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CROP WATCH

By Staff | Jun 26, 2009

A week ago we were hoping for sunshine and drier weather. Now we are sweating through the days and wishing it weren’t quite so hot. Now why can’t the weatherman find and deliver conditions somewhere in the middle?

We and the crops greatly needed the heat to maintain the normal pace of crop development and give us hope that the crops will beat the frost this fall. The warm nights and daytime temps in the mid- to upper-90s has sped plant growth dramatically.

A few weeks ago it looked like a certainty that we would have corn in central Iowa that was going to be starting to tassel the week after July 4. That goal won’t quite be reached, but if the corn plants keep growing as they have the past week we should see tassels starting to appear between July 5 to July 8 in southwest Iowa and across more of central Iowa in the following week.

That would place that critical event ideal time for pollination and early grain fill to occur. In retrospect it was strange that until two weeks ago most Iowans were still wearing mid-weight jackets during the middle parts of the day in order to stay warm. Many of us were hoping Al Gore would show up to explain why global warming was providing such cold weather so close to the longest day of the year.

Can it be that the longest sunlight-hour day happened this week? It seems like all growers have been struggling to maximize the daylight hours to get their crops and weed sprayed on the few days when the soils have been dry enough.

After experiencing extremely wet weather in 2008 and now trying conditions in 2009, one could expect that an even higher percentage will utilize residual herbicides in 2010 to eliminate early weed growth.

Trying to accurately guess what the markets are going to do each day is as tough as it has ever been.

The best way seems to be to track what crude oil prices are doing, then expect corn and bean prices to move in the same direction. Having all of the ethanol plants operating at peak capacity will help consume more corn.

It has to be easier than expecting livestock feeders to pay higher feed prices for their animals when their returns are in the red.

Crop conditions

Many fields of corn were able to add at least four leaf stages and as much as two feet of growth in the past 10 days. Prior to that time, reaching knee high by July 4 didn’t seem possible. After this spurt more fields are either getting close to or have shaded the row already. The tallest corn I have been in this summer was Wednesday down by Atlantic where the V12 corn is already over my head. Once four more leaves push out of the 19 leaf hybrid the first tassels should be appearing.

With these warm temps the pace of growth has greatly accelerated. Last week’s V5 to V6 corn is now V8 to V9 and those plants should reach the V18 normal tasseling stage in about three to three and a half weeks.

That would now put tasseling in the July 10 to July 16 time frame. That is still favorable for the plants in that they will complete that process and be well into grain fill during days with more heat, more hours of sunlight and expected adequate moisture supplies.

What has been noticed by more growers and agronomists is how a substantial percentage of the corn-on-corn acres were exhibiting poor growth and unhealthy appearances.

There were several likely reasons for those problems. One is that where there was a surplus of residue the nitrogen was being tied up by the soil dwelling residue decomposing micro-organisms. Another was that the thick residue cover was lowering the soil temperatures reducing the mineralization and availability of nutrients contained in last year’s plant parts.

Third was that the non-decomposed residue likely still contained the organic acids blamed for causing allelopathic symptoms in the new plants. The best corn-on-corn acres seem to be those planted early where the residue was moved away from the planting trench and nitrogen was placed close to the small root system.

Finally, having warmer soils is helping with nutrient release and the expanding root systems are finally able to function normally.

Most soybean fields have been at about the same development stage they were at the same time last year. Plants in most fields are still going to need a boost to form the desired 18 to 20 podded nodes and additional side branches that add to yield.

Several of us have been inspecting the plants growing from seeds treated with the patented U of MD hormone overproducing bacteria. What we began noticing last week is that the plants are no longer adhering to the rule of apical dominance.

The plants that were barely in the V2 stage had already formed four or more expanding side branches. You have all seen isolated plants that formed numerous side branches. These plants are doing that even when the population is at 130,000 to 140,000. Right now we feel it is a reaction that is very desirable.

I will keep you updated on those fields. We anticipate it will be possible to reach 40-plus podded nodes when the additional branches are induced. The task will be to retain a commensurate number of pods.

In fields where plants seemed to be regressing, scouts and farmers were trying to make diagnoses of what was causing any problems. In many cases an inspection of the roots revealed tissues that showed a browned-colored lesion caused by an infection by one or more root pathogens.

Those organisms love to invade roots of weakened and slow-growing plants that are sitting in cold, saturated soils. It was likely that the effectiveness of the systemic fungicides was reduced to below the critical level and diseases had invaded the plants. Few products can be expected to give complete control eight or nine weeks into the season.

Weed control

During the cold weather many of the applied herbicides took longer to produce symptoms and results. Where the mode of action was systemic or dependent on the inhibition of growth critical metabolites, poor growing conditions often translate into poor weed kill.

With warmer conditions the plants are growing very rapidly and the challenge might be to cover the acres quick enough and to promote effective uptake of each product.

Each species of weed also typically has an optimum thermal window where the requirements for germination are met during warming weather in April or May. Typically most species of weeds, with pigweed or waterhemp as noticeable exception, don’t germinate well after about May 25.

This year many weeds seem to be fooled into thinking that window is still open. The small weeds are still very plentiful and need to be scouted to make sure weed control programs not offering any residual action don’t allow lots of escapes.

Insect news

Things are now happening in the bug world. First of all crop scouts and growers are now finding the small corn rootworm larvae in fields where eggs were laid last July and August. They are finding the small, early instar larvae, which have dark heads and small white bodies. Accompanying them will be the chewed on browned roots.

About two weeks ago the big news was the detection of soybean aphids in Ohio and other eastern states. Then last week several crop advisors and researchers in Iowa began finding the little sap suckers in northeast and central Iowa. I found my first one on Monday in the Nevada area.

This is early for them to appear, but it looks like the winged adults are moving around and leaving the small aphids behind in the fields they visit. It looks like growers will have to remain vigilant this entire season.

Earlier we were hoping to not have plants adding new growth after the July 20 time frame, as that is friendly to the aphids, but that is likely to happen again. Thus it appears that with this expected long infestation event we will have to manage the aphids in a manner friendly to beneficial insects.

Events

A few events have been on the calendar. The first was an informational meeting with Green Leaf genetics in Ames two weeks ago. Green Leaf is a joint venture between the plant breeding arms of Pioneer International and Syngenta Seeds.

Right now there is lots of justifiable interest in their hybrid offerings. Stay abreast with their interaction with your local seed company.

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