Russian Thistle (Tumbleweed)
The Sugarcane Aphid (Melanaphis sacchari) is rapidly becoming a significant insect pest in Sorghum (Milo) and related crops across the south. Originating as an identified pest of sugarcane and sorghum in tropical and subtropical regions around the world, it was first discovered in Hawaii in 1896 and identified in the continental US in sugarcane in 1977. Populations didn’t seem to build in the temperate climates of the southern US at first, declining with each winter.
However, all that has changed recently. Sugarcane Aphids appear to have essentially changed their primary host from sugarcane to plants of the genus Sorghum (grain sorghum, forage sorghums, sorghum x sudan crosses, and johnsongrass) in the US. Small populations have been identified in corn, but do not seem to thrive. Since 2013, southern states have ramped up scouting, research, and control efforts of this building economic pest.
Identification of Sugarcane Aphid
The sugarcane aphid differs from other aphid-type insects in sorghum. Greenbugs, for example, have a distinctive dark green stripe down the back, unlike sugarcane aphids. Yellow sugarcane aphids have a significantly greater amount of pubescence (hairs) on the body. Corn leaf aphids have darker legs and heads than the sugarcane aphid. It sometimes takes a magnifying glass to differentiate these traits. Sugarcane aphids have a characteristic dark, paired cornicles (tubes that project from the abdomen, usually in single pairs. They are used by the aphid to emit secretions or pheromones). Their tarsi (or feet) are dark when under high magnification. These dark features contrast distinctively from the lighter body color of the insect.
Symptoms and Consequences of Sugarcane Aphids
Sugarcane aphids reproduce at very high rates once they set up on the leaves of the host. Consequently, they can produce copious amounts of ‘honeydew’ across the leaf surface; impacting photosynthetic processes and nutrient transport in the plant. The honeydew wrecks havoc with combines, and yield losses occur due to reduced pollination and even severe lodging.
The shiny honeydew across the leaf surface is the most easily observed symptom of damage. With time, the leaves become colonized by a sooty mold, skins of larvae, and other secondary diseases. Yield losses of up to 100% have been reportedin high infestations prior to heading left untreated.
Management of Sugarcane Aphids
The first step to effectively managing for sugarcane aphids is field scouting. Scouting protocols are being developed and fine tuned as this insect becomes more prevalent in the US. Always consult your local or regional entomologist or Certified Crop Advisor for your specific area’s best management practices.
Most of the commonly used insecticides on the market labeled for seed treatment against aphids will provide up to 6 weeks of control. Additionally, there are several commercial hybrids available which have been shown to tolerate sugarcane aphids. Once the crop is emerged, scouting should commence; preferably on a weekly basis. Once found, scouting interval should be accelerated. Look for the ‘honeydew’ excretion on the lower leaves. Each region and/or state may vary in what is considered an economic threshold for in-season foliar insecticide treatment. A general rule of thumb is that when 25% of the plants have reached 50 aphids/leaf, treatment is recommended. Again, this is only a guide, and your state recommendations should be consulted.
Early detection and timely treatment are very important. If the grain has reached physiological maturity (‘black layer’) and honeydew presence is heavy with established colonies in the head of the plant, treatment at this stage will only prevent harvest problems.
Always follow label instructions and only use materials that are labeled for aphid control.
Read more about it:
- Texas A&M - Agrilife - The Sugarcane Aphid (pdf)
- AgFacts.com - Kentucky Sorghum - Sugarcane Aphid - Identification and Management
- The Sorghum Checkoff - Steps to Manage Sugarcane Aphid
- The Sorghum Checkoff - Seed Selection - Sugarcane Aphid Tolerant Seeds
- Southeast Farm Press - 9 tips to control sugarcane aphids in sorghum - 2015
- My Fields: Pest Profile - Sugarcane Aphid
- Kansas State University - Sorghum - Sugarcane Aphid