I’m assuming we can say March came in like a lion, so hopefully, it goes out like a lamb! My thoughts have also been with our livestock producers, especially everyone calving with this extra difficult winter. It’s also been an interesting winter programming season for me-probably the worst travel wise ever with some scary trips. Grateful winter programming is concluding and extra grateful for safety on all the bad roads. My out of state travels often were to speak on palmer amaranth management. I don’t claim to be an expert on this, just seek to read, observe, and learn for helping our farmers. Well, palmer had another ‘win’ with the announcement this week of a population in Kansas being confirmed to be 2,4-D and dicamba resistant. Populations in Kansas had already been confirmed to be resistant to ALS, atrazine, glyphosate, and HPPD chemistries. The 2,4-D and dicamba resistant population was found at K-State Agronomy’s long-term (45 year) conservation tillage study in southern Riley County. This study compares long-term monocrops to various crop rotations. The seeds from plants that survived in the field were collected, grown, and exposed to dose rate studies at the K-State Agronomy Department greenhouse. Twenty-one days after treatment, the resistant progeny survived up to a 16X rate of 2,4-D (8 lb acid equivalent/acre (ae/a)) while susceptible progeny were killed with 1 lb ae/acre or less. The seed from plants that survived in the field were also treated with 0.5 lb ae/acre rate of dicamba with 81% of the plants surviving. Studies are ongoing to determine the level of resistance and additional cross-resistance to other growth regulator (Group 4) herbicides.
That’s why when I talk about palmer, waterhemp or frankly any of our weeds, to me, it’s about a system’s approach. We can’t rely on herbicides alone. I think of weed control beginning at harvest by not combining patches of weeds or extra weedy endrows. There’s research documenting 99% of palmer seed survives the combine. There’s also research proving seed dispersal from the combine throughout the field the following growing season by counting plants that resulted from the first several combine passes. Instead, I recommend to consider disking once or shredding those areas at harvest. Then get a small grain seeded to reduce light interception onto the soil surface. Why? Natural and red light has been proven by the research to stimulate germination of palmer seed more than soil temperature. Light interception onto bare soil can allow for a flush of palmer to germinate. So in managing palmer, I’m thinking of anything we can do that can delay or reduce germination. Palmer seed in general is short lived…7-10 years. But plants are prolific seed producers. A plant inside the field can produce up to ½ million seeds. The large plant at the field edge can produce up to 1.8 million seeds. Adding a small grain such as wheat or rye for grain back into the rotation can delay palmer germination for a few months as the crop canopy delays germination until after harvest. Research and observation has proven this as well. The exception to this has been when tram lines were in the field as the bare soil in the tramlines has allowed for palmer germination. After using a burndown to kill the germinating palmer flush after small grain harvest, a cover crop can keep the ground covered for the rest of the season and allow for managed livestock grazing if desired. Even if the small grain crop isn’t taken for grain, the cover alone helps reduce light interception onto the soil surface and palmer germination.
Going back to the tillage, the southern U.S. has gone back to the plow. We can’t afford that. There’s also many no-till guys where disking is a hard option to consider. Several research studies showed that a 1 time tillage to bury the seed at least 3-4” and keep it buried for at least 3 years reduced palmer seed viability by 80-100%. That’s why I’ve mentioned the tillage. I did ask Dr. Jason Norsworthy from the University of Arkansas about the possibility of just shredding weed patches at harvest instead. He doesn’t have research on that and I don’t have observation but it could be another option to consider instead of running the combine through weed patches at harvest. Regarding herbicides, I’m so proud of an increasing number of farmers last year using pre’s with residual followed by posts with residual. Herbicides are part of the strategy, but we’ve got to look at the whole system. And, we’ve got to rotate our use of dicamba! We rely on dicamba a lot for our corn apps. But if we use it in corn and soybeans, we have the potential in 3-4 years to have resistance develop here. Take Home Considerations: palmer/waterhemp/weed management begins at harvest by not combining major weed patches; Consider one-time tillage (or shredding) of endrows on fields with heavy palmer pressure. Then plant a small grain to remove light interception; Plan herbicide program for burndown, pre with residual, post with residual, and potentially a second post if in beans; Narrow row beans may help with canopy closure; Consider adding a small grain in the crop rotation; Use at least two effective modes of action; Rotate use of dicamba to maintain as a tool. What is perhaps positive is we have an opportunity to learn from the southern U.S. and manage palmer better here! If you missed the palmer amaranth webinar by Dr. Jason Norsworthy, you can view it here: https://unl.box.com/s/al5zrhxjwml7s31liv1bryne320bf6r6.
Palmer Amaranth: I’ve been speaking a lot this winter on palmer amaranth and a few shared it’s fairly depressing. The positive side of this is we have an opportunity to learn from the research conducted in the Southeastern U.S. regarding palmer management so we don’t get to where they’re at! Their top question for cash renting or purchasing ground is “do you have palmer?”…so we have an opportunity to manage it here now!
In order to do that, though, we need to think of a system’s approach. This approach may not be economical for every year, but a system’s approach looks at the long-term benefits as a whole.
The keys for palmer (or any weed) are to keep it from germinating and then, once germinated, keep it from seed production. Palmer germination has been found to be induced more by natural and red light than soil temperature. Thus, bare soil in the first few weeks of May allow for a good situation for palmer germination and emergence. Management to avoid early germination include: keeping the soil covered with residue, small grain, or cover crop; burndown apps and pre-plant herbicide applications. Palmer can continue to germinate throughout the growing season to mid-September. During the growing season, quicker canopy closure and post-herbicide apps with residual are key.
At harvest, management includes seriously considering not running your combine through palmer patches. We’ve had farmer success stories in 2016 when farmers didn’t harvest their soybean endrows but did harvest the rest of their fields. Instead, some chose to disk down endrows with heavy palmer pressure and planted a wheat or rye cover crop in them. In 2017, they shared it made a big difference in reducing palmer in those fields. I’ve also received farmer testimonials sharing the opposite; they wish they didn’t harvest the endrows or the one patch that had palmer in the field as now they’ve spread it throughout the field. Research has shown 99% of the palmer seed going through the combine is still viable; thus we’re just moving it throughout the field and from field to field.
Fire was not found to be effective to get hot enough to kill the seed when the whole field was burned. Instead, crews carry black trash bags, pull the female palmer plants, and haul them out of the fields burning them in burn barrels.
The University of Georgia found they had to hoe the plants 2” below the soil surface in order to kill them. An average palmer plant can produce 500,000 seeds/plant. The plant on the edge of the field can produce up to 1.8 million seeds. I had a hard time believing the seed production research from the soil surface (22,000 seeds on average) and 1” stem (36,000 seeds on average), until I saw it walking fields last summer. I remember tweeting out the pictures saying #hatethisweed.
A study conducted in Kentucky compared 1-Wheat with double crop soybean 2-Wheat fallow (no herbicides were applied) 3-Full season soybean. They counted palmer plants in 100 square feet in each replicated treatment. No palmer could be found in the wheat other than in the tram lines; the double crop soybean into the wheat stubble only had 5 plants/100 sq. ft. In comparison, the full season soybean
ranged from 18-40 plants/100 sq. ft. while the fallow ground had 80 plants/100 sq. ft. A system’s approach is considering adding a small grain like wheat back into the system. Or, at least consider wheat/rye as a cover crop to help reduce light interception onto the soil surface in early spring.
We’ve also heard more about tillage in the southern states. Palmer is a small seeded plant and the seed can actually germinate within the top two inches of soil. Spring tillage doesn’t appear to significantly reduce palmer germination compared to fall tillage. So the following is all from fall tillage research. Research has found that burying palmer seed at least 2” can reduce densities similar to control with pre- and post-herbicide applications. Research from at least three studies has shown burying palmer seed with a plow to 4” or using inversion tillage reduced palmer germination anywhere from 50-80%. Leaving the seed
buried for three years reduced palmer germination further. So, the suggestion is if you deep till, do it once and then get a small grain cover on the field to knock out the early spring light interception. At least two studies showed that fall inversion tillage followed by cover crop resulted in 85% reduction of palmer the next spring. I share this knowing we can’t afford plowing for soil loss, soil moisture loss, and tillage doesn’t fit some of your systems. It is a management option to consider if other options aren’t working for you. Summary: fall tillage once, get a cover on it, and then leave it alone.
Ultimately, the management keys are to ‘start clean and stay clean’ using burndowns, pre’s, several effective modes of action, keeping the ground covered to reduce light interception, and incorporating a small grain and/or cover crop into your system. Hopefully this helps as we think about managing palmer this coming growing season.
On-Farm Research Updates: One of my favorite winter programs is our Nebraska On-Farm Research Updates because of our growers presenting the research they conducted with us. These are upcoming next week starting Feb. 19 at former ARDC near Mead and Feb. 21 at College Park in Grand Island. Programs most days run from 9 a.m.-4:30 p.m. with registration beginning half an hour before each day’s program. Full details of dates, locations, and RSVP can be found at: https://cropwatch.unl.edu/2018/growers-statewide-share-farm-research-5-sites. Over 80 on-farm research projects will be presented this year including a wide range of topics: cover crops, variable rate seeding, planting populations, multi-hybrid planting, starter fertilizer, etc. Certified Crop Advisor Credits are applied for. Growers take an active role in the on-farm research project sponsored by Nebraska Extension in partnership with the Nebraska Corn Growers Association, the Nebraska Corn Board, the Nebraska Soybean Checkoff, and the Nebraska Dry Bean Commission. To learn more about the Nebraska On-Farm Research Network, visit http://cropwatch.unl.edu/farmresearch. Hope you consider attending!
Crop Insurance, Farm Bill Policy Update: Also reminding you about the final “Farmers and Ranchers College” program for our area this year to be held Feb. 23 in Geneva at the Fairgrounds. This workshop on Crop Insurance, Farm Bill Policy Update and More, will run from 10 a.m.-3 p.m. with registration beginning at 9:45 a.m. You can view the whole agenda and speakers at: https://vandewalleviews.wordpress.com/2018/02/02/crop-insurance-farm-bill-and-more/
Introductory Beekeeping Classes: Was asked to share about upcoming beekeeping classes. There are two course levels: one for beginning beekeeping and one for those who are currently keeping bees and want information on colony health and maintenance. Workshop details can be found at: https://entomology.unl.edu/bee-lab#tab2.
Mixer/Loaders and RUP Dicamba: Mixer/loaders are now required to have RUP dicamba training; however, they may not have a pesticide applicator license. On the RUP dicamba training registration sheets, just put “mixer/loader” instead of a pesticide applicator number. New pesticide applicators who haven’t received their number yet can just put “pending”.