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:
Boxwood blight has been present in Virginia since 2011 and has since spread from its original location in Carroll County to a number of other counties around the state by movement of infected plants. Because much of Virginia’s greenery production industry is located in areas where boxwood blight is known to occur, the potential for spread of the disease on boxwood greenery also exists. Last year we notified agents regarding the potential for spread of the disease via holiday boxwood greenery. Now that potential has become a reality in North Carolina. The North Carolina Department of Agriculture and Consumer Services recently discovered boxwood blight in holiday boxwood greenery sold at several retail locations in North Carolina. Although the fungus that causes boxwood blight is not active at cold temperatures, it produces structures that can survive on plant debris over the winter. The fungus could potentially infect nearby susceptible plants in the landscape when favorable weather conditions return. Therefore, it is very important that boxwood greenery be properly disposed after the holidays by double-bagging and removing to the landfill. Do not compost boxwood greenery and do not leave it in cull piles in the landscape. Inspect boxwood greenery carefully for symptoms of boxwood blight before introducing it to a site containing susceptible boxwood plants and discard symptomatic greenery as described above. Symptoms of boxwood blight include brown leaf spots with dark border, black streaks on green stems, and leaf drop. Be aware, however, that even asymptomatic greenery could potentially harbor the pathogen. If clientele have highly valued boxwood in their landscape, they may want to avoid introducing boxwood greenery altogether.
For more information on the North Carolina situation, refer to the NCSU Plant Disease and Insect Clinic blog at: http://ncsupdicblog.blogspot.com/2014/12/pest-alert-boxwood-blight-on-holiday.html.
For more information on boxwood blight in general, including Best Management Practices for the greenery industry, landscapers, home growers, and retail and wholesale nurseries, visit the Virginia Boxwood Blight Task Force web site at:http://www.ext.vt.edu/topics/agriculture/commercial-horticulture/boxwood-blight/index.html.
Please make sure that property managers of historic sites in your area are informed about this update.
Leaf spots on boxwood caused by the boxwood blight pathogen (photo by A. Bordas)
Black streaking on boxwood stems caused by the boxwood blight pathogen (photo by A. Bordas)
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
Many fields are exhibiting symptoms of interveinal chlorosis and necrosis. In the some areas (hot spots), leaves are burning up and dying. In the worse fields, entire plants are dying. Sometimes the leaves are falling off the petiole; in other cases, the leaves remain attached. The symptoms look similar to, but usually worse than, various nutrient deficiencies. Actually, what is occurring is very similar to a nutrient deficiency in that something is restricting the roots and/or vascular system from moving water and nutrients through the plants. If you start seeing such symptoms, dig some roots and examine them. Then, split the stem and tap root. If you see any discoloring, then you likely have a stem/root disease.
Is this sudden death syndrome (SDS)? Maybe. We tend to hear a lot about this disease in the media, in a seed catalog ratings, and throughout many extension bulletins in the Midwest. Although the name makes the disease sound like the entire field is getting ready to die, this is not usually the case. Up until this year, SDS was neither devastating nor widespread in Virginia. However, we are seeing more than the usual cases this year.
SDS in Virginia Soybean
It appears that the disease spreads suddenly; you don’t see it one week, but the parts of the field begin dying the next. In reality, it has been building up slowly as the season progresses. The infection actually took place much earlier in the year. Regardless, SDS will rarely result in widespread death of the soybean crop. Instead, you will usually see it in spots and patches in the field. Worth noting is that SDS is commonly associated with soybean cyst nematode infestations. So, if your field has been diagnosed with SDS, then you may want to sample for nematodes. Below is a photo of one of our on-farm soybean variety tests. It is one of the worst cases of SDS that I have ever seen. Although a few varieties are more tolerant to the disease than others, it appeared to affect all of the varieties to some extent.
SDS in On-Farm Variety Test in Virginia
Although SDS is turning up in several fields this year, the same above-ground symptoms are also association with brown stem rot (BSR), which has been the most common root/stem disease in Virginia. Some of the plant samples that have come through our plant pathology lab have been diagnosed as BSR. It usually doesn’t cause widespread death and it usually limited to small spots or patches in the field. In general, it will not continue to spread over the rest of the field; however, the patches will enlarge over time. Yield loss is usually minimum and restricted to the infected areas.
SDS Symptoms in Soybean Stem
As mentioned earlier, if plants begin suddenly showing above-ground symptoms, dig the roots and split some stems. If the pith (center) of the stem and taproot right at the soil level is brown, then the cause is likely (but not always) BSR. If you see a white pith and the rest of the root is brown, then the disease could be SDS. Another diagnostic tool is to look at the leaves. If the leaflets fall off but leave the petiole attached to the stem, it is likely SDS. if the leaves don’t fall, it’s likely BSR. Finally, you’ll seed more rotted roots with SDS. But, to find the rotted roots, you’ll need to dig them up and wash the soil from the roots. Jerking the plant out of the ground will likely strip off most of the roots.
The last disease that could be a problem and exhibit the same symptoms is red crown rot (in peanut, this is called cylindrocladium black rot or CBR). This disease can however be recognized by red fruiting bodies found at the base of the stem. Red crown rot was more common when Virginia’s peanut acreage was greater and soybean and peanut were being rotated with each other.
Red Crown Rot in Soybean
Regardless of the disease, what can you do about it? Unfortunately, there is nothing that can be done this year. Foliar fungicides will not control a disease that is inside the stem and roots. But, in the future, rotate out of soybean for one or more years. Also, you may want to select a variety with resistance to that disease when you plant soybean in the field. Finally, as mentioned earlier, take a nematode sample. Just because you’re seeing SDS or BSR in your field this year doesn’t mean that you have nematodes. But anything that is restricting root growth could aggravate SDS or BSR; therefore the symptoms would be more evident in fields infested with nematodes.
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.
