Sugarcane aphid sorghum update

Brent Bean, Director of Agronomy, United Sorghum Checkoff Program, forwarded the following information on sugarcane aphid (SCA):

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, an insecticide application is justified when 50 aphids per leaf 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 Crisis Exemption label in Mississippi, Arkansas, Tennessee and North Carolina for use on sweet sorghum in 2016.

NOTE from Ames Herbert, VT: Note that the ‘yellow’ sugar cane aphid mentioned above is a different species than SCA. Yellow sugarcane aphids are covered with small hairs and the two cornicles (pair of small upright backward-pointing tubes found on the top side of the last segment of the bodies) are small and pale (see attached image).  The SCA is also called ‘white’ sugarcane aphid. It does not have hairs on the body and the two cornicles are dark (see attached image).  Yellow sugarcane aphid is a known pest in Virginia of forage grasses like orchardgrass. Like Texas, we are also finding yellow sugar cane aphid mixed with SCA, and in a few fields also mixed with corn leaf aphid, another known pest of corn and sorghum. Corn leaf aphid is easy to distinguish from the other sorghum aphid species as they have a dark head and legs, a dark green body color, and dark cornicles (see attached image).

This sorghum aphid problem is new for us so we are having to make some ‘educated guesses’ about what constitutes a threat, and what the best control options might be. For now, we suggest that SCA numbers should guide control decisions, that is, abide by SCA thresholds—and stick with the products that are recommended for SCA. Avoid the use of pyrethroids since they will not be effective against SCA, and could flare secondary pests by disrupting natural enemy populations.  Natural enemies including tiny aphid parasitic wasps and a variety of lady beetles can be very effective in helping reduce aphid and other pest populations, so we need to conserve them whenever possible.

white sugarcane aphid yellow sugarcane aphid grantham osu corn leaf aphid

Nodulation deficiency in peanut

Indeed, 2016 was not a good year for effective nodulation and early peanut root growth in the Virginia and Carolina region. The growing season started relatively cool and wet. Under this condition peanut developed only a few roots with a reduced number of nodules. These plants were smaller and less green than “normal” plants in particular when planted in crop residue because this maintained soil cooler and wetter. Figure 1 is an example and shows three peanut plants planted on May 9 and picture was taken on June 25. Two plants at the left are smaller, yellower, and with less root growth and number of nodules. These were planted in sorghum residue. The plant at the right is bigger, greener, and has more roots and nodules, but was planted in cultivated and sandier land.

Smaller and yellower two plants at the left are due to poorer nodulation than for plant at the right, even though planted at the same time.

Smaller and yellower two plants at the left are due to poorer nodulation than for plant at the right, even though planted at the same time.

What can be done to prevent poor nodulation, then? One very important thing is to inoculate at planting. But even then, in cool and wet soil roots grow slow for fast inoculation and Bradyrhizobium bacteria may die in absence of oxygen if the soil is too wet. Ammonium sulfate can be used up to 150 pounds of nitrogen per acre, which is about 714 pounds of ammonium sulfate per acre. Usually at beginning flowering poor nodulation will show up in yellow and smaller plants, and right then inorganic nitrogen needs to be applied. The sooner, the better.

It is, therefore, important to scout not just for disease and insects but also for the number and size of the nodules in the first 45 days after planting. To establish a threshold of nodules a farmer should look for during this time, my program has found that after two weeks after planting an average number of 5 big nodules on the main root is to be expected; at 30 days, 70 nodules of any size on the main and lateral roots; and about 130 at 45 days after planting.

Corn earworm and brown marmorated stink bug update for July 21, 2016

Black light trap captures of corn earworm (bollworm) moths remain low, averaging zero to 2 moths per night in area traps.  The brown marmorated stink bug averaged zero to 2.3 per night.  Thanks to Livvy Preisser and Neil Clark (Southampton), Mary Beahm (Warsaw), Mike Parrish and Ray Clarke (Dinwiddie), Scott Reiter (Prince George), and the Tidewater AREC Entomology crew for their reports this week. Please click on the attached pdf at the end of this sentence for the weekly data tables for these two insects. BLT_21_Jul_2016

Our pyrethroid resistance monitoring of corn earworm (bollworm) in the adult vial tests indicate an average survival rate of 38.6% for a 24-hour exposure to 5 micrograms of cypermethrin.  Weekly percent survival has ranged from approximately 36-45%.AVT_21_Jul

Sugarcane Aphid Found in Dinwiddie County, Virginia

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.

SCA_20_Jul

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. 

Growth Stage Threshold
Pre-boot 20% infested plants with localized area of honeydew and established aphid colonies
Boot 20% infested plants with localized area of honeydew and established aphid colonies
Flowering-milk 30% infested plants with localized area of honeydew and established aphid colonies
Soft dough 30% infested plants with localized area of honeydew and established aphid colonies
Dough 30% infested plants with localized area of honeydew and established aphid colonies
Black layer Heavy honeydew and established aphid colonies in head (treat to avoid problems at harvest)

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. 

Insecticide Active Ingredient Application Rate Max Annual Application Rate Pre-Harvest Interval
oz/A oz/A/year days
Sivanto flupyradifurone 4-7 28 7 (forage) AND 21 (grain)
Transform WG sulfoxaflor 0.75-1.5 3.0 7 (forage) AND 14 (grain)

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.

 

 

Corn earworm and brown marmorated stink bug update for July 14, 2016

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.

Sugarcane aphid update for July 14, 2016

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.

Link

Initial results from the 2016 Virginia state wheat and barley tests are available in excel format at:

www.grains.cses.vt.edu

The full document and summary is coming soon.

 

Corn earworm update for July 7, 2016

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

Corn earworm moths in the cypermethrin vial test

LATE BLIGHT IN VIRGINIA

Late blight was found in Accomack County, VA yesterday on potato. Growers on the Eastern Shore and other areas of the Commonwealth should scout their fields and take preventative measures. Please let us know if you have any questions. For more information on this potentially devastating disease of potato and tomato visit: https://pubs.ext.vt.edu/ANR/ANR-6/ANR-6_pdf.pdf

IMG_4227

Do we need to bump up our soybean seeding rates?

It’s hard to believe, but June is here and we need to start thinking about increasing our soybean seeding rates.  I’ve been recommending only 100 to 115 thousand seeds per acre for full-season production, enough to give you 70 to 80 thousand plants – yes, that’s all you need to maximize yield.

But as the season gets shorter, yields will start falling with delays in planting date.  On average, we lose about 1/2 bushel/acre per every day we delay planting after the middle of June.  The graph below shows the results of last year’s 4-state early wheat harvest/soybean planting double-crop study.  Note that yield does not decline very much during the first week or two of June, but rapidly drops off afterwards.

2015 DC Soy Yield across Plant DateThe main reason for this yield decline is that the crop struggles to develop enough leaf area to capture 90-95% of the sunlight by early pod development, due to the shorter growing season.  We can alleviate some of this by narrowing rows and increasing seeding rate.

I usually suggest that farmers plant enough seed to result in a final plant population of 180,000 plants/acre for double-crop soybean.  That means planting 200,000 to 220,000 seed/acre.  Yes that is a lot of seed, but my research shows that yields (and profit) continue to increase up to this seeding rate, especially when planting is delayed until late-June and early-July.

There are stipulations.  More productive soils and irrigated soybean usually require less seed.  Good years that allow lots of quick growth require less seed (but who can predict a good year?).  Later maturity groups may require slightly less seed.  Less seed are needed as you move south (growing season is longer and you can plant a later relative maturity).  I think that a soil profile that is full of water at soybean planting (this year) might allow less seed to be planted – but I have not documented that – It just makes sense to me that plants will grow better when the small grain has not depleted most of the subsoil moisture.

What about now?  How many seed/acre do we need to plant in the first week of June?  Here are my suggestions.  Keep in mind that these are general guidelines; you need a gradual increase in seed/acre.  I’m assuming 80 to 85% emergence for June/July plantings.  To easily determine how many seed you need per row foot, see VCE pub 3006-1447, Suggested Soybean Seeding Rates for Virginia

May: 100 to 115K

June 1-7:  120-140K

June 8-14: 140-180K

June 15-21: 180-200K

June 22-30: 200-220K

July: 220-250K