By Sarah Zukoff, J.P. Michaud and Brian McCornack, Extension Entomologists, and Wendy Johnson, Entomology Extension Associate
The sugarcane aphid (SCA) has now been reported in four counties in Kansas: Sumner, Reno, Kiowa, and Haskell. Grain sorghum producers in Kansas should begin scouting their fields on a routine basis.
What can we expect this season? It’s impossible to know for sure at this time. Infestations in Kansas in 2017 and 2018 were sporadic, and most issues were late season (Figure 2). But in 2016, sugarcane aphids were a significant problem on grain sorghum in Kansas, Texas, Oklahoma, and most Southern states, and fields were justifiably sprayed to protect yields.
Early detection is key to the management of this pest, but treatments should be based on established thresholds. One heavily infested plant does not equal a yield loss. Applying insecticides too soon can result in repeated applications, which occurred during the 2015 season. See scouting and treatment recommendations below.
Figure 1. Current status of the SCA. The map indicates only the counties in which the SCA has been found, and does not indicate how many or how few aphids were found in that county. Source: https://www.myfields.info/pests/sugarcane-aphid
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.
Issues arising from SCA in Kansas are likely to become increasingly uncommon with each passing year. However, there is a good amount of late-planted sorghum this year that is going to be more at risk going into late summer. Producers would be wise to scout these late-planted fields.
- 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.
Figure 2. The distribution of SCA in 2018.
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 (Table 1).
For ongoing current information on SCA in Kansas, check out the myFields web site often in the coming weeks and months: https://www.myfields.info/pests/sugarcane-aphid
It would be helpful if producers would report findings of SCA in their fields on the myFields web site as soon as the insects are found. Reports of findings are used in developing the maps seen in Figures 1 and 2.
The reports used to develop each map are, in part, those submitted through the myFields web site from account holders that also have special permissions as “Verified Samplers.” Only reports submitted by these verified samplers get mapped so that we can account for data quality. However, we do encourage any account holder to report their observations on the SCA. Web site administrators can see these reports and can contact the submitter for a confirmation, a great way to get an early detection in new areas. Web site visitors will need to: 1) sign up for an account, 2) log in, 3) to get access to the 'Scout a Field' feature to make reports. The Scout a Field tool is easy, you just map the observation location and select yes or no for SCA presence.
Here is the sign up page: https://www.myfields.info/user/register
Also, if sorghum producers are interested in receiving alerts, which are triggered by new reports submitted by verified samplers, they just need to sign up for a free myFields.info account using the link above.
Signing up for an account automatically signs them up for SCA alerts, but they can also opt out of them in their user preferences.
The alerts include a statewide email notice when SCA is first detected in the state, and then are localized by county as SCA moves into the state. The notices will also contain latest recommendations and contact info for local Extension experts.