Why is my Corn Purple?

Many Manitoba corn fields are showing some degree of leaf purpling this spring. Here’s a quick look at why leaves turn purple and what possible causes may be.

 

Leaf purpling is a sign of stress. The leaves are actively producing photosynthates (sugars) but conditions are not allowing normal sugar metabolism or translocation in the plant.  The purple anthocyanin pigment is associated with this sugar buildup in leaf tissue.  The amount of purpling is genetically controlled, so hybrids with more of the purpling genes will appear worse than others, even though all suffer the same stress.

Common stress conditions triggering this purpling are:

  • Warm sunny days but cool nights (4-10oC) – this allows sugar buildup but not metabolism
  • Restricted root growth and development – soil compaction (Figure 1), herbicide injury (such as Edge carryover- Figure 2), standing water.
  • Impaired phosphorus uptake due to insufficient soil phosphorus, lack of phosphorus starter fertilizer (Figure 3) or following non-mycorrhizal crops like canola.
  • Physical injury – recently wind has crimped leaf tips (Figure 4) causing sugars to buildup without being translocated to other growing parts of the plant

Purpling will often dissipate with warmer days and nights and yield loss is slight if any. But severe purpling is a symptom of crop stress, so the astute crop advisor or farmer will exploit it as a visual signal and will investigate the cause so to manage better next year.

 

 

 

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Quick Tips – Effective Post-Emergent Weed Control in Conventional Soybeans

If you have only grown glyphosate tolerant soybeans in the past, the move to conventional soybeans can offer up new challenges in regards to weed control. Good weed control is critical for maximizing yield.  Here are a few quick tips:

    • Remember!! You can’t apply post-emergent glyphosate – Unlike glyphosate-tolerant soybeans, conventional soybeans are not a clean-up crop for weedy fields. They are a crop that needs to be planted in fields that have already been cleaned up.
    • Get in touch with your weed spectrum – If you have not done so already, determine what weeds are present or likely to be present in your conventional soybean fields. Are the herbicides you intend to use going to control the weed spectrum you have identified? A mismatch between weed spectrum and herbicides used is a frequent cause of weed control problems in conventional soybean fields.
    • Did you take advantage of pre-emergent weed control opportunities? If so, how is that working? – The advent of pre-emergent soil applied residual products has been a benefit to weed control in conventional soybeans. If this is a tool you decide to use, it is important to assess its effectiveness before you do post-emergent applications to ensure that weeds you are assuming have been dealt with have been controlled.
    • Amp up the Aggression!! Early and thorough weed control is key – Important regardless of the type of soybean you are growing. Research has demonstrated the critical weed free period for soybeans is emergence to the third trifoliate, where the removal of weeds provides the greatest protection of yield potential. Be timely with control and selective with products that may provide some residual control for an extended weed free period.
  • Know your crop growth stage, know your weed growth stageKnowing your crop and weed growth stages as you time herbicide applications is very important in conventional soybean production. Most of the herbicides available have tighter application windows than glyphosate

 

  • Overgrown weeds are less susceptible to herbicides – this can lead to growers dishing out more money on higher cost options that might not work due to size of plants. Please take note that some herbicides can cause crop damage if they are used at the wrong growth stage. In this competitive fight for yield, you don’t want to set back your crop.

 

 

  • Assess the effectiveness of herbicide applications and adjust your plan – Fields should be scouted after each herbicide application to assess effectiveness. If weeds have shown up that the previous herbicide would not have controlled, you might have to change products for your next application or add extra herbicide passé. Were the weeds that you expected to be controlled, actually controlled? Don’t assume that you have dealt with target weeds until you see the evidence. These post-spraying inspections are key opportunities to detect the development of herbicide resistant weeds before they get out of hand.
  • Weed control in conventional soybeans is going to cost more – Seed may be cheaper, but the cost of an effective weed control program in conventional soybeans is almost always more expensive than in glyphosate-tolerant production. But remember, poor weed control remains the #1 threat to maximizing yield and profit in conventional soybeans. Weed control is a key point of investment in this crop and there are no shortcuts if the weed control situation demands action.
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Post-Emergent Weed Control in Xtend Soybeans – Slow Down and Be Careful

The future of side by side soybean fields using different herbicides is here with Xtend soybeans commercially available in 2017.  Having more herbicide tools to combat the herbicide resistant weeds is important, but careful use is critical, to prevent crop damage and stay friends with our neighbors. Here are a few things to consider:

  • Non Xtend soybeans (and other crops) are easily damaged by dicamba – dicamba on sensitive crops always causes crop damage with very dramatic looking symptoms. As glyphosate -tolerant soybeans made up the majority of acres in the past and usually only sprayed with glyphosate, drift went unnoticed. The addition of Xtend soybeans to the cropping mix will be a reawakening to anyone who has gotten careless.
  • Should your pre-emergent application have been the one that included dicamba? – preferred timing for dicamba containing herbicides for use on Xtend soybeans is pre-emergent. Research has demonstrated the critical weed-free period in soybeans is emergence to the third trifoliate, early weed removal provides the greatest yield potential. Additionally, dicamba provides residual control for some weed species during that critical period. Another important point is, chances of application mistakes like drift on sensitive crops are greatly reduced during pre-emergent applications.
  • Only use herbicides specifically designed for the Xtend system – do not tank mix dicamba and glyphosate that you might have on hand in an attempt to make “homemade” herbicide for Xtend soybeans. The herbicide manufactured is designed specifically for use in Xtend soybeans, with reduced levels of volatilization, to prevent herbicide drift. Keep in mind the reports on the U.S. experience in 2016.  Homemade concoctions are a very bad idea, plain and simple.
  • The label is your friend…follow it! – the labels contain important information that will help minimize chances of accidental herbicide drift onto susceptible crops. Key points include:
    • Use nozzles delivering extremely coarse to ultra coarse spray droplets (volume median diameter of 450 microns or more) as defined by ASABE standard S572.1 and as shown in the nozzle manufacturer’s catalog.
    • Do not apply:
      • when risk of severe temperature fall in the night;
      • under high humidity, temperatures above 30oC, or fog conditions, to prevent drift to sensitive crops;
      • when wind is blowing toward a nearby sensitive crop;
      • when winds are below 3 km/h or above 15 km/h.

Source: Guide to Field Crop Protection 2017 p. 163

  • All soybeans look alike – know what field you are in – there is no way to visually discern between the different types of soybeans. When in doubt, make sure that the applicator is in the right field. Herbicides specifically designed for the Xtend system applied to Roundup Ready or conventional soybeans will cause significant crop damage. Additionally, knowing the types of soybeans in the adjacent fields is important to indicate increased risk for off target crop damage. Remember, dry beans look like soybeans from far enough away….never make assumptions.
  • Sprayer cleanout requires careful attention – If producers are growing two or more types of soybeans on their farms, careful consideration has to be given to sprayer cleanout as they move between soybean fields. Even a small amount of dicamba will serve as a contaminant in the next spray load being applied, causing significant damage. Especially if you have only grown Roundup Ready soybeans in the past, recognize that the situation has gotten more complicated.
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Don’t Overlook Group 2 Herbicide Resistance

You’ve probably read about media dubbed ‘superweeds’ like glyphosate-resistant palmer amaranth and giant ragweed. Glyphosate-resistant weeds often earn this distinction because they are viewed as a greater management hardship for producers than weeds resistant to other herbicide mechanisms of actions (MOAs).  And maybe rightly so.  Farmers dealing with glyphosate resistant weeds elsewhere in the world have been reduced to tillage and hand rouging for weed control in some crops.

But, while glyphosate use dominates the Roundup Ready corn, soybean and/or cotton rotation in the US, group 2 herbicides play an (equally?) important role in our more diversified cropping system. For example, group 2 herbicides are used in crops like alfalfa, corn, dry beans, field pea, potato, soybean, sunflower, and in Clearfield and other group 2-tolerant crops.  These herbicides are also a popular choice for group 1-resistant grassy weed control in cereals.

The point of this article isn’t to downplay the importance of glyphosate resistance but to elevate consideration of group 2 resistance. In Manitoba, over 10 weed species are known to have biotypes resistant to group 2 herbicides.  And herbicide-resistant weed surveys led by AAFC indicate that the prevalence of certain species is increasing (Figure 1).

Figure 1: Prevalence of group 2 resistance in Manitoba in 2003 and 2008 as a percent of the weed species population surveyed (Beckie et al).

 

The following practices can help reduce the risk of developing herbicide resistant weeds and/or managing existing resistant weed populations:

  • Diversifying your crop rotation;
  • Using multiple herbicide MOAs effective on target weeds (e.g. herbicide ‘layering’, tank mixing);
  • Practising good basic agronomy (variety selection, seeding rates, etc.);
  • Judicial use of tillage.

If you suspect group 2 resistance in a weed species on your farm, it’s best to verify this by herbicide-resistance testing. Unfortunately there‘s no quick method – seed from the suspect population needs to be allowed to mature and collected.  Samples can be submitted to AgQuest for testing in Manitoba.

In my opinion, knowing if you have group 2 resistance and assessing your risk factors is worth it. Because while glyphosate resistance is grabbing headlines, group 2 resistance may be quietly growing in your fields.

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Blackleg in Canola – to spray or not to spray?

Things to consider:

  1. Crop rotation – the tighter the rotation the higher the risk of blackleg
  2. Historic levels of blackleg in that field – have you experienced yield loss from blackleg?
  3. Weather forecast – infection requires free moisture (light-moderate rainfall, not soil saturation)
  4. Presence of inoculum –can you see leaf lesions on first true leaves? or pseudothecia present on canola stubble?
  5. Yield potential – what is your target yield, return on investment expected?

If you have made the decision to spray, what else do you need to know?

  1. Application timing – apply at the 2 to 4 leaf stage, later applications are not as effective at reducing disease.
  2. Fungicide type – strobilurin fungicides (Group 11) are more effective at reducing disease than triazoles (Group 3). For more information on what products are registered for blackleg management, see the MB Guide to Field Crop Protection http://www.gov.mb.ca/agriculture/crops/guides-and-publications/pubs/crop-protection-guide-disease.pdf.
  3. Yield increase….not guaranteed – while strobilurin fungicides applied at the 2 to 4 leaf stage did significantly reduce the severity of the disease, yield bumps were only observed when a susceptible cultivar was grown.

 

 

 

Reference: Liu, C. 2014. Evaluation of fungicides for management of blackleg disease on canola and QoI-fungicide resistance in Leptosphaeria maculans in Western Canada. Master of Science Thesis. University of Manitoba. 172 pp.

 

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What is Waterpod?

Waterpod is:

  1. an annual weed occasionally found in agricultural fields;
  2. a mobile irrigation system; or
  3. a one person submarine?

 

 

If you chose a), you’d be right. Waterpod (Ellisia nyctelea L.) is an annual broadleaf plant native to Manitoba.  It’s often found in shaded, wooded areas but can also thrive in ditches and agricultural fields.  Our wet soils and cool spring must have provided ideal conditions for waterpod emergence as it’s being found in abundance in fields across the province.

The good news is waterpod isn’t much of agricultural pest.  Although it’s an annual, it emerges and flowers early and usually dies off in June.  It’s also very susceptible to glyphosate and most other burn-off and post-emergent herbicides.

Identifying characteristics:

  • oval cotyledons with a flat top;
  • deeply lobed and hairy leaves;
  • small, white 5-petaled flowers.

 

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When to Roll Your Soybeans

Most growers will roll their beans shortly after seeding in order to prevent stones from entering the combine at harvest time and to make harvesting easier and quicker. On dry springs when soil conditions could lead to soil drifting a grower can wait and roll there beans after they are up and are at the first trifoliate stage..

When rolling after emergence

  1. Do not roll at the Hook Stage- This is when beans are first emerging.
  2. Do not roll in the morning wait until air temperature are around 25C before you start to roll to avoid damage to the plants.
  3. Check for damaged plants to ensure plants are not breaking off.
  4. If damage is too sever wait for a warmer day.

 

The attached video outlines some of the reminders about rolling beans.

Soybean School West: Why Rolling Matters & Timing it Right

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What’s Wrong with My Spruce Trees?!?

Spruce is a common grown shelterbelt tree in Manitoba. They prefer acid soils, that are coarse textured with good drainage, have adequate water and sheltered from extreme weather conditions.  If conditions are not ideal, the trees will begin to decline and become more susceptible to pests.  If your trees are declining and you are considering using a fungicide/insecticide, read the label carefully to make sure the product is registered for use on the trees species and to control the pest identified. Spruce problems can be divided into three categories – Physiological, Disease and Insect.

Physiological

Winter burn or evergreen browning – caused by excessive water loss from the needles. In late winter/early spring, they take on a reddish brown appearance toward their branch tips and/or on one side of the tree.  The south and southwest side may be worse due to more exposure to sun at potentially wind. If conditions are highly favorable for winter burn, buds can also lose moisture and be killed.

Natural Needle Drop – late August or early September, coniferous trees will naturally shed their older needles (usually needles which are 3 or 4 years old or older). During this process, the innermost needles will turn to yellow or brown and drop off. Although this process takes place every year, in some years it becomes more pronounced due to environmental factors. Needle loss can appear to be very dramatic and is often mistaken for a disease or insect problem. Nothing can be done to prevent natural death of needles since they do have a finite life span. Good maintenance can minimize environmental stress.

Competition Stress – if spruce are planted too close to each other, trees can suffer from competition stress. This occurs when the feeder roots from two or more trees take available water and nutrients from the same soil area resulting in slightly stronger trees taking most, while the weaker trees, deprived of water and nutrients, grow poorly and may decline and die. If the branches of two trees are in contact or intertwining, competition stress could be occurring.

Disease

Branch Canker – characterized by browning and death of entire branches. Individual diseased branches can occur anywhere on the tree, although the disease may start on lower branches and move upward. White or grayish crusty or resinous patches appear at the canker site and can also occur on the trunk. Pitch may ooze from these cankers and drip onto lower branches. During wet weather, some cankers can produce spores that disseminate to cause new infections. Pruning out areas affected is the only means of control once the disease has been initiated. Prune when the weather is dry, with pruning tools sterilized between cuts with alcohol (isopropyl alcohol), or a household disinfectant such as Pinesol or Lysol and all diseased material should be removed or destroyed.

Needle Cast – characterised by irregular tan, yellow, red-orange, reddish brown or black spots, specks or bands being produced on the needles from previous seasons of growth. The fungi can infect the new growth from the current season, but do not usually show symptoms on those needles until the following season. Affected needles generally drop early. Twigs of infected trees may appear stunted and may dieback. To prevent spreading, the new needles should be protected by applying a copper fungicide containing copper oxychloride just as growth begins in spring. Repeat applications 3 or 4 times at 10 day intervals. If the planting is not too large, it would be helpful to rake up and remove fallen needles from under the trees to remove them as a source of reinfection. There are currently no fungicides available for home use but fungicides with commercial or agricultural registration are available. Consult with an arborist or tree care service for fungicide options.

Insects

Spider Mites – all evergreen trees have a resident population, but during hot dry spells populations can explode. Visual symptoms start as dingy yellow or dusty needles and progress to brown and dry, then needles drop. There may also be a fine webbing, between the needles. In severe or prolonged infestations, dust particles, shed needles and dead mites catch in the webbing giving the tree an unhealthy appearance. Damage to the tree is caused by both adults and nymphs sucking sap from the needles. Mites can be controlled by using any insecticide listing mites and spruce on the label, at a rate recommended on the label. Dormant oil sprays can also be used to control spider mites. See directions for use on the labels.

Spruce Needle Miner – webbing is produced and may contain dead needles and frass (droppings). Damage is done after tiny larvae hatch from eggs that have been laid along the sides of a needle and begin to chew a hole at the base of it. The insects feed on the needles and exit from the same hole in search of new needles. Full-grown larvae are green with a brown head and are about 6 mm long. The larvae remain active until October when they construct a cocoon inside a nest of dead needles and frass to overwinter.  Adults emerge as small greyish brown moths that have a 12 mm wingspan. If a tree has a large number of needle miner nests it can appear quite unsightly, as airborne material such as dust and poplar cotton become easily caught in them. Heavy infestations can severely weaken the tree through loss of needles. Before bud break in spring, the nests can be washed away with a strong stream of water from a garden hose. The debris should then be gathered and destroyed. This may help to reduce the current year’s infestation.

White Pine Needle Scale  evident by tiny white flecks on the needles that resemble spots of paint. Each white scale contains a dead body of a female scale insect and her overwintering eggs.  During the summer the crawlers moult to become adults after which they begin to secrete a white scale covering. Scale insect feeding damage causes large yellow areas on the needles that can coalesce if the population density becomes excessively high. Sustained heavy attack for 2 or more years can cause trees to lose most of their needles. Insecticides or dormant oil sprays listing spruce and scale insects on the label can be used for control. Follow label directions.

White Pine Weevils – weevils kill the top 2-3 years growth of their host trees. Damage very conspicuous, causing the terminal leader (very top of the tree) to wilt and take on a crook shape, turn brown and die. Located below the damaged area, there can be found small exit holes made by the emerging adult weevils. Adult weevils overwinter in the litter on the ground. There are no insecticides registered for control. Prune and burn infested leaders before mid-July to remove and kill the insects. Cut back all but one live lateral (side) shoot by at least half their lengths to maintain single-stem dominance. Avoid planting the highly susceptible Colorado blue spruce in areas where white pine weevils have previously caused damage.

Spruce Bud Scale heavy infestations can result in twig and branch dieback. The presence of sooty mold on twigs, needles and branches may be the first clue to the presence of the insect. The sooty mold does not cause any damage to the tree but is unsightly and since it is highly visible is often mistaken for the cause of needle and twig dieback if these are occurring in association with the scale infestation.  The female adult scales cluster along the stems of twigs. They closely resemble the buds of the spruce tree, lower branches on the trees are often the most heavily infested. Heavy scale infestations result in discoloration and loss of needles, twig dieback, dieback of lower branches and reduced tree vigour and growth. Infested trees are also reported to be more susceptible to winter injury. Any insecticide listing spruce and scale insects on the label can be applied to reduce damage from this insect. Follow label directions. Insecticides should be applied while the crawlers are still active.

 

 

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How Can I Reduce Fertilizer Losses in Dry Spring Soils?

Dry spring weather is great for seeding but may play havoc with some fertilizer applications and losses.

1.Seedplaced fertilizer – Where seedbed moisture is low or when weather is hot and windy, reduce the rates of seedplaced nitrogen  by approximately 50 per cent. Table 7 of the Manitoba Soil Fertility Guide  http://www.gov.mb.ca/agriculture/crops/soil-fertility/soil-fertility-guide/nitrogen.html indicates safe rates of seedplaced urea under different soil texture, moisture and seedbed utilization conditions.  But as conditions dry, these rates should be reduced accordingly.

2.Surface applied urea or urea-forms (like UAN solution 28-0-0) – are vulnerable to volatilization losses.  The soil and environmental factors increasing risk of loss are well known and include:moist soil conditions, followed by rapid drying

  • high wind velocity
  • warm soil temperatures
  • high soil pH (> pH 7.5)
  • high lime content in surface soil
  • coarse soil texture (sandy)
  • low organic matter content
  • high amount of surface residue (Zero Till)

Volatilization losses can be reduced with dribble placement of UAN versus broadcast applications and the use of an urease inhibitor.  The active ingredient NBPT used in Agrotain Ultra is now marketed by a number of companies.  To expect the same level of protection as Agrotain Ultra, ensure the application rate is similar, since formulation strength and recommended rates differ among suppliers.  Agrotain Ultra contains 27% NBPT with an application rate of 3.1 l/tonne urea or 1.6 l/tonne UAN.

3. Last year the lack of rainfall through much of May left surface applied nitrogen stranded at the surface.  If possible, a portion of the crops nitrogen for cereals and canola should be in-soil placed.  In season applications should be targeted prior to stem elongation of cereals and bolting of canola.

 

 

 

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Crop Germination – What Soil Temperatures are Needed?

Soil temperature drives germination and seedling emergence, so how cold is too cold?  What is your soil temperature at your targeted seeding depth….today? Finally, when should you be measuring the soil temperature?

The following are the minimum temperatures needed for germination to begin in various crops.  These values should be regarded as approximate, since germination depends on factors other than just temperature.  But, if soils are too cool, germination will be delayed and cause uneven or poor seedling emergence.

 

Crop Temperature     (°C)
Wheat 4
Barley 3
Oats 5
Corn 10
Canola 5
Flax 9
Sunflower 6
Edible Beans 10
Peas 4
Soybeans 10

Sources: North Dakota State University Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada

Getting an accurate measure on soil temperature

Determine how deep you will be seeding. Then place your soil thermometer at the targeted depth. Take two measurements throughout the day: one in the morning (8am) and one in the early evening (8pm).  Average the two readings to determine the average soil temperature. The recommendation is to take readings for two to three days to establish a multiple day average and to measure at a number of locations in the field, to account for field variability.

Still not sure and short on time?  See the soil temperature data for various locations across Manitoba from the MB Ag-Weather Program: https://www.gov.mb.ca/agriculture/weather/soil-temperature.html.  This can be used as a guideline for an area, but in-field measurements are going to tell you what is actually going on in your field!

 

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