Category Archives: Grain Sorghum

Grain Sorghum Dessication

Sorghum-Morningglory

We still have some late grain sorghum left to harvest and we’ve been talking about dessication. We discussed this with UGA Extension Weed Scientist Dr. Eric Prostko who has received more questions this year about the dessication of grain sorghum. Dr. Prostko says, “Growers need to know that the use of harvest-aids in grain sorghum has shown little effect in reducing grain moisture content.”  A summary of 2 older papers is as follows:

1) Hurst, Harold.  1991.  The Use of Dessicants For Field Drying Grain Sorghum With and Without Weeds.  Mississippi Agricultural and Forestry Experiment Station Bulletin #974.

“Overall, these studies did not result in any distinct advantage for application of dessicants to reduce grain sorghum moisture.”

2) Olson, B.L.S, T. Baughman, and J.W. Sij.  2001. Grain Sorghum Dessication with Sodium Chlorate and Paraquat in the Texas Rolling Plains.   Texas Journal of Agriculture and Natural Resources 14:80-83.

“Results from our 2-year study indicate that dessicant applications were generally ineffective (and most likely uneconomical) in reducing grain moisture in late-planted grain sorghum.”

In my opinion, the major (only?) benefit of using a harvest-aid in grain sorghum would be to reduce the amount of green plant material that goes through the combine and might end up in the grain.  I know of only 3 things that will dry down grain sorghum seed: time, a hard freeze, and/or a grain dryer.”

When we treat as a harvest aid, keep in mind that the grain needs to be past the milk stage of development. Dr. Prostko recommends treatment as close to harvest as possible to lessen the chance of morningglory regrowth.

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Grain Sorghum Harvest

MiloHarvesting

We are almost done harvesting milo for grain in Thomas County. This is the first season all of us have dealt with sugarcane aphids from beginning to end. The majority of fields in the county have been treated 4 times for aphids. This does seem like a lot of sprays; however, in these fields, yield reports are good. In these fields, SCA was spotted early and treated at or below threshold.

There was a few fields that were treated late, according to threshold. SCA reached the top of the plant before spraying. A couple of weeks later, the lower leaves completely desiccated due to aphid pressure. These yields are much lower than average. Other reports are were volume is high, 17%-19% moisture, test weight is low. Could this be from SCA?

UGA Extension Entomologist Dr. David Buntin says, yes, this can be the result of SCA. However, test weight be also be related to wet and dry cycles. And this season will certainly be marked by wet and dry cycles. Another issue we have noticed are small heads and large heads. Dr. Buntin says when heads are in two or three different stages of growth, this is result of SCA. SCA don’t have huge phytotoxic effect of feeding, but lots of feeding over time delays heads emerging.

At this stage, we still need to check heads for aphids. Mississippi saw a 20% yield reduction when aphids persisted into the heads.

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Sorghum Heading – Scouting For Insects

Sorghum 017

Our early planted sorghum is heading now and is past flowering stage. We are looking at a few different insect pest I want to write about. Some fields have sprayed 3 times now for sugarcane aphids. At this point, we want to watch for aphids in the grain heads. Also we are seeing caterpillars in grain heads. Last week, we were checking for midge.

Midge

Midge can be more difficult to scout for. Once grain heads come out, we need to be looking for midge. Once flowering is complete, midge is not an issue. One way to scout is take a paper plate, and slap the head in the plate. Dr. Angus Catchot, entomologist in Mississippi, shows on Scouting For Sorghum Midge With Confidence, a method of putting a gollon ziplock bag over the grain head and thumping it. The midges fly to the top of the bad, and you don’t have to close the bag.

Scouting for midge

Scouting for midge

UGA Extension Entomologist Dr. David Buntin says we need to avoid pyrethroids and insecticides that would flare aphid populations. Do not do automatic sprays for this reason.

Sorghum Midge - Photo by Ben Thrash

Sorghum Midge – Photo by Ben Thrash

Caterpillars

We are also seeing caterpillars on the grain heads. Most of the caterpillars we are seeing are corn earworms. We were also seeing armyworms. Our threshold is to treat when an average of 1 or more (1/2 inch or larger) of any of these worms are found per grain head. Below is a photo of corn earworms on this head. Flowering is complete here, and they blend in to the grain.

Sorghum-Caterpillars 031

Sugarcane Aphids

One of the four fields we checked yesterday is at dough stage of development. Dr. Buntin says when we get to dough stage, we do not have the concern for sugarcane aphids. We still need to check for aphids in the grain heads, because of issues with harvest equipment from aphid honeydew. Here is a photo of some aphids in the grain head. This field is in the dough stage and past flowering, so pre harvest intervals are more difficult as we move to heading.

Sorghum-SugarcaneAphidsinHead033

Some milo fields have been sprayed three times for sugarcane aphids. It is difficult to assess thresholds following a devastating 2014 season where aphids hurt us before we knew what was going on. However, Dr. Buntin believes we should be able to get SCA with two sprays during the season. We have learned to scout by not only checking aphids on a plant, but walking fields and looking for honeydew. It is easier to see honeydew on the leaves from a distance and you can check more than one row at a time. Where honeydew exists, this indicates a high aphid population – one that is treatable. Below is a photo of sooty mold on leaves. Sooty mold grows on the honeydew left from aphids. This is another indicator, however, I have not seen sooty mold show up until now. This is not an issue for the plants, just sign of aphids.

Sooty Mold

Sooty Mold

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Sugarcane Aphid Populations Increase

SugarcaneAphids 018

Our earliest planted milo is booting now where sugarcane aphids were found two weeks prior. Infestations have increased to treatable thresholds. This field is 5 miles south of where SCA were originally found and are 100% infested with aphids covering 30-50% of the plants. This level is very high.

In many fields, I only find aphids in 1 or 2 spots. This makes scouting difficult if we want to catch them early. One thing to look for is shiny or glossy appearance on the leaves (as seen above). This is honeydew which is the sugary-rich liquid excreted from aphids and soft b0died insects. Even in a low infested field, you will see a little bits of a glossy substance on the tip of a leaf. Once you see this, turn it over and inspect for aphids. This is where I have found most of our hits in the field.

Threshold/Treatment

Threshold – Several threshold levels are being used in the Delta region for 2015.  One conservative threshold is 25% infested leaves with 50+ aphids per leaf at whorl from preboot stage through dough stage.  In MS, the threshold at pre-boot and boot stages is 20% infested plants with large aphid colonies (100+) and localized areas of heavy honeydew present.  From bloom through dough stage the threshold is 30% infested plants.  I think either of these sets of thresholds will prevent serious yield losses and would suggest using whichever threshold is easiest for you to use.   Once threshold is reach do not delay application because infestations can very quickly go from the threshold level to 100% infested plants and hundreds of aphids per leaf.

Insecticide – PYRETHROID INSECTICIDES ARE NOT EFFECTIVE and may flare infestations by killing all the aphid predators. Regardless of the insecticide, rapidly expanding populations are difficult to control.  Foliar insecticide options for SCA are:

  • Transform WG (Dow AgroSciences) – Transform WG is not fully registered yet, but Georgia, Alabama and several other states haves a section 18 emergency exception approved for 2015 until Nov. 20, 2015. 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. The label allows for 2 applications per season and not more than 3 oz per acre per crop and has a 14 day PHI.
  • Sivanto (Bayer Crop Protection) – Sivanto has a full section 3 label and a supplemental 2ee label for lower rates on sorghum and other grain crops. The 2ee rates are 4 – 7 fl. oz per acre.  Sivanto was very effective in my trials at rates of 3, 5, and 7 fl. oz. per acre, so the 4 fl. oz. rate should be effective.  At the 4 oz rate it can be applied up to 7 times during the season but has a 21 day PHI.
  • 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 and 1 pint a 30 day harvest interval.  The 2 pint rate was 80-90% effective in my trial last year but could not be used after the boot stage due the 60 day PHI. The 1 pint rate was variable and only partly effective.  DO NOT USE CHLORPYRIFOS ON SWEET SORGHUM.
  • Dimethoate ( Dimethoate, Cygon) – Is labeled up to 1 pint per acre with a 28 day PHI.  Most dimethoate products cannot be used after head emergence. Dimethoate was variable in my trials and not recommended without further testing.

SugarcaneAphids 015

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Sugarcane Aphids In Sorghum

SugarcaneAphids-Sorghum 001

In summer of 2014, this new invasive pest of grain sorghum appeared in Georgia. We knew it would be back this season, probably earlier, and it has. The first documented 2015 appearance on sorghum was identified this past week in Brooks County and now Thomas County. Yesterday I checked waist high sorghum and found aphids and cast skins on a few plants. You can see the white cast skins on the leaf. The aphids are black, which is likely from a parasitic wasp. UGA Extension Entomologist Dr. David Buntin says Aphelinus sp. wasp is reported in the Delta and Texas region but was not seen here last year. We mailed the leaves to him to observe for this wasp. Wasps have hatched from some aphids that appear more brown. You can also see an exit hole.

Sugarcane Aphid Mummies & Cast Skins

Sugarcane Aphid Mummies & Cast Skins

Identification

White Sugarcane Aphid

White Sugarcane Aphid

We need to begin scouting and actively managing sorghum fields for the sugarcane aphid.  SCA is difficult to manage cost effectively but planning and scouting are our best hope in managing this pest successfully and preventing losses. The sugarcane aphid can be identified by the pale cream to yellow color with no bumps or tubercles on the body, but with black feet and black cornicles (small tubes located on the end of the abdomen).  A hand lens or microscope evaluation is most likely required to confirm physical characteristics and positive identification. The sugarcane aphid will feed on the sorghum leaves and stem, resulting in reddish colored lesions from the injury.

Management & Thresholds

To see recommendations on management from Dr. David Buntin, visit my previous blog post: Managing Sugarcane Aphids In Sorghum.

Sorghum-Aphids-LeafSpot 004

 

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Sorghum Weed Control

Sorghum-3-5Leaf

Here is some of our latest planted milo in the county that are approaching 5 leaves. I’m mostly seeing pigweeds come up now. With Concept treated seed, most growers applied either Dual or Warrant pre-emergence and come back with Atrazine post. I’ve been asked about post-emergent herbicide timing. UGA Extension Weed Scientist Dr. Eric Prostko says with sorghum, just check the leaves coming out of the ground. Once we have 3 leaves, it is safe to spray Atrazine as our post emergence. This can be done from 3 leaf until 12″ tall. If nutsedge is an issue, Basagran can also be sprayed between 1 and 5 leaves and tank mixed with Atrazine.

Sorghum-3-5Leaf (3)

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Managing Surgarcane Aphids In Sorghum

GrainSorghum

Here is some grain sorghum coming up on a field south of town. We have planted a good bit of milo so far in Thomas County. With the presence of sugarcane aphids in 2014, this is an ongoing concern for us and I’ve had lots of questions about management. Below is a photo of white sugarcane aphids on a sorghum leaf last year. You can see the white cast skins in addition to yellow aphids on the stalk.

White Sugar Cane Aphid - Sorghum 005

Below is a close up photo of the sugarcane aphid (SCA) under a dissecting scope. The wingless forms are a uniform pale cream to yellow with black feet and black cornicles. (Cornicles are the small tubes present on the end of the abdomen).

Adult & Wingless White Sugarcane Aphid

Adult & Wingless White Sugarcane Aphid

Here is information from UGA Extension Entomologist Dr. David Buntin on managing sugarcane aphids:

1) Plant early – Although the aphid was not in Georgia at planting time last year, experience in the Delta region found that aphids did not usually infest sorghum until later in the season and early planting may avoid very large infestations.   In other words, late double-crop plantings are at greater risk of severe infestations.

2) Use an insecticide seed treatment – Trials in the Delta region last year found that insecticide seed treatment would limit seedling infestations for 30 – 40 days after planting.   All registered neonicotinoid insecticides are effective including thiamethoxam (Cruiser), clothianidin (NIpsIt Inside, Poncho) and imidacloprid (Gaucho others).

3) Scout early and often – Fields can quickly be inspected for the presence of aphids by looking are on the underside of leaves.  Once aphids are detected, scout at least once, preferably 2 times per week, because aphid numbers build very quickly.  Shinny lower leaves with honeydew are a clear sign of infestation.

4) Beneficial insects usually do not control infestations – SCA and their honeydew attract large number of beneficial insect predators such as lady beetles, syrphid fly larvae and lacewings. No aphid parasites were observed in Georgia last year but a parasitic wasp is present in TX and LA and could move eastward. No aphid fungal disease has been observed either.  Generally the rapid rate of increase in aphid populations overwhelms the beneficial insects and severe plant damage usually occurs.

5) Treat when aphids reach threshold levels – Several threshold levels are being used in the Delta region for 2015.  One conservative threshold is 25% infested leaves with 50+ aphids per leaf at whorl from preboot stage through dough stage.  In MS, the threshold at pre-boot and boot stages is 20% infested plants with large aphid colonies (100+) and localized areas of heavy honeydew present.  From bloom through dough stage the threshold is 30% infested plants.  I think either of these sets of thresholds will prevent serious yield losses and would suggest using whichever threshold is easiest for you to use.   Once threshold is reach do not delay application because infestations can very quickly go from the threshold level to 100% infested plants and hundreds of aphids per leaf.

6) Use an effective insecticide – PYRETHROID INSECTICIDES ARE NOT EFFECTIVE and may flare infestations by killing all the aphid predators. Regardless of the insecticide, rapidly expanding populations are difficult to control.  Foliar insecticide options for SCA are:

  • Transform WG (Dow AgroSciences) – Transform WG is not fully registered yet, but Georgia, Alabama and several other states haves a section 18 emergency exception approved for 2015 until Nov. 20, 2015. 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. The label allows for 2 applications per season and not more than 3 oz per acre per crop and has a 14 day PHI.
  • Sivanto (Bayer Crop Protection) – Sivanto has a full section 3 label and a supplemental 2ee label for lower rates on sorghum and other grain crops. The 2ee rates are 4 – 7 fl. oz per acre.  Sivanto was very effective in my trials at rates of 3, 5, and 7 fl. oz. per acre, so the 4 fl. oz. rate should be effective.  At the 4 oz rate it can be applied up to 7 times during the season but has a 21 day PHI.
  • 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 and 1 pint a 30 day harvest interval.  The 2 pint rate was 80-90% effective in my trial last year but could not be used after the boot stage due the 60 day PHI. The 1 pint rate was variable and only partly effective.  DO NOT USE CHLORPYRIFOS ON SWEET SORGHUM.
  • Dimethoate ( Dimethoate, Cygon) – Is labeled up to 1 pint per acre with a 28 day PHI.  Most dimethoate products cannot be used after head emergence. Dimethoate was variable in my trials and not recommended without further testing.

7) Good coverage is key to effective control – Use tips and GPA for maximum coverage especially lower in the canopy. A minimum of 10 gpa by ground and 5 gpa by air is highly recommended.

8)  Avoid pyrethroid insecticides for other sorghum pests – For sorghum midge try to avoid routine pyrethroid sprays for sorghum midge.  Instead scout and treat at 1 adult per panicle.   Chlorpyrifos (1 pint per are) for low to moderate infestations.   Early plantings often avoid serious midge infestations.  For fall armyworm in the whorl, the threshold is 50% infested whorls.  Use Belt, Prevathon or Lannate which are specific to caterpillars.  For headworms, corn earworms fall armyworm, sorghum webworm, the threshold is 1 worm per head and use Belt, Prevathon, Beseige or Lannate.

9) Check fields 2-3 weeks before harvest for infestations – A treatment may be needed if large numbers are in the head to prevent damage to combines.  Hybrids with taller stalks and more space between the grain and upper leaves may make harvest easier by reducing the amount of leaf material going through the combine.  Large infestation producing large amounts of honeydew and sooty mold may interfere with harvest desiccants.  Transform WG can be applied up to 14 days before harvest.

Summary – Most likely SCA will infest sorghum statewide in Georgia and occur much earlier than in 2014. SCA will be difficult to manage cost effectively.   Planning and scouting will be keys to successfully managing this new invasive pest and prevent serious losses to sorghum in Georgia in 2015.

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Grain Sorghum Planting

PlantingSorghum 002

We have an increase interest in planting grain sorghum (milo) in Thomas County this year. Here is some going into a field this week (above). Milo performs best on soils suitable for corn production and is more tolerant than corn to short term drought stress. We need to have 65 degree soil temperature for five consecutive days to play. Many of our plantations use the seed for wildlife. Most, if not all, of our fields planted in milo are non-irrigated, and this changes things in terms of plant population. Without water, we don’t want to plant too much with higher input need. Here are planting population recomendedations from UGA Grain Agronomist Dr. Dewey Lee:

Dryland Fields

  • 40-45K in very sandy soils
  • 50-60K in sandy loams and 60K in heavier soils.

Irrigated Fields

  • 60 to 75K in very sandy soils
  • 75 to 100K in sandy loam soils
  • 100K + in heavier soils
PlantingSorghum 006

Twin row grain sorghum

 

We’ve also looked at twin row. Dr. Lee says we can increase our population for twin row sorghum. It is not recommended to go any higher than 10%. Basically, we want to divide the single row population in half and plant that in both twin rows.

Example:  100,000 seeds per acre is roughly 7 seeds per row foot (6.89) in 36 inch rows.  Set the twin row planter (if its is set on 36″ row centers) to drop 3.5 seeds per row.

Below is a table from the Planting Guide for Row Crops in GA that can help when looking at plant population.

GrainSorghumPlantPopulation

 

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Grain Mold In Sorghum

HeadMold (2)

We’ve seen many different pest and environmental issues play out with during this season. A new insect pest has come in the state affecting sorghum (white sugarcane aphids). We confirmed charcoal rot which correlates with hot, dry weather especially post-flowering. Now we are seeing “grain mold” aka “head mold.” The symptoms are the pink, orange or white seeds on the heads infected by Fusarium and black seeds on heads infected by Curvularia, Alternaria or Helminthosporium.

UGA Extension Grain Pathologist Dr. Alfredo Martinez says, “Grain mold is caused by a complex of several fungi including Fusarium, Phoma, Curvularia and some others. High humidity/ rains which coincides with grain maturing can be the main effector of this disease. Nothing can be done at this point in terms of fungicides. Next season, planting date might be an option (trying not to coincide grain maturity with rains), genetic resistance.”

HeadMold

“Head blights and molds can be partially avoided by adjusting planting dates so that plants mature during a period without frequent rains. Some sorghum genotypes are more resistant than others but none are considered to be completely resistant. Although the fungi infect seeds, there is no clear evidence that seed-borne infections greatly influence the occurrence of these fungi on seeds in subsequent crops.” – Common and Important Disease of Grain Sorghum (Dave TeBeest, Terry Kirkpatrick and Rick Cartwright)

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Charcoal Rot In Sorghum

Sorghum-Cotton 013

We were looking at sorghum where damage form WSCA has been evident. But also seeing heads and stalks that are brown. The brown color on the outside and inside of the stalk turned out to be Charcoal Rot (Macrophomina phaseolina). Grain sorghum plants affected by this fungus won’t fill grain properly and may lodge in the latter part of the season. Infected stalks show an internal shredding at and above the ground line. When you split the stalk, you can see the small black dots from microsclerotia (below):

CharcoalRot 004

Below is information regarding control from UGA Extension Grain Pathologist Dr. Alfredo Martinez:

“Charcoal rot is particularly damaging under hot, dry weather specially post-flowering periods. Therefore maintaining soil moisture during these periods can help minimize the incidence of the disease. A balanced fertility program is beneficial, high N and low K should be avoided. Excessive plant populations should be also avoided. Growing drought tolerant sorghum can reduce losses.”

Microsclerotia under dissecting microscope

Microsclerotia under dissecting microscope

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