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.
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
Last week Monsanto received EPA registration for XtendiMax with Vapor Grip Technology for use on XtendFlex cotton and Roundup Ready 2 Xtend soybean. Attached is an article authored by Dr. Alan York at NC State pertaining specifically to cotton. I share Dr. York’s sentiments concerning this technology and will echo these same points at winter meetings.
At this point in the season, many cotton fields have been treated once for mid-season plant bug/stink bug. The next decision will be focused on bollworm control—whether it is needed, and if so, what insecticides to use. We are seeing a general increase in bollworm moth activity at TAREC and have gotten recent reports of some pretty large worm infestations in a couple of peanut fields in the cotton area, and outbreaks in a couple of soybean fields in the Suffolk area. Caution: if the earlier applied mid-season plant bug/stink bug spray included a pyrethroid (e.g., bifenthrin), the beneficial populations in those fields will have been depleted—which makes them more susceptible to bollworm.
We have plenty of data that shows that cotton varieties with bollworm protection traits can be damaged by worms. Some escape the toxin, survive, and feed on bolls. We have seen as much as 9% or more boll damage in some varieties which is 3 times our working threshold of 3% live worms/fresh boll damage. But, that was in years when bollworm pressure was high. In years like 2014 and 2015 when bollworm populations were very light, we saw essentially no boll damage in any of the varieties. So what is the 2016 situation? So far it looks like we may be looking at heavier pressure than last year, light to moderate depending on the field—but—we won’t know for sure for another few weeks—as the main flight out of field corn has not kicked in yet. The corn crop is generally a little behind and a little less mature than normal for this time of year because of later planting and good rainfall.
The best approach for managing bollworm in cotton is to scout fields for worms by inspecting small bolls, the terminals, and under flowers (boll tags) for live worms or damage. As mentioned, our current threshold is 3% of the fruit or positions inspected with either live worms or damage.
We have a history of bollworm resistance to pyrethroids in Virginia and this year is no exception. Of the 650 or so moths tested so far, we are seeing about 40+% survival. This is high. So for the best control results we suggest using a non-pyrethroid (e.g., Prevathon, Belt, Blackhawk, or Intrepid Edge). Note that Belt is not widely available this season due to the registration being canceled by EPA. Distributors and growers can use existing stocks according to label, but when that is gone, that will be it—at least as far as we know.
We also recommend adding a pyrethroid to the worm product to clean up any plant bugs/stink bugs that may be in the cotton. There are several pyrethroid options, and I would use the highest labelled rate for stink bugs—for better kill and longer residual. Besiege is the only product that contains both the non-pyrethroid (= Prevathon) with a pyrethroid (= Karate). With all the other non-pyrethroids, you will have to do the tank mixing on the farm. And, it is past time to include any of the insecticides in the neonicotinoid class as they do not provide good control of either bollworms or stink bugs.
The following invitation is being posted on behalf of Dr. Hunter Frame:
There will be a twilight cotton tour at the Virginia Tech Tidewater AREC Research Farm (1045 Hare Rd., Suffolk, VA) on August 31, 2016 from 4-6 pm. Supper will be provided after the tour. Please RSVP to Mrs. White by phone or email. The flyer is attached here: Tour_31_Aug_2016
Trial summaries for applied research on field crop disease and nematode control conducted in Virginia in 2015 are now available.
The following advisory is posted on behalf of Dr. Hunter Frame:
I want everyone to check out this letter for stakeholder input on the pollinator protection plan that is being developed by VDACS. So for the cotton producers the nearest meeting will be on February 22 from 6-8 pm at the Tidewater Agricultural Research and Extension Center in Suffolk, VA. This is an important issue that needs to be discussed and solutions need to be developed so no tools for producers are lost and bees/beekeepers are able to thrive next to cotton and other crops! Look forward to seeing everyone there!
The Eastern Shore of Virginia Ag Conference & Trade Show is on! We are snow free, and looking forward to a great event on January 26 and 27, 2016. The event will take place at the Eastern Shore Community College Workforce Development Center in Melfa, VA. The full program can be found at: http://issuu.com/esarec/docs/flipbookfinal/1. We have been approved for Certified Crop Adviser (CCA) CEU credits (details at: https://www.dropbox.com/s/f34f3spg4quni7a/CCA_Credits_Handout_2016.pdf?dl=0), Virginia Nutrient Management Credit (1 credit), and Virginia Pesticide Recertification credits (information in the program). See you there! Directions can be found at: http://es.vccs.edu/about/mapdirections/.
As of last week, we found bollworm eggs in cotton fields in numbers high enough to indicate that fields may need to be treated. The bollworm (= corn earworm) moth flight from corn is light and spotty, but it does not take many moths to cause concern in cotton.
In the old days before Bt cotton, we relied on the two spray system to control bollworms—the first spray applied at egg threshold followed by an automatic second spray 5 to 7 days later. This system worked very well to protect cotton from economic levels of boll damage.
With the advent of Bt cotton varieties (now TwinLink, BG2 and WideStrike) we found that even with these technologies, there were enough worm escapes (worms not killed by feeding on the plant toxins) to warrant a single insecticide spray. And—we determined that the best time for that single worm spray coincided with the second of the original two spray system—i.e., 5 to 7 days after the egg threshold.
Egg thresholds were found towards the end of last week in fields near the Tidewater AREC. The same is likely happening in fields across the region. So now is the time for applying a bollworm treatment. Based on our history of bollworm resistance to pyrethroids, the best control results will be obtained using a non-pyrethroid (e.g., Steward, Belt, Prevathon, Blackhawk). But we also recommend adding a pyrethroid to clean up any stink bugs that may be in the cotton. There are several pyrethroid options, and I would use the highest labelled rate for stink bugs—better kill and longer residual. Besiege is the only product that contains both the non-pyrethroid (= Prevathon) with a pyrethroid (= Karate). With all the other non-pyrethroids, you will have to do the tank mixing on the farm. And, it is past time to include any of the insecticides from the neonicotinoid class as they do not provide good control of either bollworms or stink bugs.
The following advisory is from Dr. Hunter Frame: Tissue Testing During Bloom in Virginia Cotton