Crop Disease Update

UGA Extension Plant Pathologist, Bob Kemerait, gives us the following plant disease update.

Fungicides and Corn:

My graduate student Suzette Arcibal has spent much of last season assessing the impact southern corn rust, northern corn leaf blight and southern corn leaf blight.  Her graduate studies have been sponsored by BASF and I am grateful for their support.  Based upon her findings, here are my comments for use of fungicides on corn:

1.  For management of foliar diseases on corn planted in March and April:

a.  Watch sentinel plot reports for detection of southern corn rust.

b.  Control of southern corn rust:  In most situations I believe that a fungicide application made at first tassel (VT) will be sufficient to lay a good foundation to rust control and may be all that is needed for the season; however depending on the pressure, growers may be advised to make a second application within 3 weeks of the first.

i.  Triazole and strobiluirn fungicides are effective against rust; the combination of both will have a longer protective window and broader activity against other pathogens.

c.  Control of northern corn leaf blight (NCLB):  Unlike southern corn rust which must be reintroduced into Georgia in 2013, the northern corn rust pathogen is already here surviving in last year’s crop debris.

i.  Northern corn leaf blight will not be a problem in every field, but in fields where it is a problem, timely use of fungicide program can protect yield.

ii.  From Suzette’s data, northern corn leaf blight is most effectively managed by a combination of an early application (for example the 5th true leaf stage) and a follow-up application at late tassel-early silking stage.

iii.  The spores of the NCLB fungal pathogen can be spread between fields; however the earliest infections will likely occur as rain and irrigation splash the spores from the crop debris and soil to the lower leaves of the corn plants.

iv.  I recommend that as the corn crop approaches the 5th-true-leaf stage, growers should scout to determine if northern corn leaf blight is developing.  Again, not all corn fields need to be treated with a fungicide for management of northern corn leaf blight; however it is important note if the disease is likely to be severe.

v.   I believe that northern corn leaf blight is more difficult to control than is southern rust (assuming you are on time with applications) and that a combination of strobilurin and triazole fungicides is an important consideration.

2.  For management of foliar diseases on corn planted after April:

a.  The threat from southern rust becomes more severe.

b.  The threat from southern corn leaf blight increases.

c.  The threat from northern corn leaf blight remains important.

d.  The potential benefit to beginning a fungicide program 

e.  The potential yield benefits from use of a fungicide becomes even greater as a percentage of potential yield for late-planted corn.

f.  The benefit of planting a rust-resistant hybrid becomes more important with late-planted corn.

Two web sites to note:

www.sbrusa.net (National site to follow the progress of Asian soybean rust)  We have not found any soybean rust on NEW GROWTH kudzu but did find some on OLD GROWTH kudzu in Miller County.  Those old leaves have been destroyed.  Soybean rust is present in northern Florida, Alabama, and Louisiana.

scr.ipmpipe.org  Sentinel plot site for southern corn rust.  Southern corn rust has not been found in Georgia yet in 2013.

Soybeans for 2013

Here’s some information concerning planting dates for soybeans.

The optimum period for planting soybeans in Georgia is from May 10 to June 10.

Planting can begin as early as May 1 if soils are warm (>70°F) and tall-growing MG V or VI varieties are used. Planting before May 1 usually causes premature flowering, plant stunting and reduced seed quality, especially in MG VII or later varieties. Very early-maturing soybean varieties tend to have a more narrow range of favorable planting dates than do late-maturing varieties. This occurs because at southern latitudes the photoperiod response induces early varieties to flower before obtaining adequate growth necessary for optimum yields.

Planting after June 10 reduces plant growth, auxiliary limb branching, root nodulation and nitrogen fixation, and yield.

However, the planting period can be extended as late as June 30 if adapted tall growing late maturing varieties are used.

These varieties should be used in conjunction with approved late-planting practices of higher plant populations and close rows when planting cannot be made during the optimum period. Typically, all planting should be completed before July 1. Growth and yield, even with the best of efforts, may not be economicalafter this time.

Expect soybean yield with good varieties and management to decline about ½ to ¾ bushel/A for every day planting is delayed after June 10.

Planting date guidelines above can be modified slightly for the Early Soybean Production System which uses MG IV or early MG V indeterminate soybeans and the Ultra-Late Soybean Production System which consists of planting soybean following corn harvest. See the section in the soybean production guide “Early and Ultra-late Soybean Production Systems in Georgia” for more details.

Here’s a link to the newly revised Soybean Production Guide for 2013.

http://www.caes.uga.edu/commodities/fieldcrops/soybeans/documents/2013GeorgiaSoybeanProductionGuide.pdf

Plant Disease Update

 Dr. Bob Kemerait, UGA Extension Plant Pathologist Gives us this plant disease update.

Our weather may not be as cold as it was in Zac Brown’s song, but…. Our continued rains and cooler-than-usual temperatures for this time of year will have likely have a significant impact on seedling diseases and other diseases this year.

 

1.  COTTON:  Cooler and wetter soils will increase the risk to seedling diseases (Pythium and Rhizoctonia) as a) the fungal pathogens enjoy the moisture and will grow well and b) the cooler soils could make germination and early-season growth less vigorous allowing the pathogens to jump on the seedlings.  If current wet conditions continue, this is the kind of season when growers are most likely to see a benefit (improved stand and vigor) with use of additional fungicide seed treatments.

 

2. PEANUTS:  Cooler and wetter soils as planting increase the risk for seedling disease caused by Rhizoctonia but actually DECREASE the risk for Aspergillus crown rot which is most common in hot and dry soils.  OUR MOST IMPORTANT concern in peanut production with a cooler and wetter planting season is CYLINDROCLADIUM BLACK ROT (CBR).  We have not seen much of this disease in recent years because of our warm conditions at planting time, but if we stay cooler and wetter, growers should be prepared.  Counties I expect the most CBR in include Miller, Terrell, Randolph, Webster, Tift, Burke, Jefferson and Worth. CBR will occur in other counties as well and can be devastating in specific fields.  Our best tactic to manage CBR is to either fumigate with metam sodium or VAPAM or to make in in-furrow application of Proline at 5.7 fl oz/A.

 

3.  SOYBEANS:  We know that some kudzu successfully overwintered in lower Alabama and last week we found soybean rust on kudzu that survived in Miller County.  Current wet-weather will likely help to spread the disease to kudzu that is now rapidly emerging.  If these conditions continue, 2013 could be our biggest year yet for soybean rust…. Remember that fungicide application at late bloom-early pod set…\

Kudzu and Some Soybeans Surviving

Dr Bob Kemerait, UGA Extension Plant Pathologist, says that “Kudzu with active Asian soybean rust is surviving in at least Seminole, Grady and Lowndes Counties,  likely elsewhere. If we do not get killing frost and cold weather this winter, soybean rust could affect us sooner in 2013 than any of us would like.  Stay tuned… “

There are also some soybean plants still surviving, see below photo of some we saw near some grain bins growing this week. Also, Mark Hanna reported that the worse weed in his wheat a couple of weeks ago was volunteer soybeans.  It was a field where he had beans in last year. He says that if we had had more rain and soil moisture maybe the seeds would have rotted but they didnt and emerged and may be carrying the rust like the kudzu?

Here’s a photo below of a few kudzu leaves that Thomas County Agent, Andrew Sawyer, and I found this week near the railroad tracks west of Donalsonville. We found Asiatic Soybean Rust on them.

Gramoxone/Reflex Herbicide Tank-Mixtures

Over the last few years, growers have experienced a few problems when tank-mixing the herbicides, Gramoxone (paraquat) + Reflex (fomesafen).  Dr. Eric Prostko, UGA Extension Weed Scientist, gives us this advice concerning this problem.

 In order to prevent these potential compatibility problems, consider the following recommendations developed by Syngenta:

1) When tank-mixing Gramoxone and Reflex, use a non-ionic surfactant (NIS) that contains a minimum of 80% active ingredient.

2) With spray volumes of 10 GPA or more, use NIS at 2 qt/100 gal (0.5% v/v).

Use 1 gal/100 gal (1% v/v) when spraying less than 10 GPA.

3) Mix chemicals in the following order:

     a) Add half of the required amount of clean water to the spray tank.

     b) Start the sprayer agitation system and continue agitation throughout mixing and spraying.

     c) Add the required amount of non-ionic surfactant to the spray tank.

     d) Add the required amount of Reflex to the spray tank.

     e) Add the required amount of Gramoxone brands to the spray tank.

     f) Add the remaining amount of clean water to the spray tank.

30 inch Ultra Late Soybeans

I was watching the harvest of Brantley Broome’s 30 inch Ultra late soybeans last week. These were planted after corn harvest. The field I was in was the last field planted, about August 3rd. The earlier planted fields were taller and they all yielded well. Most of the Ultra Late Soybeans here are drilled in 7.5 inch or 15 inch rows. Here they burned the stubble and planted in rows. It worked well and I liked the harvest with the row crop header. I was told they don’t make them anymore but they sure worked well with these beans. It looks like a corn header but it cuts the whole plant and takes everything through the combine. There seemed to be less loss involved. We normally use a grain table on drilled soybeans.  I’ll include some photos, here, and this first one is a very short video.

View from the Elevator

I climbed up a grain elevator, 80 feet, to get a good view of the crops surrounding it, yesterday.  They were harvesting soybeans and cotton nearby. Cotton ready to pick is really shining and I’m getting reports of good cotton yields. You can see some fine fields of rye planted for cattle grazing as well.

Here’s also a 360 degree video from that height. Just click on this image. Below it are various shots taken from the elevator.

 

 

 

 

 

 

 

 

Ultra Late Soybean Harvest Going Strong

Ultra Late soybeans planted after corn harvest in late July are now being harvested. The quality looks good and the yield reports are good as well.  I’ve heard yields from 2 different farms of close to 50 bushels per acre. In talking to Jimmy Clemons of Pineland seed, he says that the maturity and harvest is almost a week ahead of normal. Here are some photos taken yesterday. I also have a short video of soybeans being combined. Click on this photo to go to it.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Soybeans Maturing

Soybeans planted after corn harvest are starting to yellow up and drop some leaves. These ultra late beans are looking good and should yield well this year. It has been a challenge with disease and insect problems.

Ultra late soybeans look good.

Question of the Week – Predacious Stinkbug

Last week we had a predacious stinkbug, a good guy, helping us control pests in soybeans, he was eating a three cornered alfalfa hopper. I saw another one consuming a caterpillar this week. Here are some of the metallic eggs of the Spined soldier bug(predatory stink bug). You can tell them from the bad stink bugs by the width of their mouthparts. The good guys have wider mouth parts. I picture it more like a sword to defeat the enemies.  The plant feeders have a narrow “straw” to feed on plants.

This week’s question is concerning this that I found under a soybean leaf. What is it and is it a good thing that this happened?

Later,

Rome