Category Archives: Commodity

Corn earworm update—slow to develop but some surviving the pyrethroid vial test

Posted on July 30, 2014 by Ames Herbert

The corn earworm population is very slow to develop this year. We are only getting a couple of moths each night in our black light trap here at TAREC and our pheromone trap catches are way down compared to this time last year.

Sean Malone will be posting the results of our annual corn earworm field corn survey later this week. Those results, the percent of ears damaged by corn earworm, give us the best indication of what to expect in the coming weeks. Worms feed in corn, drop the ground to pupate in soil chambers, then adults (moths) emerge to fly to other hosts like soybean, cotton and peanut fields. So the size of the population in field corn is our first indicator of what the season may bring.

As in past years, we are also subjecting moths to the AVT (Adult Vial Test) with a pyrethroid insecticide. With the low population, mentioned above, we have not tested a lot of moths but the survivorship numbers are high 13-46 percent. I cannot forecast if this will increase as the season progresses, as it has in the past, but starting at this level is significant. Given these early results, regardless of the crop growers should be prepared to use some non-pyrethroid product ‘designed’ to target difficult to control corn earworms. These can be used alone, or tankmixed with a pyrethroid if other pests like stink bugs or kudzu bugs need to be controlled.

Predator profile: Damsel bugs

Posted on July 28, 2014 by Rebecca Whalen

Adult Nabis roseipennis. Photo by John F. Carr 2010

Damsel bugs (10 mm in length) are common predators in southeastern row crops. These insects feed on corn earworm larvae and eggs, other caterpillars and thrips among other prey. Both adults and immature damsel bugs are predators. Adults are brownish with an elongate torso and head with long thin legs. Immatures have a similar appearance with shortened wings. According to a 2013 survey in Virginia soybean, damsel bug populations are highest in August and early September. Damsel bug feeding rates are highest at night, in contrast to high daytime feeding rates common to many predatory insects such as lady beetles. Keep in mind that broad-spectrum insecticides will significantly decrease damsel bug populations in soybean fields.

Soybean kudzu bug update—July 24, 2014

Posted on July 24, 2014 by Ames Herbert

Our scouts have reported finding kudzu bugs in soybean fields in 4 counties. Nymphs as well as adults were found in two of those counties, Lunenburg and Prince William. Adults and nymphs were found in kudzu, only, in two other counties. All are near the southern border of the state. We are expecting this to change pretty rapidly so we strongly recommend that you start checking fields. This is most easily done with a sweep net. Go to several areas of a field, especially along the edges, and do several 15 sweep samples. At this point in the season, treatment thresholds should be based on the 1 nymph/sweep threshold.

Cotton stink bug update—July 24, 2014

Posted on July 24, 2014 by Ames Herbert

We are finding (and hearing about) a few cotton fields that have reached or exceeded stink bug damage thresholds—not all by any means, but some. For the most part, these are fields in the 3^rd or 4^th weeks of bloom. If you are following our recommended cotton stink bug thresholds, the threshold for the 3^rd, 4^th and 5^th weeks of bloom is 10 percent internal stink bug damage. The research that these thresholds are based on showed that these weeks are the most critical for boll production and the bolls present during this period are the most susceptible to stink bug feeding injury.

If you have not started checking fields for stink bug damage to bolls, you might want to consider starting. In each field, pull a random sample of at least 25 bolls that fit in the ‘holes’ in our scouting card (contact us or your local extension office if you need a stink bug scouting card). Using bolls in this size range guarantees that you are sampling the right boll population. Crack each boll and inspect for internal stink bug feeding injury symptoms.

What products will give you the best control of stink bugs and longest residual activity? Our field trials, and others, show pretty consistently that pyrethroids and products like Bidrin provide the best control. Insecticides in the neonicotinoid class, if applied alone, are weak. Although products do a decent job of killing the adults and nymphs, none provide much residual activity —even 7 days would be a stretch. If adult stink bugs continue move in to field, more than one application may be needed.

Black light trap catches for the week ending July 24, 2014

Posted on July 24, 2014 by Sean Malone

Nightly average catches of corn earworm moths in local black light traps were: Charles City=18.5; New Kent=8.0; Warsaw=1.0; Essex=zero; Petersburg=1.1; Eastern Shore AREC/Painter=zero; Hampton Roads AREC/Virginia Beach=zero; Southampton=3.0; Sussex = 1.9; Suffolk=2.5.

Means per night for brown marmorated stink bug were: Charles City=1.3; New Kent=zero; Warsaw=0.7; Essex=zero; Petersburg=26.9; Eastern Shore AREC/Painter=zero; Hampton Roads AREC/Virginia Beach=zero; Southampton=zero; Suffolk=zero. Thank you to our trap operators for their reports this week: John Allison, Mary Beahm, Keith Balderson, Mark Kraemer, Helene Doughty, Chris Drake, Kelvin Wells, and Ames Herbert and his entomology crew.

IMPORTANT—New Name and Transitioning to an Updated Delivery System

Posted on July 23, 2014 by Ames Herbert

After 12+ years, the Virginia Ag Pest Advisory has been ‘modernized’. As of this week, it will be transitioned to a new format, powered by WordPress and MailChimp software. We are also adding new authors to cover crop updates so are changing our name to the Virginia Ag Pest and Crop Advisory.

As with the old system, you will still receive weekly emails containing important advisories on your mobile or desktop device, and as before, you can scroll the titles and select only those that are important to you. Normal advisories will be delivered each Friday at 1 am and available for reading first thing on Friday mornings. And as before, there is an ‘Urgent’ option that will be used to provide any advisories that need immediate attention.

In addition, all advisories will be posted to the new Blog site: http://blogs.ext.vt.edu/ag-pest-advisory. You may want to ‘bookmark’ this url. If you are not currently on the old Virginia Ag Pest Advisory email recipient list and want to be added, the Blog site provides an easy way for you to do that.

We hope you will be pleased with our new advisory system.

Thanks,
Ames Herbert

Late blight found on Tomato in Leesburg, VA

Posted on July 22, 2014 by Steven Rideout

Unfortunately, late blight has been confirmed in Leesburg, VA by the Plant Disease Clinic in Blacksburg. Potato and tomato growers (especially in the northern part of the Commonwealth) should take precautionary actions and increase scouting. For more information on late blight please refer to the extension publication link about this potentially devastating disease. Please let us know if you have any more questions.
http://pubs.ext.vt.edu/ANR/ANR-6/ANR-6_pdf.pdf

Southern Rust on Corn in North Carolina – Update

Posted on July 21, 2014 by Hillary Mehl

Southern rust was confirmed on a sample from Camden County, NC on July 21. At this time, southern rust has NOT been reported in Virginia. Yield of corn at or near the dent stage is unlikely to be impacted by the disease, but less mature corn may need to be protected with a fungicide application. Contact your local extension office for recommendations if you suspect southern rust is in your area. Samples of corn plants with symptoms of southern rust should be submitted to your local extension office or the disease clinic at the Virginia Tech Tidewater AREC (contact Dr. Hillary Mehl, hlmehl@vt.edu). Typically the disease has little impact on Virginia corn since it arrives too late in the season to affect yield, but if southern rust is confirmed in Virginia prior to corn reaching the dent stage (R5), fungicide applications may be warranted. Updates will be provided as more information is obtained.

Where are the kudzu bugs–soybean update

Posted on July 17, 2014 by Ames Herbert

The big question today is—where are the kudzu bugs we expected to see in our soybean crop? As of this week, we have not seen any adults or nymphs in the early planted full season crop. In fact, the same situation is being reported for much of the eastern US. Dominic Reisig at NCSU says that even in NC, the only reported infestations are from southernmost counties.

Last summer by this time we were seeing many full season early planted files with infestations of adults that have moved from adjacent overwintering sites. The only bugs we have found so far have been in kudzu patches. So, what’s the difference in years and why the delayed movement of adults? All we can say is that it must be related to the colder than normal temperatures we experienced during the winter. We know that in the Suffolk area there were at least two nights when temperatures dropped below zero (æF), and of course it was even colder north and west of us. Could those cold temperatures have killed some of the overwintering adults reducing the overall population levels?

We do know from our adult overwintering emergence traps that were placed throughout much of the state that adults survived and emerged this April and May in about 12 counties in the southern part of the state. Why they did not move into early planted soybean fields is another unanswered question.

From what I can gather from reading and talking with other entomologists in the southeast, 2014 is shaping up to be similar to 2011 when the first generation of kudzu bugs developed in kudzu (mostly) and other alternate hosts and only the second generation moved into soybean fields. This certainly seems to be what is happening this year. In some ways this scenario, if it plays out, will simplify the field scouting and threshold determination. The ‘original’ kudzu bug threshold developed in the southeast was based on this second generation that moved into reproductive stage (flowering—early pod) soybean fields—and it is based on number of nymphs (see below). We have initiated our 2014 soybean insect pest survey so will be reporting updates as they come in so stay tuned.

Treatment Thresholds for 2nd Generation Kudzu Bugs, Nymphs Present

Sweep Net
” An average of 1 nymph/sweep, 15/15 sweeps
” Take at least ten 15-sweep samples to represent the entire field
” Sampling should not be biased by sampling close to field edges where populations may by congregated
Canopy Observation
” At least 10 observation spots representing the entire field
” Nymphs easily found on main stems, leaf petioles or leaves

Black light trap counts for the week ending July 17, 2014

Posted on July 17, 2014 by Sean Malone

Low numbers of corn earworm in black light traps this week (July 11-17). Nightly averages were: Southampton=0.5; Petersburg=0.4; Prince George-Templeton=0.3; Prince George-Disputanta=zero; Warsaw=0.4; Isle of Wight=zero; Suffolk=zero. We had some high brown marmorated stink bug catches in Petersburg’s black light trap (average of 6.6 BMSB per night). Other locations had either zero BMSB (Southampton, Prince George, Isle of Wight, and Suffolk) or 0.1 BMSB per night (Warsaw). Thanks to the following for their report: Chris Drake (Southampton), Mark Kraemer (Petersburg), Scott Reiter (Prince George), Mary Beahm (Warsaw), Janet Spencer (Isle of Wight), and Ames Herbert and crew (Suffolk).