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CROP WATCH

By Staff | Jul 21, 2017

Now we, our crops, pastures and countryside get to enter a gauntlet of 90 plus degree temps with only a minor chance of rain in the forecast for the next ten days. Will we luck out and have enough popup showers to help or have an unexpected front cross the Midwest and drop enough moisture to help our plants recover and see them thru the next few weeks? Might a tropical storm move into the Gulf and push moisture north? Or will it continue hot and dry? The official tally as of July 11 was that 64 percent of Iowa was rated as abnormally dry or in a moderate drought. In comparison, South Dakota now has 72 percent categorized as droughty while its northern counterpart has 94 percent affected. Nebraska surveys show that 87 percent is in those categories. There is not much we can do on an individual basis for this season. Making plans to develop a deeper root profile, either by mineral applications or the use of biological products, should be in many growers plans. What does make it seem surreal is that this is all happening when many forecasters are predicting the return of El Nino conditions by late summer.

What becomes apparent when traveling the state and region is how spotty rainfall has been this entire season. While central and western Iowa bakes there are lucky regions in the northern or northeast part of the state and rainfall has been very plentiful. Their crops, save for early drowned out spots, look very good.

Drought effects

I mentioned last week that in a trip to Cherokee that lots of the corn was only as tall as or a foot shorter than the fence posts. Have the plants been sitting still or continuing to form new cells that will expand when moisture is finally available? What I saw on my sweet corn patch on Friday a week ago were plants that were about 5.5 feet high with only two or three tassels poking out. After applying about 1.5 inches of water in that after four days the corn was 8 fee tall with 100 percent tasseled. Apparently the cells at the plants apex kept forming but formed no new growth appeared until there was moisture available to help the cells fill out. A good rain would have the same effect on corn plants and they could shoot up one to two feet in a few days tasselling would commence.

The more modern hybrids were partially selected for their ability to form the ear shoot and send out the silks almost as early as the tassels begin to shed pollen. This development offers the advantage that there is less chance of a mismatch between pollen shed and silk emergence. In the flash droughts of 1983 and 1988 there were problems with timing of these events resulting in ears often having no kernels on the ear tip, halfway down or zero kernels.

The often asked question to researchers by growers is if there is anything they could do to their crops that would help minimize potential loss of kernels and overall yields. I have looked at yield trials results, where foliar sprays containing ammonia based N, a blend of sea minerals and humates helped to invigorate the plants and help prevent the cannibalization that occurs when plants slip into an advanced stress state. Those steps can work. Other current trials off the beaten path showed that a mid-season application of a silicon based fertilizer could reduce water and heat stress significantly. I hope to view those trials in about three weeks.

One other new idea and service offered is camera imaging from Air Scout Inc. Airplanes equipped with their cameras can fly fields on a regular basis taking pictures using a system called ADVI or advanced difference vegetation indexing, which refers to picking up the temperature difference in various crops appearing when they become stressed due to an insect or Goss’s Wilt infection or ECB infestation. This system works and become valuable when paired with a curative product or action plan. In work done around Orange City they can spot when Goss’s moves into a field or see the signature of when the fields are sprayed and the disease departs or insects are controlled

Dicamba news

The use of Dicamba and the problems with drift keep increasing as the end to the spray season moves north. While in 2016 the problem arose when none of currently registered herbicides was available for use and application specifications were an unknown. There continue to be problems even when every rule was followed and the low drift formulas were sprayed. This week the complaints encountered in Indiana, Ohio and Iowa have gotten publicity and several states have enacted bans on its sale and application. Now two states announced that their ban on its use may be dropped. What is the correct answer on how to proceed?

In fairness the big question posed by one knowledgeable person is ‘what gives any company the right to cause any person’s collateral vegetation to be damaged or killed by the use of its product?’ Namely the use of Dicamba was always known to be risky due to vapor drift. No amount of publicity or cajoling changes that. Wouldn’t it be fair that before any bans are rescinded that the lawsuits over 2016 Dicamba damage in Missouri and Arkansas be settled and damaged parties be awarded settlements before letting more problems be caused? Those class action and individual suits were sometimes in excess of $250 million and will only compensate damaged parties for their actual losses.

In one article the question was asked if this was orchestrated to force soybean growers to buy certain soybean varieties out of fear of being trespassed upon in future years. It makes sense.

All of this action is being played out in the season we hoped would not happen in the northern bean belt. In other words a year where most growers found that various weeds had become very costly and time consuming to grow, increasingly resistant to previously effective herbicides. It is likely that weeds will never get easier to control. I am looking forward to the seeing end of the season ratings on any new products or combinations used in weed research plots this season. Will cover crops and a new burndown product be part of the answer?

Crop diseases being seen

In a year with such dry conditions we would normally not be expecting major problems with fungal leaf disease. Yet in Nebraska and Iowa there are reports of leaf and stalk diseases being diagnosed. Among those being diagnosed are GLS, common rust, Physoderma leaf and stalk infections, Goss’s Wilt and the recently diagnosed bacterial leaf stripe/streak (BLS). Inside the canopy the humidity levels are higher and dews are more common, which allow penetration by a fungal spore if the plant is nutritionally deficient in Mn, Cu, Bo or Zn.

Perhaps the big ‘unknown’ going into this disease season is how to assess the BLS infection. It was first found in South Africa where it was quite damaging. We believe we have been seeing it for a few seasons already in the Midwest but did not recognize it as a separate disease.

No one has worked with BLS prior to 2016 and no one can state that is can or can’t affect yield by a certain percent or can interact with other pathogens. Being it is gram negative and has no cell wall it is more difficult to fight. The staff at UNL under Tamra Jackson will be conducting studies this year to learn more about the disease. Until then we have to assume that BLS subtracts from overall leaf area and plant health is important and contributes to yield loss.

As of about two weeks ago soybean aphids were only being seen as increasing in population in South Dakota. Now they have moved into northern Iowa and assumed to be spreading to more regions in the state. Be alert to their presence as they became a problem in a dry 2003. One interrelated factor to know in 2017 is that a portion of the aphid population has become resistant to the pyrethroids. The tools to know about in that case are two: one is that the application of one mineral can make the plants unattractive to the insects as it allows the conversion of nitrate nitrogen to a different compound; the other is that Dow AgroScience has a new class of insecticide called Sivante which belongs in the Butenolide family.

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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