Category Archives: Grain Sorghum

2017 Sugarcane Aphid Management In Grain Sorghum

Sugarcane Aphids

Here is the newest management prodecdures for sugarcane aphids in grain sorghum from UGA Extension Entomologist Dr. David Buntin:

1) Plant early – Because the aphid migrates northward in the spring, early plantings may avoid may avoid very large infestations.   Late planted double-crop plantings are at greater risk of severe infestations.   

2) Plant a tolerant hybrid/variety – Some hybrids have been shown to have some partial tolerance to the aphid.   This table from the Sorghum checkoff program and ratings for the Georgia Statewide variety trial lists grain sorghum hybrids with some degree of tolerance to SCA.   In my own trials the most tolerant grain types were in alphabetical order Alta AG1201, Dekalb DKS 3707 and DKS 4807, Pioneer 86P20, Sorghum Partners 73B12 and Warner W-7051 (tall, late variety).

http://www.sorghumcheckoff.com/farmer-resources/grain-production/hybrid-selection

http://www.swvt.uga.edu/2016/sysr16/AP103-8-sr-resist.pdf

Sugarcane aphids populate under grain sorghum

3) Use an insecticide seed treatment – My trials 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 (Poncho, NIpsIt Inside) and imidacloprid (Gaucho, others).   Most grain sorghum seed was treated with one of these seed treatments in 2017.

4) 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. 

5) 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.  A parasitic wasp is present in and caused infested aphids to turn a dark blue-gray color.  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. 

6) Treat when aphids reach threshold levels – The current threshold is 50 or more aphids per leaf on 25% pf plants preboot stage through dough stage.  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.  

7) 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 in Georgia are:

  • 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 2ee 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 re-instated last year but sorghum is not on the full federal label. But Transform WG has an approved Section 18 emergency exception for use on sorghum in Georgia in 2017 but the label has not been issued yet. The label will allow for 2 applications per season and not more than 3 oz per acre per crop and has a 14 day PHI. Transform cannot be used during bloom to protect pollinators. 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).   Chlopyrifos 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 about 10-14 days. 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.  

8) 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.

9) 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.   If pyrethroids are used they can be tank mixed with Sivanto (Do not use Transform during bloom). 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.

10) 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.  

11) Silage/forage sorghum control. No work was done specifically on SCA control in silage/forage sorghum.   So the same recommendations for grain sorghum also apply to silage and forage sorghum.   Both Sivanto prime and Transform can be used on silage and forage type sorghums.   Grazing / hay interval is 7 days for both products.  Chlorpyrifos at 2 pints per acre has a 60 day grazing forage, hay interval so is usually not an option for forage and hay sorghum.  In forage/hay types, the later cutting were damaged last year.  Spray coverage is difficult when plants get tall.  If aphids are present but below threshold consider a spray application as late as possible before the crop gets too tall.

12) Sweet sorghum. Sivanto prime, Transform and chlorpyrifos cannot be used on sweet sorghum. There currently are no effective treatment options for sweet sorghum. A section 18 request for use of Sivanto prime on sweet sorghum has been submitted to Us-EPA but the request is still pending.

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Zest Approved For Use In Inzen Grain Sorghum

Zest™ 75WDG (nicosulfuron) has received Georgia approval for use on Inzen™ herbicide-tolerant grain sorghum varieties. Grain sorghum growers who use this technology will now be able to get better POST control of Texas panicum and other grasses. Nicosulfuron is the same active ingredient in Accent, which is registered for use on field corn.

A couple of reminders from UGA Extension Weed Scientist Dr. Eric Prostko:

1) Zest can only be used on Inzen herbicide-tolerant grain sorghum varieties. The use of Zest on conventional sorghum varieties will result in crop death! Inzen grain sorghum varieties are not GMO’s.

2) The current formulation of Zest is a WDG.  I have been testing a liquid formulation so rates would be different in any slides you have previously seen from me.

3) UGA has limited variety performance data (i.e. none).  As far as I know, the only company with Inzen varieties is Advanta/Alta (http://altaseeds.advantaus.com).  Pioneer will likely have some varieties in 2018 or 2019?  Thus, I would suggest Georgia sorghum growers proceed with caution until an adapted variety is identified.  I have not been overly impressed with the varieties that I have been testing up until now.

4) I would still recommend the use of Concep treated seed + a PRE application of Dual or Warrant in this system.  Atrazine should be tank-mixed with Zest to improve the control of broadleaf weeds.

5) A copy of the complete Zest label can be accessed from the following location:
http://www.cdms.net/ldat/ldDEH000.pdf

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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.
GrainSorghum-005

Sooty mold grows on the top of the leaf on honeydew excreted from aphids

GrainSorghum-014

Aphids present in the heads

GrainSorghum-015

“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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Grain Sorghum Dough Stage: Terminating Insect Sprays?

SorghumFlowering,Dough 004Our grain sorghum is past flowering and moving through the soft dough stage. Grain fill is rapid with about half the total dry weight of the grain accumulating during this time. We may see nutrient stress and leaf loss since mobile nutrients are transolocated from the lower to the upper leaves. Between soft dough and hard dough stage, irrigation increases yield by improving grain fill test weight. We don’t see much if any response from water once grain reaches hard dough stage.

Sugarcane Aphids

Once we get to hard dough stage, color, we no longer have to worry about sugarcane aphids. Also, keep in mind should try to avoid using pyrethroids for other insects and aphids. We need to check fields 2 – 3 weeks before harvest. We had issues with honeydew from SCA messing up the combines. 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.

The best way to tell hard dough is by pinching the kernel. The hard dough color is still similar to soft dough. MSU Grain Scientist Dr. Erick Larson says, “Grain Sorghum kernels change color and accumulate hard starch much the same as corn kernels mature. Kernels will mature first at the top of the head, so focus scouting on the kernels at the base of the heads. If you can quickly see a considerable amount of green kernels, rather than the burnt orange / brown color of mature kernels, you need to give the crop some more time to fully mature.”

Like corn, grain sorghum also forms ‘black layer’ from crown of the kernel to the base. Here is a photo by Dr. Erick Larson showing the progression from hard dough to ‘black layer.’

Sorghum Kernel Maturity - Dr. Erick Larson

Sorghum Kernel Maturity from hard dough (left) to physiological maturity or ‘black layer’ (right) – Dr. Erick Larson

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.

Sorghum Midge

The susceptible damage period for midge is bloom. Treatment after bloom is too late. The adults are hard to find. We either put a plastic Ziploc bag over the head. The midge will fly to the top of the bag. You can also use a white paper plate, but the midge can fly off. If it’s wings are wet in the morning, it may not fly as well. In either case, we only treat when an average of 1 adult per head is observed after 25 – 30% of heads are blooming. We can treat again 5 – 10 days later if midge is present. The eggs and larvae cannot be killed inside the glumes with insecticide.

NOTE: For midge, try not to use a prethroid because it may flare sugarcane aphids. If SCA are present and pyrethroid is used, we would have to tank mix with Transform or Sivanto.

Sorghum Midge - Photo by Ben Thrash

Sorghum Midge – Photo by Ben Thrash

SorghumFlowering,Dough 005

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Corn-Leaf Aphids

Corn-LeafAphid (7)

Grain sorghum is now booting and we applied initial insecticide sugarcane aphids (SCA) last week. This week we are seeing another aphid – corn-leaf aphid (CLA) in sorghum. Unlike the SCA, this aphid was seeing on the top of the leaves and near the whorl of the plant.

UGA Extension Entomologist Dr. David Buntin says (CLA) normally occur in the whorl leaves but can be found lower down on the plant too. They are not a significant pest unless they build to large numbers, but they do not cause the feeding damage that SCA do. Usually rain and beneficial insects will control them. Our SCA insecticides should kill them.

How do we know exactly when to treat for corn-leaf aphids if they become a problem? Dr. Buntin says, we do not have a definite threshold for corn leaf aphid, so just treat when aphids are numerous and leaves begin to look damaged (or chlorotic, yellowing).  If only in 2 spots I would wait and see if they get worse.

Corn-Leaf Aphids

Corn-Leaf Aphids

Sugarcane Aphids

Sugarcane Aphids

 

 

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2016 Sugarcane Aphids

SugarcaneAphids 001

On Wednesday, Stephanie Holliefield in Brooks County confirmed sugarcane aphids in grain sorghum. I got calls from two growers in Thomas County today reporting SCA also. In both fields reported, no honeydew is present. Last season, we observed that once honeydew was present on the top of leaves, populations spread fast. Here is a picture of an adult and immatures under a leaf in a field today.

Sugarcane Aphids

Sugarcane Aphids

Threshold

At pre-boot, we really don’t treat until 50-100 aphids are found in 20% of the field. Last season, we found ourselves pulling the trigger later than we should have. Each situation will be different. It can be difficult to asses. We need to remember that if aphids are present in one corner of the field, they may be present in another corner, and in another spot.

Treatment

Here is updated information on our Section 18 in GA from UGA Entomologist Dr. David Buntin:

We have 2 products available, Sivanto Prime and Transform.  Things we should know about application and use of these products include;

  1.  Sivanto Prime – can be applied at 4-7 oz/acre.  The 4 oz rate will do a good job and last for at least 21 days.  Sivanto Prime last a little longer than Transform.  This product is full labeled on sorghum with a supplemental label for the 4-7 oz rates.
  2. Transform WG – has been approved again by a Section 18 for Georgia, at the 0.75 to 1.5 oz rate/acre.  However, one big change from last year is Transform CANNOT be used during flowering.  Also, we need to remember that there are only 2 applications per season.  Dr. David Buntin, UGA Entomologist recommends at least the 1 oz rate and the 1.5 oz rate is even more effective and will provide approximately 14 days of control.

Both of these products can be used on grain, silage,  forage type sorghums, and sorghum/sudangrasses.  But please remember that these products can not be used on sweet sorghum.

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Grain Sorghum Varieties Resistant/Tolerant To SCA

We had a great meeting last week with UGA Extension Grain Entomologist Dr. David Buntin. He came to address insect issues in corn and also update us on sugarcane aphids. I worked with many growers on the aphid last season, and our information was very helpful to Dr. Buntin as well. 2015 was our first full year with the aphid. Here are some notes I put together from his meeting which includes some varieties that show resistance/tolerance to SCA:

The varieties below were researched by UGA Extension Entomologist Dr. David Buntin and researchers from LSU or Texas for tolerance/resistance to sugarcane aphids. Remember, no variety is completely resistant to sugarcane aphids. For us in South Georgia, planting with a seed treatment is still advised. Grain sorghum should also be scouted for sugarcane aphids within two weeks of emergence.

Biology

The good news is sugarcane aphids do not overwinter in Georgia. But we have to look for them within 2 weeks of planting, especially if we don’t have a seed treatment. All the females are born pregnant, and they have a very high reproduction rate. They are also not known to transmit any viruses.

Varieties reported as having tolerance/resistance to SCA

Georgia State Variety Trial (Dr. David Buntin, UGA)

UGASCAVarieties

Dr. David Buntin: Upon evaluation of all grain, silage and forage sorghum entries in the GA state variety trial for SCA resistance/tolerance, DKS 3707 was the most resistance. However, none of the entries were highly resistant. There was very little resistance/tolerance in the silage and forage types.

United States Sorghum Board Results (Researcher at LSU or in Texas)

SorghumCommissionSCAVarieties

Seed Treatments

SorghumInsecticideSeedTreatments

Insecticide Summary for SCA

Foliar Insecticides

  • Threshold: Treat when 50 or more aphids are found on 25 percent of the crop.
  • Sivanto 200SL @ 4 – 10 oz, (21 d PHI); 2ee for 4-7oz.
  • Transform @ 1.0 – 1.5 oz, (14 d PHI); IF Section 18 approved for 2016.
  • Chlorpyrifos @2 pt (60 day PHI), ? Efficacy, 7-10 days.
  • Dimethoate, Lannate, malathion & chlorpyrifos @ 1pt are not effective.
  • Pyrethroids are not effective, because they flare aphids.

SCA Program

  • Add neonicotinoid seed treatment if available.
  • Start with Sivanto, follow with Transform (if available) to rotate chemistries.
  • Transform for harvest infestations (14 d PHI).
  • 2015 research showed adjuvants have little benefit.

Coverage

  • Ground: 10+ GPA
  • Aerial: 5 GPA

No chemigation for Sivanto or Transform.

No labeled insecticides for sweet sorghum!

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