As potato planting is on everyone’s mind, control options for wireworms are of importance, particularly since some of those need to be made immediately prior to or at planting.
Below is a document on wireworms and their control in potatoes to assist in the management of this important pest:
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 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
Counts were low this week. The nightly average corn earworm moth counts were Warsaw-0.4, Petersburg-1.6, Suffolk-2.4, Prince George-Templeton-0.1, and Prince George-Disputanta-0.6. The Petersburg black light trap caught a mean of 1.6 brown marmorated stink bugs per night, Prince George-Disputanta had 0.1 BMSB, and there were zero caught at Warsaw, Suffolk, and Prince George-Templeton. Please see the attached tables for trap histories. Thank you. BLT_18_Sep_2014
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.
Please see the pdf attached below (BLT_11_Sep_2014v2) for the corn earworm moth and brown marmorated stink bug nightly average catches in area black light traps. Thanks to the following for this week’s reports: Scott Reiter, Mary Beahm, Mark Kraemer, Keith Balderson, and Ames Herbert and his entomology team. BLT_11_Sep_2014v2
Please click on the attached pdf document (BLT_4_Sep_2014) for tables containing the weekly corn earworm moth and brown marmorated stink bug black light trap catches. Thanks to the following for their reports this week: John Allison, Scott Reiter (Scott also found BMSB in Prince George soybean), David Moore, Mark Kraemer, Mike Parrish, and Ames Herbert and his entomology team. BLT_4_Sep_2014
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.
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.
We received a sorghum head sample today from Dinwiddie County with sorghum webworm (see image on right). This is a known pest of sorghum and we have seen them before, but because of their smaller size compared to other head worm species, the threshold is an average of 5 per head across the field. To date, we have never seen nearly this many in any field, but this is a pest that should be scouted for. We are also seeing a very large number of fall armyworm moths in our pheromone traps here at the Tidewater Center. Fall armyworm is another sorghum head pest (see the image below), along with corn earworm, and the threshold for these species is an average of 2 per head. We recommend scouting sorghum fields until heads have hardened seeds. If fall armyworm is found in threshold numbers and a treatment is needed, pyrethroids will not do the job. The best results will be with non-pyrethroids like Belt, Prevathon or Besiege.
