Sugarcane Aphid Management for Sorghum

There are several aphid species that feed on sorghum; however, sugarcane aphids (SCA) look different and can cause more damage.

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Figure 1

Figure 1. Sugarcane aphid. Photo courtesy of Dr. J.S. Armstrong, USDA-ARS, Stillwater, OK.

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Generally, SCA has a white to light-yellow colored body, and has dark, paired tailpipe-like structures called cornicles at the rear. Legs are light colored but their tarsi (feet) are dark (Figure 1). Other aphids that attack sorghum look distinctly different. Greenbugs have a distinctive darker green stripe down the back which is absent in SCA. Yellow sugarcane aphid can be differentiated from SCA by the presence of numerous hairs on the entire body (can be seen with a magnifying glass). The legs, head, and feet of corn leaf aphids are dark.

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Feeding and Damage. SCA suck sap from sorghum plant tissue and deposit a sticky honeydew. The aphids feed primarily on the underside of leaves and the stem then move to the upper leaves, before moving to the grain sorghum head. Leaves infested with aphids turn yellow to red or brown on both sides. Early infestation with heavy populations of SCA can kill young sorghum plants. Later infestations can prevent grain from developing.

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Honeydew secreted by SCA can hamper plant transpiration and may support the growth of a black, sooty mold fungus. During harvest, honeydew coated plants may stick to the inner parts of combines, causing clogs and preventing efficient movement of chaff through the combine. When honeydew prevents separation of grain from stalks and leaves, significant grain can be lost on the ground.

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Management. Scout fields early for the presence of SCA to reduce potential yield loss. If SCA are found on lower or mid-canopy leaves, consider scouting twice-a-week as populations can build-up rapidly. SCA economic thresholds warranting an insecticide treatment are influenced by the current sorghum growth stage (Table 1). The generally accepted economic threshold for soft dough and dough sorghum growth stages is to treat if 30% of the plants are infested with localized area of heavy honeydew and established aphid colonies.1 Treating too soon may increase the potential for additional treatments later, as SCA populations can rebound, due to immigration events from other fields.

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Table 1: Sugarcane aphid threshold by sorghum growth stage.
Sorghum Growth StageThreshold
Pre-boot20% plants infested with localized area of heavy honeydew and established aphid colonies.
Soft Dough30% plants infested with localized area of heavy honeydew and established aphid colonies.
Black LayerHeavy honeydew and established aphid colonies in head. *Only treat to prevent harvest problems. **Observe pre-harvest intervals.
Source: Modified from McCornack, B., Zukoff, S., Michaud, J.P., and Whitworth J. 2015. Scouting sugarcane aphids. Kansas State Research and Extension.
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For more information, contact your agronomist. You can also access Scouting Sugarcane Aphids, from Kansas State University, which contains field scouting protocol and photos of SCA sorghum leaf damage and different aphid species. The resource can be accessed at https://www.myfields.info/sites/default/files/page/ScoutCard%20KSU%20reduced%20v3.pdf.

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Kansas State University recommends Sivanto 200™ SL or Transform® WG as insecticide options for SCA infestations because they are not toxic to beneficial insects which may help suppress SCA populations.2,3 Complete crop coverage is important to achieve effective control.

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If considering treating for economic thresholds of headworms (corn earworms) and SCA, realize that Sivanto 200™ SL or Transform® WG are not effective in controlling headworms.2 Pyrethroid insecticides are commonly used for headworm control and are also effective against SCA, but will kill beneficial insects. After a pyrethroid insecticide application, SCA populations later may rebound due to the initial lack of beneficial insects.

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If headworms are present at economic levels, talk to your agronomist first and then consider an insecticide treatment. Fields should continue to be scouted regularly for SCA and beneficial insect populations.