Sugarcane Aphid (Kansas Sorghum)

Scouting time

Plants are vulnerable to infestation by SCA at any growth stage, but Kansas sorghum is most at risk from boot stage onward. The ability of sugarcane aphid to overwinter on Johnsongrass and re-sprouting sorghum stubble represents challenges to the management of this pest in more southerly regions. In 2016, the SCA overwintered as asexual females on Johnsongrass rhizomes just north of Lubbock, Texas. No sexual forms or egglaying females have been observed; asexual females will survive only where some plant tissue remains green throughout the winter. Therefore, SCA cannot overwinter in Kansas and infestations are initiated annually by winged aphids carried from southern latitudes; the timing, extent and exact regions affected are difficult to predict and largely a function of wind direction during periods of aphid flight in Texas and Oklahoma. Infestations begin when swarms of winged aphids settle in a field and begin to establish colonies. Their daughters can mature in less than a week, lack wings, and have a much higher reproductive rate than their winged mothers. Established colonies of wingless aphids quickly become large and crowded, which causes winged forms to develop, until the final generation is exclusively winged once again. Thus, the trend will be for Kansas to receive SCA only after infestations to the south mature and produce winged migrants. Growers are advised to plant sorghum as early as agronomically feasible to maximize plant growth and maturity before aphids arrive. In 2016, large flights of winged sugarcane aphid arrived in Kansas somewhat earlier than in 2015 and a larger area of the state was affected, despite cold wet spring weather in the south that delayed the aphids initially. Given suitable weather for the aphids, and wind conditions to disperse them, the potential exists for even earlier infestations in the summer of 2017, which would be more damaging and more costly to control since it would extend the period of crop vulnerability.

Sampling method

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

  • If honeydew is present, look for SCA on the underside of a leaf above the honeydew.

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

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

  • Check at least 4 locations per field for a total 4 locations per field for a total of 60-80 plants.  

If no SCA are present, or only a few wingless/winged aphids are on upper leaves, repeat this sampling method once a week thereafter.

If SCA are found on lower or mid-canopy leaves, begin twice-a-week scouting. Use the same sampling method, but be sure to include % plants with honeydew. Estimate the % of infested plants with large amounts of SCA honeydew (shiny, sticky substance on leaf surface) to help time foliar insecticides for SCA control on sorghum (refer to Thresholds section below).  

 

Submit a sample

Thresholds

Growth Stage

Threshold

Pre-Boot

20% plants infested with localized area of heavy honeydew and established aphid colonies

Boot

20% plants infested with localized area of heavy honeydew and established aphid colonies

Soft dough

30% plants infested with localized area of heavy honeydew and established aphid colonies

Dough

30% plants infested with localized area of heavy honeydew and established aphid colonies

Black Layer

Heavy honeydew and established aphid colonies in head *only treat to prevent harvest problems **observe preharvest intervals

 

Chemical control

 

Sugar Cane Aphid Management Options

Insecticide

 Rate

Flupyradifurone (Sivanto)

 0.052 - 0.091 lb. ai/acre (4.0 - 7.0 fl oz/acre)

Sulfoxaflor (Transform)

 0.375 - 0.75 oz a.i./acre (0.75 - 1.5 oz / acre)

 

Field trials show good efficacy of the above materials against the sugarcane aphid; both have the ability to penetrate leaves through translaminar movement and kill aphids feeding on the undersides. Maximum efficacy will be achieved by application in a large volume of water, preferably 20 gallons per acre or GPA (minimum 10 GPA) by ground or 5 GPA from the air. Laboratory trials indicate that sulfoxaflor (Transform) is relatively safe for important aphid predators such as lady beetles and lacewings and thus can be considered IPM-compatible. This is true to a lesser extent for flupyradifurone (Sivanto), but various trials have indicated a much longer period of residual activity for this material. Both insecticides have annual application limits and growers are advised to rotate them if follow-up applications are required. Note also that preharvest intervals will be a factor to consider when treating late-season infestations, so applicators should read labels carefully and keep a log of all treatments for each field. Because sulfoxaflor and flupyradifurone are absorbed by leaves and eventually metabolized by the plant, reinfestation can occur if large numbers of winged aphids continue to settle in the field. When inspecting fields for treatment efficacy, note whether any live aphids are winged or wingless, as the former may indicate continued immigration rather than control failure. DO NOT attempt to control sugarcane aphid with contact insecticides that have broad-spectrum activity; these include all pyrethroid and organophosphate materials and combinations thereof. Replicated field trials indicate these materials are not effective, harm beneficial species, and often result in higher aphid numbers than unsprayed conrol plots. Sorghum headworm infestations are often present when SCA is observed in a field, since this pest migrates using the same weather events. When choosing an insecticide to control headworms, use products that are less harmful to natural enemies such as Prevathon or Blackhawk, as these have proven compatible with Transform and Sivanto and less selective materials risk flaring the aphids. Insecticidal seed treatments are useful for protecting seedlings from sugarcane aphid infestation in southern regions where the pest is active year-round, but are not recommended for this purpose in Kansas where infestation during seedling stages is unlikely, unless sorghum is planted after June 1.

 

Non-chemical controls

 Although the majority of commercial hybrids are susceptible to SCA damage, many have shown varying levels of SCAresistance in field performance tests and almost all seed suppliers report having one or more varieties that have performed well despite SCA infestation. Resistant hybrids will slow sugarcane aphid population growth and reduce the chances an infestation will surpass the economic threshold, thus facilitating the evolution of natural biological control by our native complex of aphid predators and parasitoids. Farmers should ask their seed suppliers about regionally adapted hybrids that have yielded well under high SCA pressure.

Content authors

Disclaimers

This content is replicated from a Kansas State University Agricultural Experiment Station and Cooperative Extension Service Publication, MF743, dated January 2015. This information may not apply to pest management for states other than Kansas.