Category Archives: Commodity

Tarnished Plant Bug Update

My name is Seth Dorman, and I’m a graduate student with Dr. Sally Taylor in the Virginia Tech Department of Entomology. My research focuses on tarnished plant bug (Lygus lineolaris) management and distribution in Virginia cotton. In recent weeks, large numbers of tarnished plant bug have been active throughout southeastern Virginia in fallow fields and ditch banks with an abundance of flowering, weedy hosts as well as in corn. Plant bugs have begun migrating into some early-planted cotton fields and were observed in cotton fields in Suffolk and Southampton counties last week.

Tarnished plant bug feeding on weedy host, daisy fleabane (Erigeron annuus).

Tarnished plant bug may move from preferred alternative hosts into cotton fields as flowering weeds senesce, and cotton plants begin to develop small, pinhead squares and subsequent flowers. Feeding during early squaring can cause plants to abort squares. Feeding on larger squares and small bolls may cause anthers in flowers to turn brown (“dirty bloom”), and small bolls to shed. Sustained feeding by tarnished plant bug from first square to early bloom can delay maturity and result in substantial losses. Scouting cotton fields once or twice a week is highly recommended after squares become visible on plants. The best indirect method for sampling plant bug is estimating square retention. Square retention can be measured by calculating the percentage of squares in the top two or three nodes of 25 randomly selected plants in a given field. If square retention drops below 80%, direct sampling for plant bugs with a sweep net is recommended. For sweep net sampling, conduct a minimum of eight 25-sweep samples randomly throughout your cotton field. We recommend using Admire Pro or other neonicotinoid products until bloom. Adult plant bugs can reinfest quickly following applications. Use restraint when treating early in the season when plants have time to compensate for injury.

Scar of an aborted square at the fruiting site on a cotton plant.

More updates on plant bug activity throughout Virginia’s cotton regions will be posted soon!

Soybean Planting Dates, Seeding Rates, Re-planting, Weeds, etc.

June is usually the time of the year when full season soybean is kicking into high gear and we begin planting double-crop soybean.  And like always, various issues are beginning to arise, whether its the weather or finding out mistakes made a few weeks earlier.

Unbelievably, double-crop soybean is wrapping up in many areas due to small grain maturing earlier than normal.  Out of necessity, we were forced to harvest wheat and plant soybean at the same time we were trying to make timely postemergence herbicide applications and generally trying to pay attention to the rapidly growing soybean that we planted in April and May.  But, issues such as these are not unusual.

This week, I thought I’d mention a few things that we are facing and continue to remind you of the need to plant as soon as possible and adjust seeding rates accordingly.

Planting Date.  We are now losing about 1/2 bushel per acre per day with each delay in soybean planting.  Plant as soon as possible, but don’t cause more serious problems by planting into too wet or dry soils.

Seeding Rate.  My data indicates that seeding rates now need to be at least 180,000 seed per acre, even on the best of soils.  I would bump those up about 20,000 seed for each week’s delay in planting.  See Soybean Seeding Rates for June and Later for more information.

Replanting.  Generally, replanting does not pay this time of the year (due to the planting date penalty) unless the stand is horrible.  For more information, see Soybean Replant Decisions or contact me.

Seed Treatments.  I’ve seen few benefits of fungicide or insecticide seed treatments this time of year.  Plants usually emerge and grow quickly.  The exception is wet soils – soybean will emerge very slow when soils are saturated.  With that in mind, you may consider a fungicide on the seed if you have poorly-drained soils, your soils are already wet, and rain is predicted.

Seeding Depth.  Those of you know that I usually don’t like to plant soybean greater than 1 inch.  But, I’ve found that planting soybean at 1.5 inch (and occasionally 2 inches) works just fine when soils are warm.  Sometimes, it’s better to plant deeper to hit moisture than to plant into dry soils.

Weeds.  First, Drs. Charlie Cahoon and Mike Flessner is who you need to consult regarding weeds, but here are a few of my observations.  We may have let a few weeds get too big for adequate control – this is especially a problem with glyphosate-resistant weeds.  Marestail continues to be a problem.  When this weed is glyphosate resistant and you’re not growing Liberty-Link soybean, about the only somewhat effective herbicide that we have left in our arsenal for Roundup Ready soybean is FirstRate, although a few other herbicides may burn the weed – just don’t expect very much from anything.  I’ll let you mull over your other options if you have planted Xtend soybean.  Finally, don’t depend on glyphosate alone – even if you weeds are not yet resistant, its a good practice to diversify to insure that they do not become so.

Stink bug numbers continue to climb

Brown stink bug numbers have continued to increase in eastern Virginia from the Northern Neck to the Tidewater region. We have scouted fields in Suffolk and Caroline County with higher than threshold infestations spanning the entire field. Infestations in most fields remain confined to border rows and the majority of infested fields are near where wheat has been recently harvested.

Many growers are facing the decision to treat. Previously I had reported a threshold of 1 bug per 4 plants. In order to be extra protective during ear formation and elongation, treatment at the 1 bug per 10 plants threshold can be justified for heavily infested fields. More information about stink bugs in corn can be found here – NCSU corn stink bug management considerations. 

The ability of stink bugs to injure corn depends heavily on corn growth stage. Trials at the Tidewater Research Station have shown that stink bug feeding does not always reach developing ears. The photo below shows a healthy ear developing  (VT growth stage) despite multiple feeding lesions to the outside of the stalk. This may be good news for Virginia growers. We cannot determine if yield was effected in these plants until later this season.

This week, we will be rechecking fields  that were treated with aerial applications and post updates on the effectiveness of these sprays.

 

 

 

Herbicide Resistant Common Ragweed Plot Tour

Having trouble controlling herbicide resistant common ragweed? Make plans to attend the field tour, this coming Thursday (June 22nd, 2017) near Lawrenceville, Virginia. Complete information is below. Please RSVP as soon as possible.

View a complete spectrum of preemergence and postemergence herbicides in soybeans in the field to see what works best for yourself. Also, learn about integrated weed management approaches that work within our cropping systems. 

Stink bug numbers increasing in corn

Coinciding with the wheat harvest, brown stink bugs have been moving into pre-tassel corn in the southeastern region of our Virginia. The entomology department has scouted fields over threshold in Chesapeake and Virginia Beach. So far this season, stink bugs are present in low numbers in northern, central, and western regions of the state.

Thresholds for stink bugs in field corn are (From Dominic Reisig at NCSU):

one stink bug per four plants during ear formation, elongation, and pollen shed

one stink bug per two plants nearing the end of pollen shed to the blister stage.

Plant injury from stink bugs may include:

Holes in leaves and, in severe cases, twisted plants.

It is important to remember that this bug typically infests on edges of fields and in spotty locations. It is possible, though unlikely, that stink bugs will infest an entire field. Spray volume is critical if you decide to spray – use a high volume to ensure that sprays penetrate the canopy. Insecticides labeled for stink bugs in corn (e.g., Baythroid XL, Karate Z, Warrior II) must come into direct contact with insects to kill them.

 

 

Save the date: Virginia/Northeastern North Carolina Cotton Field Day on July 20, 2017

You are invited to attend our cotton field day at the Virginia Tech Tidewater AREC on Thursday, July 20, 2017. The tour will begin promptly at 8:00 am, ending with lunch. The location is our research farm at 1045 Hare Road, Suffolk, VA. The event is free and open to the public, but pre-registration is required–please contact Gail White by phone at 757-657-6450 extension 430, or by email at guwhite@vt.edu by July 10th. Private Pesticide recertification credits (cat. 90, 91) are being offered. More information will be made available in the upcoming weeks. Thank you.

Greater Yields are Possible for Double-Crop Soybean in 2017!

It appears that wheat harvest will be 1 to 2 weeks ahead of schedule this year.  We actually harvested some high-moisture wheat and planted soybean plots behind it today (May 31) in northeast N.C.  This is good news for soybean.  Earlier planting means greater yields!  This is clearly shown by the recent data obtained from our multi-state, multi-year double-crop project.

With earlier planting, have my recommendations for double-crop soybean changed?  In general no.  But below are a few things to consider.

Seeding Rate:  In general, you can probably back off on your seeding rates from what you were planning if you get your double-crop soybean in by mid-June.  I’d suggest that you start out with 120-160,000 seed/acre (depending on when you start planting) and gradually ramp that up by 20-30,000 for each week delay in planting.  For more information, see my recent blog, Soybean Seeding Rates for June and Later.

Relative Maturity:  Actually, my standard recommendation still stands, more or less.  Plant as late of a relative maturity (RM) as possible that will mature before the frost.  However, there are now some caveats.   By planting a week earlier, you’ll gain about 3 days in maturity.  Although a slightly later RM may work, I wouldn’t count on it – frost date will affect this more than planting date.  So, don’t plant a later RM.

But, can you plant an earlier RM, say go from an early-5 to a late-4?  Possibly.  Why do I say this?  Two things.  First, by planting a week or two earlier you have greater yield potential (see the above graph), which is due to the ability to grow more leaves.  So your yields are not necessarily so dependent on leaf area as they are with a late-June to early-July planting.  A slightly earlier RM planting in early- to mid-June will only have slightly less leaf area than a later RM.  And, we have generally found that under greater yield potentials, early RM will yield more than later ones.  Still, these are not great reasons to change your RM.  Generally, stick with what you planned.

Soybean Seeding rates for June and Later

Due to the rainy weather over the past two weeks, we are still planting full-season soybean in some areas.  In addition, it appears that wheat harvest is not far off (some wheat at the Tidewater AREC was at 23% moisture today!).  So, should we be increasing our seeding rates?

In general, yes.  But, big increases probably will not be needed until late-June.  Below are some seeding rate data that we collected from soybean planted in early-June after barley.  First, we don’t have a lot of data of soybean grown after barley, so I don’t have as much confidence in the exact seeding rate needed.  Note that there is a wide range in the optimal seeding rates, illustrated by the area between the dotted lines in the graph.  Although, these data may not directly apply to full-season soybean (no small grain), it should be close.

I think that we should now be using 120,000 to 160,000 seed/acre.  The range will depend on the planting date.  In general, I’d suggest bumping up your seeding by 20-30,000 seed/acre per week through June.

If you remember the seeding rate data that I shared in this blog last month for May-planted soybean (see Soybean Seeding Rates – How Low Can We Go?), I stated that maximum yields could be obtained with only 95,000 to 110,000 seed/acre when the yield potential is greater than 40 bushels/acre.  That’s pretty low, but was adequate for maximum yield under good growth conditions.  For less than 40 bushel potential, seeding rates needed to be a little higher.   In the above graph, it appears that more seed is needed to obtain 55 to 70 bushels/acre after barley, I cannot fully explain why; therefore, I would assume that this response is primarily due to the location that we obtained the data (again, we don’t have a lot of data).

Once we get into mid- to late-June, I’d rather see a seeding rate of 180,000 to 220,000 seed/acre, depending on planting date.  This is based on the data to the right.    You’ll notice that, like full-season soybean, the optimal seeding rate falls with greater yields.  This is most likely due to greater leaf area with those high-yielding locations.  As I’ve stated often, the seeding rate response can usually be traced back to whether or not the crop developed enough leaf area to capture 90-95% of the light by early pod development.  Unfortunately, I don’t have any double-crop data planted following wheat with yields greater than 55 bushels/acre.  I hope to solve that problem this year with new experiments.

Potato Late Blight in North Carolina

The following advisory is posted on behalf of Dr. Steve Rideout:

Late blight was found on potato in Camden and Pasquotank counties in North Carolina over the weekend. We will be processing the samples to determine more information on race/fungicide sensitivity. In the meantime, growers are encouraged to scout their tomato and potato fields for the disease.  Preventative fungicide applications are recommended, particularly near the outbreak area in NC.

If you have questions please let us know.  You can access current recommended materials for late blight in the commercial and homeowner vegetable production guides.  Also, you can visit the following web page for more information on this disease:

https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ANR/ANR-6/ANR-6_pdf.pdf

This is a serious threat to potato and tomato production in the Commonwealth.  Please let us know if we can help.