Charlie Cahoon and Michael Flessner
Virginia Tech Weed Science
Over the past few days we have had several questions concerning replanting corn behind an already failed corn stand. Our biggest concern in this situation is how to terminate emerged corn from the first planting. The best option for small corn (4-8 inch) is clethodim (Select Max or generics). The label for Select Max (0.97 lb active ingredient/gal) specifies 6 oz/A must be applied at least 6 day prior to replanting. Clethodim products that contain 2 lb active ingredient/gal and are labeled for this situation should be applied at 3 oz/A, while adhering to the same plant-back restriction. As is the case with many weeds, timeliness is critical. Control of larger corn by clethodim is variable (> 8 inches).
Poor corn stand as a result of bird damage. Painter, VA 2017.
Producers not wanting to wait 6 days before replanting should use paraquat (at least 3 pt/A of a 2 lb/gal product or 2 pt/A of a 3 lb/gal product). Paraquat should not be used alone; adding atrazine (1 pt/A) and suggested adjuvants to paraquat will enhance control. Research conducted by Dr. Kevin Bradley (University of Missouri) and Larry Steckel (University of Tennessee) concluded Liberty did not consistently control Roundup Ready corn. Although not listed on the bag, many corn hybrids are tolerant to glufosinate (active ingredient in Liberty). For these reasons, producers should be wary of using Liberty to terminate a failed corn stand.
Another common question when replanting corn is whether to reapply residual herbicides such as atrazine. Atrazine and other residual herbicides should not be reapplied. If additional atrazine is desired in a postemergence application, just note that the cumulative total atrazine for your first and second planting of corn cannot exceed 2.5 lb active ingredient per acre per year. Other products have similar restrictions.
On a normal year, growers are usually asking if soybean can be planted behind corn. And our answer to this is usually no. This is mostly due to the fact that most everyone uses atrazine preemergence and planting soybean following atrazine if very risky. The label of most atrazine products says “Do not rotate to any crop except corn or sorghum until the following year, or injury may occur” and “If applied after June 10, do not rotate with crops other than corn or sorghum the next year, or crop injury may occur”.
Our recent warm weather has done more than wake up your plants – it has signaled to many insects that it is time to start feeding and reproducing. Prompted by a call from ANR agent Mike Parrish in Dinwiddie County, I spoke today with Kathy Flanders at University of Auburn about her recommendations to mitigate insect injury in store grain. Her #1 suggestion – turn on those fans! Your goal should be to keep the temperature inside your bin below 60 degrees. Make sure and leave equipment running long enough to cool the entire structure. If you are unable to keep temperatures below this threshold, or if our nights do not stay cool, make sure to take samples regularly to scout for insect injury. Consult this guide for management recommendations specific to the Southeast: http://www.aces.edu/pubs/docs/I/IPM-0330/IPM-0330.pdf.
Recent mild temperatures and the mild winter are setting the stage for rapid development of marestail/horseweed (Conyza canadensis) this spring. Marestail was particularly troublesome last year in soybeans. Marestail can germinate in both the fall and the spring. It is more likely to overwinter in the rosette stage during mild winters. If you wait until your typical burndown the marestail may start bolting and therefore be more difficult to control. Adding to this difficulty, many marestail populations are resistant to Roundup (and other glyphosate containing products). You should scout your fields targeted for soybeans now to identify overwintering marestail. Marestail control can be achieved with 2,4-D or dicamba now and still offer plenty of time to avoid plant back restrictions (up to 15 days for 2,4-D or up to 28 days for dicamba). Glyphosate resistant weeds and the difficulty in controlling more mature weeds underscore the need to scout fields earlier and use some alternative herbicides in your program. Always consult the product label for specific instructions.
We look forward to seeing you January 25th and 26th at the 27th Annual Eastern Shore Ag conference & Trade Show! You can find the program online at: https://onedrive.live.com/?authkey=%21AEczhxLIHkUCwmY&cid=05F6B732110DB231&id=5F6B732110DB231%2129963&parId=5F6B732110DB231%21813&o=OneUp. Virginia pesticide re-certification and Certified Crop Adviser credits will be available. See the program for more information.
The event will be held at the Eastern Shore Community College Workforce Development Center, 29300 Lankford Highway, Melfa, VA 23410. When you enter the driveway to the Community College, we will be meeting in the building to the left.
The Annual Oyster Roast will be held on Wednesday night, January 25th beginning with a social at 6:00 pm and oysters served at 6:30 pm. Along with oysters, there will be all-you-can-eat barbecue, sides and beverages. Tickets will be $35.00 in advance and $40.00 if purchased the day of the oyster roast.
If you have any questions or concerns please contact either Theresa Pittman (email@example.com) or Ursula Deitch (firstname.lastname@example.org) for accommodation. Thank you!
Join us in Melfa, VA for the 27th Annual Eastern Shore Agricultural Conference and Trade Show on January 25-26, 2017. This event is free, open to the public, and will be held at the Eastern Shore Community College Workforce Development Center. We will offer Virginia Pesticide Recertification credits for categories 1A, 10, 60, and 90. We will also offer Certified Crop Adviser Credits for nutrient management (2), soil and water (1), integrated pest management (4.5), crop management (6), and professional development (0.5). Click on the following link for topic areas being presented: ag-conf-press-release-2017
November 15-17, 2016
Princess Royale Hotel in Ocean City, MD
Registration is open for the 22nd annual Mid-Atlantic Crop Management School. This year’s school will feature 2 ½ days of timely presentations in the areas of crop management, nutrient management, pest management, soil and water management, and climate. This year, the school will also feature the popular Crop School on Wheels field tour (limited to 50 participants). Nutrient management (VA, MD, DE, PA), pesticide, and certified crop adviser (CCA) credits will be available. Register early for the best selection of sessions.
The session schedule is online at: https://cdn.extension.udel.edu/wp-content/uploads/sites/12/2016/09/23151701/2016_CMS_Program_Final.pdf
Registration information is posted at: http://www.cvent.com/events/2016-crop-management-school/event-summary-bbd4a7d2717545af9770626ef761a930.aspx?tw=E3-C1-0B-14-32-A0-CB-AB-1C-D6-9A-06-46-74-20-5F.
Contact Amy Shober (email@example.com) or Jarrod Miller (firstname.lastname@example.org) with questions about the school. We look forward to seeing you there.
The Mid-Atlantic Crop Management School is organized by Extension Specialists from Virginia, West Virginia, Delaware, and Maryland featuring speakers from across the nation.
Recent observations from around the state have found corn maturing at a fast pace this year, especially corn that was planted late. The most commonly used method for assigning corn hybrid maturity ratings is based on Days to Maturity. This typically indicates the number of days it would take a corn hybrid to reach physiological maturity or “black layer”. But temperature drives corn development, not calendar days. So the “thermal time” to maturity calculated using growing degree days (GDD) is a more accurate measure. Especially when the growing season has been particularly warmer or cooler than normal.
The chart below shows the difference in cumulative GDD between 2016 and the 30 year mean temperatures beginning on JUNE 1.
We are 6, 7, and 10% above the “normal” GDD accumulation for August 31 at Suffolk, Richmond, and Orange, respectively.
This might explain why a 110 day RM corn is maturing more quickly than expected based on the “day” count. The plant has actually accumulated heat units at a faster rate this year.
If May 1 is the starting point, we are 3, 4, and 7% above the “normal” GDD accumulation for these sites. So this effect is likely to seem greater in later planted corn.
We are seeing yellow and stunted corn around Virginia due to many different factors that range from nutrient deficiencies to cool and wet growing conditions. Take a look at this article to give you a few reasons for this poor looking corn and different things to consider prior to making your sidedress nitrogen applications. Yellow_Corn_26May2016
Our overall mild winter and wet spring are the kinds of conditions that favor survivorship and early development of stink bug populations. Because of these conditions, this could be a summer when we see higher than normal stink bug infestations in a lot of crops including field corn, cotton and soybean. Brown stink bugs are already being found in small grain fields and areas of North Carolina are reporting pretty heavy stink bug pressure on seedling field corn. See this article by Dr. Dominic Reisig at the NCSU station on Plymouth for details https://entomology.ces.ncsu.edu/2016/05/how-to-avoid-a-stink-bug-disaster-in-corn-2/
We need to be thinking ‘stink bugs’ this summer and aligning our field scouting, sampling and threshold efforts in that direction as the summer progresses—and that applies to cotton and soybean fields as they mature.
Slug damage on no-till corn.
With all of the rain during the first week of May, and with seedling corn having emerged, we are hearing about slug pest problems, particularly in no-till corn. Eastern Shore of Virginia is one area reporting issues. Slug problems are a common concern in no-till systems when conditions are wet in the spring (see VCE Factsheet No. 444-109 https://pubs.ext.vt.edu/444/444-109/444-109.html) . Another useful VCE factsheet on slug management in no-till corn from Bobby clark and Rod Youngman is: http://offices.ext.vt.edu/shenandoah/programs/anr/CropandSoilEnvironmentalSciences/Slug_Fact_Sheet.pdf
Growers must keep four things in mind right off the bat: 1) corn plants are often not killed outright by the slugs and quite often have the ability to outgrow the leaf feeding injury by these slimy little beasts unless populations are very high and weather conditions are bad. Soybean cotyledons, however, are more susceptible to being killed because their growing point can be damaged; 2) if it stops raining for a few days, then the slugs will go away and hide as they require high moisture levels; 3) replanting is an option, but a grower needs to factor in the economics see VCE Fact Sheet https://pubs.ext.vt.edu/2905/2905-1293/2905-1293_pdf; and 4) if you are considering a chemical control measure, keep in mind that there are only a select few effective options such as slug bait products containing metaldehyde or iron phosphate. These are not easy to apply (need to be broadcasted) and are fairly expensive. However, these products are efficacious and will most often alleviate the slug problem long enough for your seedling plants to reach a sufficient size to no longer be economically damaged by slugs. See VCE Fact sheet No. ENTO-178 for a recent efficacy evaluation that we did with slug baits. http://pubs.ext.vt.edu/ENTO/ENTO-178/ENTO-178-PDF.pdf