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CROP WATCH

By Staff | Jul 30, 2010

Is it hot enough for everyone? After the summer of 2009 when we got to wear winter coats to the county fairs and most of the season, it feels strange to sweat everyday and see the crop actually advance in development and maturity as rapidly as it has been doing.

Warm is good, but anything over 84 degrees is too warm. Typically with warmer weather we would worry about moisture use and the potential for drought.

After a week where many parts of the state picked up 4 to 12 inches of rain, drought is the last thing on anyone’s mind.

Being psychological about the weather, if as a producer you were asked at the start of the season whether you wanted to be 8 inches above or 8 inches below normal for the summer, you would likely chose the former.

Rain has a greater chance of making grain than does drought. For a season that started so promising and easy, the easy part of it sure disappeared quickly.

It’s hard to believe that most of the county fairs are over with and the Iowa State Fair is only about two weeks away. It seems that we were just planting the crops a few weeks ago.

Before you know it we will be heading to the fields to begin harvest. Before that happens the two major crops still need to get into the serious part of grain fill.

We will have to see if the corn crop stays green through black layer or dies suddenly. Whether or not our little soybean aphids make their big annual appearance is a question that will be answered shortly.

From now until early October can still be a long and eventful two months. Wish us luck.

The corn crop

Getting through pollination by mid-July was great and will help the overall yields versus having such cool temps that grain fill takes place during the shorter days of mid-September, like in 2009.

From now on we will have to watch the depth of grain fill. But can grain fill happen too quickly? In the high yield years of 2002 and 2004 temps during late July and August were two to four degrees below normal and the grain fill period was extended.

Kernel depth was very deep and extra bushels were added. It is too early to rate this season, but if growing degree unit accumulation continues to be at 25 to 30 per day coupled with warm nights, it will not be conducive to having an extended fill period.

Kernel depth could be shallower than optimum. It is too early to judge grain depth. What I am seeing is that row number is generally below that of past year. Ear length is no longer than last year, but that may be a function of population. Lots of ears were also observed pushing out fresh silks after all the pollen was spent.

Some of those silks are still growing.

One other thing that we are noting is that even in fields with picket fence stands and even emergence there is a much higher than normal percentage of short plants that are much smaller with pint-sized ears.

The percentage would have to be added to the sum of plants that seemed to corkscrew under or out of the ground acting like there was a thick crust, even when none existed.

After traversing the state again it has become more apparent that many second-year corn fields continue to have problems. Part of the cause appears to be either lost or tied up nitrogen.

Those growers will have to develop a nitrogen management program for future seasons that would spoon feed the crop and minimize the effects of these 6 to 10 inch weekly rainfall accumulations.

In any corn fields that appear to be going backward, one should dig the plant to split the stalk and root crown region.

Often the lower portion has turned a brownish color and it has become impossible for the plant to move nutrients and moisture upward.

The soybean crop

Most soybean plants are at or near the R3 growth stage. The lower pods have reached the .75″ or longer stage and filling of those seeds is about to begin.

Flowering is about to cease and the plants in 30-inch rows either have, or are, ready to close the row. A late foliar can add to flower number and pod counts if they are put on now. Thus more bushels can be added for the growers willing to push the envelope on yield and do the extra management things they have learned.

The first 40, 50, or 60 bushel stage has been set, but they are pushing beyond that barrier.

A scouting trip thru the fields now will detect early signs of several different leaf diseases such as septoria, downey mildew, and frogeye spot. The closing rows help hold in more moisture and a higher humidity.

Diseases love a wet leaf surface to gain entry into the plant. Thus pulling the trigger on leaf diseases and applying a fungicide is more a matter of knowing the major diseases and foreseeing what their level could become.

A proper treatment will add bushels by increasing bean size.

Aphids coming

This past Saturday we could find enough aphids in fields along the Iowa Minnesota border to know that we would be facing them shortly. On Monday it was fairly easy to find them in fields along Iowa Highway 3.

Thus it appears that our aphid season is near and growers may have to begin to scout in earnest. The air at night is also filled with what has to be the clover worm moths. The adults of what ate holes in the leaves of the soybean plants had to appear some time.

It is time to restart the light traps to help ID what is flying. Be aware that Japanese beetles, grape colaspis beetles, BLB and green clover worms are still feeding on bean leaves.

Another disease that became visible on Sunday and confirmed on Monday was the first appearance of sudden death syndrome foliar symptoms.

There had been a few leaf-scorched fields earlier, but the rotten nodules and blue-pused roots could be found on Monday.

After seeing the problems with root and crown rot in corn due to high fusarium populations and knowing that there are lots of compacted fields it doesn’t take a rocket scientist to guess that this might be the worst SDS year in Iowa. We will know in a few weeks

Fungicides

The use of fungicides is still a discussion topic in shops, cafes, and meetings. When they were first marketed a few years ago companies oversold the products saying growers should apply it on every acre and every variety.

If they had told growers to decide which third or half of their acres held the susceptible varieties, had the low or fog-holding topography, or were under stress already, growers would have been more successful in previous years and gotten better returns.

One can see that the educational process in recent seasons has improved and more of the right decisions are being made.

Over the past winter I had discussed and promoted the use of foliar micro-nutrient packages on corn. One thing is becoming apparent this summer. They work beautifully.

Everyone needs to look at using them. Applied early those fields are now dark green with almost no leaf symptomolog.

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