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CROP WATCH

Be aware of insects and diseases

July 7, 2017
By BOB STREIT - Columnist , Farm News

It's July already and in arrears have a happy Fourth of July holiday. Having it fall on a Tuesday means quite a few people will have a five day weekend. However those that work for themselves will wake up Monday thinking that they have a million things to do that day so they will knock off early to view any local ceremony and the fireworks with their family.

We are having a college get-together in Ames on Saturday and carrying on into Sunday. Needless to say it will be a much calmer event than back in the 70s.

The state of the crop

In viewing the crop many of us see the best of it as well as the warts. I mentioned last week that a friend who has traveled across the entire Midwest in the last month seeing and looking at the crops said the sweet spot with the best crops is the area from Albert Lea south to Des Moines and east to west about 100 miles +/-. So in spite of the extreme and ongoing challenges our Midwest producers deserve a pat on the back for all their hard work to try to make a buck. Pride and perseverance are the words that come to mind.

After hearing the ominous forecasts for deluges of 3 to 5 plus inches of rain for late last week it was disappointing to only receive about a third that much. While they were off in their estimates there was an area in a line thru Maryville, Mo and points east where rainfall amounts of 5 to 7 were common with up to 12.5 inches recorded in spots.

While filling the moisture profile before we enter the hottest and dries month would have been nice getting anything more than 3 inches would have prevented some of the fertilizing and spraying tasks that needed to get done yet. After this year growers realize that it is much easier to farm in a dry year rather than a wet one. While I am mentioning that topic the latest forecast is calling for an El Nino to possibly set up again later this summer. The required warm body of water in the Pacific exists but it has to do it for the required 5 months to meet the official qualifications for that phenomenon to be declared.

So do we have global warming or not, and if so what is it? Trump is getting lots of flack for pulling out of the Paris agreement. But quite a few renowned meteorologist plus top NASA Scientists recognize that the sun has been going into a quiet phase that may be the 58 year cold Maudner phase of the regular 300 year weather cycle. For humans that is too many generations and too long of term to recognize. Why some growers are asking questions is that they keep records that track GDUs and crop growth between different years. With the GDUs being about normal and planting dates for the early fields to be planted why are the most advanced fields north of I 80 only in the V9 to V12 growth phase instead of near tasselling. Is something out of whack? What these people have noticed is that on days when the temps are in the 70s and low 80s the air still seems cool. There just does not seem to be the same quantity of heat contained in the air. One weather prognosticator explained it in a big picture scenario. I could just send it to people who are interested in hearing this explanation.

Why this could be significant is that quite a few acres of corn and soybeans were planted weeks later than normal and are now at the V5 to V6 stage. This has led to having many corn fields that seem to be growing at a very slow rate, heading for corn that will be tasselling sometime in early August. If not much dry matter is deposited until the same plants reach the late blister how much grain fill will be completed by the time the plants die their early death around August 20. An aggressive management step that may be necessary would be an application of a P and possibly a hormone containing fertilizer.

In soybeans the majority of plants are typically flowering by June 21st. In my scouting this week very few plants were showing any flowers. If they have not reached the V5 stage this typically is not possible. This makes the plants more likely to have a low podded node count and a subsequently lower yield.

Insect awareness

The sales of conventional seed corn was up this year as it fit into tight budgets better and yields have been comparable or better in many locations. But without the Bt protection each grower with such acres has to be aware that the populations of corn borers has been on the rise this season and this year is scheduled to be a peak ECB year. This past Saturday night we noticed many of the .5 to .75 inch brownish colored moths flying along the gravel roads in Story and Boone counties shortly after dark.

These are the moths that survived the winter as larvae or pupae inside the corn stalk, and are emerging from those stalked fields. They spend days hiding in the grass boundaries around fields eating, drinking dew and waiting for the calm nights to fly to any nearby corn field with taller ears where they can lay their eggs.

A person could buy and set up their own light traps, or they could go to the UNL light trap count site and look to see what the daily trap counts were for each adult moth. The Concord, Nebraska site is most applicable for fields in western and northwest Iowa. In my scouting in far northwest Iowa this week I was seeing high enough shothole feeding in the whorls to justifying treating with an approved insecticide. At times as many as nine consecutive plants held live larvae. When moths can lay 250 eggs in clusters of 25 eggs and small larvae can migrated down a row of plants their growth can be exponential.

Before making any insecticide applications a grower needs to make calculations that incorporate the expected yield gain or bushels protected along with the expected cost of treatment and the projected value of the crop.

In a high number of the fields there was a high incidence of leaf streaking. Might there be some correlation between mineral deficiencies in certain plants and the attractiveness of those plants to migrating moths and their egg laying. By Tuesday we hope to have analytical results in hand.

Bacterial and fungal diseases

The lesson as taught to most Midwest corn growers has been that plants develop diseases if the inoculum increases and the weather is conducive to those spores to infect. Then it would be time to start spraying. Some of that is good, but a pertinent question is "why are the plants so susceptible to diseases that used to be controlled? " We think that the best way would be to pull tissue samples from each field and get the samples analyzed for mineral levels. Then apply foliar fertilizer to supplement the minerals deemed deficient and keep scouting for any insect or disease problems.

I mentioned last week that the signs of the New Goss's were appearing in many corn fields across the state. Those same infected fields were some of those showing the most leaf streaking. If you have not scouted your fields yet, do so to lessen the chances of Goss's from multiplying and progressing into an early death, lower yield field. We have seen for the last two years that the BioEmpruv kept the plants greener, longer with a much longer fill period and higher yields. The latest NASS report has the market moving in the right direction. Additional bushels of corn coming out of your fields would help you generate extra revenue

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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