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CROP WATCH

By Staff | Jul 18, 2014

Mid-July is here and in certain ways and certain parts of the Midwest the crops exceed expectations.

In others, we look around and wonder what all the hype is about.

Flat ground looks more attractive and is easier to farm, but it is not the ground to farm when excess rainfall arrives causing work to go undone, crop drown out, and the only thing that keeps growing are the weeds.

Thus far this El Nino thing has not worked out for the better for many growers in northern and central Iowa. While it does not seem possible, getting a few straight weeks without rain is exactly what we need.

To this point, the hot and baking drought that several prognosticators foresaw for after July 4 has not arrived. All we can do is slog through mid-summer and hope we can get all tasks done before crops and weeds get too tall.

The county fair season is well underway in Iowa. It seems much earlier than ours used to be, which is affected by the date of the state fair.

Attending any of the local events makes most of us remember what we did at our county fairs, whether it was showing calves, putting on a demonstration, going to the grandstand shows or challenging a rival 4-H club to a water balloon fight.

Here is to all of the 4-H’ers, club leaders, volunteers to the many events and the Extension people for the dedication to make each and every event memorable.

Field happenings

The most noticeable happening in the corn fields now is that many fields have been shooting tassels in the past few days. Having another 3 inches of rain and a few warm days spurred the last foot of growth and the tassel emergence.

It happened first on the fields planted before Easter and then a few of the earlier maturing hybrids planted the few good days right after that holiday. This was a few days earlier than expected.

During my scouting what can be detected is that many varieties are putting on 17 leaves instead of the normal 19 or 20. That hastened the event by four to five days.

A trait that is becoming evident again is that corn breeders continue to advance varieties that force out silks even before the tassels have fully extended and before any pollen is shed. Two decades ago one of the worst or perhaps talked about fears was that in a dry year the pollen was going to be all shed before any silks came out, leaving many kernel sites and perhaps entire ears blank.

When those two crucial events coincide it removes that fear of having poor pollination in a stress year.

Now that the corn is, or will soon be, tasseling, which is the reproductive phase, the plants enter a time period where they become more disease susceptible.

Any lack of several micronutrients increase disease susceptibility. Energy that until now has been used to repel fungal attack has to be dedicated to the formation or pollen and silks.

Scouting for the small disease lesions becomes an important part of managing the corn crop.

There are still many fields in different sections of the state where the saturated soil conditions existed too long and a significant amount of nitrogen was lost to leaching or denitrification.

The yellow-leafed plants show up as a surrender flag that growers have to recognize and respond to correctly if they are going to meet yield goals.

Sidedressing nitrogen at this point requires high-clearance sprayers and either drops or dead-on-dribbler attachments.

In soybeans, the issues growers faced were either bean plants that were competing fiercely with taller weeds or remained yellowish and stunted.

With the weeds there were both fields where a variety of broadleaf weeds kept growing through residual herbicides for a number of reasons and had to be knocked back with some of the burner mixes, or fields that had been clean until 15 inches of rain diluted the residual products.

While scouting both 30-inch and 15-inch beans, it was possible to think of two or three reasons why either row width was best. Having an earlier full canopy does help keep weed growth down, but makes it tougher to get the spray to penetrate the canopy.

It was easy in the narrow rows to find waterhemp plants just below the weed canopy waiting to burst above the bean plants just after the sprayer had passed.

Herbicide issues?

It can be a ticklish situation when any herbicide, or herbicide by soil type or variety, situation appears. Those products will act differently out in a field than in a growth chamber, where inclimate weather does not occur or when herbicides applied during the drought of 2013 complicate the picture.

What farmers and agronomists are seeing is that the hydroxyphenol-pyruvate dioxygenase (HPPD) and protoporphyrinogen oxidase (PPO) herbicides applied either in 2014 or 2013 are acting differently this spring, partly due to this year being very wet and last year being very hot and dry after application.

Both of those families, as do the sulfonylureas (SUs) and acetolactate synthase (ALS), offer residual activity that can vary in timing and effectiveness depending on soil types and soil properties, amount and timing of rainfall, sunshine and growing degree unit amounts, and varietal characteristics.

The products used last year, the timing of their application and rainfall between their use and fall freeze up, and degree of degradation can and do influence the percentage and amount of product that can be carried over from the 2013 to 2014 season.

A number of companies have had reps out walking fields and trying to determine what actually transpired. They actually want to formulate what series of events led to any problem.

What is worth knowing is that one product, sold as Authority, is not at fault and is giving good performance. Back when it was an experimental product 15 years ago, it was found to burn a few late-group 4 varieties from a major seed company.

This year we might be able to safely say everyone learned how to manage it best. With some of the more recent releases those products may have encountered the wettest conditions since they began being tested.

After learning more from several excellent fertility texts, and recognizing that most herbicides work by chelating minerals such as copper, manganese, or zinc, we recognize that dry conditions or those unfavorable to nutrient release via biological activity have a bearing on herbicide activity and phytoxicity.

If those minerals are only present in the oxidized form, rather than the reduced state, it may not be available for the plant to use to detoxify a herbicide or allowing a saftener to function.

In a conversation with a herbicide product manager on Monday, we were discussing what products could be used for broadleaf control in beans or corn if the PPOs and HPPDs fell by the wayside with the previous No. 1 not being effective anymore or considered unsafe by growers.

Thus the physiological herbicide degradation pathways known as glutathione-s-transferase (GST), Cytochrome P450 pathways, and glucose conjugation are terms that growers intent on learning about the older herbicides and their characteristics are things they will have to understand and master.

A good battle plan on stunted, yellowed beans might be to apply a micronutrient mix and a biology stimulator like Foliar Blend to spur growth.

Be ready for corn rootworm beetles that should be emerging over the next two weeks.

If and when they appear have your battle plan in place if you have seen lodging problems in your fields.

Does controlling the egg-laying beetles sound like a good plan to you?

It seems early due to our shorter bean plants, but aphids are already floating in and having babies. They are not the cuddly kind.

Good luck in your fields.

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

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