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eturn to table of contents SUGARCANE APHID: BIOLOGY & MANAGEMENT IN SORGHUM by Sandy Endicott, Senior Agronomy Manager, and Marlin E. Rice, Ph.D., Senior Research Manager SUMMARY • 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 plants 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 DuPont Pioneer to better understand differences in hybrid tolerance. • Best management practices include removing volunteer sorghum plants, using tolerant sorghum hybrids, utilizing high quality seed treatments, maintaining good grass weed management, scouting, and using insecticides, if needed. 160

eturn to table of contents INTRODUCTION 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 U.S. 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. Mouthparts are piercing/sucking, which enables them to feed on the sap of plants, 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. Figure 2. Infested sorghum leaf with all stages of aphids present. 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 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. 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 on 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. Figure 1. Sugarcane aphids: A winged adult, non-winged adults, and nymph. Sugarcane aphids can reproduce without mating. Most sugarcane aphids are female and give birth to one to three live, pregnant offspring daily. Nymphs pass through four stages and can reach reproductive adult stage in five days, resulting in exponential growth rates under ideal conditions. The life span of the female is around 28 days with a range of 10 to 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 nearby fields or to be carried by wind, potentially across long distances. 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. 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. 161

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