Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Archive for the ‘Corn’ Category

Corn Getting Closer

Posted by romeethredge on June 9, 2015

Looking at some of our oldest corn yesterday, I saw that it is in the Dough stage or R4. Still a little milky inside the kernels but the lower kernels beginning to dent just a little on some ears. Kernel moisture is about 65% now and will steadily decrease to about 35% at black layer formation.  This corn was planted March 8th, so it’s 93 days old and has accumulated 2008 Growing Degree Units. We accumulate about 30 units per day now and we need to get to 2,800 or so for most hybrids.

So we need about 4 weeks or so to get to full maturity, black layer.  We need healthy leaves and stalk to get there and to have good stalk strength. We need to protect the plant with fungicides if needed. We need to keep it wet as well. Water needs start decreasing slightly from here on, but not much. Stress during this time will result in reduced kernel weight.

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Corn Shorter ? Pollination?

Posted by romeethredge on June 8, 2015

We have noticed that some corn stalks are shorter than usual this year.

Here are some comments from Dr. Dewey Lee, UGA Grains scientist. “Some corn hybrids are slightly shorter this year than the previous two years. In most cases, it’s simply due to our slightly warmer season and the faster accumulation of growing degree units.  It is most noticeable in 112 to 114 day hybrids as would be expected because they are our shortest season hybrids.” Link to Dewey’s Blog.

If corn has lacked anything; water, nutrients, or has nematodes or other root problems, then it’s shorter still.

 

Some folks have asked whether or not irrigation or rainfall in the morning interferes with corn pollination.

 Dewey Lee, has this response.  “Yes, peak  pollination generally occurs early morning and late afternoon when the temperatures are generally cooler, however, the silks are very sticky ( you feel the trichomes when you touch the silks) and easily capture pollen.  Once this happens, rain nor irrigation wash pollen off the silks.  

 Anthers on the tassel though will not shed pollen when wet either from rain or irrigation.  Once dried they will shed pollen.  Pollen grains will germinate within a few minutes after adhering to the silk and fertilize the ovule within 24 hours.”

Each silk receives a grain of pollen that goes to one kernel of corn. Before pollination the silks have a strong attachment to the kernels. After pollination they fall away easily. 

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Corn – Southern Rust in the Area 2015

Posted by romeethredge on June 8, 2015

There has been some southern rust found in Mitchell county Georgia by County Agent Andy Shirley. It’s now also been found inTerrell County, by Agent Nick McGhee.

Here’s a photo from last year when we had a bad problem with it in our corn fields.

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Here are comments from Dr. Bob Kemerait, UGA Plant Pathologist.  “Corn growers in south Georgia should be very much aware NOW that rust is here. 

Current weather patterns increase the risk. 

I believe that any irrigated field corn with good yield expectations and that is at tassel or beyond is a good candidate for treating with a fungicide.

 Corn approaching tassel is also certainly at risk.”

Here are some comments from Dr. Dewey Lee, UGA Grains Scientist.

“Even though this southern rust infection is earlier than usual, most of our corn crop is a little head of schedule.  While this might not be much comfort, it does mean we might have saved at least one spraying.  Last year, it was extremely difficult to stay a head of southern rust because the infectious time was longer than normal due to favorable conditions for infection.  Some corn in the southern areas of the state is as far along as the R3/R4 stage.  This makes it easier to control rust and reduce the impact since it is much closer to maturity.  Much of the corn crop though, is silking to early ear development (R2/R3) which adds roughly 2 to 3 weeks of time to our potential spraying.

If you have good yield potential (and most irrigated growers do), I would consider spraying a combination of fungicides to provide both a curative and preventative type of action.  There are great choices today from lots of sources.  You may not have a current infection taking place, but spores are active and an application of a combination of fungicides will be great insurance and likely prevent yield loss.  As long as southern rust is active, I would consider staying on a 14 day spray schedule or shorter.  This disease can certainly undermine all your efforts this year and significantly reduce corn yields.”

Link to Dewey’s Blog.

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Corn Looking Good

Posted by romeethredge on June 5, 2015

Field corn is looking good and many folks ate roastin’ ears from their fields last week, which is early for that. Here’s Mark Davis with some late last week.  Pollination has been good for the most part as well. The biggest concern now is keeping the water to it. IMG_6545

We are seeing and increase in stink bug numbers in many fields this week. I found 3 on one ear at this field’s edge.  There are reports of Southern rust in Florida so we are on the lookout but it has just been reported in Georgia in Mitchell county by County agent Andy Shirley.  Some preventative sprays have gone out. _DSC2635

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Common Corn Rust 2015

Posted by romeethredge on May 28, 2015

We are now seeing some common corn rust in our fields. It is not the bad rust that causes us yield losses. This rust is a cooler season rust that perhaps infected when we had a series of cool nights a week or so back. It causes damage on both sides of the leaf whereas southern rust is just on the leaf tops usually. This rust is darker  brick red as well in color. The bad southern rust is a more orangish color.

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When you look at it under the mircoscope it is more round in shape and has thicker walls than southern rust. common rust2

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Purple Leaf Sheath

Posted by romeethredge on May 28, 2015

 Purple leaf sheath is a harmless disorder that results when pollen or other debris become trapped in the leaf sheaths by the stalk.  It looks bad and can be confused with one of the stalk rots. Upon cutting into the stalks there is no damage however with this. UGA Diagnostician Jason Brock confirmed the disorder on plants from Seminole County today. I see it often in fields, especially after pollination, sometimes it seems like fertilizer burn and other problems can make this worse.

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Bacterial Stalk Rot in Corn

Posted by romeethredge on May 23, 2015

I’ve not seen this Bacterial Stalk Rot before but crop consultant, Jim Griffin, brought me some diseased plants from far eastern Decatur county yesterday. We confirmed it with Dr. Bob Kemerait, UGA plant pathology, by photos and discussion.

We scouted the fields and found it in the areas irrigated from a pond. In areas not irrigated by that pond, we didn’t see it. It is in low amounts maybe half of one percent of plants, more in some areas, but it is startling to see. Fortunately, it is reported not to usually spread within the field. The bacterium causes a type of meltdown and you can sometimes smell it before you see it. It really stinks, especially if you cut into the stems. Univ of Nebraska has a good writeup about it. Here’s an excerpt…

“The initial symptom is discoloration of the leaf sheath and stalk at a node. As the disease progresses, lesions develop on the leaves and sheath. Disease then develops in the stalk and rapidly spreads up the stalk and into the leaves. As the decay progresses, a foul odor can be detected and the top of the plant can be very easily removedfrom the rest of the plant. The stalk rots completely and the top collapses. Bacterial stalk rot can affect the plant at any node from the soil surface up to the ear leaves and tassels. Infections that occur high on the plant may impair normal tasseling and affect subsequent pollination. Although it may spread along the plant to infect additional nodes, the bacteria do not usually spread to neighboring plants unless vectored by an insect. Splitting the stalk reveals internal discoloration and soft slimy rot mostly initiating at the nodes. Because the bacteria usually do not spread from plant to plant, diseased plants are quite often found scattered throughout the field. However, there are reports of plant-to-plant transmission by certain insect vectors.

Bacterial stalk and top rot is favored by high temperatures and high relative humidity. It can be a problem in areas of heavy rainfall or where overhead irrigation is used and the water is pumped from a lake, pond, or slow-moving stream.”

 

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Corn Spraying

Posted by romeethredge on May 23, 2015

Some corn spraying is going on now by plane or helicopter. Much of our field corn is now tasseling and especially in fields where Northern corn leaf blight (NCLB) has been found and where growers are going for very high yields, they are choosing to apply a fungicide.  Fortunately the real bad yield stealer, southern rust, hasn’t been found yet and we’re hoping it will hold off a while.  Stink bugs aren’t at high levels at this time but a few have been sighted.

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We flew over a few corn fields this week and they are looking good. The heat this year is pushing the corn on and it is a week or more ahead of the past 2 years, which is good news. In cases where corn has been stressed due to water or nutrient needs, it is short and not looking as good.

Now is a very critical time in the corn fields, the slight cooling this week has been better for pollination and water use but may cause NCLB to increase.

I  read the following from the University of Nebraska:

“Corn was originally a tropical grass from the high elevation areas of central Mexico about 7,400 feet above sea level, 2,000 feet higher than Denver. Today, corn still prefers conditions typical of that area — warm daytime temperatures and cool nights. Areas that consistently produce high corn yields share some significant characteristics. These areas — central Chile, the west slope of Colorado, etc. — are usually very bright, clear, high light intensity areas with cool nights.

Corn maximizes its growth rate at 86°F. Days with temperatures hotter than that cause stress. In the high yield areas, cool night temperatures — at or below 50°F — reduce respiration rates. These are optimum conditions for corn.

In years when we get high day and nighttime temperatures coinciding with the peak pollination period, we can expect problems. Continual heat exposure before and during pollination worsens the response.

Corn is a “C4 Photosynthesis” plant, making it extremely efficient at capturing light and fixing CO2 into sugars. One drawback of this system is that with high daytime temperatures, the efficiency of photosynthesis decreases, so the plant makes less sugar to use or store. High nighttime temperatures increase the respiration rate of the plant, causing it to use up or waste sugars for growth and development. This results in the plant making less sugar and using up more than it would during cooler temperatures.

Heat, especially combined with lack of water, has devastating effects on silking. If plants are slow to silk, the bulk of the pollen may already be shed and gone. Often in dryland fields we see seed set problems because of “nick” problems between pollen and silking.

Even in some stressed areas within irrigated fields (extreme sandy spots, hard pans or compaction areas where water isn’t absorbed and held, and some “wet spots”) we can see stress-induced slow silking and resulting seed set issues. Once silks begin to desiccate, they lose their capacity for pollen tube growth and fertilization.

Heat also affects pollen production and viability. First, heat over 95°F depresses pollen production. Continuous heat, over several days before and during pollen-shed, results in only a fraction of normal pollen being formed, probably because of the reduced sugar available. In addition, heat reduces the period of pollen viability to a couple hours (or even less). While there is normally a surplus of pollen, heat can reduce the fertility and amount available for fertilization of silks. It’s been shown that prolonged exposure to temperatures reduced the volume of pollen shed. Even with adequate moisture and timely silking, heat alone can desiccate silks so that they become non-receptive to pollen.

For each kernel of grain to be produced, one silk needs to be fertilized by one pollen grain.”


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NCLB 2015

Posted by romeethredge on May 14, 2015

We are finding some Northern Corn leaf Blight (NCLB) in field corn now at low levels. I had not found any until today, myself but crop consultant, Jim Griffin sent me some this photo yesterday of some he found in Baker county. Some of the lesions we are seeing may be Northern Corn Leaf spot which isn’t a big problem, but there is some NCLB at low levels in some fields.

He said it was in tall corn with a close rotation, every other year corn, not quite to tassel stage.

I found some at low levels in tasseling corn in Seminole county today.  I also saw some stinkbugs in corn at low levels. There are more of them near small grains fields that are drying down.

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Corn Tasseling

Posted by romeethredge on May 13, 2015

Lots of field corn is now tasseling in deep southwest Georgia. Some fields have ears that are silking now, too. All the photos below were taken this week.

Heat units are moving it along and lots of irrigation water is being put on it. Water use is at about 0.30 inch per day at this point. Here’s an excerpt from UGA Grain Scientist, Dewey Lee’s blog post about Corn.

“For those that are irrigating, you have every opportunity to prevent water stress if you have the capacity to meet the water demands.  It is extremely important that nitrogen and water not be limiting particularly as the crop advances towards silking.  The number of potential kernels per row is completed about one week prior to silk emergence. The most common stress at this point is usually from drought or some nitrogen deficiency.”

 

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You can count the rows of kernels on this ear, it had 18, which is very promising as the grower has 32,000 plants per acre.

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