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CROP WATCH

By Staff | Jul 31, 2009

A week ago we were wondering where the summer weather went? The 50- and 60-degree weather during the day and 40s at night during the middle of July had us wondering if we are being blessed or cursed.

It was nice to not sweat while working or walking the fields, and not having the AC running for long hours makes the summer more pleasant. But, when will be pay for it?

It was interesting to note everyone wearing jackets last weekend and asking the really senior citizens if they could remember anything like it. Of course they were used to sweating profusely during most mid- and late-July days every year they could remember. They all wondered exactly what was going on and how long the cool temperatures were going to be with us.

How many meteorologists went on the record last fall or spring and predicted one of the cooler growing seasons on record? I know of one. The last analysis I saw was published on May 15 and announced that if the July 1 through July 14 cold trend continued we would end up with the fourth coolest July since 1900.

In time we will be evaluating how Iowa growers were or will have been affected by the slow pace of GDU accumulation. Right now what seems to be apparent is that the corn crop that was predicted in early June to be tasseling between July 3 and July 10 is still in the process of completing that task. Some crews working in the seed fields have observed that some of their closely-monitored inbreds virtually sat still for about 10 days.

Plant physiologists have shared their opinions over the years and typically say that corn plants are up and running at peak efficiency within hours of a sub 50 degree night, especially if the sun shines.

Counter to that are soybeans in that they seem to take two or three days to return to peak photosynthetic efficiency after enduring such cool temperatures.

During those cooler days the plants benefit from maximum sunshine hours, but the cloudy weather slowed them down even more. The just don’t receive those photons from the sun in normal quantities.

Most fields that have silked appear to be pollinating very well. In the evening one can smell the pollen in the air and know that the pollen sacks and silks are doing their job of fertilizing those kernel sites.

Checks that agronomists have made by pulling down the husks and shaking the silks are indicating that pollination looks good.

What we have to be thankful for in most of Iowa is that we got planted relatively early and the soils dried enough to keep the seedlings out of super-saturated soils. The weather seems to have switched and now many growers in western Iowa have gone since early July without rain.

In fact there are fields where high numbers of spider mites can now be found on the lower corn leaves. Many areas need rain as the tasseled corn is now using about a quarter inch of moisture per day or over 1.5 inches per week.

The soybeans have continued to improve, but there are fields that still seem to be growth challenged. Heavy residue conditions and packed soils seem to be at the heart of those problems. If any of those challenged fields belong to you it is time to realize that Aug. 1 is here and Sept. 1 is only about four weeks away.

Those plants can still be or should have been prodded with foliar products to put on more branches, flowers, and pods. Enough work has been done to prove that such tactics work well if the soils are healthy and microbial activity is high in the soils.

Looking forward

So what is going on in the fields? In corn the things on the agenda are to scout susceptible fields and varieties for foliar diseases and western bean cutworm eggs. By now most of the nitrogen has been side-dressed, typically with good results.

The high level of infection by four or five corn diseases is still cause for worry. We saw in 2008 that ignoring such diseases can be costly, as their presence combined with late-planting created weakened corn plants that often lodged severely. If you haven’t done so already, pick up the Corn Scouting Pictorial Guides from your Extension office to be able to identify those spots and lesions. The tendency with the lower grain prices will be to decide to not spend any more money on the crop.

But if spraying your acres of corn-on-corn, those varieties already identified as susceptible, or those on fog-prone fields gives a 3:1 or greater return, then it should be done. Educating yourself about what products are most likely to do the best job and recognize that if the lesions are already present on your plants, then a Triazole is likely to be needed.

What I am seeing is lots of the easily-recognized eyespot, anthracnose, and GLS. The smaller anthracnose leaf spots are smaller and require a 20- to 30-X lens to identify. Even then a trained eye is valuable in spotting and recognizing them and then able to draw up any needed treatment plan.

One product that was tested in 2008 and compared well with other commercial available fungicides was a bacterial-based, biologically-based product called Ballad. It is a bacterial product that can be mixed at half rates of one quarter per acre, along with a half rate of other labeled traditional products. Basically it adds a curative product with residual to strobe mixes.

At this time it is used on many high dollar crops such as veggies, tomatoes, and grapes in warmer states with very good results and affordable costs. Remember that Safe Strike is a dual purpose product that can do a good job of controlling diseases and insects at a reasonable price.

I sent plant samples in from fields that were diseased and the analysis came back indicating a major shortage of MN and copper. This leaves the plants less able to ward off pathogens and prevents them from operating at peak efficiency.

Is this a trend repeated across all varieties of certain genetic lines or more a function of N-P-K only fertilization? Time and more sampling will answer that question.

In soybeans more fields have reached row closure or are within a week of doing so. The insects that are showing up are the first true generation of bean leaf beetles as well as grass hoppers, flea beetles, grape colaspis, and sometimes Japanese beetles.

We are expecting aphids to be a problem, but their appearance in large numbers is running a week or two late. That delay can upset planned applications if you had planned to make one final trip this or next week to take care of weed escapes, diseases, and insects at the same time. The word from entomologists in states to our north is that their aphid populations increased dramatically last week.

Be on guard and continue scouting. Find out what is happening to the south as well as what is going on to your north. That can help you with your planning. This week I found many fields with aphid numbers of 1 to 25 per plant. There have also been fields with hot spots of over 2,000 per plant in western and northwest Iowa.

Near Story City we found close to 200 per plant in certain fields with populations around 10 to 20 per plant being more common. In other words the populations are now climbing.

Best of luck with your scouting.

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