September 5, 2018
Sugarcane aphids have been a minor pest in sugarcane for many years. However, in 2013 the aphid was found feeding on sorghum in the Beaumont, Texas, area and later that year found in northern Texas, southern Oklahoma, Louisiana and Mississippi. By 2017, they had been found in sorghum fields in over 17 southern states. Also in 2017, a low population was identified in a southeastern Nebraska county.1
Two different sugarcane aphids feed on sorghum. The yellow sugarcane aphid has been feeding for years at less than economic levels while white sugarcane aphids are new to grain and forage sorghums, and their prolific birthrate can quickly cause extensive damage.
All sugarcane aphids are female and give birth to live young. The young develop into adults in about five days and live about four weeks. They feed by sucking out juices (sap) from the leaves. Injected toxins have not been found in plants that were fed upon by sugarcane aphids. Infestations on pre-boot sorghum can cause significant yield loss and lessen the development of forage sorghums. The sticky honeydew which contains plant sugars and water can cause harvest problems by coating threshing machinery, reducing the ability to separate grain from chaff. Frequent washing may be needed to remove the sticky coating.
Sugarcane aphids have a smooth body, light-colored head, light-colored legs, dark feet, and dark colored, short cornicles or tail pipes with no shading at the base.2 When looking for sugarcane aphids, start scouting when the plants are in the four-to-five-leaf stage and continue scouting once a week, observing for honeydew and aphids on the bottom of leaves above the honeydew. If plant death doesn’t occur, the sugarcane aphid usually moves up the plant and into the sorghum panicle. Honeydew secreted on seeds can affect harvest efficiency. Economic thresholds suggest that 50 to 125 sugarcane aphids/leaves are high enough for an insecticide treatment.
Syrphid fly larva, lady beetles, parasitic wasps, and green and brown lacewings feed on aphids and can help suppress sugarcane aphids. However, with the ability to increase populations rapidly, beneficial insects can have a hard time controlling the aphid. Additionally, insecticides can kill beneficial insects.
Research and agronomic field observations are demonstrating that some sorghum products show less leaf damage and host fewer aphid colonies than others. Sorghum products may be listed as susceptible, moderately resistant or resistant; however, resistant products can host aphids and some damage can occur.
An insecticide application with activity on aphids requires good coverage of the entire canopy, including the lower leaves. This can be a problem in forage sorghum; therefore, early harvest of forage sorghums might be needed. Within four to seven days after an insecticide application, fields should be reexamined and a reapplication should be applied if necessary. Be sure to read all pesticide labels.
Sources:
1Wright, R. 2017. Sugarcane aphid in Nebraska. CropWatch. University of Nebraska. https://cropwatch.unl.edu
2Zukoff, S. and Michaud, J.P. 2017. Sugarcane aphid. Department of Entomology. Kansas State University. https://entomology.k-state.edu/
Bowling, R.D., Brewer, M.J., Kerns, D.L., Gordy, J., Seiter, N., Elliott, N.E., Buntin, G.D., Way, M.O., Royer, T.A., Biles, S., and Maxson, E. 2016. Sugarcane Aphid (Hemiptera: Aphididae): A new pest on sorghum in North America. Journal of Integrated Pest Management 7(1): 12; 1-13. Entomological Society of America. Oxford University Press.