White Sugarcane Aphid: A Potentially Devastating Pest of Grain Sorghum
In 2013 a new aphid pest called the White Sugarcane Aphid, Melanaphis sacchari, was detected in grain sorghum in 38 counties in Texas, Louisiana, Oklahoma, and one county in Mississippi. This species has apparently been around for years but the hosts switch to grain sorghum appears to be new. This pest can be devastating to grain sorghum if populations reach high densities. In fact, some fields have seen 100% yield loss. Another major factor is this aphid is difficult to control with currently labeled products.
On Tuesday (6/23/14) I was randomly checking a few grain sorghum fields in the Delta, and found this aphid in 3 fields in Washington County. At this time number are very low, but they are present. Like any other aphids, damage is caused by high numbers. Simply having the pest is no reason to be alarmed but finding it in Mississippi now does reinforce the importance of scouting. Currently Louisiana is reporting some severe problems where aphid populations were high and treatments were not applied to control this pest in a timely manner.
Identification: There are several aphids that may be found in grain sorghum in Mississippi that rarely pose a problem. This one can be identified by its light color with dark tips on the cornicles (tail pipes) and dark colored feet. It is very common in MS to see corn leaf aphids in grain sorghum, sometimes even in high numbers, but rarely do they infest whole fields or cause economic damage. One of the differences is they will be green in color. Also, greenbugs are found at times. This aphid can be serious because of the toxin it secrets when feeding but rarely causes a problem for MS farmers. Also, greenbugs will be light green in color with a thin black line running vertically down the back. If you see yellow or light colored aphids in a grain sorghum field please let us know.
Damage: Like most aphids, the white sugarcane aphid causes damage by feeding with piercing sucking mouthparts and secretion of honey dew. When numbers get really high, especially on stressed grain sorghum, the overall general vigor of the plant is reduced and can severely stunt and even kill plants. Excessive honey dew accumulation can result in sooty mold that blocks photosynthesis as well. It is not thought at this time that the aphid has a toxin associated with it like greenbugs. Because this aphid can persists all the way until harvest it has been reported to cause problems with combine efficiency due to excessive foliage covered with sticky honey dew going through the combine also. Generally the aphid begins to show up pre-boot stage.
Threshold: We are going to currently work off of LSU AgCenter’s recommendation until more information is gathered on this pest. Treat when 30% of the plants have at least 1 aphid with the average running 100-250 per leaf. Be more aggressive on water deficit stress fields.
Control: This aphid is difficult to control. In fact, MS has just received an emergency exemption for the use of Transform WG by Dow AgroScience should we need it. Foliar applications of Transform WG can be applied by ground or air at a use rate of 0.75-1.5 oz product per acre. A maximum of 2 applications per year with a 7 day pre harvest interval and minimum of 14 days between applications. Other products such as Dimethoate and Lorsban have activity but it is inconsistent and marginal.
Word of Caution: Disruptive sprays such as pyrethroids for midges may flare aphids, so scout closely if you make a midge spray.
For further information see the following links:
Sugarcane Aphid: A New Pest of Sorghum
