Category Archives: Insect

Corn earworm update for September 5, 2019

Average nightly black light trap captures of corn earworm moths this week were: Chesapeake=33; Greensville=13; Southampton=10; Suffolk=27. Hanover had 12 per night if averaged over the past 2 nights, but 3 if averaged over the entire week. Here is the table:

In our corn earworm pyrethroid resistance monitoring experiment (adult vial tests), the seasonal average is 36% survival to a 24-hour exposure of 5 micrograms of cypermethrin per vial.

Corn earworm update for August 29, 2019

Nightly corn earworm/bollworm moth averages for reporting black light trap stations this week were: Greensville=22; Prince George (Templeton)=12; Prince George (Disputanta)=10; Southampton=13; Suffolk=32. Please see the link to the table below and also compare this year’s Suffolk, VA numbers to the past several years.

I have seen a large number of corn earworm moths in our soybean at the Tidewater Agricultural Research & Extension Center in Suffolk this week. Remember to scout for larvae and use the threshold calculator for soybean: https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html

Our pheromone trap catches at Suffolk have also increased and we were able to conduct more adult vial tests for resistance monitoring using the pyrethroid cypermethrin. The average survival for this season is now 37%.

Corn earworm update for August 8, 2019

Black light trap catches of H. zea (corn earworm/bollworm) moths increased at most locations this week. Please see the data table for more information.

We have tested 168 corn earworm moths in our cypermethrin vial tests so far this season, with a seasonal average of 39.5% survival. Here are the results by month (we’ll be conducting more tests throughout August):

We have updated our corn earworm survey of field corn (as a predictor of infestation risk in other crops such as soybean) to include Rockingham County’s 10.8% infested ears. Thanks to all cooperators for their efforts. Statewide average infested ears was 15.3% for 2019. The updated table and map are here:

Corn earworm update, including field corn survey results, for August 1, 2019

Corn earworm moth catches are increasing for most black light stations; nightly averages this week were: Greensville=25.1; Prince George (Templeton)=5.7; Prince George (Disputanta)=3.7; Warsaw=46.4; Southampton=9.0; Suffolk=14.6.

Preliminary results from our annual survey of field corn show the following percent infested ears (based on sampling 5 corn fields/county, 50 ears per field, for evidence of corn earworm larvae): Accomack=16.0 percent infested ears; Amelia=15.6; Chesapeake=5.6; Dinwiddie=19.6; Essex=11.6; Greensville=32.8; Hanover=32.8; Isle of Wight=17.6; King & Queen=13.6; King William=24.4; Lancaster=4.8; Northampton=11.2; Northumberland=4.0; Prince George=12.8; Southampton=11.2; Virginia Beach=17.6; Westmoreland=12.8. Thanks to the following for collecting data from their counties: Eastern Shore AREC entomology; Laura Siegle; Watson Lawrence; Mike Parrish; Robbie Longest and Brittany Semko; Sara Rutherford; Laura Maxey-Nay; Livvy Preisser; Trent Jones; Scott Reiter; Joshua Holland; Roy, Bailey, and Fletcher Flanagan; and Stephanie Romelczyk and Amerah Thompson.

We have found bollworm eggs and small larvae in our cotton experiment in Suffolk. Please be sure to scout your fields.

Plant bug / bollworm update for VA cotton

The much needed rain earlier this week also heralded the start of the moth flight in southeastern VA. Both eggs and adult moths are being picked up by scouting teams. So far, only a handful of fields are over recommended thresholds. I recommend scouting 2-gene cotton (Bollgard II, Widestrike, Twinlink) for eggs and applying Prevathon or Besiege when you find 25 or more per 100 terminals and/or leaves. If you planted 3-gene cotton, you are likely protected. We have measured very little benefit to spraying Widestrike 3, Bollgard III, and Twinlink Plus varieties for bollworm. In these varieties, finding 3 or more live second-stage larvae in one trip (or two worms in two consecutive trips, or one worm in three consecutive trips) triggers an application.

Other insecticides can control bollworm in cotton, but timing is critical. If you are using a pyrethroid, for example, target small worms. No product will clean up a problem field once worms are inside bolls.

Our team, lead by PhD student Seth Dorman, ANR Agent Josh Holland, and Dr. Sean Malone are scouting fields this week for lygus. Few problems fields were detected in southern counties today. However, fields were observed over recommended thresholds. At this point, many people have sprayed. Some may need to spray again and some may not. The only way to know is to scout.

Northern counties will be scouted this Friday and I will update the blog with our findings.

As always, you can reach out to me with your questions and concerns.

 

Corn earworm report for July 18, 2019

Very low numbers of corn earworm moths were reported by our network of black light trap operators this week. Nightly averages ranged from 0.3 to 1.0 moths. Here are this week’s numbers (trap operators listed in parentheses):

Greensville (Sara Rutherford): 0.7 per night

Hanover (Laura Maxey-Nay): 0.9 per night

Prince George-Templeton (Scott Reiter): 0.8 per night

Prince George-Disputanta (Scott Reiter): 0.5 per night

Richmond County-Warsaw (Mary Beahm): 0.3 per night

Southampton (Josh Holland): 0.3 per night

Suffolk (Sally Taylor and crew): 1.0 per night

Here is a pdf of the data table: BLT_18_Jul_2019

We will be conducting vial tests to monitor insecticide resistance in corn earworm/bollworm again this year, but so far we have only captured and tested a handful of moths.

The value of scouting for plant bugs

The entomology program recognizes the logistic difficulty in scouting. We know that you have to cover a large acreage in a limited amount of time, you manage multiple crops, and some weeks, frankly, you would rather spend the time with your family. We get it.

So, let’s chat about how to scout cotton for plant bugs, and the amount of money that it will make you, in the fewest possible bullet points:

  1. Decisions can be quick and easy – if scouting multiple locations in a field (either by quadrant or on the diagonal) results in numbers over threshold (8 per 100 sweep or 2-4 per beat sheet sample), spray the field. Likewise, if you are seeing consistently below threshold numbers, don’t spray. The only scenario where more time is warranted is when you capture near-threshold numbers in multiple spots. In this scenario, you must decide: 1) how much yield you want out of this field, 2) whether you have time to revisit this field in 3 to 5 days to scout again, and 3) how spraying right now fits into your schedule. Remember two things: 1) it always pays to spray on threshold, and 2) spraying in this hot, dry year increases your risk of secondary pests with any insecticide application. I favor treating the problem that I have and dealing with the problem that may occur, but this is entirely up to you and your operation. An additional 15 minutes of scouting may be more profitable than spraying an entire field. It’s ultimately your choice.
  2. Any sampling method works. Our data (below) from 2018 show that when you scout with a sweep net, a beat sheet, or both combined, you are profiting over not scouting at all. This is why we are distributing beat sheets free of charge at the Tidewater AREC. The companies that have paid for your beat sheets (Corteva, BASF, and FMC) agree. No one wants you to spend money unnecessarily – especially in this difficult time.

Figure 1. Comparison, in terms of lint yield, of different sampling methods for tarnished plant bug (sweep net, drop cloth, and sweep net until 2nd week of bloom combined with drop cloth after) and different thresholds (low, medium or recommended, high, and very high). Favoring the low threshold (1 per drop cloth sample) was profitable when using a drop cloth alone, but this did not make money over using a medium threshold in the combined method. Regardless, you make money if you sample and spray by any method. Not every Virginia field will experience this high pressure.

 

 

 

Table 1.  Net economic returns (per hectare) for threshold trial in 2018 above the untreated control. Cotton was priced at $0.77 per acre for 2018; nitrogen (32-0-0) was priced at $49.18/acre (120.0 lb/acre); bifenthrin (6.4 oz) was priced at $2.90/acre; acephate (8 oz) was priced at $3.12/acre; sulfoxaflor (2.25 oz) was priced at $13.80/acre; thiamethoxam (2 oz) was priced at $15.61/acre; chlorantraniliprole (27 oz) was priced at $26.35/acre

 

 

 

 

 

 

As always, best wishes for a profitable 2019. Please reach out to Sally or myself if you have questions or concerns. I hope that you have the opportunity to spend this weekend with the people and activities that you value most. Happy 4th y’all!

Plant bugs in cotton update

Plant bug populations have been spotty, and lower overall than this time last year (click to see map). 10% or fewer of Virginia fields need insecticide applications this week, but, unfortunately, a much higher percentage will end up treated. Before making a decision to spray without scouting consider several things:

  1. Your risk of aphids and spider mites increases, especially if it does not rain soon.
  2. Your risk of subsequent plant bug infestations increases.
  3. You spend money that you did not have to spend.

Spraying for plant bugs at or exceeding threshold will pay off. Keep in mind that sprays during flowering typically yield higher returns. These two Focus on Cotton presentations by NCSU (click here) and VT (click here) will tell you what you need to know about plant bugs in our region (follow links).

If you need help scouting, ANR agents Josh Holland (Southampton) and Elizabeth Pittman (Suffolk) will be hosting scouting clinics in July. More information coming soon. Beat sheets are available to you free of charge at these events and at the Taylor lab at the Tidewater AREC. Stop by anytime Monday through Friday 8 am – 4 pm. We are closed next Thursday and Friday.

A big thank you to FMC, BASF, and Corteva for sponsoring this round of beat sheets!!

A big thank you to Josh Holland for his help scouting this week!

Click this link for interactive map with insect density and square retention data (click points for summary data).