Warm weather with sunshine this time of year prompts a tiny insect looking for final
food before winter to cause a painful bite on humans. I’ve received several questions about “what is that tiny black bug with white marks on back that bites?” The insect, known as the minute pirate bug (and insidious flower bug), is actually a beneficial predator of thrips, mites, aphids, tiny caterpillars, and insect eggs. People will even purchase these insects for biological control, particularly in greenhouse settings. They’re found throughout crop, garden, landscapes, and wooded areas in the summer preying on other insects. However, this time of year they start biting humans they land on. One doesn’t need to worry about them injecting a venom, feeding on blood or transmitting disease. People’s reactions to the bites range from no reaction to swelling like a mosquito bite. Unfortunately there’s also no method of controlling them. Insect repellents don’t work as they aren’t attracted to carbon dioxide like mosquitoes are. They are attracted to light colored clothing, so wearing darker colors and long sleeves can help when being outdoors during warm, sunny days. Otherwise, work outdoors on cool, cloudy days.
Bagworms: This year was a heavy year for bagworms and I’m still receiving calls about treating for them as people find damage. We would recommend it’s too late to treat now as eggs have been laid in most bags at this point and insecticides, including systemic ones, won’t move inside the bags to kill any adults or eggs within the bags. Wherever feasible, you can reduce next season’s load by picking off bags and either squishing them or drowning them in soapy water. Simply throwing them on the ground doesn’t help. I was even finding bags that had dislodged from windbreaks in adjacent crop fields this year with larvae traveling back towards the windbreak! Between 500-1000 eggs can be found in one bag. Aim for insecticide applications next year when larvae hatch and feed, usually at some point in June.
Harvest Thoughts: Several times the topic of palmer amaranth came up this week while in the fields with palmer in patches or especially on field edges. I believe the first step of palmer management begins at harvest by choosing to not run the combine through those patches. Research from the southern U.S. showed 99% of palmer seed survives the combine and we also know the combine is very effective at seed dispersal. Several farmers have shared they could see the worst palmer spreading in their fields the following year where the first combine pass occurred. Research supports this. The highest number of new palmer plants counted in a field were found the successive year where the first combine pass occurred after combining a patch of palmer. So some suggestions to consider: 1-Consider disking or shredding patches of palmer. 2-Plant a small grain like rye or bin-run wheat into endrows and/or patches where palmer was present. Research has shown that burying palmer seed 3-4” and leaving it buried for 3 years can reduce germination 80-100%. I realize disking doesn’t necessarily go that deep and that it’s difficult for no-till guys to want to do any tillage. Shredding won’t kill seed, but it will keep the seed from going through the combine. The small grain will help reduce light interception to the soil surface next spring. That’s the #1 trigger for palmer germination-light penetration on bare soil.
Also, I realize it’s difficult to achieve, yet a reminder to check your beans and harvest as close to 13% as possible. A number of fields last week even with green stems and some leaves remaining on lower plants were actually at 13% when harvested. Delivering soybeans below 13% reduces profits while there’s a dock for delivering wet beans. While not a dock, less than 13% moisture results in fewer bushels to sell (load weight divided by 60 lbs/bu assuming 13% moisture). Selling soybeans at 8% moisture, you’re losing about 5.43% yield; at 9% moisture, it’s 4.4%; at 10% moisture, 3.3%; at 11% moisture, 2.25%; and at 12% moisture, it’s 1.14% yield loss. That doesn’t take into account additional risk for shatter losses during harvest. So another consideration as we consider economics and profitability this year.
Crop Updates: It was nice to see corn greening up and getting some growth this past week! Also on people’s minds is the 45 day post-planting application deadline for RUP dicamba herbicides. The announcement that Risk Management Agency (RMA) adjusted the 2019 final haying and grazing date from Nov. 1 to Sept. 1 for prevented planting this year opened up additional options for our farmers affected by flooding and/or excess rain. An additional option was that “silage, haylage, and bailage should be treated in the same manner as haying and grazing this year. Producers can hay, graze or cut cover crops for silage, haylage or baleage on prevented plant acres on or after September 1 and still maintain eligibility for their full 2019 prevented planting indemnity.”
So how did this change things? Many I talked with, including my family, were originally planning on going with cool season covers like oats planted the first week of August. However, with the ability to harvest a cover crop for forage on Sept. 1, interest increased in utilizing warm season cover crops. For those planning on haying, our forage specialists recommend using millets. The regrowth after haying could then be used for grazing in the late fall/winter. They also said if you’re planning on a mix, don’t add brassicas into whatever you decide to hay as they don’t dry down and tend to create a moldy spot within hay. If you’re looking at grazing only, sudangrass, sorghum sudan, millets, and/or mix with other species are great options. Forage sorghum is a great option for silage.
The other consideration is that some of this ground going into prevent plant already had PRE herbicides applied, making legal options for cover crops that could be grazed or hayed difficult. So Friday was kind of a crazy day for me walking people through options. Honestly, sometimes corn or milo for silage ended up being the most feasible option based on labels. There are also acres of corn and bean fields that were drowned out due to recent flooding and are now considered a “failed crop” by FSA. Herbicides that were applied can make planting covers in those fields difficult too. Some farmers had contracts with seed companies providing free seed for replant. Thus, once again, corn for silage seemed like a feasible and economical option. So, I called Jeff Peterson at Seward Co. FSA to see if this could be an option. He said that it would be a feasible option in 2019 if it was also approved by the person’s crop insurance agent. The first step is to contact your crop insurance agent to discuss your options for prevent plant and/or failed crop. Then go to your FSA office and fill out their form for failed crop and/or prevent plant. Your crop insurance company may require a letter from Extension stating that corn can be used as a forage crop for silage. Again, it will be important to talk with your crop insurance agent and your FSA office about your options for the fields in your counties as I can’t guarantee these are options for every situation.
Tree Problems: The rain and humidity have allowed for numerous fungal diseases on our evergreen and deciduous trees. On deciduous trees, leaves with black/brown spots may be found. We don’t typically recommend fungicides for them and if the diseases get bad enough, the leaves may eventually fall off the trees early. A new flush of leaves typically follows 10-14 days later. On evergreen trees, we’re seeing a number of needle blights and shoot tip blights. We do recommend fungicide applications for them (typically in April or May). However, it is recommended to repeat them every 3-4 weeks when frequent rains occur. Product options for most evergreen diseases include chlorothalonil or a product containing Copper that is labeled for evergreen tree diseases. Bordeaux mixture is often recommended, but I have a hard time finding anyone that carries that.
Also, be checking trees for bagworms. They’re later this year and just forming new bags. In order to see them, what I do is walk up to the trees (especially cedars or spruces) and just watch the branches for any movement occurring on them. If you’ve had a bagworm problem in the past, what you’ll see is tiny, new brown bags moving as the larvae is building a new bag. I have more info and a video to help visualize what to look for: https://jenreesources.com/2015/06/27/bagworms-in-evergreens/. The best time to spray them is when the bags are less than ½ inch in size. More info and products can be found here: https://go.unl.edu/rgju.
Crop Updates: A great deal of timely information was provided in this week’s CropWatch at http://cropwatch.unl.edu including information about high heat and pollination, applying fertilizer during pollination, western bean cutworm scouting, forecasted yields, etc. Please check it out!
Several called me asking about applying fertilizer during pollination. I shared that while
I wasn’t aware of research, I personally was concerned about anything potentially interfering with pollination and that I do recommend 30 lbs of N at brown silk if needed or if you were originally planning split nitrogen apps. This is based on research from Purdue sharing today’s hybrids use 30-40% of their total Nitrogen from flowering through maturity. After discussing with Dr. Tom Hoegemeyer, Adjunct UNL Professor of Practice, he offered the following insights: “Pollination mostly occurs between 8:30 a.m. and Noon. Thus, as a precaution, I would not run a pivot on pollinating corn from 6 a.m. to Noon. When the temperature is 90°F to 95°F, the pollen is killed by heat and is seldom viable past 2 p.m. That leaves lots of time to run pivots, apply N, etc. when it won’t harm pollination. Silks tend to be viable for three or four days at these temperatures, so if a plant isn’t pollinated one day, generally the next day will work just fine. (If nitrogen is needed), I’d recommend that nitrogen go on as soon as practical. Corn nitrogen use is very high during the pre-tassel growth phase and again at kernel growth, from one to three weeks post pollination. About seven to ten days post pollination (before brown silk) lower N will start causing kernel abortion and serious yield loss in corn.” The UNL recommendation for fertigation is to use 30 lb of N with 0.25″ of water or 50-60 lb of N with 0.50″ of water.
Last week also brought questions regarding thresholds and difficulty in finding Western Bean Cutworm egg masses with moth flights at their peak. You can view light trap data from UNL’s South Central Ag Lab thanks to Terry Devries at: https://scal.unl.edu/ltr2018.pdf. There’s also a great article in this week’s CropWatch on how to scout for them, insecticide options, and additional recommendations. Thresholds for western bean cutworm are 5-8% of corn plants in the field containing egg masses or larvae. Egg masses can be difficult to find during pollination with pollen hiding them. ‘Typically’ egg masses are found in the top third of the plant on the upper sides of leaves and near midribs or leaf axils. However, with higher heat, I tend to find them closer to the ears and have even seen masses laid on the ear husks and on the backsides of leaves (not common). While larvae are generally known to move up the plant to feed at the tassels, I’ve seen high heat force larvae into ears earlier. It typically takes 5-7 days for larvae to hatch and the egg masses turn purple just prior to hatching. A number of insecticide options are available for both aerial application and via chemigation; these products are listed in the CropWatch article.
With insecticide applications occurring in corn for both western bean cutworm and also corn rootworm beetles, many have also called or talked with me about the recommendation of fungicide applications. Right now, I haven’t found gray leaf spot above 3 leaves below the ear leaf in several counties. There’s been some mis-diagnosing bacterial leaf streak as gray leaf spot. Southern rust was just confirmed in a Kansas county this week, but we still have yet to confirm it in Nebraska. Even the longest residual products won’t get us through August if a fungicide application occurs now. I can appreciate that economics are tight so the thought is to save an additional application cost by applying a fungicide now with the insecticide. And, I can appreciate economics are tight regarding why apply a fungicide right now when disease pressure doesn’t warrant it? Perhaps, at least those of you with the ability to chemigate could consider waiting till disease pressure warrants it for your field, if it does. Always in the back of my mind is the need for late-season protection with southern rust eventually showing up and gray leaf spot often worse then.
My perspective is from a resistance management and research-based one. We have 5 total modes of action for fungicides with 2 of them being in nearly every fungicide product we use in corn, soybean, and wheat because they work against foliar fungal pathogens. At some point, our pathogens will also adapt, as we’ve seen our weeds and insects do…it would be like losing our ability to control gray leaf spot and southern rust similar to palmer amaranth on the weed side. In Nebraska, Dr. Tamra Jackson-Ziem’s research has not shown an automatic yield increase to fungicide application in the absence of disease. And, it has also not shown an automatic yield increase when applied at tassel. In a high heat and low disease year like 2012, there were no statistical yield differences with fungicide application vs. the untreated control. Even in years with some disease pressure such as 2008-2010, she found no statistical yield differences between when various products were applied from Tassel through Dough stages. In high disease years, her research shows the benefit of fungicide application for reduced disease pressure and increased stalk strength. Fungicides are great tools to help us with disease pressure and stalk strength. Just would encourage all of us to consider when we really need to apply them and to understand that research in Nebraska does not automatically show increased yields with the use of them or with the timing of Tassel/Silking vs. later in the year. Also, hybrids may vary in their response due to disease susceptibility and other factors. Not all her data is listed at this site, but you can view it for yourself at: https://go.unl.edu/ni3y.
Bagworms: I’ve been seeing shelter belts and various trees turning brown from heavy
bagworm infestations. Please be checking your trees if you are noticing them turning brown. Additional information can be found at: https://go.unl.edu/rgju.
This past week contained many off-target herbicide concern calls. Prior to Memorial Day I had made a note that post-herbicide applications to corn began in much of the area and anticipated phone calls to begin in about two weeks. Most of the conversations this week were more FYI to let me know they had soybean leaf cupping.
Here’s a few things to consider if you are having soybean leaf cupping.
- First, was a post-herbicide application made to your soybeans? If so, check for any potential tank contamination (Check out this CropWatch article: https://go.unl.edu/fnig). If not, check out this publication (http://ipcm.wisc.edu/download/pubsPM/dicamba2004.pdf) to determine if any of the criteria mentioned could possibly be contributing to the problem.
- Determine how old the plant is by asking when the soybean was planted and even better when it emerged. A soybean plant will produce a new node every 3.75 days.
- To determine the timing of damage, I count the total number of nodes on the plant to the last trifoliolate where leaf edges are not touching. The total number of nodes may differ in different parts of the field such as irrigated and non-irrigated especially after herbicide damage and drought-stress (Example 8 nodes irrigated and 6 non-irrigated). Take the number of nodes X 3.75 to get total approximation of plant age. Then count back on the calendar to determine approximate emergence date. If I use 8 nodes in this example X 3.75 = around 30 days ago the plant emerged.
- I then count the number of nodes to the very first damage I see on leaves (Example 3). Multiply this number of nodes times 3.75 and count forward on the calendar from emergence to that date. For instance, in this case, damage occurred around 11 days after emergence.
- I also like to count how many completely unfurled trifoliolates are affected (Example 6 trifoliolates). Take that number and multiply by 3.75 (Example 6 X 3.75= approximately 23 days ago the damage occurred).
- In this example, it worked to count either direction (from emergence and from current date) to determine approximate timing of off-target movement occurring. In all the situations I’ve looked at thus far, the timing goes back to around Memorial Day with post-dicamba herbicide applications applied to corn.
- Auxin-like herbicides affect only cell division. Thus, fully developed leaves (no longer expanding via cell division) are not affected even though they may be expanding by leaf cell enlargement. Only the tips of the newest exposed soybean leaves may experience damage to dicamba as they are still undergoing cell division. Otherwise, it can take 7-14 days for leaf damage from dicamba injury to appear on susceptible plants and damage will occur typically 4-6 nodes. This is because dicamba is also translocated once inside leaf cells. Thus it impacts cell division of the leaf primordia at the stem apex. We may not even see those leaves yet because they are still enclosed in the stem apex tissue.
- In a matter of weeks, affected fields can go from appearing to have minor damage, to looking really bad, to growing out of damage. It looks worst when those affected nodes push upward giving the field a grayish/white cast to it as the leaves become much reduced in size and are tightly cupped. Eventually the leaves will begin to look more normal again in time (as long as a second off-target movement doesn’t occur).
What can you do? Water via irrigation and/or rainfall is the best recovery tool for dicamba damage. Waiting is another. We’re blessed to grow indeterminate soybean in Nebraska which continues to produce nodes and leaves upon flowering which allows our soybean to grow out of damage.
- Wait till harvest to determine any yield impacts if there are areas impacted vs. those which aren’t. Otherwise, field-scale damage is difficult to discern yield impacts.
- You can talk with your neighbors/ag retailers regarding what they sprayed. In our area of the State, it’s often difficult to pinpoint the source of off-target movement with so many applying dicamba products to corn for palmer control often around the same time-frame. Now that post-apps to soybean are also occurring, that may also become a challenge. Of all the fields I visited last year, less than a handful of farmers sought any sort of compensation and those were more often due to tank contamination issues. If you wish to pursue that route, you need to file a complaint with the Nebraska Department of Ag.
- For future dicamba applications, check out these best management tips: https://go.unl.edu/97ok.
- For those of you reading this in a source outside of my blog, I created a video to hopefully be more visual and clear on understanding this method of diagnosing timing. You can check it out at my YouTube site: https://www.youtube.com/user/jenreesources.
Bagworms: It’s June and one of my top questions has been “Have I found bagworms yet?” Well, they’re now feeding and forming new bags on junipers and spruces. What you’re looking for are not the old bags at this point, but very small (fingernail size) new bags that move as the caterpillar is feeding and making the larger bag. This video from Backyard Farmer (https://youtu.be/05A2quj9nO4) does a great job of showing various stages of bagworms and sharing on control methods. Check it out!
Irrigation Scheduling Workshops: Steve Melvin, Extension Educator in Hamilton/Merrick Counties asked I share about upcoming irrigation workshops hosted by UNL and Upper Big Blue NRD. The program will focus on installing the equipment and making irrigation scheduling decisions using the data generated by Watermark sensors. The workshops will be held from Noon-1:30 p.m. on June 25th at the Corner Café, 221 Main St in Stromsburg and also at the same time June 28th at the Hordville Community Building, 110 Main St. The Upper Big Blue NRD will provide the lunch. The first presentation will be Installation of Watermark Sensors and Data Logger presented by Dan Leininger, Water Conservationist with the Upper Big Blue NRD. The second will be Deciding When and How Much Water to Apply Using Watermark Sensor Readings presented by Steve Melvin. The irrigation scheduling strategies presented in Steve’s presentation can be used with any soil water monitoring equipment data. More information is available by calling Steve Melvin at (308) 946-3843 or visiting https://extension.unl.edu/statewide/merrick/.
Somehow April flew by without me reminding you to apply fungicide sprays to Austrian and Ponderosa pines that have had problems with Sphaeropsis tip blight in the past. I’ve also received several scotch pine samples in the office to diagnose for pine wilt nematode. While there is no cure for pine wilt, I recommend to take a 6” long, 1-2” diameter sample of a dead branch to your local Extension office for diagnosis before cutting down the tree. Pine wilt affects Austrian (long needles groups of 2) and Scotch pines (short needles in groups of 2) as they are non-native trees while the nematode is native. Since ponderosa pines (long needles in groups of 2 and 3) are native to Nebraska, they don’t seem to be affected by pine wilt nematode.
Pine wilt is caused by beetles carrying pine wood nematodes vomiting them into the water-carrying vessels of the tree (xylem). The tree senses the nematodes and essentially blocks water to those branches. Often you will observe a branch then perhaps a side of the tree and eventually complete death of the tree within 6-9 months. While I have diagnosed many samples of pine wilt, more often when I visit homeowners the tree problems are due to fungal diseases which occur on the needles. If you look closely at your needles and observe dark bands or rings on them followed by death of the needle either direction from the band, the tree problem is most likely due to a fungal needle blight like dothistroma in Austrian and Ponderosa pines or brown spot in Scotch pines. They can all be prevented by spraying a fungicide containing copper sulfate in the spring.
With everything about 3 weeks early this year, now is the time to spray Ponderosa and Austrian pines for needle blight and spruce trees that have had problems with needle cast or shoot blight where the new growth has died in the past. In early June spray for needle blight problems in Scotch pine and cercospora blight on cedars. If you have a windbreak of combinations of these trees and don’t want to spray twice, I recommend at least spraying in early June to catch all of them. Increasing air flow by cutting out some trees is another way to reduce fungal diseases on your trees.
Also watch trees for bagworms as you may be able to tank mix a fungicide/insecticide application in early June if needed. We would recommend picking the bags off trees and burning them, but that’s just not feasible in windbreak situations. To know when to spray, take a few of the bags off the tree, place them into a plastic ziplock bag, and place outside on the south side of your house. When the larvae emerge from the bags, check your trees to see if larvae can also be observed on them. Pyrethroid insecticides are recommended for managing bagworms because they cause an irritation that makes the larvae leave the bags and allow them to be exposed to the pesticide.
Great brochure! Evergreen Diseases