JenREES 8-26-18


Reminder of South Central Ag Lab Field Day August 29th from 8:25 a.m.-4 p.m. (Registration at 8 a.m.)! 10.5 CCA credits have been applied for. More information at: https://go.unl.edu/zvwx

Crop Update: The rain last weekend was a blessing to many. It along with cooler temperatures has allowed for deeper kernels and delayed corn maturity. In fact, if we were to stay at the high temperatures we were experiencing, the Hybrid Maize model was predicting maturity in our area anywhere from 1-3 weeks early. Now, it’s mostly just predicting one week early (for anything that isn’t already mature). It also is showing above average yields for non-irrigated corn where drought-stress and hail weren’t a factor. Irrigated yields are showing near average according to the model for most fields in the area. You can see all the graphs and read more in this week’s CropWatch at http://cropwatch.unl.edu. Corn has reached black layer in many of the hail damaged fields I’ve looked at and some of the drought-stressed fields will begin harvest in a few weeks. The rain also greatly helped the soybeans, even in drought-stressed areas.

However, the rain also greatly increased stalk rot in fields, particularly in hail damaged ones. We weren’t seeing a large amount of mold in the first 7-10 days post-hail  in hail damaged fields that were late dough to early dent. Now, nearly 21 days later, we’re seeing fungal growth increasing with the moisture and humidity within the husks of corn ears. It will be very important to check your fields to determine worst ones and worst areas of fields regarding stalk rot and kernel damage. Those areas should be harvested first if they’re being taken for grain and we’re recommending to fill any contracts with grain from those areas first. In checking for stalk rot, I prefer a ‘pinch test’ compared to a ‘push test’. With the pinch test, take your thumb and first finger and pinch the stalk internode that occurs between the lower nodes above the soil line. Do this for 20 plants in an area and get a percentage for those that crush. Then do this for several areas of your field. This gives you an indication of the level of stalk rot for your field and worst affected areas.

Cover Crops: With recent crop insurance determinations on these damaged fields, I’ve received an increasing number of questions regarding cover crop use. We’re already seeing weeds germinating in these fields due to open canopies, so weed control is one considerations for using a cover crop right now. Other reasons expressed have been for excess nitrogen uptake and also for a forage option. Dr. Mary Drewnoski, Extension Beef Nutritionist, Dr. Daren Redfearn, Extension Forage Specialist, and I talked through options to consider right now.

Always check with your crop insurance agent before seeding a cover crop into hail-damaged fields. It’s also important to check replant, forage and grazing restrictions regarding the herbicide program you used and any delay necessary before seeding a cover crop and any forage restrictions to grazing a cover crop. (See Replant Options and Herbicide Rotation Restrictions and Forage, Feed, and Grazing Restrictions for Row Crop Herbicides, both excerpted from the 2018 Guide for Weed, Disease, and Insect Management in Nebraska, EC130.)

In general, we’re at an interesting time for making cover crop decisions. Typically we use September 1 as the divider between planting small grains such as oats that will winterkill and winter hardy cereals such as rye or triticale (planted after September 1). Even with brassicas such as turnips, collards, or rapeseed, we’d recommend the cutoff for seeding to be within the next two weeks. Because of this time frame, mixes may be beneficial because they’ll take advantage of whatever weather we have for the rest of the season. Simple, inexpensive mixes may allow for at least something to become successfully established. So, for those looking at something to winterkill, oats could be planted yet this week as could a mix of oats and brassicas. However, after this week, we’d be looking at either adding something like rye or triticale to the mix or just switching to the more winter-hardy small grains. And honestly, while it isn’t mentioned in the table, if a person’s goal is cover the ground for weed management, bin-run wheat is also an inexpensive option. Your local seed supplier can provide seeding rates for cover crop options and we’ve provided a table with these options, depending on your goals, at http://cropwatch.unl.edu.

Yellow or red tops in corn plants: For a month now, we’ve observed yellow tops in cornIMAG5726 plants. Plants that contain ears and are turning yellow from the top to the middle of the plant can be occurring because of anthracnose top dieback or another disorder called ‘top leaf death or dieback in corn‘. Some plants with this discoloration truly do have anthracnose spores present on the stalk and sheaths. However, there have been other situations where I couldn’t find the presence of anthracnose spores. In those situations, the plants were often on compacted areas of field edges, always had a nice ear on the plant, and sometimes had tillers as well. Dr. Bob Nielsen at Purdue mentioned they had found what’s called ‘top leaf death’ in corn in situations where they experienced more drought or heat stress. Those plants had leaf discoloration similar to anthracnose top dieback, but without the presence of the spores. So, for those situations where I’m not finding anthracnose spores, I’m calling it this top leaf death disorder. You can read more about this at: https://www.agry.purdue.edu/ext/corn/news/timeless/topleafdeath.html.


Table 1. Cover crop considerations for late-season hail-damaged crops
COVER CROP USE/GOAL WHEN TO PLANT HOW TO SEED RATE
(PER ACRE)
ADDITIONAL NOTE
OATS Weed Management By Sept. 1 Drill best. Can fly on. 30-40 lbs *
OATS/RYE MIX Weed Management By Sept. 1 Drill best. Can fly on. 30 lbs each *
OATS Forage By Sept. 1 Drill best. Can fly on. 80-90 lbs *
OAT/RYE MIX Forage By Sept. 1 Drill best. Can fly on. 30-40 lbs of rye and 50-60 lbs oats *
BRASSICAS (TURNIP, COLLARD, RAPESEED)-NOT OILSEED RADISHES Cover ground, forage, nitrogen uptake By Sept. 1 Fly on for quicker establishment. 5-6 lbs  —
RYE Weed management, cover ground, forage, nitrogen uptake After Sept. 1 Drill best. Can fly on. 50-60 lbs  *
*If adding a brassica to any of these small grain options, only 2 lb/ac is needed. Rapeseed isn’t as well known, but is an inexpensive and good option for consideration.

About jenreesources

I'm the Crops and Water Extension Educator for York and Seward counties in Nebraska with a focus in irrigated crop production and plant pathology.

Posted on August 27, 2018, in JenREES Columns and tagged , , , , . Bookmark the permalink. Leave a comment.

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