Category Archives: Insects
Japanese beetles: Hopefully this is the last week I talk about these! Hoping they’re coming to an end for this year as I’m not hitting as many while driving! Seems like each week brings new questions that I hope will be helpful to share. For tree and garden products, please check the handout which can be downloaded from the front page of york.unl.edu.
In replant corn and soybean fields, the beetles are attracted to the older plants (check strips/original bean plants); they shouldn’t be going after the replant ones. I’ve heard areas (not hail damaged) have sprayed beans at least twice. People wondered if this is to be expected with products that should have 14 days residual. In talking with Bob Wright, he says there’s little research on Japanese beetles on chemical efficacy. The soybeans continue to produce new leaves and the herbicides, although there’s residual in the pyrethroid products, doesn’t translocate to new leaves. Sunlight also breaks down the herbicide in leaves. Increasing water helps with coverage (helpful if increase to at least three gallons in aerial applications-same for fungicide applications). Chemigation is an option too.
I’ve also been asked about adding other nutrient and biological products, etc. to tanks to increase the plant health. While I’m not opposed to the concept of healthy plants fending off insects/pathogens, I don’t know of research to comment on that for Japanese beetles. Sidenote (not necessarily Japanese beetle related), when I’ve been called out to problem situations in fields this year, numerous times there’s been a large number of products placed in the tank. I just wonder how all these things are truly interacting together and if we’re potentially creating problems (increasing selection pressure and resistance) on weeds, insects, pathogens by potentially reducing efficacy of the original pesticide product that was meant to be sprayed before everything else (plant growth regulators, micros, etc.) was added. Again, no research, just a consistent observation in field calls with problems this year.
White Grub Prevention/Control in Lawns: Been getting questions about grub prevention as well since the Japanese beetles lay eggs in lawns. Control depends on proper timing of the application and moving the insecticide into the root zone where grubs feed. Preventive control applications are made from mid to late June. They can work in early July (it’s potentially too late now). Curative or rescue treatments are made in August or September and I will talk about those products next month.
Preventive – Most of the preventively-applied insecticides are systemic in nature and will be taken up by the plant and translocated to roots. The following products are effective against young grubs and are labeled for homeowner use: Chlorantraniliprole –Scotts GrubEx; Imidacloprid –Bonide Grub Beater, BioAdvanced Season Long Grub Control + fertilizer.
Check Grain Bins: With all the work of starting crops over the month of June, checking grain bins wasn’t as high on the list for many in this area. Two farmers suggested I mention checking grain bins this week as they had found some hot spots and were thankfully able to get things under control.
Take Care of Yourself! I know how worn down I’m feeling each week, and I’m not in the shoes of you as the farmers and landowners who have went through so much loss. These storms keep giving as people find additional damages to buildings, equipment, trees, crops, etc. I realize with the heat it’s not realistic for many to get away for long. There will always be a list and few of us ever ‘catch up’. But there’s only one of each of us. My challenge for us this week is to take some intentional time to reset…whether a half hour or a few hours. Spend the time doing a hobby, resting, strengthening your faith, catching up with someone. We need these breaks and I’m doing that as well. Be sure to stay hydrated with the heat too!
Cover Crop and Soil Health Field Day: This snuck up on me and I failed to talk about it sooner; it will be held this Tuesday July 19th from 10 a.m.-2 p.m. (Registration at 9:30 a.m.) at the 4-H Building at York Co. Fairgrounds. Topics include: understanding soil health, the Nebraska soil carbon product cover crop study; On-Farm research cover crop study update; and Cover crops for upland game birds. Following lunch there will be a cover crop field site visit with a demonstration of how to conduct a soil health inventory. There is no charge but please RSVP for meal count to Nate Pflueger at 402-646-5426.
Grateful for some rain last week! Hail damaged trees (particularly evergreen trees) need water now to help them heal all the open wounds on the branches, stems, trunks.
Western Bean Cutworm Moths should be around 25% flight for corn nearing or tasseling in much of the area. It was predicted for Guide Rock on July 5, York on July 10, and Clay Center on July 11. This CropWatch article shares dates to watch for around the State: https://go.unl.edu/nmye.
Japanese Beetle Control: I posted a second blog post last week on organic and conventional control products that are sold in this area at local farm stores, lawn/garden centers, Wal-Mart, and Ace. You can print it out from the font page of the York Co. Extension website: https://go.unl.edu/bvqf.
Even after applying pesticides, beetles will continue to emerge and fly in from grassy areas (ditches, lawns, pastures) for a good 4-8 weeks. Plants that are being chewed on elicit responses signifying they’re in trouble. It’s those responses that signal other beetles to come. Even though linden, fruit, and other trees and plants are rapidly defoliated, they should not die. On younger trees that were hail damaged, I’m unsure if the hail + the beetle defoliation is too much stress for survival; we will have to see. I’m also unsure if we will see new leaves in general after beetle defoliation this year or not; trees are super stressed already from all the hail damage. I’m observing new leaves are very slow coming back on broadleaf trees post-hail and that was before we also had the beetle defoliation.
I probably should’ve realized this, but another thing I learned this week is there’s two formulations of ‘Sevin’ being sold. I don’t mention that on the print-out mentioned above. One is the traditional carbaryl that lasts 5-7 days. The other is zeta-cypermethrin which has a residual of 14 days (farmers would recognize this ingredient in Hero and Mustang Maxx). I’m not sure why the company branded both products the same name. The Sevin carbaryl product says it will ‘cause damage to boston ivy and virginia creeper’…both of which are favorites of Japanese beetles. So, that was something new I learned by reading the labels and being called out to an unfortunate incident with boston ivy. I didn’t see that same warning on the Sevin zeta-cypermethrin product, but please check it for yourself if you use it.
Japanese beetles are in corn and bean fields as well. Watch silk clipping in corn and pod clipping in beans (seeing both occurring). Tasseled corn threshold: three or more Japanese beetles per ear, silks have been clipped to less than ½ inch, and pollination is less than 50% complete. Soybean has 20% defoliation once flowering occurs. It’s been interesting seeing beetles defoliating palmer, waterhemp, smartweed, etc. Too bad we couldn’t train them to just eat the weeds!
Hail Damage and Corn Pollination: This one is just hard and I’m genuinely hoping this isn’t as big of an issue as what it looks like. For corn that was V9-V11 during the June 14th storm, check the tassels and the ears. What I’m seeing in fields that were severely stem bruised but not totaled, are ears that are hip high on me with silks that are up to 5” long right now. Tassels are mostly 1-2 leaves from tasseling. Opening up the leaves shows severely damaged tassels with minimal to no anthers. Some anthers are trying to pollinate within the leaves (pics on my blog). It’s normal for silks to emerge before tassels as that’s what breeders have bred corn to do. It’s not normal for the tassels to emerge this much later than the silks and to be so severely damaged. It will be something to watch in all the hail damaged fields that were kept from June 14 storm to see if the pollination timing is impacted in them as well. What I’m recommending is for now, check your fields and take pictures of the tassels and ears for documentation of any problems if crop insurance can’t come out. I’m hoping I’m wrong and that we can still get some decent pollination in these fields.
This is one of a few fields looked at that was between V9-V11 during the June 14th hailstorms. It had severe stalk bruising at the time and around 22-24K for population. Long silks with very few tassels out. Top left tassel was a decent tassel found that was out. Most tassels are within 1-2 leaves of emerging, are severely damaged from the hail, and some were shedding what pollen they were producing while inside the leaves (bottom left photo).
Japanese Beetle Organic and Conventional Products Found Locally
With the Japanese beetle invasion in the area and their territory spreading further each year, I checked with local retailers (nurseries, lawn/garden centers, farm stores, Wal-Mart, Ace) to see what they have on hand to hopefully be of help.
First, Please Read the Label on any product before you purchase it to make sure:
1: the product says it controls Japanese beetle adults
2: the product is labeled for where you wish to apply it (vegetables, trees, ornamentals, fruit trees, berries, etc.)
3: follow all pre-harvest intervals (PHI) for when you can safely harvest vegetables, fruits, and berries after a product is applied.
Last year I had to unfortunately tell three people they couldn’t eat the produce from their gardens due to the product they sprayed.
Second, there are a number of insecticide options available. Know that most anything applied to flowering plants will also impact pollinators. For flowering plants like roses, cannas, etc., knocking the beetles off around 7 p.m. in the evening into soapy water will protect pollinators visiting them.
There are also ready to use and concentrate versions of chemicals available. The easiest are ones where you simply attach the garden hose and spray. Others need to be mixed with water into a sprayer.
Organic Insecticide Options include Neem, Pyola, Spinosad Soap, Pyrethrin products (ex. Beetle and Boxelder bug killer), and Bt. Neem may repel more than kill Japanese beetle adults. These products will all last around 3-7 days and will need to be reapplied. Products containing these active ingredients should be safe on fruits, vegetables, in addition to using on flowers, shrubs, and trees. Be sure to read and follow directions as there may be a temperature restriction on applying some of them that contain oils to avoid burning leaf tissue.
Conventional insecticide Options can provide up to two weeks of control. I’m going to separate these into products I found locally based on the location they can be applied. Ultimately, this is NOT a complete list and many other products can also be found online. There are also products containing insecticide + fungicide that I don’t list here. Please be sure to read the label for yourself as to the insects controlled and where it can be applied before purchasing.
1. Ornamental shrubs, plants, trees (like linden, elm, birch): DO NOT use these products on vegetables, fruits, or berries. Hi Yield 38+ and Tempo. There’s home defense products labeled for Japanese beetle adults but they don’t mention they can be applied to trees or shrubs.
2. Vegetables, fruits, ornamentals, shrubs, trees: BioAdvanced Rose and Flower Insect Killer, BioAdvanced Tomato and Vegetable Insect Killer, BioAdvanced Vegetable and Garden Insect Spray, Eight, Spectracide Acre Plus Triazicide Insect Killer, Hi-Yield Lawn/Garden/Pet/Livestock Insect Control, Sevin, Ortho BugClear, and Ortho Bug B Gone.
Many of the conventional insecticide products contain pyrethroids such as bifenthrin or permethrin. Thus, there are also products that just say ‘bifenthrin’ or ‘permethrin’ that can also be purchased. Be sure to read the label as some have restrictions such as “can’t be applied to apples” while others can.
Fall Armyworms: Received numerous reports of fall armyworm damage this past week from Kansas-Nebraska state line north to York. Damage was occurring in new alfalfa seedings in addition to established alfalfa, a new triticale seeding, and several lawns. With moths still being observed, we may see fall armyworms around for a few weeks yet, so it would be wise to be watching any alfalfa, wheat, rye, triticale and lawns for them. There’s no good way of knowing where they’ll appear; it’s all based on where the moth chooses to lay her eggs. Several reports of one field affected while the field next to it is fine. Same with lawns. Egg masses are fuzzy white masses that can include up to 200 caterpillars and the eggs can hatch in 2-5 days. Newly hatched larvae will be thin and often black/gray in color. I have some pictures from my colleague Jody Green at jenreesources.com.
In town, if you find the egg masses on lawn furniture, siding, or garden features, simply wipe them up with paper towel and discard in the garbage. They’re far easier to control when the larvae are ¾ inch or less. When they get larger than this, insecticides aren’t as effective, and usually, by that time, so much damage has occurred that the area will need reseeded. Products with active ingredients such as bifenthrin or permethrin are effective and are options for both farmers for fields and also homeowners with lawns. Sevin is also an option for both. Kentucky bluegrass lawns may be able to recover from rhizomes regrowing in the spring. However, fescue and ryegrass will need intervention this fall for reseeding. An organic insecticide option is Dipel which will take a little longer to work, but is still effective on smaller larvae. For lawn situations, it’s important to water the insecticide product in the ground to get the granules off the leaf blades and into the soil.
(Photo caption: Fall armyworm moth, egg mass, and larvae. Photos via Jody Green and UNL Entomology).
Large grubs on concrete: Had several reports last week of large white grubs on concrete stairs, sidewalks, and driveways. They are really large, up to 1.5 inches. What’s interesting about them is they crawl on their backs! These are grub larvae of the green June beetle which is a large beetle that often sounds like it’s ‘buzzing’ during June and July. The adult beetle can cause damage to ripening fruits such as stone fruits and berries. However, the grub larvae are not a major turf pest, unlike other grub species. They feed on thatch layers and organic matter, but don’t really attack lawn roots. They make holes in the soil, so rain and irrigation will drive them out onto concrete.
Small Grains and Weed Control: Last week I mentioned considerations for wheat planting. Even if small grains aren’t taken for seed, they do a tremendous job for weed and erosion control, provide an option for grazing, and uptake excess moisture and nutrients (helpful in seed corn field situations). Small grains, particularly oats and rye, have been proven to help with reducing soybean pathogens such as fungi and nematodes causing SDS and SCN. I’ve been watching a couple side-by-side soybean fields in which one was planted green into rye and the other didn’t have rye. Even the farmer commented on it to me this week how the quarter without rye has senesced earlier and has problems with anthracnose and Diaporthe complex (including pod and stem blight) while the other is essentially disease free.
Wheat provides an option for both grazing and grain. Rye provides the best option for earliest green-up/growth in the spring and longest seeding time as it can be seeded into December. Triticale provides the most biomass, including for haying and small grain silage, but produces the latest into late May/early June. It’s too late to plant oats for the fall, but they are an option for the spring. All keep the ground covered from light interception penetrating the soil surface which allows weed seeds to germinate.
Researchers from K-State looked at marestail (horseweed) and palmer amaranth control from 2014-2015 in no-till soybeans at six locations in eastern Kansas. They also found the majority of marestail emerged in the fall (research from UNL showed up to 95% does). They compared five cover crop treatments including: no cover; fall-sown winter wheat; spring-sown oat; pea; and mixture of oat and pea. Cover crops were terminated in May with glyphosate and 2,4-D alone compared to a control of no herbicide use. Ten weeks post-termination, palmer amaranth biomass was 98% less in winter wheat and 91% less in spring oat compared to no cover crop and no herbicide control. The same cover crops were also compared to a no cover crop treatment where all received a May herbicide application of 2,4-D and glyphosate with residual herbicides of flumioxazin + pyroxasulfone (Fierce). With the addition of residual, there was no difference in palmer amaranth biomass in the no cover crop with residual herbicide and all the cover crop species where a residual herbicide was added. I share the Research Figure on my blog site which is incredibly visual and have shared it in pesticide trainings as well. To me, it so visually shares how well residual herbicides can work, which we’re aware of. However, what strikes me the most is how much work that residual had to do on its own to achieve the same control as a cover crop + residual herbicide. Adding the cover crop reduced the load of the herbicide alone and is another tool in the toolbox. It also shows how effective cover crops for weed control can be for organic systems if there’s a solid way for terminating them. I realize cover crops don’t fit every field or every situation. Just some considerations as we especially think of situations where planting a small grain this fall could be used for weed and erosion control and/or grazing.
Congratulations to all the 4-H youth who competed at the Nebraska State Fair this past weekend! The talent of our youth never ceases to amaze me. It’s also so encouraging to see life skills being developed such as public speaking, plant and insect identification, and the responsibility and care for animals.
Also so grateful to receive rain last night! And, that should finish up irrigation, or get it pretty close, for many that didn’t have late-planted crops. It’s really important to know your crop growth stage and to finish well. There’s some fields that are obviously over-irrigated with water standing after this last rain. On the flip side, it’s important to monitor soil moisture and crop growth stages to not stop too soon in spite of the long irrigation season and how tired farmers are. Several questions last week on ‘how’ to finish with irrigations and when physiological maturity occurs in soybeans.
Last irrigation: if you’ve been triggering irrigation during the growing season based on the recommended 35% depletion (average of 90 kpa on watermark sensors), you would have around 1.28” of moisture available in the top 4 feet for the plant in silt loam soils. A consideration for a step-wise approach I’ve used is this: Corn at ½ milk line needs around 13 days or 2.25” to finish the crop to maturity-so subtracting that from 1.28 would be 0.97”. As we consider allowing the soil moisture profile to deplete to 50-60% for recharge over the winter, a person could delay to 40-45% depletion (around 130 kpa average on watermarks) before triggering irrigation the first 7 days and then allow for 50% depletion (around 150 kpa average on watermarks) that last 7 days to finish irrigation for corn.
Soybeans range from full seed (R6 end of seed enlargement) which needs 18 days or 3.5” of water; R6.5 (leaves yellowing/pod membranes still clinging to seed) which needs 10 days or 1.9” yet; or physiological maturity in which the pod membrane has separated from the seed and no more water is needed. The NebGuide, “Predicting the Last Irrigation of the Season”, speaks to yellowing leaves as the beginning of physiological maturity. But the question I kept getting last week was “how yellow is considered yellowing leaves?”. Perhaps a better indicator for today’s varieties would be to also look at the pods. Until the pods reach R7, physiological maturity, the plant is still utilizing water. At R7, at least 50% of the field plants will have one mature pod anywhere on the main stem. A mature pod is considered when the pod membrane no longer clings tightly to seeds in that pod (this is like black layer on corn where the nutrient/water supply is cut off from the kernel forming the black layer). So essentially, if you pull off a pod on the main stem, carefully open it up and look at the membrane surrounding the seed. If it’s still clinging tightly to it, it’s not quite mature. If you see separation of the membrane and seed, it’s considered mature and will no longer use water. There can be a range of pod stages on a plant, but between yellowing leaves and pod color changes, one can get a pretty good idea when R7 has occurred and no additional water is needed for the plants. The timing of the ending R stages in soybean is determined by planting date and varietal maturity group, though the date of R7 can be hastened if water stress and high temperatures prevail in August — something we are seeing this year.
Soybean stems typically turn brown shortly after R7 begins, though the stem can remain green longer due to a number of reasons, including fungicide use. The final soybean stage is R8, which occurs when 95% of pods have attained maturity and have a variety-dependent color of brown or tan. Seed moisture in a soybean pod dries down from 70% at R7 to about 13% at R8. This has shown to be around 12 days based on research, but can be faster or slower depending on solar radiation, humidity, temperature, wind speed and soil surface moisture.
So, for scheduling last irrigation in beans: if we use the same example of having 1.28” of available water at 35% depletion in silt loam soils in top four feet, soybeans would need 2.22” with 18 days to finish at R6 or 0.62” with 10 days to finish at R6.5. Using the stepwise approach, one could again allow the soil moisture to dry down to 40-45% the first week and 50-60% the second week. This also allows room to catch rain like we finally experienced last night.
Fall armyworms have been on the increase in alfalfa and pastures recently, so please be scouting as they can decimate a field quickly in the late larval stages. The threshold is 3 or more per square foot and they’re easier to control if the larvae are ¾ inch long or less. When they’re larger than this, they’re more difficult to control and choosing to harvest the alfalfa may be a better control method. Insecticide options include products with active ingredients including the pyrethroids, Alpha-cypermethrin (Fastac CS), Beta-cyfluthrin (Baythroid XL), cyfluthrin (Tombstone), Gamma-cyhalothrin (Proaxis, Declare), Lambda-cyhalothrin (numerous products), permethrin and Zeta-cypermethrin (Mustang Max), organophosphates, chloropyrifos (numerous products), and carbamates, carbaryl (Sevin) and methomyl (Lannate).
Japanese Beetles: Areas of the State have seen Japanese beetles for a few weeks. They’ve shown up strong in the York/Seward county area this past week with the number of calls I’ve received.
Unfortunately they cause two problems. The larvae are grubs that can impact our lawns. The adult beetle is ½” in length with a metallic green head and white ‘tufts’ that look like spots on its abdomen. Adults emerge from grassy areas like lawns, ditches, and even fields; however, they don’t emerge at the same time. They emerge over a 4-6 week period beginning in late June and last for around 4-6 weeks. There’s one generation per year. Adult beetles feed, mate, and lay eggs in lawns and grassy areas. The eggs hatch 10-14 days later into grub larvae and feed on turf and grassy areas in the August time-frame. They also over-winter in turf and grassy areas.
Adults feed on 300 plant species, but their favorites are ones that are in many of our
landscapes (roses, cannas, marigolds, grapes, Virginia creeper, and trees such as lindens, birch, Japanese and Norway maples, cherry, plum, peach, American elm). They also feed on soybean and corn crops. They love hot weather and full sun and feed on leaf tissue during the day (leaf tissue will look skeletonized or lacy and turn brown). Trees may be severely impacted with browning occurring from the top to bottom. Thankfully healthy trees will re-leaf next year since the underlying twigs and branches aren’t damaged-even if the entire canopy is impacted this year. It’s not recommended to remove branches or trees.
DO NOT use Japanese beetle traps!!! Research shows they attract beetles to the landscape and many homeowners I’ve talked with will attest to this!
Beetle Control: Wait till dusk (7-9 p.m.) before trying to control beetles as they are less
active then and to reduce impact to pollinators. Organic means include hand-removing beetles by knocking them into soapy water. You can also spray trees with water to knock them down to the ground and then drown in soapy water. This takes diligence over many days. With heavy beetle infestations, it’s not uncommon to literally have scoop shovels full of the beetles when removing from trees. Neem and Pyola are two organic sprays that will protect for 3-7 days. Applying these products regularly (once per week) can also be effective as a repellent.
Japanese beetles often impact the same flowering plants that other pollinators visit. Use insecticide products correctly to avoid damage to pollinators. Avoid spraying insecticides on windy days or when pollinators are present (best to spray late in day near dusk) and be sure to read and follow all label instructions and harvest intervals (for cherries, plums, etc.). Conventional insecticides can provide 2 weeks of control: pyrethroid products like Tempo and Bayer Advanced Lawn & Garden Multi-Insect Killer (cyfluthrin) or Ortho Bug B Gone (bifenthrin). Sevin (carbaryl) is another option although more dangerous for bees.
Grub Control: Turf damage can be evident in Aug./Sept. Products that control common white grub can also provide control of Japanese beetle grubs and should be applied mid-to-late June. Dylox can be used as a rescue treatment if grub control is needed later on and no grub products were applied in the spring.
Next Year: Systemic products like imidacloprid can be used as a soil drench around plants (apply around Mother’s Day). These products can’t be used on Linden trees. You may also wish to swap out more susceptible plants for those less susceptible as you observe which plants they tend to impact most in your backyard.
Also seeing green June beetles and this shows the difference between them and Japanese beetles. Green June beetles don’t have the same impact on leaf damage. They do lay eggs in turf which become grubs as well.
Heat and Pollination: With last week’s heat and anticipated heat later this week, we were receiving questions regarding the impacts of heat and humidity on pollination. You can view the entire article in this week’s CropWatch at https://cropwatch.unl.edu. Key points include: Heat over 95°F depresses pollen production and prolonged periods of heat can reduce pollen production and viability. When soil moisture is sufficient, one day of 95-98°F has little or no impact on yields. After four consecutive days, there can be a 1% loss in yield for each day above that temperature. Greater yield loss potential occurs after the fifth or sixth day. High humidity, without a drop in humidity during the day, can delay pollination or prevent pollen from leaving anther sacs. We’ve been blessed we only had days of extended high heat around pollination, received a break in the heat in addition to weekend moisture.
Insect Pests: From light trap reports, peak western bean cutworm (WBC) flight appears
to have occurred last week, so scout for egg masses and live larvae with a 5-8% treatment threshold. Thistle caterpillars grew rapidly last week. Others are with me in considering spraying closer to 15% (instead of 20% threshold) with stressed fields from flash drought and/or off-target dicamba injury that don’t have canopy cover yet. In CropWatch, check out the articles regarding scouting for grasshoppers in field borders and what to expect for insects depending on crop growth stages yet this year.
Cattle Losses from High Heat: If the recent heat/humidity conditions are determined to be an extreme weather disaster event, then livestock losses would be covered by the Livestock Indemnity Program (LIP). Livestock producers who lost livestock should document losses in the expectation that they may be covered by LIP and contact your local Farm Service Agency (FSA) to report those losses.
South Central Ag Lab Field Day Aug. 1: View current field trials on improving crop production and profitability at UNL’s South Central Ag Lab (SCAL) on August 1 near Harvard. Guests can customize their day to select the tours they’re most interested in. Presentation topics include: Cover crops, pollinators and weed management; European corn borer, corn rootworm, and cover crop insect control; Herbicide-resistant weed management; Assessing injury and management decisions in corn and soybeans; Corn and soybean disease updates; Sensor-based nitrogen management in irrigated corn; Corn stover harvest management and impacts; mobile beef lab and hail machine demonstrations. Registration is at 8:30 a.m. followed by tours through 4 p.m. Lunch and refreshments are included. CCA credits have been applied for. For more info. see the program brochure and register at: https://go.unl.edu/2019scalfieldday.
Silage Webinar Aug. 2: With this year’s challenging weather and the need for forage, there may be more opportunities for harvesting corn for silage. Aimed at feedlot, cow-calf, and dairy producers, a silage webinar on August 2 at Noon CST will focus on moisture at chopping, chop length, inoculants, proper packing, silage covers and more. Pre-registration for the webinar is necessary and can be done at: https://go.unl.edu/vau7.
Trees Losing Leaves: The wet spring and humidity allowed for fungal diseases on leaves of shade trees with flowering pears and crabapples in particular dropping leaves early. I’ve also had a number of questions regarding red maple leaves (Autumn Blaze and Sunset) suddenly turning brown on trees. These symptoms may also be experienced on ash, tuliptree, and other maples. We think it’s environmental stress from having so much cool and wet early to almost a ‘flash drought’ situation in eastern Nebraska prior to this weekend’s rains. Sarah Browning has been recommending watering and mulch as the best ways to reduce stress and to prevent additional root death and tree decline. I’ve been seeing new growth starting to occur on trees so my hope is if your tree is experiencing this, that 10-14 days from now you will also see new growth occurring on your trees.
Interesting, memorable don’t seem to capture this year. While portions of Nebraska are flooding again, many growers in this part of the state and east would like some rain. Dr. Suat Irmak shares on understanding matric potential and water content thresholds on sensors for irrigation scheduling in this CropWatch article: https://go.unl.edu/miym.
Soybean: The large number of painted lady butterflies we experienced in late May/June was due to a wet season in Mexico that allowed for greater vegetative growth and survival for northern migration, according to Bob Wright, Extension Entomologist. The cooler conditions may have caused more to stay here instead of move north. Saw newly hatched to early instars of thistle caterpillar (the larvae of painted lady butterflies) this week. Yet, a tremendous number of butterflies are still laying eggs. A painted lady female can lay up to 500 pale green eggs on plants individually instead of in egg masses. The larvae hatch in around a week and can feed from 2-6 weeks depending on weather conditions. Other defoliators including various worms, grasshoppers, Japanese beetles are also present. Thresholds for damage for all soybean defoliators is 20% defoliation of plants during the reproductive stages. If you’re unsure what 20% defoliation in soybean looks like, check out the graphic in CropWatch at: https://go.unl.edu/v0ts. If your primary defoliator is thistle caterpillars, it’s important to use insecticides that can be effective on them once their ‘tents’ are built. The 2019 Guide for Weed, Disease, Insect Management gives information regarding products that may work better on pages 308-314.
Gall Midge in Seward County: My colleague Aaron Nygren found soybean gall midge in
Seward County north of Bee this past week. I was a few miles away so met him at the field. Being a new insect pest, little is known about it. Infected plants show signs of wilting from larvae feeding within the base of the stem. These plants will eventually die. To scout for soybean gall midge, focus on plants that are close to the field edge and adjacent to fields that were planted to soybean in 2018. If you’re seeing wilted/dying plants, particularly in early planted beans this year, please contact your local Extension educator. More information at: https://cropwatch.unl.edu/gallmidge.
Bob Wright is asking for help to understand distribution of the green June beetle, Japanese beetle, and brown marmorated stink bug. If you see these insects, please take a picture and upload it to: inaturalist.org, including information on where the photo was taken. You need to make an account with inaturalist.org before you can upload photos. And, if you’re unsure what these insects look like, you can view them at: https://go.unl.edu/uzd0.
Corn: Looked at numerous corn leaves but so far, only common rust in Nebraska. Southern rust was confirmed in southern Kansas and Missouri this past week. You can view U.S. counties where southern rust has been confirmed at: https://corn.ipmpipe.org/southerncornrust/.
As we approach tasseling: 1-Areas of fields that had water ponded this
growing season may show crazy top of corn. Crazy top symptoms include when the tassel appears strange and leafy. Plants can be barren, have barren kernels on ears, or have multiple ears at shank. 2-Automatic fungicide applications at tassel: I prefer waiting till disease warrants application & Nebraska research shows fungicide applications later in the season are effective. Be careful if you automatically spray at tassel! Canopy closure covered problems in fields, including uneven growth stages. Plants in the field may have tassels with others several growth stages behind. Arrested ear development primarily occurs on plants from 12-14 leaves when surfactants (particularly non-ionic) are applied with fungicides. So, it’s important to know your growth stages and consider what you’re applying. 3-Japanese beetles in corn threshold: Three or more Japanese beetles per ear with silks clipped to less than ½ inch and pollination is less than 50% complete. 4-It’s OK to fertigate pollinating corn. Avoid running pivot from 6 a.m.-Noon during pollination. Can apply 30 lbs N in 0.25″ water or up to 60 lbs N in 0.50″.
Linden trees and Japanese beetles: Last week I didn’t stress the importance of insecticides and impact to bees when spraying linden trees. ‘Sevin’ is effective but highly toxic to bees. It’s better to use heavy streams of water in late afternoon to knock Japanese beetles down (then drown in soapy water), pyrethroids, or permethrin like ‘Eight’ as those products are not taken back to the hives.
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 Update: This past week was fairly interesting with southern rust being confirmed in a few Fillmore, Thayer, and Saunders County fields. We would recommend to continue scouting fields as the disease was low incidence at all these sites. There also were a number of questions regarding fungicide applications.
For those asking about chemigating fungicides, it’s important to ensure the fungicide
product label allows for chemigation and to follow the recommended irrigation amount if specified on the label. If an irrigation amount isn’t specified, Tamra Jackson-Ziems and I were talking about trying to apply with as small amount as possible (perhaps like 0.25″). She has chemigation data at 0.25″ vs. 0.50″ vs. ground application from 2005-2007, but not vs. aerial application. The data had a high degree of variability numerically in the yield data in spite of non-statistical differences. The only other info I could find was the University of Georgia recommends only 0.10″ on chemigation using fungicides, but they didn’t show any data. I encourage those who can to please consider doing this as an on-farm research study where chemigation occurs in pies throughout the field with other pies left untreated. I realize it’s not popular to leave areas untreated, but it may be of interest to you. For those asking about comparing aerial vs. chemigation for corn, that would be very difficult with one pivot with true research involving replication. Perhaps it could be done if a producer had a couple of quarters side by side, planted the same day with same hybrid and crop rotation where we could truly compare via research. If you do and that’s of interest to you, please contact either Tamra or myself. A couple have also discussed maybe applying half a pivot aerially and the other half via chemigation and just taking observations, which may also be beneficial to you.
We also released a few CropWatch articles this week on differentiating growth regulator herbicide injury in soybean and using a forensic method to diagnose off-target dicamba
injury in soybean. Please check them out at http://cropwatch.unl.edu. I hadn’t heard anyone really explain the difference between 2,4-D and dicamba in how they work in plants so felt that information was important in addition to the fact dicamba is highly translocateable and 2,4-D isn’t. That also has been important in home-owner discussions regarding off-target movement to garden produce. And, a reminder to all home-owners that weed control products used in lawns and empty lots often contain dicamba and/or 2,4-D…so it’s important to read those labels regarding environmental conditions in applying them and also when you can/can’t use grass clippings as mulch.
Buzzing Beetles: This past week, several people came to the office or called
regarding large green beetles flying around that sounded like bumble bees. These are called Green June beetles. They only fly during the day. There are also smaller green beetles with white spots (tufts of hair) around the abdomen; those are Japanese beetles. Japanese beetles feed on crops in addition to favorites such as Linden trees and knockout roses. Both have larval forms that are white grubs and both have a one year life cycle. In the beetle form, both adult beetles are fond of ripe fruit such as grapes, berries, plums, and peaches. As larvae, the grubs feed on decaying organic matter and grass roots in the soil. However, the June beetle larvae can reach 2″ long creating larger tunnels in lawns and pastures as they move in the soil.
Some have said, “I thought June beetles were golden/tan!” And you would be correct! There’s several types of “June” beetles. The most common and perhaps most damaging is known as the June beetle or masked chafer which is golden/tan in color and has a one year life cycle. There’s also a May/June beetle (also known as the 3 year grub) which tends to do more damage in range/pasture ground. Those beetles are tan to brown/near black in color.
When it comes to damage, start looking for browning areas of turf occurring late July, throughout August, and early September. The turf may look like drought stress or fungal disease; however, if you can gently roll the turf back like a carpet, it’s most likely grubs (and you should also find the presence of grubs). Other signs of grubs can include birds, skunks, etc. tearing up your lawn. White grubs in general feed on decaying organic matter, lawn and ornamental roots in the soil. Grubs don’t tend to be an issue in fescue lawns or lawns that are low maintenance or newly established. They tend to prefer Kentucky bluegrass lawns that are highly maintained with fertilizer and irrigation. They also may be spotty in their feeding such as under yard lights or on irrigated slopes. The threshold level for turfgrass damage by masked chafer larvae is 8-10 white grubs per square foot of lawn…so I would assume that to be the case for all grub species. One or two grubs per square foot is normal and does not require control. If grub control is needed, products like Sevin or Dylox provide the best control for mature grubs and should be watered in after application.