Sugarcane Aphid: Biology and Management in Sorghum
By Sandy Endicott, Senior Agronomy Manager, and Marlin E. Rice, Ph.D., Senior Research Manager
The sugarcane aphid has become a severe pest of North American sorghum production over the last few years.
Sugarcane aphids were first documented in the United States in 1977 but did not become a pest of sorghum until 2013, after which they spread rapidly across sorghum-producing areas of the U.S. and Mexico.
Aphid populations can grow exponentially due to their live-birth reproductive behavior.
Sugarcane aphids feed on the sap of plant and can cause severe yield losses, with instances of 100% loss reported.
Sorghum hybrids vary in their ability to tolerate sugarcane aphid feeding. Research is underway at Pioneer to better understand differences in hybrid tolerance.
Best management practices include removal of volunteer sorghum plants, the use of tolerant sorghum hybrids, high quality seed treatments, good grass weed management, scouting, and the use of insecticides if needed.
The sugarcane aphid, Melanaphis sacchari, also known as the white sugarcane aphid, has become one of the most important insect pests of sorghum in the southern United States and Mexico.
Sugarcane aphid has long been a pest of sugarcane and sorghum outside of North America, including parts of Africa, Asia, Australia, and South America. It was first discovered in the United States in Florida in 1977. In the following years it spread slowly through the Gulf Coast states where it was a relatively minor and sporadic pest of sugarcane, making its way to Louisiana in 1999.
In 2013, it was found feeding on sorghum for the first time in North America. Over the next two years, it spread rapidly across most of the sorghum-producing areas of Mexico and the U.S. By 2015, it was present in Puerto Rico and in every sorghum-producing state in the South from Texas to Florida, reaching north from Kansas to North Carolina.
Sugarcane aphid is capable of causing significant damage and reductions to yield in sorghum. Its rapid spread has quickly made it a major pest of sorghum production in North America. This article will discuss the life cycle of the sugarcane aphid, crop damage potential, field scouting, and management practices.
Identification and Life Cycle of Sugarcane Aphid
Sugarcane aphids may either be wingless or winged. Wingless aphids are pale yellow to white in color with dark cornicles (tailpipes) located at their rear end. Winged aphids are darker yellow in color.
Sugarcane aphids can reproduce without mating. Most sugarcane aphids are female and give birth to 1 to 3 live, pregnant offspring daily. Nymphs pass through 4 stages and can reach reproductive adult stage in 5 days, resulting in exponential growth rates under ideal conditions. The life span of the female is around 28 days with a range of 10-37 days.
Winged adults generally develop as a result of stress conditions. As population density increases and food quality declines, a proportion will develop wings as adults, which enables them to fly to other nearby fields or to be carried by wind, potentially across long distances.
Mouthparts are piercing/sucking, which enables them to feed on the sap of plant, ultimately impacting plant growth. Generally, they reside on the underside of the sorghum leaves before they move to other areas of the plant. As is typical with aphids, they leave behind “honeydew,” a sticky liquid excrement. The honeydew serves as a food source for saphrophytic fungi, such as sooty mold, which turn the plant leaves black in color, thus reducing the plant’s photosynthetic capability.
Spread of Sugarcane Aphid in the U.S. and Mexico
The sugarcane aphid was present for many years in the U.S. before becoming a pest of sorghum, having been first discovered in Florida in 1977 on sugarcane. It spread very slowly as a pest of sugarcane, taking over 20 years before it was first found in sugarcane in Louisiana.
In 2013, sugarcane aphid was discovered feeding on sorghum, with instances of economically significant damage reported in Louisiana and Texas. This change in behavior may have been due to a host shift in the existing North American populations or the introduction of a new biotype from outside the U.S. Sugarcane aphid is a pest on sorghum in other countries including Argentina, South Africa and India.
Following its change to sorghum as a host species, spread of the sugarcane aphid has been rapid in North America. In 2013, the pest was found in Texas, Oklahoma, Mississippi, and Louisiana. In 2014, sugarcane aphid was reported in northeastern Mexico and more areas in the U.S. By the end of the 2015 season, it was found throughout the sorghum-growing regions of both countries.
Sugarcane Aphid Feeding on Sorghum
Overwinter populations feeding on volunteer sorghum plants can be a significant source of spring infestation. The population can start to build during the early seedling stages if the crop is not protected by an effective seed treatment. As populations increase, sugarcane aphids remove nutrients from the plant that would have been used for plant growth and, ultimately, yield. Plants become stunted, and leaves may become necrotic. Severe infestations of the aphid in sorghum produce large quantities of honeydew, which allows sooty mold to blacken the leaves and can cause harvest problems.
The plant may have uneven and/or poor head development and emergence, poor grain set, potentially increased stalk lodging, and harvest issues. Yield loss in sorghum can be severe with cases of 100% loss reported.
Sugarcane aphids need living host plants to persist. In addition to sorghum, they can feed on shattercane (Sorghum bicolor), Johnsongrass (Sorghum halapense), as well as volunteer sorghum plants. Aphids also overwinter on these same plant species. In Mexico, the sugarcane aphid has been found colonizing barnyard grass (Echinochloa crus-galli).
Scouting for Sugarcane Aphid
Scouting should begin a few weeks after sorghum emergence. Scout at least once per week until aphids are found, then increase frequency to 2 field visits per week. In 4 or 5 areas within the field, inspect the underside of an upper leaf and a lower leaf for aphid presence. When populations begin to build, honeydew will be present on the top side of leaves. Take notes on the number of aphids present in each area. Several southern universities recommend an action threshold of 50-125 or more aphids per leaf on 25% or more of the plants.
Sugarcane Aphid Management
Insecticides for Sugarcane Aphid Several insecticides are labeled for use on sorghum in the U.S. Insecticide trials conducted by Texas A&M University have shown that Sivanto™ 200 SL insecticide (flupyradifurone) (Bayer CropScience) has provided significant reductions in aphid populations up to 2 weeks after application. Transform™ insecticide (sulfoxaflor) (Dow AgroSciences) was previously used in some states but its registration was canceled by the EPA in November 2015. Existing inventories of sulfoxaflor may not be sold and distributed to end-users; however, some states are pursuing an emergency exemption (Section 18) from the EPA.
When applying insecticides by ground equipment, University of Arkansas recommends that insecticides be applied in 10 gallons of water per acre. Growers should consult their Cooperative Extension Service for a current list of registered chemicals in their respective states and updated results on the efficacy of sugarcane aphid insecticides. Read and follow all label directions before applying an insecticide.
Understanding Differences in Hybrid Tolerance Sorghum hybrids vary in their ability to tolerate sugarcane aphid feeding. Significant work is underway with third party collaborators and at Pioneer to understand sorghum hybrid tolerance to sugarcane aphids. Pioneer® hybrid 83P17 and 83P56 are known to possess at least some degree of aphid tolerance. However, tolerance is not the same as immunity and tolerant hybrids must be scouted and sprayed if populations reach the action threshold. Contact your Pioneer field team for the latest information on hybrid results.
Best Management Practices Best management practices include removal of volunteer sorghum plants, the use of tolerant sorghum hybrids, high quality seed treatments, good grass weed management, scouting, and the use of insecticides if needed. Here is a brief checklist:
1. Control volunteer sorghum to remove source of early infestation.
2. Plant a sorghum hybrid with aphid tolerance.
3. Use an effective insecticide seed treatment.
4. Plant early.
5. Scout fields early and weekly.
6. Apply an approved insecticide when the action threshold is reached. Avoid pyrethroid insecticides, which are harmful to beneficial insecticides and may cause aphid populations to rebound rapidly.
7. Consider using a harvest aid when sorghum nears maturity (25% grain moisture in the lower portion of the head) to kill and dry down the crop.
Thanks to Dr. Robert Bowling, Texas A&M AgriLife, for providing information and insect close-up photograph.
Field photos of sugarcane aphids on plant leaves, tolerant vs non tolerant plants, and tractor are courtesy of Pioneer Mexico Agronomy team.