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Seeing Blast in Oats? It’s Not Just Heat Related!

Origingally published July 21, 2014

Over the past week, I have seen pictures or samples of oat panicles where there are empty florets on the panicle.  Oat samples displaying the same symptoms have come into Manitoba Agriculture’s Crop Diagnostic Centre.  Mardi Desjardins, formerly of Manitoba Agriculture, provided the following information on Blast in Oats.

oat blast

Blast in Oats. Photo by Manitoba Agriculture (2014)

Blast in oats can be caused by stresses such as unfavorable growing conditions prior to emergence of the panicle, any time from floret initiation to panicle emergence.  It is a little different from heat sterility related to high temperatures at anthesis and “blasted” florets typically appear incompletely developed.

Factors most commonly linked to blast in oats include insufficient light due to cloudy conditions, temperature extremes, moisture stress, or physical damage from hail.  Florets begin forming several weeks prior to emergence of the panicle and if stresses occur during the development, the least developed florets at time of the stress tend to be aborted. The ones most commonly affected are those toward the base of the panicle and on inner branches of the panicle which are the youngest.  Blasted florets can however, potentially occur throughout the panicle or in a different area of the panicle.

The lower part of the panicle location in the picture above and the incompletely developed nature of the florets in the picture are classic for the environmentally caused “blast”.

Submitted by:  Pam de Rocquigny, Cereal Crops Specialist, Manitoba Agriculture & Mardi Desjardins, formerly of the Crop Diagnostic Centre

Manitoba Agriculture website: www.manitoba.ca/agriculture
Manitoba Agriculture on Twitter: @MBGovAg
Manitoba Agriculture on YouTube: www.youtube.com/ManitobaAgriculture

 

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Fertilizer Implications in a Dry Spring for Winter Cereal Crops

Prior to the precipitation that started Wednesday, May 25th, it had been unusually dry this spring (Figure 1 below) and there are nitrogen fertilization implications.

Picture1

Figure 1. Rainfall received in Carman, 2016.

Farmers and agronomists may be wondering about the fate of previously applied surface fertilizer. The 2 main concerns would have been stranding at the soil surface where it is isolated from the crop root zone, and volatilization loss.

Rainfall is the only solution for the positional stranding at the soil surface. For spring seeded crops this rainfall will likely have moved N into the root zone before any malnutrition of the seedling.  However surface applied N to fall rye and winter wheat may have been stranded during the main yield building period, since both crops are at the boot stage now (Figure 2 below).  So in the Carman area, topdressed N applied after April 17 was probably stranded.  Nitrogen moving into the root zone now will contribute more to protein than yield.

N Uptake by Wheat for Yield & Protein

Figure 2. Nitrogen uptake pattern by wheat (from C. Jones., Montana State University)

The other concern is of volatilization loss of surface applied N. But much of the surface applied N to spring seeded crops was onto dry soil – and we have had several  field demonstrations to measure volatilization loss using dosimeter tubes (see photo below). In the cases we have followed, the soil surface must have been dry enough to prevent measurable hydrolysis (where the urea molecule is cleaved into carbon dioxide and 2 ammonia molecules).  In fact urea pellets were observed intact for several weeks on the soil surface.  So unless a light shower had been received, I anticipate losses were minimal.  Where some soil moisture was present, the losses would have proceeded until the soil surface dried up.

figure 3

Figure 3. Dosimeter tubes to monitor ammonia loss from surface applied urea or UAN. Note intact urea pellets at soil surface some 10 days after application. There were no ammonia losses.

 

The best way to sense any N shortage in the crop is comparing to a N Rich Strip. Many farmers no longer overlap fertilizer so this is difficult to detect. If there is little to no colour difference between a N rich strip and the general field, then losses are probably minimal.

Submitted by: John Heard, Crop Nutrition Specialist, Manitoba Agriculture

For more information on soil fertility, visit Manitoba Agriculture’s website at http://www.gov.mb.ca/agriculture/crops/soil-fertility/index.html
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Warm Conditions & Winter Wheat in Manitoba

Record warm temperatures across Manitoba at the end of November and start of December 2015 have producers asking what impact the weather conditions will have on their winter wheat crop.

The quick answer is the warm weather isn’t having a negative impact on winter wheat right now. 

Here is why. Over the past several weeks, winter wheat in Manitoba has been undergoing two important physiological changes – cold acclimation and vernalization.  It is the cold acclimation process that enables winter wheat plants to ‘harden off’ in order to survive numerous stresses during the over-wintering period.

The optimal conditions for developing the full genetic potential of cold hardiness in winter wheat are:

  1. Late August or early September seeding into standing stubble, with adequate moisture and temperature conditions to develop plants with 3 to 4 leaves and well-developed crown tissue.
    • In Manitoba, majority of these conditions were met this fall, leading to a winter wheat crop that is well-hardened.
  2. Open field conditions, with little or no snow cover until freeze-up, allowing soil temperatures to gradually decline to freezing levels.
    • Once again, Manitoba’s open fall with minimal snow cover to date has allowed our winter wheat crop to become well-hardened.

Winter wheat normally does not reach its maximum cold hardiness potential until after freeze-up in late fall. In Manitoba, full acclimation is usually achieved by late November to early December (see figure below). And although we have seen above normal air temperatures, soil temperatures have ranged between minus 1 to minus 4 degree Celsius over the past few weeks – many degrees away from having plants undergo complete dehardening and breaking of dormancy.

Picture1

However, one more factor to consider is regardless of the amount of cold acclimation, we typically need to receive good snow cover to protect the crop from the sustained cold temperatures we normally see in January and February in Manitoba.

For more detailed information on winter hardiness in winter wheat, take the time to read the article “Basics of Cold Tolerance and Winter Survival in Winter Wheat’ from the 2001 Manitoba Agronomists Conference at http://www.umanitoba.ca/faculties/afs/MAC_proceedings/2001/pdf/struthers.pdf.

There is also real-time monitoring of soil temperatures in the five winter wheat fields in Manitoba (see the CropChatter post at http://cropchatter.com/monitoring-real-time-soil-temperatures-in-mb-winter-wheat-fields-2/.)

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD

For more information on Winter Wheat – Production and Management, visit: http://www.gov.mb.ca/agriculture/crops/production/winter-wheat.html
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GOT JIMSONWEED?

According to reports from across the Prairies, you’re not alone. In Manitoba, the weed has been found in fields from Swan River down through the south-central region.

Jimsonweed (Datura stramonium) is an annual broadleaf with white/off-white trumpet-like flowers on stalks that can grow over 5 feet tall. It reproduces by seed that is contained in spiny pods (see Figure 1). This weed isn’t new to the Province but it’s only occasionally a problem. Although seed contamination is being considered, it’s just as likely that warm temperatures and less competitive crop stands contributed to increased germination and establishment of existing weed seeds.

Jimsonweed seed pod

Jimsonweed seed pod

Recommendations for Control:

Crop Rotation: Jimsonweed is not overly vigorous, so rotating to competitive crops like cereals or canola will help with control. The weed tends to be a bigger issue in less competitive and later season crops, including corn and soybean.

Herbicides: Although Jimsonweed doesn’t show up on many product labels there are lots of pre- and post-emergent herbicides that should provide control including glyphosate, glufosinate and various group 2’s, 4’s 6’s, 14’s and 27’s (www.msu.edu/~zandstra/Weed-Chem/jimsonweed-Chem.htm**; 0= no activity, 1= good to excellent, 2= fair to good). **Only use labelled applications of herbicides registered by Health Canada.

Application timing: Like most weeds, herbicides are most effective on Jimsonweed when it’s small. Because it’s a later germinating weed, it might be ‘missed’ by early herbicide applications but be too large for some later herbicide applications.

Rouging or cutting: Hand-pulling or cutting Jimsonweed before it sets seed is also an option, depending on the number of plants and their distribution in the field. Seed growers may need to put this option into play this fall since Jimsonweed is a prohibited noxious weed seed under the Weed Seeds Order (http://laws-lois.justice.gc.ca/eng/regulations/SOR-2005-220/page-2.html#h-4). Jimsonweed seed can be similar in size to canola.

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, MAFRD

Visit MAFRD Crop webpage for more current topics: www.gov.mb.ca/agriculture/crops/seasonal-reports/current-crop-topics.html#agronomy

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Effect of Temperatures, and Natural Enemies, on Soybean Aphids

Effect of temperature on soybean aphids: As with other insects, soybean aphids have a temperature range where development is optimum, with development being slower below and above the optimum range. For soybean aphid the temperature for optimum growth is around 27C. At lower temperatures development will be slower. At the other extreme, in experiments where soybean aphids were kept at high temperatures, nymphs did not complete development at 35C and died within 11 days (J. Econ. Entomol. 2004: 854-861).
Soybean aphid consumption by natural enemies: High levels of natural enemies have been reported by some monitoring levels of soybean aphid. Predaceous insects are the easiest natural enemies to recognize; levels of parasitism and insect pathogens are not often as obvious but with training can be estimated as well. Lady beetles, lacewings, and larvae of hover flies are some of the common and easily recognizable predators in soybean fields. When checking soybean fields, consider whether the aphid populations are increasing or decreasing, and the level of natural enemies present.
Common species of lady beetle that may be noted in soybean fields include the sevenspotted lady beetle and the multicoloured asian lady beetle (Figure 1).
asian-lady-beetle-larva

Figure 1. Larva of multicoloured asian lady beetle

A study looking at predation rates by these two species of lady beetles on soybean aphids found that for sevenspotted lady beetle third instar larvae could each consume up to 105 aphids per day, adult females could each consume up to 115 soybean aphids per day, and each adult male up to 78 aphids per day when soybean aphids are high. (Environmental Entomology: 2009. 708-714). For multicoloured asian lady beetle, third instar larvae could each consume up to 112 aphids per day, adult females could each consume up to 95 soybean aphids per day, and each adult male up to 53 aphids per day when soybean aphids are high.
Some have been sending in photos of hover fly larvae, which may be found in many crops where aphids are present, wondering what they are. Although the adults, which are good bee mimics, are easy to recognize, the larvae may not be as well known. Note that hover fly larvae (Figure 2) are legless, and narrow towards the head. There are different species that can vary in colour, often brown or green.
hover-fly-larvae-on-soybean-leaf

Figure 2. Larvae of 2 species of hover flies and soybean aphids

The above information was submitted by John Gavloski, MAFRD Entomologist.  It is available in this week’s issue of the Manitoba Insect and Disease Update which is posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2015-08-17.html

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Soybean Aphids & Importance of Economic Thresholds

Soybean aphids have been showing up in many fields, but so far populations have stayed below the economic thresholds. A few things to note regarding economic thresholds for soybean aphid:

  • The economic threshold for aphids in soybeans is 250 aphids per plant, and the population is increasing, and the plants are in the R1 (beginning bloom) to R5 (beginning seed) growth stages.
  • The reason that “and the population is increasing” is part of the threshold is because the actual economic injury level, where control costs will equal yield loss, is actually about 670 aphids per plant. The economic threshold, where control is suggested, has been set much lower than 670 to allow time for the spray to be applied before increasing populations could potentially reached 670 per plant. The population doubling time for soybean aphids can be as low as about 7 days if they are not being regulated well by natural enemies or weather.
  • Aphid populations do not always continue to increase. So we can not assume that because a certain number is present this week that even more will be present the next week. Populations can plateau or start decreasing due to natural enemies or weather conditions or events.
  • The above-mentioned economic threshold is based on the average of multiple plants selected from throughout the field and not just hotspots or field borders. Avoid making treatment decisions based on field borders. Small aphid hotspots often collapse from predation, parasitism or emigration.
  • When the value of the soybean crop is high, it is a mistake to try to lower the economic threshold below 250 per plant and the population increasing. There is already a large gap between the economic injury level and the economic threshold that is suggested. But what also needs to be considered is that the damage boundary, which is the lowest insect pressure where any yield loss can be detected, is well above the 250 economic threshold that used. So it would be illogical to try to reduce a threshold which is already below a level where yield loss can not be detected. Although economic injury levels (where control cost = yield loss) do change with commodity prices, damage boundaries do not. And given that aphid populations do not increase in linear fashions, there would be no advantage, and potential costs, to spraying at levels below the suggested economic threshold for soybean aphids. The research publication where the economic thresholds for soybean aphids are presented states “setting an economic threshold at lower aphid densities increases the risk to producers by treating an aphid population that is growing too slowly to exceed the economic injury level in 7 days, eliminates generalist predators, and exposes a large portion of the soybean aphid population to selection by insecticides, which could lead to development of insecticide resistance (Journal of Economic Entomology. 2007: 1258-1267). So to summarize, monitor fields and use the suggested economic thresholds.
  • When aphid levels are high, exact counts are not possible and would consume too much time. Estimates after a quick examination of the plant will be sufficient. Note in figure 1 below the soybean aphids, and the white shed skins from aphids that have molted. Avoid including the shed skins in your counts.
Soybean Aphids on Soybeans

Figure 1. Soybean aphids and shed skins.

The above information was submitted by John Gavloski, MAFRD Entomologist.  It is available in this week’s issue of the Manitoba Insect and Disease Update which is posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2015-08-04.html

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Stripe Rust Reported in Manitoba

As reported in the June 16th Insect & Disease Report issued by MAFRD (http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2015-06-16.html), stripe rust has been found in Manitoba.  The first report came from a winter wheat field southwest of Killarney, followed by symptoms being found in MCVET winter wheat plots in Carman (see Figure 1). And on June 18th, stripe rust was reported in spring wheat west of Altona.

Stripe Rust in Winter Wheat 2015 (P.de Rocquingy)

Figure 1: Stripe Rust on Winter Wheat. Photo by Pam de Rocquigny, 2015

Producers are encouraged to continue scouting their winter wheat and spring wheat fields as early detection is important. The good news is wheat stripe rust can be managed by timely fungicide applications.  If the disease pressure, weather conditions and crop yield potential warrant application, foliar fungicides should be applied before the disease is well-established in the crop to provide maximum benefit. There are numerous products available for the control of stripe rust; please refer to the Guide to Field Crop Protection.

If rust infections are only noticed later, especially past the flowering stage, a fungicide is likely unwarranted as the yield effect will be minimal.

For more information on stripe rust, its symptoms and control measures, visit MAFRD’s website at http://www.gov.mb.ca/agriculture/crops/plant-diseases/stripe-rust-puccina-pathway.html.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD with information from Holly Derksen

 

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Cereal Crops Recovering from Frost Injury

The May 30th frost impacted spring cereal crops across Manitoba. Fortunately, majority of spring wheat, oats and barley were at the tillering stages of development where the growing point is still below ground and therefore protected from the cool air temperatures (the growing point moves above ground at jointing or stem elongation).

However, this doesn’t mean cereal crops escaped without some symptoms of injury.  In MAFRD’s June 3 webinar (available on YouTube at http://youtu.be/UDa3uWMmZzg), I covered some of the basics of frost injury symptoms in cereal crops and what to look for in terms of recovery. (And for those interested in canola and flax, my colleague Anastasia Kubinec of MAFRD covered some excellent material for those crop types in the same webinar).

For cereals, you want to look for new leaf growth (normal green color) from the growing point that should follow within 2 to 3 days after the frost event. It can go upwards of 5 days if growing conditions are cool.  Below is a great photo by Lionel Kaskiw with MAFRD which shows barley impacted by frost recovering.  You’ll also notice the water-soaked appearance of some of the older leaves, a classic symptom of frost injury.

Frost Damaged Barley

Frost-Damaged Barley Recovering; Note New Leaf Growth Emerging from the Growing Point – Photo by Lionel Kaskiw, MAFRD (2015)

Fortunately, the loss of leaf tissue at this early stage should have little impact on yield.  But be cautious when applying herbicides in the coming days.  Generally, you want to wait for at least 48 hours after the frost event, as well as seeing the crop resuming growth.  However, please check with your local chemical representative in terms of when it should be safe to apply herbicides after a frost event as it can be product-specific.

More additional information on frost damage, refer to MAFRD’s Spring Frost Damage Bulletin.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD

 

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Thinking about Reseeding Cereals? Read this First.

I have been receiving a few calls on producers considering reseeding poor barley stands, or concerned about their cereal crops in general. So I thought I would take this chance to review some key points producers and agronomists should think about if considering reseeding their cereal acres. A lot of the information is derived from a great article by North Dakota State University staff titled “Replanting or Late Planting Crops” (Publication A-934; Revised). I have included some of that information and added Manitoba-specific data and comments.

Why are some cereal fields impacted? Many producers were able to start seeding their cereal crops early in 2015. However, slow and/or uneven emergence was noted in many fields due to cool soil temperatures, dry soil conditions (in some areas of the province) and below normal temperatures following emergence. The slow growth was further complicated by excessive rainfall, wind, snow and frost over May Long weekend, and then another frost event on May 30. Not only do these conditions bring with it concern for erratic crop emergence and poor plant stand establishment, it can also promote a number of seeding diseases and root rots.

The Main Question to Answer. At the end of the day, producers must try and answer the question “Will which result in greater net return – keeping the original stand or replanting to the same/different crop?”.

The final decision should be backed by sound agronomic and economic information as well as taking into consideration AgriInsurance coverage and contracts. Agronomic information to consider should include: level of injury, crop uniformity and overall plant health of the original stand, alternate crop choices if reseeding, and management practices related to crop growth and development for either the original stand or the replanted crop. Producers and their agronomists should accurately assess all these factors in order to make an informed decision. I realize that is a lot of information to gather. Perhaps it is easy to think of it in a few steps.

Step 1: Evaluate original crop stand and yield potential. The best possible evaluation of the surviving stand is needed because the critical yield comparison ultimately will be between the original stand versus the replanted stand with a later than optimum planting date.  Remember, you need to allow time for crop to recover from injury prior to assessing plant stands!

To accurately evaluate the existing stand, stand counts should be taken at random from several areas of the field. For more information read the article “Doing Plant Stand Counts in Your Cereals”: http://cropchatter.com/doing-plant-counts-in-your-cereals/.  Typically for cereals, minimum stand levels that should be considered acceptable before reseeding is done ranges from 8 to 14 plants per square foot (NDSU). During early growth stages, most cereal crops can sustain some stand loss without experiencing significant yield reduction due to increased tillering. Keep in mind barley and oats typically tiller more than spring wheat.

However, the minimum stands stated is assuming plant stands are relatively uniform in distribution; what can complicate this assessment is the damage in fields can be distributed randomly throughout the field.

In addition to the direct effect of stand reduction, indirect effects of crop injury, such as increased weed competition and increased disease potential, should be considered. Damaged crops usually grow slowly until they have recovered, which provides the potential for greater weed competition.

Step 2: Evaluate yield potential & agronomics of replanted crop options. Crops replanted later in the season almost always will yield less than those planted at an optimum time. Figure 1 shows the yield potential of various crop types as seeding moves into June in Manitoba.

Figure 1: Percent Average Yield from 2005-2013 for Manitoba Crops Planted in Week/Month as Reported to MASC

Picture1

Not only yield potential should be considered however. A short growing season increases risk of damage by fall frost affecting both yield and quality of the replanted crop. Increased risk of high daytime temperatures can also affect crop development. For example, there is increased risk of the crop flowering when daytime temperatures are high which can increase probability of floret abortion.

Delayed seeding may also increase potential of yield loss due to disease and insects. MAFRD articles Crop Choices in a Late Planting Scenario and Mitigating Risks Associated with Delayed Seeding will provide additional information to producers.

Step 3: Determine Reseeding Costs. Comparison of the estimated yield of the original stand with expected yield of the replanted crop minus any costs associated with reseeding must be considered.

The decision to reseed ultimately must be made by comparing the economics of the original plant stand with that of a replanted crop. This can be subjective and each case must be considered individually in terms of time of year, alternate crop choices, previous herbicide use, crop economics, AgriInsurance coverage and contracts, and other related factors.  If a producer has AgriInsurance, it is recommended they contact their MASC agent prior to terminating a field and replanting.

Once again, I’d like to acknowledge information from NDSU’s article “Replanting or Late Planting Crops” (Publication A-934; Revised).

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist

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Assessing Spring Frost Damage after Corn Emergence

Although there isn’t many acres of emerged corn in Manitoba, some corn has emerged and was recently impacted by the weekend’s frost events.

Corn in the V5 stage (5 leaves with collars showing) or less will recover from light frosts because the growing point is still below the soil surface.  Symptoms of frost damage will start to show up about 1 to 2 days after a frost. Symptoms are water soaked leaves (see Figure 1) that eventually turn brown and necrotic. Frost will often kill young corn leaves but plants, even with extensive leaf damage, will likely recover if the growing point was not injured. The death of leaf tissue above the growing point has only a small effect on corn growth and yield at early stages of development.

While extremely rare, if air temperatures drop to temperatures of -2°C or less for more than a few hours, the growing point region of a young corn plant can be injured or killed even if it is still below the soil surface.

frosted corn 2009

Figure 1: Frost Damaged Corn. Photo by Pam de Rocquigny (2009)

To assess corn plants, look at the growing point approximately 3 to 5 days after the frost occurred.  By this time, surviving corn plants should be showing new leaf tissue expanding from the whorls (see Figure 2).  Note, it is not unusual for the new leaves to get ‘caught up’ in the dead leaf tissue.  You can also check the growing point, which can be found by pulling up the entire corn plant, including roots, and splitting the entire plant lengthwise. If the growing point is white or creamy in appearance injury didn’t occur.  However, damaged tissue in the growing point region will be discolored and soft or “water-soaked”. There will also be lack of new regrowth from the whorl.

Frosted Corn CDS 2009 Day 6 (2)

Figure 1: Frost Damaged Corn, 6 Days after Frost Event. Photo by Pam de Rocquigny (2009)

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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