Cropping Issues in Northwest Minnesota

Kernels demand sugars. Developing corn kernels place a very high demand on the plant for sugars. Stress reduces the rate of photosynthesis, thereby reducing the amount of sugars that the plant is able to produce. Many different stresses can reduce the rate of photosynthesis: too much or too little moisture, nutrient imbalances, plant injury (ex.: hail, insects, diseases), excessive plant populations, and even long-periods of cloudy weather. Stalk rots. If the plant is unable to keep up with kernel sugar demand, the plant can rob sugars from stalk tissue, predisposing it to stalk rots. Corn plants are top-heavy and stalk rots increase the chances that plants will fall over (lodge) due to either gravity or wind and other weather events.

Pinch or push test. To better understand how much stalk rot might be present in a given field it is recommend that each field is scouted in one of two ways, by pinching or pushing plants. Regardless of the test, walk each field in a zig-…

Silking (R1) through dough (R4). Depending upon your location in northwest Minnesota, your hybrid maturity and planting date, silking (R1), pollination and fertilization likely happened some time in early to mid-July.  Right after fertilization kernel development begins, with the blister (R2), milk (R3) and dough (R4) stages following approximately 10 to 14 days, 21 days, and 24 to 28 days after pollination, respectively (Ritchie et al., 2005; Nleya et al., 2016; Hicks et al, 2018). During the dough stage, one is no longer able to easily squeeze kernels and see milky liquid come bursting out of the seed coat.  This is because this milky fluid is being replaced with starches to form a pasty, dough-like consistency.  While kernels are approximately 70% moisture during the dough stage, as starches continue to accumulate more of the doughy consistency is lost to firmer dry matter (Ritchie et al., 2005).
R5.The R5 or dent growth stage is the last remaining stage for the crop to get through …

As soybeans approach, reach and blow past the R6 or full seed growth stage, it is worthwhile to take a moment to ponder what is happening in the crop. Even though soybeans will have flowers, pods and seeds in various stages of development, all on the same plant, one can easily growth stage a plant if after pods begin to develop one only pays attention to the four uppermost nodes that house fully-expanded leaves. R5.Soybean plants that are at least halfway through the R5 or beginning seed growth stage will have reached their peak in nitrogen fixation, number of leaf nodes, leaf area and height.  As soybeans reach the full seed growth stage, the nutrients they have accumulated in their leaves will peak and begin the process of being redistributed to developing seeds (McWilliams et al., 1999; Unknown, 2018).  It takes an average of 15 days for soybeans to progress from the R5 to R6 growth stages (Naeve, 2018). R6. The R6 stage is also referred to as the “green bean” stage as at least one …

Traveling throughout Kittson, Mahnomen, Marshall, Norman, Pennington, Polk, Red Lake and Roseau Counties in northwest Minnesota this week to survey soybeans, revealed various pest and disease issues. Soybean aphid. 

Soybean aphid (Figure 1) population densities remain either undetectable or very low, with most plants housing fewer than 20 aphids. With so few soybean aphids present, I was also unable to find Asian lady beetles or their larvae or aphid “mummies” that had been parasitized by the Asian parasitic wasp, two of the many insects that provide biological control of the soybean aphid.
Spider mites.  Two-spotted spider mites were widespread throughout the lower and middle canopies at all except northernmost locations. One may notice that infested leaflets have a duller appearance than those that aren’t infested due to the dull-yellow ‘stippling’ symptoms characteristic of mite feeding injury (Figure 2). If you have a hand lens (or just very good eyesight) you may be able to see the…