Author Archives: Ames Herbert

Black flag seen in some Virginia cotton fields

Posted on June 19, 2015 by Ames Herbert

As you may have heard, reports out of northeastern North Carolina are talking about infestations of plant bugs (Lygus) causing a symptom called “black flag” by feeding on presquare cotton. This is very rare in US cotton. This symptom is termed “black flag” due to the death and blackened appearance of the expanding terminal leaves. The danger is creating “crazy cotton”, which is loss of apical dominance, causing multiple terminals per plant, delayed squaring, or yield loss. Terminals can be destroyed from only 20 minutes of feeding.

But it is important to remember that given good conditions, cotton can recover later in the season without yield loss. We did research earlier in Virginia that showed that even this far north, cotton can easily compensate from removal of squares—even up to 20 percent—so this black flag injury may not be as big a threat as you may be thinking it is.

The plant bugs that are causing this problem are from a generation that developed on weeds and is moving through the system. It is important to keep in mind that plant bug infestations are very erratic. Some fields may be infested, or even some areas within a field—but not every field. We and others have checked a lot of cotton fields in Virginia and are finding just a few with very limited amounts of black flag.

We don’t want to overreact to this and spray all of our cotton just because we have seen this problem in a few plants in one area. If you do see these symptoms you should use a sweep net to see if plant bugs are still present (see recommendations below). Overreacting could certainly help flair other problems as well as waste money if plant bugs are not present at damaging levels.

Management on presquare cotton (borrowed from NCSU)

1. Use a sweep net to make 25 sweep samples and count the adults. Realize that bug numbers will be higher in field edges, so move around. A sample of 25 sweeps per location (one set of 25 “swooshes”) should be adequate.

2. Where you sweep, look for black flag, wilted leaves, or injured terminals. If you see this injury, and have plant bugs present, spray if the number of injured terminals is greater than 1 plant in 10 feet of row (borrowed from Mississippi State). If you do decide to spray, use a neonicotinoid at the highest labeled rate at this point in the season. They tend to be less effective as the season goes on, but should do the trick, while preserving some beneficials. Examples include Admire Pro, Belay and Centric. DO NOT use an organophosphate or pyrethroid this early in the season. These will kill the beneficials and could help flare spider mites and/or aphids. We are seeing some of both in a few fields so the risk of flaring these pests is pretty high—and would be very costly.

3. Monitor the situation after the spray. A visit and sweeping 24 hours following the spray should give you a good idea of knockdown. Since you’ve swept and know the plant bug numbers prespray, another good visit would be 4-5 days later. See if plant bugs have migrated in again and if the terminal injury is holding steady or increasing.

4. Once the plants start squaring, you need to use a threshold that incorporates plant bug numbers with square retention measurements. You can find scouting recommendations and the threshold for squaring cotton in the Virginia Cotton Production Guide, http://www.pubs.ext.vt.edu/AREC/AREC-124/AREC-124.html.

Syngenta Pest Patrol Hotline…another good source of information

Posted on April 16, 2015 by Ames Herbert

The Syngenta Pest Patrol Hotline gives retailers, consultants and producers valuable information about local pest spectrums to help customize pest management plans based on real-time advice from experts in their area.

Those who are interested can subscribe to receive regional updates from local experts through text messages. Sign up today for Pest Patrol text alerts, so you know immediately when Dr. Ames Herbert has posted a new update.

How to register for Pest Patrol text message alerts?

Step one: Register online at www.syngentapestpatrol.com or register via text message by texting “pestpat8” to 97063.
Step two: reply to the confirmation text by texting the letter “y”, to complete registration.

Upon receiving an initial text message from Syngenta, the cell phone user is agreeing to receive future text message communications from Syngenta under the Pest Patrol campaign. Standard text message rates apply and are the sole responsibility of the cell phone user. To stop receiving messages, the cell phone user must reply to a Syngenta text message with the message ‘STOP’.

First kudzu bugs found in 2015 in VA

Posted on April 7, 2015 by Ames Herbert

We just received confirmation that kudzu bug adults have been found in two counties, one on a trap at the VT Tidewater Ag Research and Extension Center in Suffolk, and several on the side of a building in Mecklenburg County (see the attached map). These adults are the overwintering population getting active as the weather warms. They are about a month later than our first reports in 2014–the first in that summer emerged the first week in March in Chesapeake. This winter has been pretty cold and wet compared to some and could have caused this delay. Most likely more reports will start coming in soon. Updates will be posted. Kudzu_bug_traps_7_Apr_2015

Field corn insecticide seed treatment chart

Posted on October 15, 2014 by Ames Herbert

There are many insecticide seed treatment combinations available on commercial field corn seed. Although there are only 4 main active insecticide ingredients involved (imidacloprid, thiamethoxam, clothianidin, and chlorantraniliprole), there are currently at least 20 different trade names with different combinations and amounts of active ingredient per seed. The chart provided here (see below) was created as a collaborative effort by corn entomologists from across the southeast. It shows the combination and rate of the active ingredients of each product and the relative efficacy against the most common soil pests. Because of the diversity of soil pests of corn in Virginia—depending on location, soil type, crop rotation system and history of pests—product selection should be made to fit each situation. This chart can be used to select the most effective product for the most common pests of a particular field. For example, if seed corn maggot has been a chronic pest, at least 8 products are ranked as Excellent (E rating on the chart) for controlling that pest—compared with only two products that provide Excellent control of wireworm. Hopefully this chart will be helpful when selecting the best insecticide seed treatments for next year’s field corn crop.

Field corn insecticide seed treatment chart

Field corn variety insecticide trait and herbicide tolerance chart

Posted on October 15, 2014 by Ames Herbert

Field corn varieties provide a dizzying array of insect toxins—at least 14 different combinations by my count—that have very different degrees of efficacy against several corn pests. The chart provided here (see below) lists the current commercial varieties, the insect toxin combination they provide, and the relative efficacy of each against the most commonly encountered corn insect pests. The chart was created as a collaborative effort by corn entomologists from across the southeast, with guidance by two in particular, Kathy Flanders at Auburn University and Dave Buntin at University of Georgia. For our purposes in Virginia, I would pay the most attention to those varieties that provide Excellent (E rating on the chart) protection against corn earworm and fall armyworm, and if you are growing continuous corn, especially in the valley and piedmont regions, corn rootworm. The chart also provides the herbicide tolerance package of each variety, and the associated refuge requirement. Hopefully this chart will help you with your choice of seed in the next season.

Field corn insecticide trait and herbicide tolerance chart

SOYBEAN LOOPER ALERT

Posted on September 11, 2014 by Ames Herbert

Soybeans in parts of North Carolina, especially in their eastern ‘Blacklands’, have been plagued by soybean looper infestations for a few weeks. I got the first report of infestations on our Eastern Shore earlier this week, and today, I got a report of a field hit in Southampton County.

Soybean loopers follow a pattern that we have seen in the past. They do not overwinter in Virginia so moths must migrate in from the south. Adult moths are transported short or long distances by weather fronts. It is not uncommon to find a few soybean loopers in any given field, any time during the season. But it is fairly uncommon to have large flights. The pattern that I have seen, and the one that is playing out this year is that when large populations build up to our south, moths are transported to our area in large numbers—and—most commonly in mid-September.

Another important factor to be aware of is that almost invariably, these large flights result in large worm outbreaks IN FIELDS THAT HAVE BEEN PREVIOUSLY TREATED WITH PYRETHROIDS. Our current research is showing that pyrethroids are hard on beneficial insects and spiders that feed on looper eggs and small worms. If destroyed, a much larger percentage of looper eggs hatch and a larger percentage of worms survive.

So, if a looper infestation is discovered in a field, what is the threshold and what products provide the best control. We do not have a threshold for loopers but lump them into a general leaf defoliators ‘guild’ which can include many leaf eaters (Japanese beetles, green cloverworms, grasshoppers, bean leaf beetles and others)—and base a treatment decision on the total leaf area destroyed by the guild. We recommend not treating fields with fully developed seed unless 35-40% of the leaf area is eaten and bugs are still present.

We also know that soybean looper is a unique pest in that large numbers can completely defoliate a field in a short period of time, in as few as 5-7 days if numbers are really high. So here is a looper rule-of-thumb. Treat if you get 12-15 or more in 15 sweeps and the field has not reached full pod maturity (pods yellowing and seed getting hard).

Do not use a pyrethroid for loopers. These critters are hard to kill and the best success will be with non-pyrethroids like Belt at 3 oz, Prevathon at 14 oz, or Besiege at 10 oz. Other products that contain sinosad may also be effective.

Corn Earworm Update, Sept. 4, 2014

Posted on September 4, 2014 by Ames Herbert

Corn earworm moth activity has increased a lot here at TAREC in the last week. We are finally seeing what may be the largest flight of the summer. In spot checking fields, we are finding worms in some, mostly only in the late planted fields that are still flowering. I get a lot of feedback from growers and others that are checking fields and so far, most have reported almost no worms. A few fields have hit threshold and were treated. With this increased moth activity, it is important to focus scouting efforts on fields that still have susceptible pods—seed filling in the pods. Full season fields that have full pods that are beginning to yellow will not be attractive to late season corn earworm, or stink bug infestations. Keep checking late planted fields for at least another 3 weeks.

The number of moths surviving the pyrethroid AVT (Adult Vial Test) is hanging at about 30-40 percent. These are not extreme numbers, but do still indicate some issue with those products. I still think you can probably get by with a high pyrethroid rate if a field is only at threshold or a little above. If a heavy infestation is found, definitely tank mix a non-pyrethroid.

BMSB and Kudzu Bug Update, Sept. 4, 2014

Posted on September 4, 2014 by Ames Herbert

Although numbers are still generally very low, our field scouts and others have found BMSB and kudzu bug in a few new counties this past week. The eight new counties added for BMSB are Gloucester, Charles City, Hanover, Spotsylvania, Rappahannock, Prince George, Suffolk and Chesapeake (thanks Stan Winslow for the Chesapeake report). The two new kudzu bug counties are James City and King William (thanks Paul Bodenstine for the King William report). See the maps below for the most recent distributions. Although there may have been a few fields treated for these pests, as far as I can determine most have not. We know of one grower in Campbell County who had some threshold numbers but only in a few patches along one field edge. He elected to spot treat only these patches and so far, our post treatment visits have shown that this strategy was successful, that is, no reinfestation and no spread.

Fall armyworm moth counts are unusually high

Posted on August 28, 2014 by Ames Herbert

For the past several years we have been using pheromone traps to monitor fall armyworm moth flights at the Tidewater Center. The numbers we have been catching these past few days are much higher than what we have normally seen. Fall armyworm has two strains. They are identical in appearance but one prefers to feed on grasses (the grass strain) and the other prefers to feed on legumes, cotton and other hosts. We cannot tell which strain we have by looking at the moths, but we do know that fall armyworms can infest peanuts, cotton, sorghum, turfgrass and many other crops. We have not found any fall armyworms in the peanut fields in the vicinity of the adult traps, but if they are going to occur, we would expect to see them next week. Moths have to mate, lay eggs on the peanut leaves, and worms hatch from the eggs—typically a 5 to 7 day cycle. In peanuts there would have to be a lot of worms to warrant a treatment. This late in the season, and with the extensive plant canopies that most peanut fields have, it would take at least 6 worms per row foot to trigger a spray. It has been many years since we encountered that many worms in a peanut field—but, we strongly suggest that you spot check fields for these critters.

Corn earworm update: few moths but with high tolerance to pyrethroids

Posted on August 28, 2014 by Ames Herbert

Although we hear rumors of worms in soybean fields, our scouting does not confirm this. We are finding almost none in either full season or double crop fields—and others are reporting the same. The full season crop is quickly approaching the ‘safe’ zone, that is, the point where pods are too tough to be attractive to insect pests. But, the summer is not over yet. Because corn is slow to dry down this year, we may still see a corn earworm moth flight into soybean fields, and if this happens, double crop fields would be a primary target. This is also true for stink bugs. As we get into late summer and early fall, stink bugs will be attracted to double crop fields. We strongly recommend that you begin checking double crop fields.

Because of the very weak corn earworm moth flight, we have not been able to capture and test nearly as many moths for pyrethroid tolerance as we have in the past. But all indications are that levels are high (see the graph below). In the most recent sample more than 40% survived the vial challenge. If this high pyrethroid tolerance level coincided with a large flight the large numbers of worms in fields, we would no question be recommending non-pyrethroids. But with this weak flight and the low numbers of worms in fields, I think we can get decent enough control with high rates of pyrethroids, alone.