Crops really look tremendous overall and got a report of some first tassels by July 4th as well! It’s been great to see people attending field days again the past few weeks and really appreciated the learning, sharing, discussion, and just watching people catch up with each other at them. I had mentioned before how the lack of freeze/thaw was impeding roots of crops, particularly soybeans in no-till fields. Irrigating and rain has helped them get some growth. What I hadn’t mentioned in my articles was being called to soybean fields with HPPD (Group 27) carryover from corn herbicides in 2020. We had a dry fall but had rain in March and May, so I wasn’t sure how to explain the carryover. One thing I learned last week from a discussion at the palmer amaranth field day was that the lack of freeze/thaw also impacts the ability of herbicides to breakdown. So, I appreciated learning that and am sharing if that helps anyone else as well.
Japanese beetles are also heavy in pockets of the area. I will share more specifics next week. For those who are asking, the threshold for soybean defoliation in reproductive stages is 20%. Tom Hunt, UNL entomologist shared that pyrethroids in general are effective. However, if there’s potential for flaring spidermites due to dry conditions, bifenthrin is a consideration as it has activity for spidermites (particularly when considering soybeans). For homeowners, beetles can be dislodged off of plants right now in evening hours by knocking them into buckets of dishsoap water. Do not use pheromone traps as they will actually attract beetles to your yard!
Western Bean Cutworm: With crops nearing tassel, it’s time to be scouting for western bean cutworm moths and egg masses. There was a CropWatch article posted this week at: https://go.unl.edu/9v4a. It was predicting 5% moth flight for York on June 30th, Harvard July 2nd, and Central City July 3. I received a text from a crop consultant saying he found the first eggmass in the Central City area July 2, so that was pretty well on target! Twenty-five percent of WBC flight occurs when 2,577 degree-days Fahrenheit are reached. Entomologists recommend field scouting should occur at this point. For 25% moth flight, it’s predicting York on July 6th, Harvard area July 8th, and Central City July 9th, so we should start watching fields for sure this week. Look for egg masses laid on the upper surfaces of corn leaves, typically on the top 1/3 of the plant.
Chiggers: I should’ve written about this last week as chigger bites tend to peak around the 4th of July with more families outdoors. Chiggers (also known as redbugs or jiggers) are the immature stages of red harvest mites. They tend to hang out in moist, tall grassy/weedy areas such as along streams, road-side ditches, forested areas, lawns. But they can also hang out in moist and dry lawns with a lot of trees too. They bite humans and other animals including pets. Eggs are laid on clusters on plants and the larvae hatch and wait for their host to come along. They latch onto clothing, shoes, and fur and can hang on while working their way to the skin (often to an area where clothing is tighter like around socks, undergarments, back of knees and under armpits). They actually don’t burrow into human flesh. They only survive on a warm-blooded host for around 3 days before falling off to molt for the next stage in life cycle which doesn’t feed on humans.
They have needle-like mouthparts that allow them to pierce the skin then inject saliva that dissolves body cells in the area to aid them in feeding. Thus, they don’t feed on blood but liquefied cells. The feeding creates an allergic reaction in which many see swelling, intense itching, and small, clustered, red bumps (which can become larger welts in some). To prevent chigger bites, avoid sitting or lying on the ground when picnicking or working outdoors. Wear loose-fitting clothing and apply a repellent like DEET to shoes, socks, and pants before going into areas more favorable for chiggers. It’s also wise to take a hot shower with plenty of soap as soon as possible after being outdoors and launder clothing with hot water before re-wearing. Also launder any blankets/sheets being used outdoors. If you receive bites, rubbing alcohol can be used then apply an anti-itch cream to help reduce itching. Thankfully chiggers can’t live in the home but they can become dislodged in bedding and on floors, so laundering bedding and vacuuming is also wise. Keep lawns and shrubs well-manicured, particularly where adjacent to dwellings. If you tend to have problems with chiggers in your lawn, they can be reduced from 75-95% for several weeks with a liquid treatment of bifenthrin. Be sure to read and follow all label instructions.
Crop Updates: I really appreciate all those in ag industry who share what you’re seeing in the fields; it’s a blessing to have a great network of people looking at fields in different areas of the state and sharing what we’re all seeing!
Western bean cutworm (WBC) moths were seen in corn whorls the past week. They’re
also showing up in UNL light traps in addition to industry ones. To view the UNL light trap reports near Clay Center, please go to: https://scal.unl.edu/ltr2019.pdf. The light trap near Mead is currently having black light issues, but the report can be viewed at: https://go.unl.edu/2usz and the light trap report from North Platte is at: https://go.unl.edu/a56b. WBC moths prefer laying eggs on upper leaf surfaces in corn that is in the late whorl to early tassel stage. UNL entomologists recommend scouting at 25% of moth flight. It’s unknown how larval survival will be impacted by corn growth stage at this time. Larvae survival is highest when they have fresh tassel tissue and pollen to feed on before moving down to developing ears and silks. Larval survival is lowest when only vegetative tissue is available to feed on. So, the delayed planting and growth in some fields may allow for less western bean cutworm damage in 2019. However, our entomologists say that air and soil temperature can also impact insect development leading to slower development of the insects. UNL Entomologists Tom Hunt and Bob Wright, along with University of Minnesota researchers, developed a degree-day model to predict when WBC moths will emerge to begin mating and laying eggs. In a recent CropWatch article, they were predicting 25% moth flight to occur for the following dates/locations: July 7th in Lincoln; July 11 in Hastings and Ithaca; July 12 in Grand Island and York; July 13 in Clay Center; July 15 in Holdrege, and July 23 in North Platte. Corn expressing VIP3A proteins are highly effective for WBC control. Corn expressing Cry1F (Herculex) proteins may provide some WBC feeding suppression but shouldn’t be relied upon for control. The current UNL economic threshold for treatment is 5-8% of corn plants with eggs or larvae.
Common Rust in Corn: The rainfall, humidity, and wet canopies have allowed for
increased common rust to be seen in corn this past week. I was seeing larger numbers of pustules on lower leaves of plants, but this week could also see pustules occurring in upper canopies. Pustules of common rust are typically brick red in color, larger, more separate, and can appear on both the upper and lower leaf surfaces. Southern rust typically has smaller, orange to tan colored pustules occurring in tight clusters on upper surfaces of leaves. However, the past few years, we’ve seen common rust looking more orange in color, including this year. The best way to confirm for sure if it’s common or southern rust is to check the spores under the microscope, and I’m happy to do that. The spores of common rust will be circular in shape whereas southern rust spores are more oval to football shaped. Samples can also be submitted to the UNL Plant and Pest Diagnostic lab. So far, every sample I’ve looked at has been common rust. Southern rust hasn’t been found further than Georgia and Louisiana to my knowledge right now. We don’t typically recommend fungicides for common rust. It will be important to continue scouting for diseases with the humidity and leaf wetness we’re experiencing this year.
Lawn and Garden Questions: The wet weather has allowed slime mold (gray-black fungal growth on leaves) in patches in lawns in addition to mushrooms in lawns and landscapes. They are harmless and fungicides aren’t effective. They will go away upon drying out and with warmer weather.
Bagworms are out and it’s time to control them if you have them. The following gives more detailed info on their life cycle: https://go.unl.edu/rgju and this YouTube video shows what you’re looking for this time of year on your trees: https://jenreesources.com/2015/06/27/bagworms-in-evergreens/.
Japanese Beetles may be causing holes in Linden trees or rose leaves. They are
green/brown beetles with white hairs that look like rows of white spots near each wing. Kelly Feehan in Platte County shares that “applying insecticides to lawns to control grubs will not prevent beetles from feeding on landscape plants. The product ‘Milky Spore’ sold to kill them, does not work. On landscape plants, hand picking or knocking beetles into a bucket of soapy water around 7 PM is the best time of day to do this as it prevents plants producing a distress pheromone that attracts more beetles. Japanese beetle traps work very well – IF you want to attract them to your yard – so traps are best NOT used. If a Linden tree has Japanese beetles, know these trees CANNOT be treated with Imidacloprid or other Neonicotinoid insecticides.” Carbaryl (Sevin) is effective to use for Lindens and landscape plants where it’s not feasible to remove beetles by hand.
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.