Category Archives: Corn

August 4, 2017 · 2:08 AM

Row Crop Disease Update

In cotton this week checking whiteflies, we are reaching treatable thresholds by the way… I am also seeing some target spot in RANK cotton. Also, it is very low on the plant and is not moving up. Cotton I’ve looked at is 4th and 5th week of bloom. Below is a current disease update from UGA Extension Pathologist Dr. Bob Kemerait:

Cotton

The current weather is very favorable for development of target spot and also spread of bacterial blight. To date, bacterial blight is only a problem in susceptible varieties…The season is not over yet, and things could change.

Target Spot seen in ‘rank’, irrigated cotton, but on the very lower leaves.

TARGET SPOT: In some, but not all, of your trials target spot is a significant issue. From your trials, some varieties are CLEARLY for susceptible. Conditions we have now are perfect for it. Should every grower spray every field for target spot? NO! But growers SHOULD BE AWARE. In one field, target spot was becoming established, and I told him I would likely treat the field with a fungicide. In another field, no target spot was found and I told him I would not treat that field.

Peanuts

We are at a critical point in the peanut season. Reports of white mold in fields are coming in every day and I am receiving some reports of leaf spot. I don’t know of any fields where leaf spot is “out of control” and only one field where white mold is “breaking loose”. However, both diseases can be explosive given the right environment and time to become established. Growers should stay on an appropriate fungicide program for these diseases and also Rhizoctonia limb rot. Timeliness and coverage are CRITICAL.

Soybeans

Asian soybean rust has been puzzling this year. We found it in kudzu very early in the season, yet to date it remains confined to kudzu in our southern tier of counties. I still expect soybean rust to “break out” as southern corn rust has done, but I can’t understand what it is doing now. Fortunately, our Sentinel Plots are being monitored, so we can keep you up-to-date. Even though the disease has been slow to develop, I still believe that there is merit, especially in southern Georgia, to protect the soybeans during late-bloom/early pod set, especially when applying something like dimilin and boron. There are other diseases, such as frogeye leaf spot, which can be problematic and that can be managed with the same fungicides at the same time.

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June 30, 2017 · 4:56 PM

Weather & Disease Update

It’s hard to say we don’t want more rain, but more and more we’re saying just that. We’re having showers nearly every day or every other day, sometimes as much as an inch and a half. It’s starting to show up in the field where cotton is getting ‘wet feet.’ Some of our rain has come with strong winds. Our largest field of tobacco took a hit from these winds knocking plants to the ground in some places. The only hope is to stand it back up as best as possible. It is still causing issues with topping since the flowers on the ground began growing straight up.

We have a good crop of tobacco this year, but it was hit hard from strong winds and rain. Some areas completely blown to the ground.

Flowers turned from wind affects topping

From UGA weather station in Cairo, here are the rain numbers since the beginning of May.

Disease Update

Here is our latest disease update from UGA Extension Pathologist Dr. Bob Kemerait:

Southern Corn Rust: I was stunned when agents in our disease diagnosis class visiting a field in Morgan County found a very active spot of southern rust. Unbelievable because until yesterday, it had ONLY been found lightly in Seminole and Marion Counties. Obviously, as we expected, southern rust could be present anywhere in Georgia now. Why it has not “exploded” yet is a mystery to me given the conditions we have had, but CLEARLY the spores have spread across the state.

The corn in that field as at hard-dough/early dent, so it does not need to be treated; however growers with later planted corn not yet at R6/dough stages should be aware there is at least some threat.

Target spot of Cotton: Perfect weather but I am NOT calling for an automatic fungicide application at first or at third bloom. BUT I am saying that every cotton grower SHOULD be aware that these can be important and critical timings. As cotton approaches bloom, I hope growers can put some eyes and boots in the field and begin looking for it, lower leaves first. Weather is very favorable- growers with a history of disease in the field and those with high-input, strong yield potential should be the growers with the greatest chance for benefit. Target spot will not steal the entire crop, but it will take away a valuable portion of the crop.

Consider: Growth stage (blooming yet?) history of disease, reports from scouting, (have early symptoms been found?), what’s the weather like now and what is the forecast? What is the value to the growing in a preemptive application “to be done with it”?

White mold and leaf spot in Peanut: We are seeing some of both. Growers, don’t get behind!

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June 16, 2017 · 5:58 PM

Southern Rust In GA

Southern corn rust has been identified in Georgia (on June 5th) by Rome Ethredge in Seminole County. Corn was in the silking (R2) state. This is likely some of the earliest southern rust to affect our state. UGA Extension Pathologist Dr. Bob Kemerait has this update for growers:

Weather condition for the past few days and over the next few days is predicted to have a significant chance of rain and humid conditions. These conditions are quite favorable for the development and spread of rust diseases to include southern corn rust and Asian soybean rust.
As of today, 5 June- Asian soybean rust has been found on kudzu in Miller County and on corn in Seminole County.
My recommendations: Corn in southern Georgia that is approaching tassel stage (or has reached) is now at some risk to southern corn rust. The risk is likely not urgent yet, but finding rust now (fairly early in the season) and coupled with the current weather conditions does increase risk.
Grower spraying for southern corn rust: tebuconazole is effective, but combination products that include multiple modes of action (e.g. strobilurins, triazoles, SDHIs) have a broader spectrum of activity against disease AND have a longer protective window (e.g., 3 weeks versus 2 weeks.)

Insects

The picture above is corn in Thomas County that is also silking. We are very fortunate with our rain these past few weeks. During this stage (70-80 DAP) corn is still using 0.3 inches of water / day. We also need to watch for stink bugs. It is common to treat during the ear elongation / tassel state (VT) is 1 SB per 2 plants is present. Because they can hide from you, it is easiest to drive down the rows and check.

During policantion and blister statges (R1-R2), SB feed through the husk and damage individual kernels. Treat if you see 1 per plant.

Pyrethroids are fine to use when we’re seeing southern green SB. If brown SB are prevalent, use a high rate of bifenthrin to get about 75-90% control.

1st Instar Brown Stink Bug

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June 1, 2017 · 9:20 PM

Corn Disease To Scout

Some of our dryland corn is now tasseling. The rest of our corn is very, very close to tasseling, and many growers will put out a fungicide. And this is okay. Should we have sprayed before now? UGA Extension Pathologist Dr. Bob Kemerait has found that early fungicide applications (V5-V6) on early planted (Spring) corn has no benefit to yield and disease, but can have “some” benefit on later planted corn. This is likely because corn planted behind corn will be affected earlier in the growth stage.

Former Seminole County Agent, Rome Ethredge found northern corn leaf blight (NCLB) last week. In corn disease, we are mostly watching for southern corn rust and NCLB. We have sentinel plots in the county to help us watch for rust. Unlike NCLB, southern rust is reintroduced each year and spores essentially blow in and re-infect corn.

Lesions o NCLB appear as a cigar shape. Photo by Rome Ethredge.

Control of NCLB

Northern corn leaf blight is more prominent where we have corn behind corn, overwintering in the leaf litter as well as irrigated corn. We have less of both situations in Thomas County. In fields with a) susceptible varieties and b) favorable conditions, you can have some NCLB in the field and NOT need to spray. When do we pull the trigger on spraying NCLB?Dr. Kemerait says treat for NCLB when lesions get as high as 3rd leaf from the ear leaf.

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May 19, 2017 · 8:08 PM

Corn Update

Both irrigated and dryland corn are looking okay. Dryland is looking as good as it can. We’ve had less rain as we move east in the county. Corn on the central and west side has had almost an 1nch of rain for the last few weeks. There is rain expected for the weekend also.

This corn is our rust sentinel plot in Thomas County and has only nitrogen burn from foliar fertilizer. You can also see a few spots from Gramoxone drift as we’re planting cotton. None of this is anything to worry about.

We’re past most of our weed control. There are only a few fields where preemergent herbicides didn’t get activated and we’re dealing with pigweed.

Etching done by thrips

Burn from gramoxone

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May 4, 2017 · 6:34 PM

Field Corn Weed & Disease Update

Some of our earlier planted corn is moving through the v8 growth stage. In this field corn, we are nearly past the time for over-the-top herbicide applications without yield loss. We’ve been applying mostly one shot Atrazine+RU+Prowl H2O when corn has about 3 leaves. It’s working great. We have a one or two fields were pigweed got past it and hurting us.

Weed Control Update

Here is an update from UGA Extension Weed Scientist Dr. Eric Prostko:

Field corn weed control does not have to be difficult. Just about any of the herbicide programs that growers are using in Georgia do a good job of controlling most weeds, especially Palmer amaranth, when applied to small plants (<3″ tall). Check out the following pictures from my field corn plots that I rated earlier today. These herbicide treatments were applied 17 days after planting with a CO2-powered backpack sprayer calibrated to deliver 15 GPA at 3.5 MPH using AIXR 11002 nozzles.

The most troublesome weed in Georgia field corn, in my opinion, is annual morningglory. Field corn growers who struggle with morningglory should seriously consider a post-directed/lay-by application of Evik (ametryn) sometime after their initial POST treatment was applied. (Check out page 70 of the 2017 UGA Pest Control Handbook for more information about Evik.) The minimum corn height for post-directed applications of Evik is 12″. If Evik is tank-mixed with glyphosate, post-directed applications can be applied up until 48″ tall corn (RR2 hybrids).

Halex+Atrazine+Adept, Dr. Eric Prostko

Atrazine+RU+Prowl H2O, Dr. Eric Prostko

Laudis+Atrazine+MES, Dr. Eric Prostko

Revulin+Atrazine+Adept, Dr. Eric Prostko

Disease Update

This is from UGA Extension Pathologist Dr. Bob Kemerait on 5/1/17:

Our earliest planted corn crop is beginning to approach times where we need to consider use of a fungicide (or not). Here are some notes…

There is no need at this point to protect against rust.
Some growers might put out a fungicide application as early as the V6-V8 stage to protect against leaf blights. Before doing so (unless the grower simply feels better doing the application anyway) scout for detection of the easily diagnosed lesions of northern corn leaf blight. Simply finding one or two scattered in the field is NO BIG DEAL. Finding the disease more widely scattered, on a susceptible variety, could be. DO NOT MIX AN ADJUVANT OR CROP OIL with fungicide applications made prior to tassel. This can result in significant ear deformation.

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April 7, 2017 · 6:42 PM

Sidedressing Corn

We are very thankful for timely rains without significant storms. We’ve had atleast 1.5″ of rain in the last 7 days. This has helped get our pre-emergent herbicides activiated. This is also good for dryland corn, as it approaches the critical V6 growth stage where much of its yield is determined.

Ground Equipment

It’s not time to sidedress. We want 1.2 lb of total N per bushel goal. UGA Extension Fertility Specialist Dr. Glen Harris recommends sidedressing at 12″ to 16″ height. If we’re using ground equipment, we’re putting out 50 to 75 lbs of N per at at / before planting on irrigated land and 20 to 50 lbs of N per acre in dryland. We put out the rest of the N at sidedressing.

Fertigation

You put out 40 – 60 lbs of N at or before planting and start ground or injected applications of 30 – 60 lbs of N per acre when corn is 8″ to 12″ tall. Keep this going every other week until the total required N is finished. You’ll need 3 to 5 applications during the growing season.

Sulfur

Corn requires about 20 to 30 lbs of Sulfur and we sometimes see sulfur deficiency. It looks similar to N deficiency except we see an overall yellowing of the corn plants. (N deficiency shows up in the lower part of the plant since it is plant movile.) To be sure of which deficiency, we need to take a plant tissue analysis. I talked about the proper way to do this for corn in this blog post.

Only on sandy soils do we split our S applications. Whatever we don’t put out at planting needs to be put out now. Research has shown that we want to correct our S deficiencies between 21 and 30 days old to not hurt yield.

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March 31, 2017 · 2:08 PM

Corn Coming Up

We looked at a good bit of corn this week that is now coming up in a few different stages. This field was actually planted before our freeze two week back. It slowed germination but would not have any injury. Any corn with just a few leaves – in the V1 growth stage – still has the groing point below the soil surface, which protects the plants from freeze.

We’re just now getting our first herbicide shot, so we’re able to mix Prowl in for grass control. Buffalo grass is all througought this field. Since some grass has already emerged, UGA Weed Scientist Dr. Eric Prostko says it’s okay to add Round Up in with Atrazine + Prowl. It’s one of the best one-shots we have in corn. We had just enough rain last night to help activiate some pre-emergent herbicides.

V1 Growth Stage – The collar (white line) is present on the 1st leaf.

V2 Growth Stage – The collar is present on 1st and 2nd leaf.

At the V1 growth stage, the growing point is still below the surface of the soil. At this stage, three leaves are visible. The leaf collar is only on the lowest leaf. At V2, four leaves are visible, but the collar is only on the 1st and 2nd leaf. At this growth stage, corn water demand is close to 1/10″ a day.

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Image

2017 Corn Short Course – Jan 24th

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January 16, 2017 · 4:26 PM

December 2, 2016 · 6:23 PM

December Row Crop Disease Update

A few things to think about with regards to disease and nematode management in preparation for the 2017 field season.

La Nina: Our UGA Extension climatologist Pam Knox has good information available on our current conditions, but here are my thoughts:

We are currently in a “weak” La Nina situation, “weak” because the equatorial waters of the cost of Ecuador are more than a half degree COOLER than normal. As best I can tell, the waters have been about 7/10 of a degree cooler which barely qualifies as a La Nina (as opposed to last year where we had a robust and sure-enough El Nino). So what does this mean? During La Nina years, the Southeast tends to (“tends to” means more often than not, but not always..) experience warmer and drier winters. Because we have a weak La Nina, this forecast could change.

Pigweed seedhead in broccoli before Thanksgiving. We are yet to have frost to knock back pigweed growth.

How does our current “La Nina” impact our recommendations?

Drier is not a good thing as it may mean we don’t fill up irrigation ponds for next year. It my mean we have a lot of trouble establishing cover crops this fall.
Warmer temperatures may mean that kudzu, volunteer peanuts, corn, cotton-regrowth, etc. pathogens (like those that cause soybean rust and southern corn rust) may survive and increase longer than they would with an earlier “killing” frost. Also, as long as the crops and volunteers are active in the field, nematode populations can continue to increase and build. This will lead to larger populations for next season. Once the plants are killed, the nematodes can no longer feed. Once soil temps drop below 65F, the activity of the todes drops off as well.
We may get some very cold weather soon, so we may not need to worry that much; however the general prediction is that we will have a warmer winter.
The weather this winter will have some effect on TSWV and insects for next year. It remains to be seen what and how… but it will impact them.

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