and glumes. If the peduncle just below the head becomes straw-colored, transportation of water and nutrients to the head has been cut off and the crop has reached physiological maturity (Photo 2). The advantages and disadvantages of pre-harvest glyphosate and swathing are listed in Table 1.

Table 1 - Advantages and disadvantages of different methods of pre-harvest management.

by Phillip Glogoza, Extension Educator - Crops

A lot of wheat is now heading in NW Minnesota. In the northern most counties, degree day accumulations are just reaching the 1300 DD mark (see map), the point where 10% of female midge have emerged. Emergence will continue through 1600+ DD (90% female emergence).

by Dr. Charla Hollingsworth, U of MN Extension Plant Pathologist

Crop growth stages of spring wheat are rapidly approaching early flower in some locations. This is the time of year that managers must make a decision to apply a fungicide application targeted for Fusarium head blight (FHB) management.

by Phillip Glogoza, Extension Educator - Crops

There could be about 70% of the region's wheat acres at the heading stage when wheat midge are emerging, based on those acres being planted in the high risk window (Figure 1). Heading is the growth stage when wheat is attractive to female midge for egg laying, and the time the plant is most susceptible to injury from midge larval feeding. Though midge populations have been small in recent years, this will be the most wheat acres we have had that are susceptible to midge in many years.

by Dr. Ian MacRae, U of MN Extension Entomologist

There have been some reports of bird cherry-oat aphids (Figure 1 and Figure 2) in small grains in NW and WC MN over the last week. The populations I've seen are at very low numbers. Add to this, the recent rainy weekend will likely have had a significant impact on those aphid populations, but it's still a good idea to scout for aphids in small grains. The most damaging aphid populations are ones that reach threshold around flag leaf stage, if populations are at or near threshold at this time, delaying treatment until heading may cost you yield.

by Dr. Charla Hollingsworth, U of MN Extension Plant Pathologist

Bacterial leaf stripe is a disease that can usually be found on wheat in the Red River Valley (RRV) later as crop growth stages progress. The disease (caused by a Xanthomonas sp.) can develop and become severe rapidly after the crop reaches the heading growth stage. Bacterial leaf stripe (BLS) can cause significant yield losses on some varieties. Like other disease issues, development is dependent on weather conditions and the presence of susceptible plant hosts. Epidemics of BLS occurred in the RRV during 2005 and again in 2008.