Sugarcane Aphid (Texas Sorghum)

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Scouting time

Sugarcane aphids can infest grain and forage sorghum from the pre-boot stage through flowering, grain fill and harvest.  Foliar applied insecticides are effective but must be applied when infestations are low. Use the sampling methods and thresholds below to determine the need for insecticide treatment.

Sampling method

Sampling Methods: Detecting Infestations

Once a week, walk at least 25 feet into the field and examine plants along 50 feet of row.

·         If honeydew is present, look for sugarcane aphids on the underside of a leaf above the honeydew.

·         Inspect the underside of leaves from the upper and lower canopy from 15 to 20 plants per location.

·         Sample each side of the field as well as sites near Johnsongrass and tall mutant plants.

·         Check at least four locations per field for a total of 60 to 80 plants.

·         If no sugarcane aphids are present, or only a few wingless or winged aphids are on upper leaves, then continue once-a-week scouting.

If sugarcane aphids are found on lower or mid-canopy leaves, begin twice-a-week scouting. Use one of the two sampling plans and thresholds below to determine if aphid densities exceed the treatment threshold and if an insecticide treatment is warranted.  

Sampling Methods and Thresholds. 

   Sampling methods and thresholds are shown for South andCentral Texas and the Texas High Plains

South and Central Texas

           Examine the underside of one completely green leaf from the lower canopy and the upper most leaf (or leaf below the flag leaf at boot to heading). Estimate and record the number of SCA per leaf.

·         Examine two leaves from each of five randomly selected plants for a total of 10 leaves per location.

·         Repeat at four locations for a total of 40 leaves per field.

·         Calculate the average number of aphids per leaf for the field (total aphids counted/total leaves inspected).

   See the Threshold discussion below to decide when an insecticide treatment is warranted.

Texas High Plains:

Once sugarcane aphids are found in a field, use the fol­lowing protocol to assess the infestation.

·         Walk 25 feet into the field and examine the under­side of green leaves from the lower canopy to the uppermost leaf for aphids. Watch for honeydew that indicates aphids on the leaf above.

·         Record the number of plants infested with any aphids. Also, record the number of uninfested plants.

·         Examine a minimum of 10 plants at four locations across the field. Calculate the percentage of plants infested (divide the number of plants with any aphids by the total number of plants examined and multiply by 100).

·         If grain sorghum is in the boot or flower­ing-milk stage, estimate the number of aphids per leaf. At these stages, it is critical to treat before aphid numbers exceed 100 per leaf.

    See Threshold Table below

 

Thresholds

South and Central Texas

For sorghum in the pre-boot through bloom stage, apply an insecticide for SCA when the field average is 50-125 sugarcane aphids per leaf.  Consider treatment at 50 aphids per leaf if you are limited to once-a- week scouting or if the weather is warm and dry.  Apply the insecticide within four days and evaluate control in three days.  Continue to monitor infestations until harvest to determine if a second insecticide application is needed. Infestations during grain fill can reduce harvest efficiency due to honeydew contamination and can result in stalk lodging.

Texas High Plains:

Use the table below to determine the treatment threshold for different growth stages.

Growth Stage

Threshold

Pre-Boot

  20% plants infested with sugarcane aphids.

Boot

  20% plants infested with 50 aphids per leaf.

Flowering-Milk

  30% of plants infested with 50 aphids per leaf

Soft dough

  30% plants infested, localized areas with heavy honeydew, and established aphid      colonies.

Dough

  30% plants infested, localized areas with heavy honeydew, and established aphid colonies.

Black Layer

  Heavy honeydew and established aphid colonies, treatment only for preventing harvest problems, and observe preharvest intervals

 

Control Options after the first insecticide application:

Check fields for control after 4 to 7 days. If control was poor and aphid colonies of 50 or more per leaf are still present, repeat application. If there was good control of the aphid, continue scouting fields twice a week for re-infestation or a rapid increase in aphid numbers.

                For whorl to early dough growth stages, use the Threshold Table above for any sec­ond applications. From dough to late dough growth stages, a sec­ond application may be required when aphids are re-establishing, 40 to 50 percent of the total leaf area has aphid damage, and predator popu­lations are not suppressing aphid populations.  At black layer growth stage through harvest, an application may be required to prevent harvest problems.

 

 

 

Chemical control

Sivanto Prime is labeled for grain and forage sorghum to control sugarcane aphid. Transform WG insecticide has a Section 18 Emergency Exemption label for control of sugarcane aphid in grain and forage sorghum in Texas. This label for Transform WG expires November 30, 2017. Information below is for educational purposes. Read and fol­low label directions.

Insecticides for SCA in grain and forage sorghum

 

Sivanto Prime

Transform WG

Use rate for sugarcane aphid

4–7 oz / acre

0.75–1.5 oz/acre

Minimum interval between applications

7 days

14 days

Minimum application volume

10 GPA by ground

2 GPA by air (5 recommended)

5–10 GPA by ground.

3 GPA by air (5 recommended)

Pre-harvest interval

14 days for grain or straw or stover,

7 days for grazing, forage, fodder or hay harvest

14 days for grain or straw harvest or within 7 days of grazing, forage, fodder or hay harvest.

Restricted entry

4 hours

24 hours

Restrictions

Sivanto is toxic to bees in laboratory studies via oral exposure, however, not toxic to bees through contact exposure, and field studies have shown no effects on honeybee colony development.

Do not apply 3 days or less pre-bloom until after seed set. Transform is highly toxic to bees exposed through contact during spraying and while droplets are still wet. Transform may be toxic to bees exposed to treated foliage for up to 3 hours following application.

 

 

Controlling Other Sorghum Pests When Sugarcane Aphids Are Present.

Sivanto Prime and Transform are not labeled for midge, headworm or stinkbug control in sorghum.  Other insecticides used to control these pests may kill beneficial insects that help suppress sugarcane aphid.  Chlorpyrifos (Lorsban, Nufos) and the pyrethroid insecticides (Asana, Karate, Warrior, Lambda-Cy, Mustang Max, Delcare, Besiege and others) are broad-spectrum and kill beneficial insects.  If these insecticides are used, scout the field frequently to determine if SCA infestations increase.  Prevathon is less toxic to natural enemies and is labeled for control of headworms.  Blackhawk is also less toxic to many natural enemies and is labeled for control of headworms and midge.

Non-chemical controls

Planting Hybrids with Some Resistance or Tolerance to Sugarcane Aphid.

Some sorghum hybrids have some genetic resistance or tolerance to sugarcane aphids.  Although these hybrids are not immune to SCA, populations on these hybrids increase more slowly than on susceptible hybrids.  Hybrids with some resistance or tolerance must be scouted and an insecticide treatment will be needed if infestations exceed the treatment threshold.  Contact your seed dealer for adapted hybrids with some resistance or tolerance to SCA.

Insecticide Seed Treatments. Insecticide applied to the seed can control sugarcane aphids for 4-6 weeks after planting. These seed treatments include Cruiser, Nipsit, Poncho and Gaucho.

For Updates on Managing Sugarcane Aphid from Texas A&M AgriLife Extension:,

Sign up to receive:    Sugarcane Aphid News In Texas:  http://txscan.blogspot.com/

and go on-line to the Better Yield in the Field:  http://betteryield.agrilife.org/

 

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Disclaimers

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Texas A&M AgriLife Extension Service is implied.