Monthly Archives: August 2016

2016 PGR Management, Cotton Varieties, & Rainfast

If I haven’t looked at cotton elsewhere, we’re watching our variety trail which was planted in late May. So, we’re putting on plant growth regulators now, but most folks have been started for a while. It’s definitely getting late to discuss this now, but there may be some points here that can help us make some decisions.

One of the biggest factors in PGR’s is variety. Below is the updated variety considerations from the 2016 UGA Cotton Production Guide. It’s good to know what varieties have lots of growth potential. Slower growering, earlier maturing varieites may not need aggressive PGRs (high rates, prebloom applications).

2016CottonPGRs

There’s a lot of good info in the 2016 UGA Cotton Production Guide. I’ve taken some points, but is worth a read on that link if you got time.

Irrigated

In most irrigated fields, Dr. Whitaker says we can confortably being low rate applications (4oz) at least by the second week of squaring and continue on a 14 day interval for three or four applications. Another approach is to apply 8 – 12 ounces at first bloom or before with a subseuqnt treatint two to three weeks later at same rate. The key for aggressive varieties may be making applications earlier, when the plant is 12 to 16 inches tall, especially in fields that frequently receive or retain moisture.

Dryland

In dryland situations, applications at or just prior to first bloom is usually a time to consider mepiquat at rates near 8 oz if growth is vigorous. If aggressive growth continues, a follow up treatment may be needed.

When is too late?

It’s important to remember that a given rate of mepiquat in a small plant has more effect than the same rate in a large plant. This has to do with concentration. Dr. Whitaker says, if we are trying for a single application program, we should target cotton in the 16 to 24 inch range. Applications not made until cotton reaches 30 inches often do not adequately control growth. If we feel like we’ve passed the 8 ball here, instead of a high rate, Dr. Whitaker has seen the best response from 1 pint of mepiquat followed by another 1 pint NO LATER than 10 days apart.

Rainfast

In 2013, we could hardly get a PGR application without rain coming in right behind it. We’ll have the same issue this week with our tropical storm thing coming through. Make sure to check each label for specific information, but here are some general guidelines:

Rainfast

 

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Bacterial Blight In Cotton

BacterialBlight-PHY444 012

We are seeing bacterial or angular blight again in cotton. I have a dryland variety trial I looked at this morning and it is showing up in different varieties. Unfortunately, we cannot do anything we can spray. We can irrigate during the night to reduce leaf wetness. Our trail was planted in late May, so we are being everything else. Cotton is not yet too rank. I’m not seeing but a few leaves here and there, but every leaf I find has already dropped from the plant. It is too early to know how much this will impact us. Here is more information from UGA Extension Pathologist Dr. Bob Kemerait:

Once again, we are finding bacterial blight, caused by Xanthomonas citri pv malvacearum, in cotton in Georgia.  The disease can be diagnosed by presence of water-soaked-to-necrotic spots on the leaves that are delimited by the veins of the leaf. This gives the spots a particular “angular” appearance.  The disease can also spread in the veins and gives a “lightning bolt” streak on the leaf.  Crater-like, water soaked lesions can form on bolls.

There is nothing that can be done to manage this disease.  Managing growth of the crop and irrigating at night to reduce leaf wetness periods can help a little. 

Photo by Jeremy Kichler

Photo by Jeremy Kichler

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Dollar Spot In Bermuda Pasture

Tift85-Hay

Last week, I mentioned seeing leaf spot in the pasture. UGA Extension Pathologist Dr. Alfredo Martinez wanted to confirm what appeared to be fungal structures on the leaves as well. The last few years, we’ve looked at leaf spot pathogens in hay fields. Usually, it is leaf blight (Helminthosporium) or leaf rust. What we looked at a few weeks ago appeared to be more damaging to the lower leaves. The lesions of dollar spot are white to straw colored surrounded by a brown border. This was affecting the lower leaves bad. This is the first time I’ve seen dollar spot in pasture. It is maintained the same as helminthosporium and/or leaf rust. Keep in mind, this pasture was burned off last season.

Dollar Spot

Dollar Spot

Looking at the pasture, Tim Flanders noticed these odd structures on the leaves. They almost looked like a fertilizer granular. Dr. Martinez plated them out and did find them to be fungal related. There were basically some saprophytic fungi that ARE NOT associated with the dollar spot.

Dollar Spot lesions

Dollar Spot lesions

Management

Management is strictly avoidance. Coastal, Tift 44, and Tift 85 have some level of resistance (to leafspot pathogens) while Alicia is extremely susceptible. But even less susceptible varieties are infected with leaf spot when potassium is low. Most reported leaf spot cases are directly related to low soil potash. Nutrients are removed from bermuda hay fields in about a 4-1-3 ratio of N, P2O5, and K2O with harvest. We need 75 percent as much potash as nitrogen  applied each season. Split applications of K are better in sandy soils. It is also advised to remove inoculum that exists in thatch. In addition to tying up nutrients, thatch holds water and reduces air circulation. This is a conducive environment for inoculum. The only practical way to reduce thatch is burning in spring before green-up.

Visit Leafspot Diagnosis and Management in Bermudagrass Forages for more information.

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Fruit Thinning & Irrigation Scheduling

Pecans 007

We’ve had scattered rain so far this season, and nuts are beginning to size. Our scab levels are low thanks to  fungicide sprays and scattered rain. This is the period where our female flower is beginning to set physiologically in the tree, so any stress now is greater impact. There have been reports of aphids, and some growers have sprayed already. Here is some information from UGA Extension Horticulturalist Dr. Lenny Wells on fruit thinning:

Pecans 008For the brave souls willing to thin some nuts from heavily loaded trees, now is about the time for most of our mid-season cultivars. Varieties like ‘Creek’, ‘Stuart’ and ‘Cape Fear’ should be ready as early as (last) weekend and certainly by (this) week for most of south Georgia. See here for a previous post on fruit thinning and how to cut nuts to determine if your crop is ready to thin.

Even though it is hot and dry, if you plan to fruit thin, it is wise to turn off the irrigation a day or two prior to thinning in order to minimize the chances of bark damage to the tree. Also, with the hot, dry weather many growers are anxious to begin running their irrigation at 100% capacity. Bear in mind that we are still in the nut sizing stage on most cultivars with the exception of ‘Pawnee’ and a handful of other very early cultivars. We don’t need to go to full capacity until we enter the kernel-filling stage. If you have a September harvest cultivar like ‘Pawnee’ you should be operating at full capacity now in order to fill the nuts. For most other October harvest cultivars change your irrigation to full capacity about mid-August (another couple of weeks).

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Sugarcane Aphids Heavy

GrainSorghum-011

We looked at some bronze sorghum yesterday that is approaching milk stage. The heads have not expanded yet. This sorghum is definitely holding out for a rain which will help advance it a little more. We did get rain across much of the county yesterday. Sugarcane aphids are now in the heads, and we can still see yield loss until hard dough stage. There are lots of lady bugs present, but beneficial cannot handle these populations of the aphids.

SCA can hurt us when we harvest. You will notice the honeydew on the leaves. SCA are up to the top leaves in this field. Lots of honeydew present and you can smell it too.

Treatment

Here is information from UGA Extension Grain Entomologist Dr. David Buntin on pre-harvest intervals, rates, and efficacies:

  • Sivanto Prime (Bayer Crop Protection).  Sivanto prime has a full section 3 label and a supplemental 2ee label for lower rates on sorghum and other grain crops. The rates are 4 – 7 fl. oz per acre. Sivanto was very effective in my trials at rates of 4 to 7 fl. oz. per acre with Control usually lasting 21 days or more. At the 4 oz rate it can be applied up to 7 times during the season but has a 21 day PHI.
  • Transform WG (Dow AgroSciences). Transform WG federal label was vacated last winter and a new federal label has not been approved yet. But Transform WG has an approved Section 18 emergency exception for use on sorghum in Georgia in 2016 through April 8, 2017. The big label change for 2016 is Transform cannot be used during bloom to protect pollinators. The label allows for 2 applications per season and not more than 3 oz per acre per crop and has a 14 day PHI. In my insecticide trails last season, rates of 1.0 and 1.5 oz per acre were effective. Use the 1.5 oz rate if aphid populations are increasing rapidly.
  • Chlopyrifos (Lorsban Advanced, Nufos, other). Lorsban is labeled at 1 to 2 pints per acre. The 2 pint rate has a 60 day harvest interval. The 1 pint has a 30 day harvest interval, but is usually not effective. The 2 pint rate was 60-90% control for up to 2 weeks. At the 2 pint rate it cannot be used after the boot stage due the 60 day PHI. DO NOT USE CHLORPYRIFOS ON SWEET SORGHUM.
  • Dimethoate ( Dimethoate, Cygon). Not recommended. In my trials dimethoate is variable in control and control if it occurs is only for a week or so.
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Sooty mold grows on the top of the leaf on honeydew excreted from aphids

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Aphids present in the heads

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“White spots” are cast skins from SCA. Blue colored aphids were parasitized by Aphelinus wasp.

Lady bug pupae

Lady bug pupae

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Filed under Entomology, Grain Sorghum

Sunburned Satsumas

SunburnedFruit-J.Price

Lowndes County Agent Jake Price coordinates our Satsuma production updates and manages a rootstock variety trial below Valdosta. He has come across some sunburned fruit I want to share.

Portions of the fruit, (blossom end mostly) are turning yellowish orange. This is from intense sunlight causing a burn on exposed fruit. This can cause the cells underneath the burn to dry up and reduce fruit quality. The fruit I have dissected do not seem to be dry underneath the burn at this time but that could change. There is really nothing that can be done about this. There has been some work done using kaolin clay to cover the fruit but it is washed away with rain so it doesn’t seem practical.

SunburnedFruit-2-J.Price

Sunburn

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