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CROP WATCH

By Staff | Jul 17, 2009

Where has the first half of the month gone? It seems like the days are now just flying by. Maybe it is because we are all having so much fun, or that every single moment has to be dedicated to another important task that needs to be done before it is too late.

Now is the time of the summer that both people and machinery are getting tired and are ready for a short break. That isn’t possible yet, but we can see that it might happen in another few weeks as the crops get too tall for most of our sprayers and most of the management steps become memories.

By now most crop forecasters have had their chance to guess on the size of the crops. We know things in 80 percent of Iowa look very good and have responded to the hard work, favorable weather and acceptable drainage. There are still the months where tasseling, grain fill and drydown will be happening with the corn crop and much can still occur.

If moisture continues to arrive and temps are favorable we might just explore the absolute genetic potential of many of the hybrids. The soybean crop finally began to grow about three weeks ago and finally got above ankle high. Now many of the fields are within one to two weeks of closing the row and appear to have decent potential.

It was good to see more foes of the Cap and Trade stand up and ask what the politicians are thinking. Don’t they realize that part of what set the economic downturn off was a huge increase in energy costs?

Just a year ago when the price of corn was making its meteoritic price rise, thanks to fund managers speculating on hard asset commodities as a way to beat inflation, the hot topic was how food prices were climbing due to ethanol production.

In the end the message got delivered that increased energy prices were more the root cause. If this country has not experienced climate change in the past why do we have coal deep within the earth in many parts of the Midwest as well as proof that glaciers shaped the landscape?

The corn crop

As mentioned much of the corn planted in rotation looks very good. Most of the fields have maintained a good green color and are now close to tasseling. Within a week of when you read this, most fields will be showing their tassels and on their way to pollinating. One trait that seemed odd and mistimed last year was that many hybrids were showing silks days before they had fully pushed their tassels out.

When that first appeared we wondered if there would be any detrimental results. It ended up seeming to be a mechanism that might help a plant avoid pollination problems resulting when the silks emerge after all the pollen has been shed.

Currently it looks like there will be a full moisture profile across the state along with moderate temperatures during pollination this year. That is a very good omen and a precursor of great kernel set. Time will tell if the weather will be favorable to grain fill in the two weeks after pollination as that is typically when the most kernels abort.

Temperatures from 78 to 84 degrees and lots of sunlight are optimal.

There are two related problems that have been or are becoming apparent with the corn crop. The first is that half of the second year corn fields contain a substantial acre percent that showed growth problems related to poor nitrogen availability. As mentioned previously by other agronomists the lack of stalk degradation last fall forced the microbial population this spring to absorb 80 to 100 pounds of nitrogen that was supposed to be devoted to the 2009 crop. The other result due to the late crop maturity and early winter of 2008/09 was that the disease inoculum, left in the residue from the pathogen-riddled 2008 corn crop, has jumped to this year’s plants.

I took corn leaves from a field in northcentral Iowa to the ISU disease lab to get cultured and see what foliar pathogen was casing the lesions. Early in their infection cycle and when they are small several diseases look very similar.

We knew that it was very early to have so many lesions on leaves No. 7 through No. 9. Typically corn pants have a high level of natural systemic resistance prior to tasseling. With high humidity levels and lots of dews, high levels of inoculums, and warm temps over the past weeks it has been like an incubation chamber within the crop canopy. Thus if you check the ISU and University of Nebraska IPM newsletters for this week there will be advisories to monitor your corn fields for leaf diseases and be prepared if full-blown infections continue to spread.

In the Nebraska newsletter Extension pathologist Loren Geisler said that it looked like a full-blown grey leaf spot infestation in his state. The significance of this is that the numerous and plentiful leaf pathogens, if allowed to spread unchecked, could lower final yields and affect late season plant intactness.

The advice commonly given is to check the tolerance ratings of the hybrids you planted, take note of the amount of residue in each field, and study the surrounding topography and prepare an action plan if needed. One always hates to spend money late in the season, but we saw in 2008 that properly managing corn disease could save lots of dollars and harvest losses in the fall.

Watch your fields and be observant of the weather through July and August. Stop by your extension offices if you haven’t already and pick up the new, well illustrated corn and soybean scouting guides they have. Ask your normal supplier questions about their fungicide prices and what products will be recommended. Remember that if you hold an infected leaf against the bright sky and you can see lots of little, yellow freckles already on the leaf you will need a curative product in any spray mix.

In a year when many of the companies don’t have huge supplies of product any fungicide that has proven effective may find a home. A number of corn growers applied foliar nitrogen products to their yellowed fields. The general consensus is that many of the fields showed a remarkable recovery.

The hope was that by spurring new top growth there was going to be a corresponding burst in root growth, with the new root tissue then able to scavenge more nitrogen. Such applications in 2008 were profitable and gave a 2:1 to 4:1 return.

Several of us are sending in plant and leaf samples from diseased plants to determine if nutrient deficiencies were the root cause of their being more susceptible. Then by applying foliar nutrition the nutrient levels might be corrected. There are studies suggesting that might be the solution.

Soybean happenings

The soybean crop looks much better than it did three weeks ago. Many plants are now at the 8th to 11th trifoliate stage and been flowering for 1 to 2 weeks. Doing the extra management things now to boost branch and pod number can pay off handsomely. They don’t happen by accident, they have to be learned and implemented.

Everyone has been predicting big aphid flights with huge numbers. Thus far we have not seen many aphids in Iowa. Around Rake, the reports tell of numbers from 0 50 per plant. I spend all last week looking for them and finally found them late Saturday afternoon in part of one field in Tama County at 0 to 30 per plant. While that should tell us that every field north and west of Tama County should be infected, where are they?

They could be bad and at ETs within two weeks, but it is possible that good living conditions in Minnesota haven’t forced the reproducing females to grow wings. Keep your fingers crossed.

Good IPM practices dictate that just throwing an insecticide in with another trip being made isn’t proper, but avoiding another custom application can make it look very attractive.

As to soybean diseases, most fields are still clean with only very light Septoria appearing. Current warm and humid conditions suggest that Septoria, Cercospora, Downey Mildew, and even White Mold could be problematic during August.

Key to disease problems is having the rows close and the humidity levels within the canopy create more hours of wet foliage. Again scouting, education and comparing known disease pictures against what you are seeing should help you identify soybean disease problems in your fields. Having an action plan in place should help you coordinate and maybe save application trips.

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