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Crop watch

By Staff | May 15, 2020

Back into the deep freeze was the message for part of the last week. Aren’t Polar Vortexes supposed to move through and bring the bone chilling weather during the winter? So what one or two of them doing marching across much of the country in the second week of May? We had to visit a friend up in semi northern Wisconsin (just north of Chippewa Falls) and the temps on Friday night in a cold air drained field where blueberries were growing were near 20 F. Lots of corn had been planted in the area but it had not emerged yet.

So the task in next few days for many crop producers and agronomists will be to trudge through many emerged fields to gauge the consequences of what happens when nighttime temps get as cold as they did last weekend and decide what, if anything, may need to get done. Fifteen years ago much of the state had several nights in early May where the corn had emerged in the early planted corn fields. At first everyone figured no damage had been done. What ended up occurring was that conditions were quite dry, the freezing air penetrated several inches into the soil, and the shallower planted seedlings on sandier soils and froze the growing points of hybrids known for faster emergence. Those hybrids known for slower emergence had the small node where the seminal roots originate from deeper in the soil and were untouched.

More farmers now have hydraulic or air assist furrow openers or seed firmers on their planters and tend to place their seed deeper with more accuracy then back in that era. It has been too early to inspect and pass judgement on fields as of Sunday night. As one moved north in the cornbelt and the temps got colder we may seed problems with some corn fields and stands in the low portions of the fields. In recent seasons aggressive soybean producers have taken advice from high yielders who profess the benefit of planting soybeans early, sometimes as early as April 15th to April 25th.

Dr. Simon Atkins in his late week weather forecasting column described the cold air intrusions, or tunneling as he called them. He had these moving all the way down into south Texas, leaving only the western 1/4th of the country with above normal temperatures. He told how these are likely to be more common occurrences both in the spring and fall and typically occur in the 12 year period and we moved from one solar cycle to the next. We are now leaving cycle No. 24 and moving into No. 25.

Freeze damage evidence

Bob Nielson of Purdue University did a good job describing how to do a good job of evaluating plants that were subjected to subfreezing temps. His first rule was to practice patience and to make any evaluation about 60 hours after the freeze, if those next two days have temps above 50 F. With Saturday and Sunday staying below 50 for most hours a person will have to do their scouting on Tuesday or Wednesday.

The Iowa Mesonet Data shows the low Thurs and Friday (May 9th) temps for these locations at: Ames-28; Burlington-30; CR-26; DM-33; DBQ-25; Mtown-26; MC-25; Ott-28; Sioux C-28; Spnc-31; Waterloo-25. Areas of low ground or where cold air collects will have reached colder temps or more subjected to radiation cooling. The early planted and emerged fields north of a line from Cedar Rapids thru Carroll may show damage.

In areas where the temps were at or near 30 to 32 F growers are likely to see plants where the upper leaf tissue has been frosted or burned, These tips may end up preventing the leave from unfurling as they should. An initial impulse is often to devise a way to remove those leaf tips with a mower. The best suggestion is to stay out of the field and let the new leaf tissue push through any wrapped tips and unfurl he damaged tips naturally.

In the case that early planted bean plants appear to have browned with no green tissue appearing after three days it could be time to take action and scout any early planted fields to determine and map the extent of the dead areas in each.

Cold weather caution with post herbicides

With cold weather questions arise about the wisdom of making herbicide applications while it is cool and cloudy. That is a good question as there are guidelines for that. With soil applied products there should be no fear as the plants have not emerged yet. If the plants have emerged and a post herbicide is being applied, the plants have to metabolize the material and continue growing in normal fashion. Typically the SU, ALS, and PPO chemistry is broken down via the P450 degradation pathway. The plants need sunlight and temperature energy to fuel that system. If those two are lacking herbicides in those families could impose a metabolic burden on the plants and the plants may stall out until warmer and sunnier temps return. The plants may quit growing and tissue could be damaged. Waiting a few days to spray would be a wise move, even if ground conditions are good.

Slow soil warmup and microbial activity

Our knowledge about how microbes function to make minerals plant available has increased significantly in the last decade. We still don’t understand everything, but have to recognize microbial activity at cold soil temps is going to lag. Mineral uptake is going to lag until soil temps warm. Recognizing that this might happen is why no-tillers like to place a sugar or other carbon source to nourish the microbes for the week or so after planting.

The need to help hailed or frost damaged corn or bean plants has been an occasional occurrence over the last two decades. Knowing what can aid the plants in recovery is valuable. We like to see growers apply a food source mixture called Foliar Blend to aid in the plants’ recovery. It both feeds the plants and is moved into the root zone to help the microbes to produce compounds used by the plants to promote root growth.

Insect issues

There are several insects on the radar in most Midwest states. The first of these that may need to be managed would be alfalfa weevils. They operate on a 48 F GDU scale and begin to feed and lay eggs after 200 GDUs have accumulated. Currently their feeding can be seen in states to the immediate south of Iowa.

A field scout should be looking for their skeletonizing feeding in the next weeks. Typically is more than 20% of the plants show this feeding action needs to be taken.

The next insect to watch for are Black Cutworms. Those overwintering moths would have traveled with the strong winds from the south from their over-wintering sites in Texas and Mexican Gulf areas. The moths will be attracted to no-till or untouched fields that carry moderate to heavy populations of early growing weeds or possibly cover crops. Their damage will show up as cut plants where the stalks have been hollowed out by the blackish larvae that spend daytime hours dug into the cracks in the dirt.

The last critter to mention would be the seed maggots. These are the small worm like larvae developing from the eggs laid by a weak flying fly. Those flies are attracted to and lay their eggs on decaying plant material that was recently killed. They typically only eat germinating seed corn but we have seen them tunnel up soybean stems and kill those plants. Once they are in the ground there are no means of controlling them.

Worker safety

At our January 22nd winter meeting up in Webster City we were blessed with the presence of two representatives from a medical company called Microbe Formulas. They are headquartered near Boise, Idaho. What their team of chemists and biochemists have done has been to develop a line of products that can be taken in pill form to removed harmful pesticides and heavy metals from a person’s body. This includes people who are around solvents, heavy metals, lead based paints, solvents, molds or pesticides. They were responsive to what we said we needed and assembled a mixture we called the Farmer Shield.

They know that in conventional ag we use a lot of products that are not completely safe to human health. Most applicators wear long sleeve shirts, jeans and maybe a mask to protect themselves from any splashing, drifting, or mixing exposure. That should help. When they were preparing their presentation I advised them to make sure they mentioned that the person doing the laundry, for those individuals also needed to be considered as candidates for the use of those products. That person (s) doing the wash and folding the clothes may actually be more at risk of exposure to such chemicals than the person spraying, Keep that in mind, especially as a year round Mother’s Day gift.

Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.

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