Management of Sugarcane Aphid on Sorghum

Summary

A new exotic invasive aphid, Melanaphis sacchari known as the sugarcane aphid, has damaged sorghum grown for grain and forage since August 2014. The insect reappeared in spring 2015 and 2016 and damaged sorghum throughout Georgia. A series of management and insecticide trials were conducted to provide sorghum producers information on the efficacy of insecticides for sugarcane aphid control. This research was used to obtain a Section 18 emergency use for Transform WG (sulfoxaflor) insecticide which was widely used in 2016 to control this invasive pest.

Situation

The sugarcane aphid was found severely damaging sorghum in Georgia in August 2014 and rapidly spread throughout central and southern Georgia over the next two months with about 90% of sorghum fields being infested. In 2015 and 2016 the aphid occurred in late April in southern Georgia and spread throughout the state. Virtually all sorghum acres were infested and needed to treated with an insecticide 1 to 4 times during the season. The aphid feeds on the leaves and stems for grain and forage sorghum and can reach numbers exceeding 1000 aphids per leaf. The feeding causes leaf injury and yield loss. Aphids also produce large quantities of honeydew (sugary substance) from feeding that is deposited onto leaves. Yield losses usually ranged from 20 to 50%, but fields not sprayed in time there usually was a complete loss of production.

Response

County extension agents were informed of management options for sugarcane aphid on sorghum and asked to report infestations when they occurred in their area. Field trials in Georgia were conducted to evaluate the efficacy of currently registered and selected new insecticides for control of sugarcane aphid. These trials and insecticide trials showed that two new insecticides Transform 50WG (sulfoxaflor) and Sivanto prime (flupyradifurone) were the most effective products. Registered insecticides such as the pyrethroid insecticides were not effective and chlorpyrifos (Lorsban other names) and dimethoate (Cygon) provided only marginal control. Transform a product of Dow AgroSciences, is not labeled on sorghum. A section 18 emergency use exemption for sulfoxaflor (Transform WG) was prepared for use on sorghum in Georgia over the last three seasons. The exemptions were approved by the Georgia Department of Agriculture and sent it forward to US-EPA where it was approved in each year. A series of other trials also were conducted to examine sugarcane aphid treatment thresholds, effective growth stages for control, sorghum plant resistance, and various insecticide trials. An integrated approach to managing sugarcane aphid based on insecticide seed treatment, tolerant varieties, planting time, and sampling with action thresholds was develop base on research in 2015 and deployed in 2016. Based on results in 2016 the management approach will be refined to improve control. Most of the estimated 35,000 acres of sorghum in Georgia in 2016 were treated at least once with Transform WG or Sivanto to control the sugarcane aphid and some fields were treated 2 to 3 times. Estimated cost of control for each application was about $10 per acre for insecticide plus application costs. No effective insecticides are legally available for use on sweet sorghum and many sweet sorghum fields were a complete loss. A section 18 emergency use exemption for sulfoxaflor (Transform WG) and an emergency crisis exception for Sivanto prime for sweet sorghum also are planned for 2017.

Impact

Sugarcane aphid is a destructive and devastating new invasive pest of sorghum. The coordinated response of the UGA Extension Service county agents and specialists quickly notified growers of the potential damage to sorghum and informed them of various management options. The rapid response of the Georgia Department of Agriculture and US-EPA in approving an emergency use exemption for the insecticide sulfoxaflor (Transform WG) provided a valuable tool to prevent serious loses to sorghum producers in Georgia. The estimated cost of insecticides for sugarcane aphid control in 2015 and 2016 exceeded $1 million each year, but this control saved sorghum grower's several millions of $ in losses that would have occurred without effective control measures.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2016
• Geographic Scope: Multi-State/Regional
• County: Spalding
• Program Areas:
  • Agriculture & Natural Resources