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Pest Alert – Sugarcane Aphid

sugarcane aphidLate summer 2014 – We can all remember the new invasive pest that occurred last year, the sugarcane aphid (SCA).  SCA infestations occurred in practically every sorghum field and in may cases resulted in production and economic losses.  Please be aware that the first documented appearance on sorghum was identified this past week in Brooks County.  I visited the field on Friday and received notice from Dr. David Buntin that this was the first confirmed finding of SCA on sorghum.  It is important that we 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.

When infestations occur the population may be several hundred aphids per plant.

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This population level can be detrimental to a sorghum field, as this fluid sucking insect can cause death of leaves and sometimes the entire plant.

 

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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.  Dr. David Buntin, UGA grain crop entomologist, recommends the following management practices:

1. Plant early – Early plantings may help avoid large infestations but the field I visited this past week was actually planted in March.  But, late double crop plantings are at a greater risk of severe infestations.

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

3.  Scout early and often – You can quickly scout for SCA by looking at the underside of sorghum leaves.  Once SCA has been detected, scout at least once per week.  Also, be aware of shiny lower leaves on the sorghum plant.  This appearance is indicative of deposits of honey dew and a clear sign of infestation.

4.  Beneficial insects usually do not control infestations – A large number of beneficial insects (lady beetles, syrphid fly larvae, lacewings) are attracted to SCA and their honeydew.  However, the rapid rate of increase in aphid populations generally overwhelms the beneficial insects and severe plant damage occurs.  Also, no aphid fungal disease has been observed.

5.  Treat when aphids reach threshold levels – There are several threshold levels beings used in different regions.

One conservative threshold is 25% infested leaves with 50+ aphids per leaf at whorl from preboot stage through dough stage.

Another threshold being utilized involves 20% infested plants at pre-boot and boot stages with large aphid colonies (100+) and localized areas of heavy honeydew present.  But, from bloom through dough stage the threshold is 30% infested plants.

Dr. Buntin suggest using the threshold that is easiest for you to utilize and follow and that both methods will prevent serious yield losses.  But, please remember that once threshold levels are reached it is imperative that we do not delay insecticide applications.  Infestations of SCA can very quickly go from the threshold level to 100% infested plants and hundreds of aphids per leaf.

6.  Use an effective insecticidePyrethroid insecticides are not effective and may flare infestations by killing all the aphid predators.  The following are foliar insecticide options for SCA:

Transform WG – Transform WG is not yet fully registered, but Georgia has a section 18 emergency exception approved for 2015 until Nov. 20, 2015.  Dr. Buntin’s 2015 trials demonstrated that rates of 1.0 – 1.5 oz/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/acre/crop.  Please not the 14 day PHI for this product.

Sivanto – 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/acre.  The 4 oz. rate should be effective and at the 4 oz rate it can be applied up to 7 times during the season but has a 21 day PHI.

Chlopyrifos – Lorsban is labeled at 1 to 2 pints/acre.  The 2 pint rate has a 60 day harvest interval 1 pint has a 30 day harvest interval.  The 2 pint rate cannot be used after the boot stage due to the 60 day PHI.  The 1 pint rate may be variably effective against SCA.  DO NOT USE CHLORPYRIFOS ON SWEET SORGHUM.

7.  Good coverage is key to effective control – A minimum of 10 gallons per acre by ground and 5 gallons per acre by air.

8.  Avoid pyrethroid insecticides for other sorghum pests – Try to avoid routine pyrethroid sprays for sorghum midge.  Instead scout and treat at 1 adult per panicle.  Use Chlorpyrifos at 1 pint per acre for low to moderate midge infestations.  Early plantings often avoid serious midge infestations.  The threshold for fall armyworm in the whorl is 50% infested whorls.  You can 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 you can 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.  Large infestations producing large amounts of honeydew and sooty mold may interfere with harvest desiccants.  Transform WG can be applied up to 14 days before harvest.

Please call if you have any additional questions.