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).
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.