As Dr. Ames Herbert mentions in his July 25, 2016 blog, we are seeing a mixture of aphids in Virginia sorghum fields this season, but we should guide control decisions based on white sugarcane aphid (Melanaphis sacchari) numbers and product recommendations (I recommend re-reading Dr. Herbert’s advisory and viewing the aphid images that he attached back on July 25).  As Dr. Mike Brewer of Texas A&M mentioned to us earlier this week, corn leaf aphids (Rhopalosiphum maidis) are rarely worth concern–they are just good food for beneficial natural enemies!  The Tidewater AREC Entomology crew, Virginia Cooperative Extension Agents, and other Virginia Tech faculty and staff (e.g., Dr. Joseph Oakes) have been hunting for white sugarcane aphid.  We have confirmed it in Greensville (through ANR Agent Nikki Norton), Nottoway (through Jim Riddell, and ANR Agent Haley Norton), Southampton (via ANR Agent Livvy Preisser, and Mike Arrington at the Tidewater AREC), and Sussex (via Mike Arrington).  You may notice that last week I reported white sugarcane aphid in Dinwiddie–that has been removed for the time being, but ANR Agent Mike Parrish is following up on a lead as I am writing this report.  In some locations, we have found yellow sugarcane aphid (Sipha flava) along with the white sugarcane aphid.  I have indicated on the attached map where these have been reported, and also where we have scouted sorghum, but have not found any sugarcane aphids (to date).  Please keep up the scouting efforts in your sorghum fields!

Corn earworm (bollworm) moth captures in the black light traps are beginning to pick up in Suffolk, with a slight increase in Prince George Co., and low numbers still in Warsaw and Southampton Co.  Pheromone trap captures of corn earworm moths (the ones that go into our adult vial tests) really spiked this week in Suffolk; additionally, we caught nearly 100 moths in one night with 3 pheromone traps placed in a field just outside of Franklin in Southampton Co.  Brown marmorated stink bug catches have increased at Warsaw, with a few reported from Prince George Co., Southampton Co. and Suffolk.  Thanks to Livvy Preisser (Southampton Co. ANR Agent), Mary Beahm (Eastern Virginia AREC in Warsaw), Scott Reiter (Prince George ANR Agent), cooperating growers, and the Entomology crew at the Tidewater AREC in Suffolk for their reports this week.  The attached pdf contains more details on the black light trap captures this season.  BLT_28_Jul_2016

We have vial-tested 444 moths in 2016, with a mean of 38.5% surviving the 24-hour exposure to the pyrethroid insecticide cypermethrin at 5 micrograms.  These moths all were captured in Suffolk pheromone traps.  While we aren’t able to say where these moths originated (they are strong fliers and could have grown up locally or far away), survival rates this high serve as a reminder that  alternative (i.e., non-pyrethroid) chemistries may need consideration for corn earworm (bollworm) management, especially if heavy infestations develop.  We are working with Johnny Parker and some Southampton Co. growers to trap in an area reported to have high numbers of corn earworm moths near Franklin–results of the vial testing in that location will be available next week.

On July 20, 2016, Virginia Cooperative Extension Agent Mike Parrish submitted an insect sample collected from sorghum in Dinwiddie County, VA, that we confirmed as sugarcane aphid (Melanaphis sacchari).  Last year, this aphid was not found in Virginia until late September (in Isle of Wight, Prince George, Southampton, Suffolk, Surry, and Sussex Counties).  Infestations can stunt or even kill sorghum plants that are in the pre-head stage, and after heading the honeydew can interfere with mechanical harvest by plugging up combines.

Researchers at the Virginia Tech Tidewater and Southern Piedmont Agricultural Research and Extension Centers (Dr. Maria Balota’s crew, including Dr. Joseph Oakes; the Entomology crew; and Dr. Chris Teutsch) have been scouting sorghum for several weeks now—please see Figure 1 for our current findings.

With sugarcane aphids’ ability to spread and reproduce rapidly, sorghum scouting should begin immediately and be conducted at least weekly.  Start with sorghum field edges, especially checking the underside of lower leaves.  Leaves that are shiny with honeydew are a clue that aphids are present on that plant.  Once aphids are found, scouting should be conducted at shorter intervals to actively monitor population growth.  The economic thresholds for treatment of sugarcane aphid are provided in Table 1 and are based on North Carolina Cooperative Extension recommendations.

Table 1.  Economic thresholds for treatment of sugarcane aphid in sorghum. 

Thresholds in this table are from Sugarcane Aphid Now Present in NC-2016 https://entomology.ces.ncsu.edu/2016/07/sugarcane-aphid-now-present-in-nc-2016/ by Dr. Dominic Reisig, Associate Professor and Extension Specialist, NCSU. 

In Virginia, two insecticides are recommended for sugarcane aphid control in sorghum, Sivanto (which has a FIFRA Section 2(ee) Recommendation for a reduced rate, including Virginia), and Transform WG (which is registered under a Section 18 emergency exemption for Virginia) (Table 2).  Repeat applications should rotate chemistries.  Good coverage of the plant with insecticides is essential for effective control.  A minimum spray volume of 10 gpa is recommended.  Please be sure to carefully read and follow the label.

IMPORTANT NOTE: Insecticides with pyrethroid as the active ingredient are NOT recommended for the control of sugarcane aphid.  The efficacy of pyrethroid insecticides against the sugarcane aphid is low and they negatively impact the population of natural predators.  This often results in a rapid increase in sugarcane aphid populations immediately following application.

Table 2.  Insecticides recommended for the control of sugarcane aphid in sorghum. 

For more information on the sugarcane aphid, please contact your local extension agent.  Contact information can be found at http://www.ext.vt.edu/offices/index.html.

Black light trap captures of corn earworm moths have been very low this past week in Suffolk (2 total moths) and Warsaw (zero moths).  Captures in the Suffolk pheromone traps also dropped off this week.  However, field corn and sweet corn samples suggest that we may see higher numbers of corn earworm (aka bollworm) in other crops this season.

We have started catching brown marmorated stink bug (BMSB) in the black light traps in Suffolk (5 total in the past week) and in Warsaw (4 total this week).  I don’t recall ever catching that many in Suffolk before.  Our soybean scouts are beginning their statewide survey for BMSB (and kudzu bug) and we will keep you informed on these pest population levels throughout the season.

Our team has been scouting sorghum for sugarcane aphid in Isle of Wight, Southampton, Suffolk, and Sussex counties, but we have not detected them yet this season.  They have been found in North Carolina, and with their ability to spread and reproduce rapidly, we recommend starting to scout sorghum for this pest.

There are several aphid species that can be found in sorghum, but sugarcane aphids are cream yellow in color with two, short dark cornicles (“tailpipes”) on their hind end.  Start weekly scouting at the field edges, especially checking the underside of lower leaves.  Once insects are found, scouting should be conducted at shorter intervals to actively monitor population growth.  Dr. Dominic Reisig, Extension Entomologist at North Carolina State University, provides these thresholds for sugarcane aphid.

When pesticides are needed, we recommend Sivanto (which has a FIFRA Section 2(ee) Recommendation for a reduced rate of 4-7 oz/A, including Virginia), or Transform WG (which is registered under a Section 18 emergency exemption for Virginia at a rate of 0.75-1.5 oz/A). Good coverage is essential.  Please refer to (and follow!) the labels for more details, including the maximum amount that can be applied annually, pre-harvest intervals, etc.  Repeat applications, when needed, should rotate active ingredients.   Pyrethroids are not recommended.

Our black light trap at the Tidewater AREC in Suffolk is just now beginning to catch low numbers of corn earworm moths–we had 4 total this past week.  The Eastern Virginia AREC in Warsaw is not catching them yet.

We have caught some corn earworm moths in our pheromone traps in Suffolk (pheromone traps often out-perform black light traps early in the season for this species).  We have conducted vial tests on 160 moths since late June, and have seen quite high levels of survival for the start of the season (an overall average of 38.6% of moths surviving the vial test).  As in the past, we are exposing these moths for 24 hours to vials treated with a standard pyrethroid insecticide, cypermethrin, at 5 micrograms per vial.  For comparison, in 2015 we had about 21% survival at this time of the season, with  a peak survival rate of 51% occurring in late August.  We will continue to provide updates on this issue.

Corn earworm moths in the cypermethrin vial test

We’re not catching many moths in our pheromone traps this time of year, but we are still conducting the adult vial tests on those that we do catch.  We are currently seeing many more dead moths after 24 hours of exposure to the pyrethroid insecticide, cypermethrin, at the 5 microgram per vial rate.  Less than 20% as you can see in the line graph below.  For the season, the average survival rate is 33.4% (bar chart, below).