As many of you know, the sugarcane aphid has moved north faster than last year. We now have confirmed reports of SCA in three southern counties of Kansas. In addition, SCA is present as far north as Kentucky and Virginia. In these northern sites SCA populations for the most part are low but have approached threshold levels in Virginia. It is likely that at least low populations will be discovered in many counties within the Sorghum Belt in the coming weeks.
It is important to note that just because a few SCA are present in a field does not mean an insecticide application is or will be justified. Those who planted hybrids with some tolerance to SCA can expect the populations to build more slowly. In addition, beneficials in many areas are reported to be in high numbers, this will also help keep SCA populations in check. Although SCA was present in South Texas this year, only a portion of the fields reached threshold levels.
Something we have clearly learned the last two years is that once SCA is present in an area, scouting of fields becomes critical. Scouting should occur at least once a week once SCA has been discovered in a region, and in fields where SCA has already been detected, scouting should take place at least twice a week. Insecticide application should begin as soon as the SCA population is at threshold levels. Research has shown yields can be drastically reduced if insecticide application is delayed for several days once threshold levels are reached. States and regions vary slightly in their recommended threshold levels, but in general insecticide application is justified when 50 aphids are present on 25 percent of the plants. Consult your state or regional extension service for specific threshold information. We are entering a critical time in the Sorghum Belt, and SCA can potentially reach threshold levels very quickly. Diligence in scouting is an absolute must!
There are two products that should be considered if an insecticide application is warranted. These are Sivanto prime from Bayer, and Transform WG from Dow AgroSciences. Both are effective, but good coverage is critical. Most entomologists recommend 4 – 5 ounces of Sivanto Prime and 1 – 1.5 ounces of Transform WG. The lower rates are usually recommended to control SCA at or close to threshold levels. If SCA populations are way above threshold levels, then the higher rates may be justified.
If other insects such as midge or headworms are present with SCA, avoid using pyrethroids for their control. Pyrethroids can lower beneficial populations significantly and cause a rapid increase in SCA populations. In the South Plains region of Texas the ‘yellow’ sugarcane aphid is showing up in a few fields, often in the same fields with sugarcane aphid. Care should be taken in distinguishing between these two aphids.
Although sweet sorghum is a minor U.S. crop, sugarcane aphids can greatly impact yield. Sivanto prime has received a section 18 specific exemption label in Mississippi, Arkansas, Tennessee and North Carolina for use on sweet sorghum in 2016.
For more information on combating SCA please visit the Sorghum Checkoff website. Several of the state extension services also have excellent SCA management information, and links to many of these sites can be found on the Sorghum Checkoff website.
Please do not hesitate to contact me by email or on my cell phone number listed below.
Have a good weekend!
Brent Bean, PhD
Director of Agronomy
United Sorghum Checkoff Program
4201 N. Interstate 27 | Lubbock, TX 79403
806.687.8727 (office) | 806.674.0006 (cell)