Category Archives: Diseases

JenREES 9-15-19

Crop Update: Thinking about harvest as we continue to watch corn and soybeans progress toward maturity. And as I write this, my desire is to be honest about what I’m seeing and the concerns growers and other agronomists are seeing too. Perhaps part of my perspective is the fact that I’m typically called out to problem situations! But hopefully that perspective helps you in some way know what to watch for in your own fields. So before harvest occurs, would encourage growers to get out in your fields and see for yourself how your crops look. It’s just a great way to estimate what your true harvest potential is prior to harvest. And, it’s always easier to diagnose yield potential problems now vs. post-harvest. There are some tremendous looking fields out there, especially non-irrigated ones! Yet sometimes (once we hit canopy closure) we forget about the early season challenges and the variability that can occur. Variability such as plant stands and plant emergence based on variable seed depth that can be seen now with variable ear sizes. There’s misshapen ears due to various stresses based on specific field practices/situations as well.

The warm, drier weather this week allowed for some noticeable changes. Perhaps the biggest one is the concern regarding tops of corn plants rapidly senescing. This could be due to either anthracnose top dieback or another disorder called ‘top leaf death or dieback in corn‘. Anthracnose can cause leaf lesions, top dieback, or stalk rot. To diagnose if anthracnose is the culprit, you can look for black fungal anthracnose lesions which may be blotchy in appearance on the stalk underneath the leaf sheaths. You can also split the upper or lower stalk looking for any discoloration in the pith or nodes. If you don’t see the lesions or pith/node discoloration, the discoloration in the top of the plant may be due to top leaf death or dieback. A Canadian researcher documented greater top leaf senescence during a period of warm, dry weather during grain fill. Another researcher documented this tends to be more common during good grain fill years. We have experienced that type of weather with a good grain fill period, so top leaf death/dieback may be the bigger culprit.

Yet, be sure to check for stalk rot in these fields. I’m finding stalk rot increasing with each week especially where there’s nitrogen deficiency, areas where water ponded, high plant populations, higher disease pressure, and areas with hail damage. There’s also something interesting happening where in specific hybrids, it appears the refuge in a bag plants are dying early (and have stalk rot) in comparison to the primary hybrid planted (I’m unsure exactly why).

The other thing noticeable this week was husk tissue turning color and ears turning IMG_20190913_114905down as hybrids mature. We’ve had a long grain fill period creating large ears with deep kernels. There are specific hybrids where I’m concerned about large ears and small shank diameters. Shanks appear firmly attached for now, but it’s still something to watch. Been recommending growers get those fields out earlier if possible.

To evaluate percent stalk rot, at least 100 plants throughout the field should be assessed. I prefer the ‘pinch test’ and do this by taking my thumb and first finger and pinching the stalk internode that occurs between the lower nodes above the soil line. Do this for 20 plants in an area and get a percentage for those that crush. Then do this for several areas of the field. This YouTube video helps show how to do this: https://www.youtube.com/watch?v=7z75VN1c51Q. Fields that have the greatest percentages of stalk rot prior to harvest may be prioritized over others. Where it worked in their operations, some growers in 2018 chose to harvest at a higher moisture content in order to get at fields in a more timely manner.

Some soybean harvest has started. Taking my final on-farm research notes in fields, I’m 00100lPORTRAIT_00100_BURST20190913160342179_COVERnoticing dead plants next to green ones. The dead plants often have anthracnose and/or pod and stem blight. In some fields early death is due to sudden death syndrome. Also noticing red/purple leaves on some varieties indicative of cercospora leaf blight. Thus, we have potential for discolored, chalky seed and also purple seed stain again; hopefully nothing to the extent of 2018.

JenREES 8-25-19

Crop Updates: An increase in disease pressure has been the theme the past few weeks. IMG_20190823_092914Sudden death syndrome is increasing in soybeans, but there’s also brown stem rot (BSR) and frogeye leaf spot in some fields. The foliar discoloration is the same for SDS and BSR with the yellow/brown discoloration between leaf veins. You can tell the difference by pulling a plant out of the ground. SDS is usually easy to pull as the taproot is rotted. Splitting the stem open, the root will show rot at the soil line but the stem pith will be white and healthy. With brown stem rot, the pith will have brown discoloration. The addition of stem borer can make it more difficult to tell the difference sometimes. Unfortunately there’s nothing one can do for SDS or brown stem rot now as both are caused by soil borne fungi. I would recommend taking soil samples for soybean cyst nematode (SCN) in areas currently impacted by SDS as the combination of diseases is synergistic in impacting yield loss. You only need 0-8” samples and they can be taken during soil fertility samples if you don’t want to take them now. The samples are free via your checkoff dollars and they can be sent to the Plant and Pest Diagnostic Lab at UNL in Lincoln.

In corn, foliar disease is increasing in mid-canopies. Most concerning are the number of stalk rot samples/situations I was called to the past week. They all appear to be bacterial stalk rot thus far. Symptoms include watersoaked nodes and below the nodes with plants breaking off/falling over. Damaged nodes are from the soil line to upper canopy. The bacteria disintegrates these stalks creating a stringy appearance within them where the nodes break and when slitting open stalks. It also has a distinct foul smell. This is more of a problem in wet years such as this and hybrid susceptibility varies. The bacteria doesn’t typically transfer from plant to plant. I have photos of what I’m seeing on my blog at https://jenreesources.com.

There have been multiple late-season hail events in the area. For those fields hit by the 00100lPORTRAIT_00100_BURST20190823133135740_COVERAugust 6th storm, the rainy, cool conditions have allowed for increase in mold on the hail damaged side since many of those damaged ears were at milk stage. However, I’m also seeing mold damage on some back-side of ears in hybrids with tighter husks. The white/pink fluffy growth on the hail damaged side is caused by Fusarium/Gibberella fungi. The presence of these fungi does not automatically mean mycotoxins are present; they do have the potential to produce mycotoxins. The green fungal growth in ears are caused by secondary and minor fungal pathogens that don’t produce mycotoxins. The white fungus overtaking ears on some tight-husked hybrids is diplodia which can cause for light test weight but does not produce a mycotoxin. It will be important to continue to watch grain quality over time prior to harvest.

Wild and Burcucumber on Trees has also been a huge question. Do Not apply 2,4-D to trees for

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Thanks to Randy Pryor for demonstrating how easy these are to pull while we were on a field call together!

control as that has been the most common question! The simplest way to kill wild and burcucumber is pull or hoe the plant at its base below the tree. There’s not much to the plant root and the vines will then die on the tree!

It’s been a hard year for our growers and livestock producers with continued challenges. Seeking to end this column on a positive note, this year is the 10th year of the Nebraska State Fair in Grand Island and the 150th Fairabration. I’m grateful for the focus on agriculture, families and youth! And, it’s encouraging to me to see youth learning life skills whether competing in public speaking, IMG_20190824_181614working with and showing livestock, or studying and competing in contests such as weed and grass ID at the State Fair. 4-H is where I got my start and it’s exciting for me to wonder at the futures these 4-H and FFA youth have ahead of them as they continue to work hard and put into practice the life skills they are learning! Hope you can make it out to the State Fair at some point!

*End of News Column. Bacterial stalk rot photos below.


 

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Plants still standing showing various symptoms of dying and death

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Some plants exhibiting bacterial stalk rot are already lodged or broke off at or around plant nodes.

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Plant nodes show discoloration with watersoaking around the nodes (notice the soaked appearance on internode where I removed the outside sheath).

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Majorly impacted nodes and internodes by bacterial stalk rot. There’s a distinct foul odor. Notice how wet and watersoaked nodes and internodes are and there’s even bacterial ooze in this case on the stalk.

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Plants break at nodes. Also notice the stringy appearance of stalk pith.

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Commonly seeing this with impacted nodes from the soil line through upper canopy…stringy appearance of pith tissue.

JenREES 7-28-19

Southern Rust in Nebraska was confirmed in Nuckolls, Thayer, and Fillmore counties last week. The lesions were typically on one leaf in an isolated portion of fields at low incidence and severity. I was recommending to watch the fields instead of spraying right away. Greatly appreciate everyone who has gotten samples to me this month and to neighboring Extension offices serving as drop off points for samples. I’ve been looking at samples since early July and honestly, common rust at times has exhibited signs similar to southern rust. At my blog site (https://jenreesources.com), I’ve posted photos showing the differences of common vs. southern rust that we’re seeing this year. Southern rust typically is orange to tan colored with tiny, clustered pustules on the upper leaf surface. Common rust has had an orange appearance to it at times with smaller lesions than the ‘typical’ brick red larger ones. However, in every southern rust sample I’ve confirmed, the pustules have not gone through the back of the leaf…there’s been indentations but nothing has produced pustules on the backside. That doesn’t mean that the fungus can’t; it just rarely does. Also, these leaves have all occurred in the mid-canopy. I realize lowest leaves of plants often have a great deal of rust on them, but it’s been common rust in leaf samples I’ve pulled and received to date. I’ve also posted photos of another disease called Physoderma brown spot on my blog. Physoderma is the disease that has purple/brown on the midribs, around leaf axils and sheaths and it also can have tiny yellow-brown spots without pustules that look a lot like southern rust on leaves of plants. It’s one that we tend to see around pollination as the fungus-like pathogen swims in water on the leaf surface and feeds off of decaying pollen.

Confirming southern rust in a few Nebraska counties thus far doesn’t mean that every field has it and we don’t know how it will progress. So our recommendation is to continue scouting and if you have a suspect sample, you can get it to me (if you’re in the area) or to our Plant and Pest Diagnostic Lab in Lincoln. You can keep updated with counties that are confirmed by checking out the Southern Rust tracking site at: https://corn.ipmpipe.org/southerncornrust/. The wide range of planting dates across Nebraska this year has resulted in a wide range of corn growth and reproductive stages in fields, some of which are still in the vegetative growth stages. Keep in mind that late planted fields are at particular risk for southern rust if it increases in development. Right now corn disease pressure in general is low. I’m anticipating that to soon change for gray leaf spot susceptible hybrids. Some growers added a fungicide in with an insecticide treatment for western bean cutworm, which made sense to save an application cost. However, in general, automatic fungicide applications when one treats before disease develops may lead to loss of full product efficacy before critical disease levels. This can also result in the need for reapplication later if the disease worsens after the previous fungicide application and residual has worn off. And, always in my mind is eventual potential for pathogen resistance…so utilizing fungicides when we need them vs. automatically applying is wise for maintaining these fungicide chemistries.

York County Fair: This week is the York County Fair! All events and details can be found at: http://www.yorkcountyfair.com/. One special addition this year is “Brownies for Bergen” on Saturday, August 3 from 5:30-7:00 p.m. The late Gene Bergen was a 4-H icon and was planning on celebrating 50 years as a York County Ag Society Member at this year’s fair before retiring. While he won’t be with us in person, the York County Ag Society, 4-H Council, and Extension Office would like to honor him and his original plans to celebrate. So please join us for brownies and ice cream and share your favorite memories and stories of Gene!


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Lower corn leaf that is dying early and has a great deal of rust on it. So far, this has all been common rust as pictured here in spite of smaller, clustered pustules or even orange colored pustules.

 

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Common rust spores are circular in shape.

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Southern rust was confirmed on this leaf in 2019. Small, clustered, tan-orange colored pustules can be seen on this leaf.

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Southern rust spores are brown and oval in shape. Sharing this photo as the clear structures are spores (condia) and spore-holding structures (conidiophores) of Cercospora zeae-maydis which causes gray leaf spot (gls) in corn. Was seeing these spores/structures with only ‘specks’ of gls lesions on this leaf. With humid weather and longer leaf wetness from dews, we may see an increase in appearance of gls lesions in the next 7-10 days.

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Physoderma brown spot. Symptoms include both the purple/brown midrib in addition to the yellow-brown lesions on the leaf. These lesions are flat in comparison to southern rust which would have raised pustules.

JenREES 7-14-19

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

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Gall midge (orange colored worm)

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

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Tassels appear leafy in crazy top of corn. Took this pic from flooded waterway area in 2017.

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.

JenREES 7-7-19

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

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Western Bean Cutworm Moth courtesy UNL CropWatch

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

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Green June Beetle (left) and Japanese beetle (right). Photo via Purdue Entomology.

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.

Grain Observations

This post shares observations of what I’ve been seeing in fields pre-harvest and during harvest during this 2018 growing season. Some of these problems stemmed from hail/wind damage and others insect damage. This is a longer post with the desire to have many resources available to you in one place. Hopefully this will be helpful for diagnosing concerns as harvest continues.

Soybean Observations

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(Photos above) Hail-damaged soybeans pre-harvest. The plants in this field weren’t pummeled into the ground, but from the road it was deceiving as to what the soybeans were actually like on these plants. The two smaller photos are all the soybeans found on 2 adjacent plants from the top soybean photo pre-harvest. There were a lot of aborted pods on stems and moldy beans in general. For those who combined hail damaged beans in the area, farmers shared they had everything from ‘lima’ beans to shriveled, moldy beans as you can see in these pics, which is also what we were anticipating may be found.

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Examples of soybeans that had sprouted in the pod pre-harvest. We may unfortunately see a lot more of this with additional rains.

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Removed a bunch of pods from a plant with Diaporthe/Phomopsis complex in which there were many flat, unfilled pods and pods of various stages of fill. This is what I found in the pods. This complex consists of diseases such as Pod and Stem Blight, Stem Canker, and Phomopsis Seed Decay. Perhaps note which varieties you notice more of this.

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Two different grain quality concerns in soybean. (Left photo) This soybean damage can be attributed to potentially a few things. I have found pycnidia of Phomopsis (Phomopsis seed decay) in samples like this. The UNL Plant and Pest Diagnostic Clinic has also diagnosed Phomopsis Seed Decay in samples. There’s also a publication from Ohio State (https://agcrops.osu.edu/newsletter/corn-newsletter/2017-24/stink-bugs-soybean) which attributes these symptoms to stink bugs. There was stink bug pressure in some fields this past year. So there’s potential that we have a few things occurring creating these symptoms. (Right photo) This soybean damage is called ‘Purple Seed Stain’ and is caused by the fungus Cercospora kikuchii. I mentioned this in this blog post.

Corn Observations

 

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Pre-harvest was seeing quite a bit of Fusarium in places where hail stones or insect damage occurred on ears such as this photo. Notice at the base of the ear, the ‘starburst’ shape occurring within kernels (I think of it like fireworks exploding when viewing the top of the kernel). Kernels infected with Fusarium will have a white/pink fungal growth that later causes kernels to become brown or gray and shriveled.

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This ear was from the same hail-damaged field as photo above and I picked this right before the field was harvested. The Fusarium and picnic beetles had greatly destroyed affected kernels. Cladosporium (green colored fungus) can also be seen affecting this ear where damage had occurred.

Cladosporium ear and kernel rot seen on kernels already affected by Fusarium, particularly in hail damaged fields. This is a lesser ear rot fungi and doesn’t produce a mycotoxin but can create increased damage to kernels. Was recommending taking grain damaged to this extent directly to the elevator.

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The deep red color on this hail damaged ear is due to Gibberella. We may see an increase in this with all this late-season rain. Other symptoms include matted fungal growth with husks sticking to ears. Gibberella has the potential to produce the mycotoxin zearalenone. The presence of the fungus DOES NOT automatically mean the presence of a mycotoxin.

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Kernels at harvest displaying damage from Fusarium and Gibberella. I received a number of samples from various farmers displaying these symptoms and picked out these kernels to show. Notice the pink/red discoloration of the kernel and also the shrunken, damaged kernels that are brown or gray in color. Grain should be dried as quickly as possible to 15% moisture to cease fungal growth in storage.

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This is another field I’ve been watching that was hail damaged. The ears themselves show very little damage; however, my concern is the ‘starburst’ pattern occurring throughout these ears throughout the field. The ‘starburst’ pattern is also characterized by the white lines observed on the sides of individual kernels. This is caused by Fusarium.

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The above photo is that same field at harvest. ‘Starburst’ pattern on kernels seen as white streaking due to Fusarium. More severely infected kernels are brown in color and dissecting them show they were trying to germinate. Also noticing cob rot occurring. Drying the grain to 15% moisture as quickly as possible will cease fungal growth. Fusarium also has the potential to produce the mycotoxins Fumonisin and Deoxynivalenol (also known as DON or Vomitoxin). NOTE: The presence of the fungus DOES NOT automatically mean the presence of a mycotoxin.

Photos above shared by a Clay County farmer who observed kernel germination and Fusarium growth (mostly due to western bean cutworm damage) upon harvesting his field. Hormonal balance within the kernels shifts towards harvest. At full maturity, very little abscisic acid (ABA) is left in the kernel (in both corn and soybeans) which allows them to germinate in correct conditions after harvest. These conditions include moisture and temperatures above 50ºF. Presence of fungi such as Fusarium and Gibberella also increases gibberellins in the kernels allowing for kernel germination with presence of moisture as we’re seeing this harvest. Increasing air flow during harvest will hopefully blow most of these damaged kernels out the back of the combine.

Grain Storage

There’s over 25 species of fungi that can produce ear molds with the majority of them ceasing growth at 15% moisture within the kernel. Thus, we recommend drying grain to 15% moisture as quickly as possible to cease additional fungal growth within the grain bin. The table below shares the days required to dry corn to 15% moisture with 1.0 cfm/bu and various temperature and humidity conditions.

Days required to dry corn to 15 percent moisture with 1.0 cfm per bu. UNL EC

“Since drying time is directly proportional to the airflow, the producer can calculate the estimated drying times when using airflows other than 1.0 cubic foot of air per minute per bushel (cfm/bu). For example: Table II shows when drying corn from 18 percent to 15 percent moisture with 50F and 50% relative humidity air, the estimated drying time is 12.5 days using a 1.0 cfm/bu airflow. If the airflow is 1.25 cfm/bu, the estimated drying time would be 12.5 days / 1.25 = 10 days. For 1.5 cfm/bu, the drying time would be 12.5 days / 1.5 = 8.3 days. For 0.8 cfm/bu, the drying time would be 12.5 days / 0.8 = 15.6 days.” Source: Management of in-bin natural air grain drying systems to minimize energy cost.

Mycotoxin Information

In 2018, we’re primarily seeing Fusarium and Gibberella species which have the potential to produce mycotoxins. Thus, the information below is directed at those fungal species and mycotoxin levels that can be associated with them. Again, the presence of fungi does not automatically mean a mycotoxin is present.

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The following toxins can be produced from species of Fusarium and Gibberella. Source: Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health, Iowa State publication, 1997.

Table 2 expected detrimental feed concentrations of common fusarium mycotoxins-ISU

Source: Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health, Iowa State publication, 1997.

 

Also, there’s a new app called “Mycotoxins” and it’s another resource with ear rot pictures and mycotoxin information put out by several Universities produced for both Apple and Android devices.

JenREES 7-15-18

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

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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

18 bagworm on Meridian Aborvitae K Feehan 7 9 18

Severe bagworm infestation on arborvitae. Photo via Kelly Feehan, Extension Educator Platte Co.

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.

JenREES 7-8-18

Crop Update:  A few diseases started showing up the past few weeks in various portions of eastern and south central Nebraska.  Phytophthora root rot in soybean is perhaps the

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Phytophthora root and stem rot in soybean. Notice wilted plant with leaves hanging on turning yellow/brown.  Also notice characteristic brown lesion from base of plant up a good six inches on this plant.  This affected plant is surrounded by healthy plants.

most common in both areas.  We normally think of this disease as seedling damping off and death; however, it can also affect plants later in the season.  What surprised me was how much we are seeing it this year in higher ground and sidehills instead of the typical lower ground we often see it on.  Dr. Loren Giesler, Extension Soybean Pathologist said that in situations where we’ve had dry conditions followed by heavy rains (as we have this year), especially on clayey or soils prone to compaction, Phytophthora can also affect plants.  He has a few videos along with additional information at the following website:  https://go.unl.edu/tdfh.  Symptoms characteristic at these growth stages include wilting of plants during the day with leaves eventually turning yellow-brown-gray and remaining on the plants.  Also, look for a brown stem lesion that goes from the soil line upward about 4-6″.  Some of these plants are also snapping off at the soil line. For those experiencing Phytophthora this year, future management includes:

  • Using resistant varieties including a combination of good partial resistance and an Rps gene. Partial resistance alone will not be as effective during early growth stages or under high disease pressure.
  • Cultural practices include anything that can improve soil drainage and compaction.
  • Seed treatment fungicides containing mefenoxam or metalaxyl should be used and you may need to consider a higher rate of them.

Regarding corn diseases, bacterial leaf streak (BLS) has greatly increased on more

bacterial leaf streak

Bacterial Leaf Streak (BLS) in corn.  Lesions are elongated and skinny staying between the leaf veins, similar to gray leaf spot (gls).  However, leaf margins are wavy and diagnostics under the microscope show the presence of bacterial streaming from the leaf veins.  With gray leaf spot, there will be the presence of fungal spores.  Thus, the importance of correct diagnosis when considering fungicide applications.

susceptible hybrids since rain events.  Early lesions can look very similar to gray leaf spot, so it’s important to correctly identify the two.  The margins of BLS are wavy vs. those of gray leaf spot are more blunt.  Both can have yellow margins when backlit by the sun.  Fungicides are not effective against BLS and hybrids do vary in their tolerance to this disease.  It’s important to scout fields as we may see an increase in fungal diseases due to the humidity, leaf wetness, and recent rain events.  Southern rust has taken awhile to develop in the southern U.S., which is somewhat unusual, yet many states have been in drought this year too.  As of July 5th, southern rust has been confirmed in Georgia with one suspected sample in a Missouri county.  You can watch the map at: http://ext.ipipe.org/ and follow @corndisease on Twitter for the latest on corn disease findings in the U.S.

Trees:  With numerous wind storms, the following resource has a lot of great information regarding pruning storm damaged trees correctly and questions to ask tree care services regarding tree pruning:  https://go.unl.edu/94fm.

Agronomy Youth Field Day:  All youth ages 9-18 years old are invited to the 3rd Annual Agronomy Youth Field Day. Youth will have exciting educational experiences while discovering Science & Agronomy/ Irrigation / Mechanized Agricultural careers for producing Nebraska crops! The field day will be held Wednesday, August 8 from 9 a.m.-3 p.m. at Nebraska College of Technical Agriculture Educational Center in Curtis, NE.

Hands-on activities (for all age levels) will focus on pest management, equipment technology, crop growth, soil management, precision farming & center-pivot irrigation technology. Several Nebraska Extension Cropping & Water Systems and 4-H Youth Development Educators along with Nebraska College of Technical Agriculture in Curtis Agronomy / Ag Mechanics Department professors will be sharing the researched based information with the students.

Participants will gain important life skills while discovering the science behind producing Nebraska crops. The six-hour field day is a great opportunity for ALL the youth to learn more about the agronomy industry and increase their basic understanding of science, ag literacy, a technology & STEM while exploring careers. Parents/Adults are welcome and lunch will be provided.

Reserve your spot today by registering online at:  https://go.unl.edu/agronomyyouthfieldday  by August 3, 2018. For more information (or if trouble with registration) contact Nebraska Extension Frontier County at 308-367-4424 or email 4-H Educator Kathy Burr at kathy.burr@unl.edu.

Corn Disease Diagnostic Workshops

corndiseasediagnosticworkshop

Corn Disease Update

corn disease meeting

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