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CROP WATCH

By Staff | Jul 4, 2014

First we went through three seasons that were extremely dry and moisture was at a premium, as crops withered in the heat.

Now, in the past three to four weeks many of us have dumped nearly 15 inches of rain out of our gauges.

More agronomists are agreeing that the crop of 2014 has likely peaked in appearance.

The corn was generally nice, green and even three weeks ago. While there are still plenty of nice-looking, dark-green fields, there are now more fields that have large areas either drowned out or are light-green from too much water.

The strong winds of the last few days continue to push the corn and small grains in many fields flat or near-flat. Will they all straighten up or will some keep the obtuse, downwind angle to their growth?

Now would be a great time to fly over fields to get a perfect view of the affected areas. In addition to the weather problems the twin challenges that more of the cornfields are going to be facing are the rootworms and diseases that have begun to appear within the last 10 days.

Storm damage

By the end of this week we will be more able to assess the damage and the chance of recovery.

The corn plants generally recover quickly and easily from early lodging. As roots grow they do so evenly, which will push the above-ground growth to continue growing towards the sun when all the brace roots are anchored.

If it pushes the plants too far they will continue the process and right the plants. I was near Carroll on Monday and what we saw was a lot of were plants that had snapped off about 18 inches above the ground.

Since the stalks were full of water and likely the calcium and silicon levels were still diluted, they did not have the physical strength to tolerate the winds.

With their strong root systems they were well anchored and something had to give. If they had not been as well anchored they may have just lodged and not snapped.

That area did not get pounded by hail as bad as around Rockwell City or Harlan.

There were fewer stones, so basically those plants only had holes punched through their leaves. Most of the leaf tissue was still attached to the stalks or mid-ribs and very little tissue had been removed from the plants.

With each corn plant adding 2 to 2.5 leaves per week the lost tissue will be replaced quickly.

Each plant generally contains enough leaf area to cover the ground five to six times, thus the plants recover quickly from early hail.

In a number of counties, the hail was heavier and damaged a high percent of the plants in those fields.

Since it is now July, it will take weeks for the ponds and lakes to dry enough to pull a planter through them. It is unlikely those drowned out spots will get replanted.

Corn root worms

A big cropping challenge in many parts of the Midwest the last few years in second-year corn is now the western corn rootworm.

Many growers had been wondering if the cold winter was going to decrease their populations. While we don’t have the final answer yet, it has to be noted that the 2014 egg crop has had a good portion hatch already.

This typically starts after 625 growing degree units have accumulated on a base-52-degree scale. According to the Iowa Mesonet and past insect research, 50 percent of the eggs were supposed to have hatched between 750 and 850 GDUs.

Thus from the middle of last week until this week is a good time to check your second-year corn fields that have a history of CRW problems to see if the small larvae are eating the roots.

There are two ways to do this. The first and easiest is to pull three to five root balls from the ground and wash them off with a hard stream of water. Then examine the roots to look for browning, nubbed off roots, and tunneling along side or into the roots.

Compare the damage you see with the pictures of the ISU Extension root feeding guide to try to put a rating on each root system. The more damage you see the greater the chance of root lodging, yield loss if stress conditions hit, and occurrence of stalk diseases.

The second method, and the only one where you can do a proper count, is to use a sand shovel to dig a foot cube of soil and crumble it over a black piece of tar paper. Then break all the chunks of soil up to look for the small, white with black head, crawling larvae. In the digs I did last week in research plots, I found from five to eight to 17 larvae per roots in second-year corn with no insecticide or traits.

Since about half the feeding is yet to happen, the damage and loss of root tissue is going to become yield damaging before feeding is over.

My recommendation is 7 ounces per acre of SafeStrike, along with WakeUp in water charged by reverse osmossis applied foliarly. The label on Furadan was canceled and the label on Lorsban was never pursued successfully. Thus no hard chemistry rescue is legally allowed.

The larvae now in the soil will molt one to two more times and will turn into pupae in 10 to 14 days. They will molt into adult beetles that will be emerging around July 20 to 28. After hatching the females will have to mate and develop the eggs before they can lay them to create the 2015 problem.

It is when those female beetles plump up with developed eggs that any adult beetle control strategy should be implemented. Any labeled insecticide could be applied at that time.

The same goes for any attractant/insecticide combination. The attractant product that will be available this year is SideTrack D from Trece, which is the bitter-tasting compound that pulls the beetles in from surrounding rows and induces them to feed on the low rate of insecticide.

In past years this program worked great. Currently such a program could reduce beetle and egg numbers dramatically and likely give hard insecticides or traits to do their job. If such a program would fit into your operation and you have a high clearance sprayer or aerial pilot who can make the applications now would be the time to line up the products.

Good luck in drying out and getting the heat and sun you need.

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

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