The sugarcane aphid has been reported in three counties in Kansas (Harper, Sedgwick, and Sumner). Only Sedgwick County is shown in Figure 1. The other two counties will be added and an updated map will be available at the myFields website. Grain sorghum producers in Kansas should be scouting their fields on a routine basis.
Figure 1. Current status of the SCA (two counties are missing from this map at time of this publication). 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
Corn leaf aphids have been in corn and sorghum in easily detected numbers since the whorl stage of corn (mid-June) and are still relatively abundant in whorl stage sorghum on August 11 (Figure 2-left panel). Corn leaf aphids rarely occur in densities to cause a negative impact on many plants. However, they do provide a good source of food for beneficials. This beneficial buildup may aid greatly in controlling sugarcane aphids just starting to colonize sorghum in southcentral Kansas (Figure 2-right panel). Hopefully, with healthy populations of beneficials, these sugarcane aphids will be kept under treatment thresholds. As south winds continue, however, expect sugarcane aphids to continue to migrate into southern counties and then north throughout the state. Thus, monitoring and early detection are important.
Figure 2. LEFT: corn leaf aphids on sorghum, RIGHT: sugarcane aphids in sorghum. Photos by K-State Research and Extension.
Scouting time for SCA
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.
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. It is best practice to scout late-planted fields, as these are more susceptible to yield loss and aphids and this a bigger window for aphids to build to damaging levels later in the season.
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 (Table 1).
Table 1. SCA 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 pre-harvest intervals |
You can download a free sugarcane aphid scouting guide here: https://www.myfields.info/sites/default/files/page/ScoutCard%20KSU%20v05312017.pdf
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
Please email R. Max Dunlap (xammax@ksu.edu) with counties to add to the map!!
Brian McCornack, Entomologist
mccornac@ksu.edu
Jeff Whitworth, Entomologist
jwhitwor@ksu.edu
Anthony Zukoff, Extension Associate, Southwest Research-Extension Center
anzukoff@ksu.edu
R. Max Dunlap, myFields.info Coordinator
xammax@ksu.edu
J.P. Michaud, Entomologist, Agricultural Research Center-Hays
jpmi@ksu.edu
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