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CROP WATCH

By Staff | Jul 23, 2010

Late July and the condition of the crops in various parts of the state is still tough to evaluate. The northwest and parts of central Iowa look good while both the east and western extremes have their moisture extreme challenges.

The continued big rains still seem to fall regularly in the areas that have already seen rainfall amounts of 20 to 30 inches since April 1.

The big storm that blew in from the Sioux Falls area early Sunday morning was a damaging one for many Iowa growers and inhabitants. It cut a swath from northwest Iowa through Pocahontas and Ames and points east. Its winds were in the 70- to 95-mph range accompanied by hail.

Seed crop challenges

Typically the Fourth of July holiday period marks the start of the rouging, cutting, and detasseling seasons for the seed companies and the kids who work to detassel the female rows. Getting those tasks done in extremely muddy fields has been a real challenge as several parts of Iowa in which seed is raised have had as much as 20 to 30 inches of rain the past month. Many times in the past two weeks it has been a challenge to simply walk in the fields much less try to slog through the wet holes or drive any sort of personnel carrier or detasseling machine through the fields.

If they aren’t successful in getting that job done on time the crop will be a loss. Any delay increases that chance that off types, be they short or small, could show up in farmer fields next season. The companies or crews don’t have the luxury of waiting until the fields dry.

The corn crop

Not much has changed the last week as the hot and humid days are pushing the corn along in its development. By now the shaking test is telling us that pollination went well as conditions were very good, except many of the ears now have fresh silks being pushed out long after the pollen has all been shed. Thus most ears lack being pollinated on the last three-quarters of an inch on the tips. Just as I wrote last week there will be corn fields that yield well above 200 bushels per acre, while others will struggle to break the 100-bushel level. One thing that we have to remember is that most farmers and scouts see the problems with their crops. They see the existing warts. If we see 50 bushels being subtracted due to fertility problems or storm damage, we have to remember that the top end yields are now much higher.

The leaf diseases are still there with grey leaf syndrome and anthracnose becoming more numerous on the lower and middle leaves, Knowing what to do exactly is always tough in that one has to know the particulars of each disease, assimilate those observations with knowing how rapidly they can increase in severity, and then factor in control levels with what treatment costs and expected returns could be.

It is tough to be 100 percent right every year, but past experience seems to be one of the best aids in making decisions.

Knowing what the proper timing of fungicide applications is has been a point of discussion. Just as in weed control, the goal of spraying a fungicide is not to prove how bad of an infestation one can knock down, but what percent of the leaf tissue can be protected so as to maximize grain fill.

Spraying too early means losing protection on the late side while spraying too late might let the plant lose too much leaf tissue and hurt yields.

Three weeks ago after our first round of heavy rains quite a few growers who saw their corn turn lighter green had intentions to go out and sidedress their corn. Then the second round of rains came and many corn growers were kept from making that application until the corn was too tall for any tractor pulled applicator.

Insect, other pests

The first generation of corn brood was generally quite small. I know of very few operators who ended up with treatable levels of shot holed corn. With July 25 fast approaching the time for the flights and egg laying by the second brood is here.

Producers with non-Bt corn planted needs to scout their fields for the next two weeks.

One critter that very few have ever had economic problems with is the common slug. They are basically snails without the shell.

They will ride their slime paths through the field and skeletonize the leaves if their populations get high enough. We have seen several fields in eastern Iowa where their presence is very noticeable.

Soybean crops

It is also time to be scouting for soybean diseases. The leaf diseases typically increase in incidence and severity just after the rows close. That happens with 30″ rows around July 20th or 25th. Thus growers who want to apply any crop protection product with their own ground rig to minimize costs and maximize coverage have to be able to recognize the early symptomology of each disease and envision what is likely to happen if frequent dews occur the next two months. Having a good crystal ball along helps a lot.

The amount of looper and clover work feeding on the leaves this season is as heavy as I have ever seen it on U.S. fields. They are a very common problem in Brazil, where farmers commonly spray for them and Bt bean varieties are being developed.

It has been almost impossible to find aphids, though populations are reported to be appearing in the NW quarter of the state. It would almost be nice to have any or higher populations in the fields so any justified application to control them could be tank mixed with any fungicide or foliar feeding product application. It would be nice to not have to worry about them at all. Last year they violated all the aphid rules and were around until the leaves dropped off.

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