Winter Canola Update and Outlook

With the recent temperatures experienced across the state in the last week, many growers may be wondering about the damage to their canola crop.  Prior to talking about the recent freezes, we need to look at the status of the crop as a whole. 

This last winter was one that had several unique challenges.  While this had not been the coldest winter we have had in recent years, periods of severe cold weather definitely hurt the crop.  Part of this was due to the overly warm fall that most of the state experienced.  These warm conditions lead to excessive growth of the crop, leading to crop stem reaching nearly 2 feet in isolated conditions.  While much of that state did receive periods of cold and chilling conditions prior to any major freezes, these were mixed with multiple day stretches of over 80°F.  This resulted in the crop not being able to properly harden-off and the crop was still somewhat sensitive to freezing temperatures.  This meant that freezing temperatures around Thanksgiving and severe freeze (-5 to -20°F) around the 14th of December resulted in fields or areas of the field seeing substantial winter kill.  Most of these fields have been seen north of the I-40 corridor; however, area agronomist, Heath Sanders, has seen a number of fields in SW Oklahoma having moderate to severe winter kill.  While the outlook may sound bleak, one of the most positive aspects of winter canola is its ability to overcome thinner stands by flexing and increasing branch production during reproductive growth.  Therefore, a couple of plants per square foot can still produce adequate yields.  Additionally, many of the canola plants may look like they have been completely winter killed but are showing “tillers” out of the base of the plant.  While these will not have the same yields as the primary stem, they can help overcome some of the yield losses that can be expected. 

This brings us to recent freezing events. The damage that spring freezes can cause to winter canola greatly depend on temperature, time at specific temperatures, growth stage, and moisture.  Soil moisture at time of freezing can drastically help save a crop that might otherwise see much higher freeze damage.  Another positive about the freezes in the last 7-10 days is that the canola crop has been in the rosette to bolting stages.  During these stages, canola can recover from mid- to low-20s temperatures for 1 to 7 hours with relatively little yield loss.  Longer consecutive hours, however, can result in substantially increased plant damage, which could state to add up to noticeable yield losses.  Therefore, the positively aspect out the crop is that most of the crop should still be in a relatively good conditions (as it pertains to freeze damage).  The major loss over the last week might have come at the expense of the “tillers” from plants that were partially killed during the winter.  Many of these lateral branches have seen significant damage and many will probably not successfully produce. 

As we look forward to the remainder of the season, it is important to be able to identify cold damage to the developing crop and know when the most sensitive periods occur.  Typical freeze damage and canola response, at each growth stage, that can be expected are below.

Rosette– Leaf burning can be expected; however, this is typically solely cosmetic. As temperatures warm, new leaves should start to emerge from the rosette. If no new growth is seen, severe enough damage could have been experienced that growth and yield may be limited. 

Bolting– Similar to the symptoms that can occur during the bolting stages as they did during rosette but these symptoms can occur not only on the leaves but the stem.  These symptoms include a discoloration of the tissue, resulting in the leaves and stems turning yellow, purple, or white.  Even with some damage, these plants should progress to flowering with little or no issue.  In more severe conditions, the still will be split or crack.  While this should have little effect on the plants ability to continue growth, these split stems may increase lodging and provide a port secondary diseases. 

Flowering and pod development– Cold temperatures at flowering can be far more damaging.  Unopened buds should still produce viable flowers (depending on temperature and time at that temperature). Open flowers or pods can be more damaged by colder temperatures. Flowers can abort or not produce viable seed following a major freeze event.  Early pods can become malformed and potentially terminate.  These will produce a permanent twisted and curled appearance. 

One thing is certain, these cooler temperatures helped slow maturation, if only for a short time.  This may help the crop in the coming weeks as freezes later in the season could potentially be more damaging the further the crop matures.  One thing must be noted, even with areas of field being killed over winter, we still must treat the field in the appropriate manner to ensure the crop following canola will still receive the benefits.  This includes making herbicide applications (as the canola crops still allows for it) to help control problematic winter weeds.

Agronomic management of sorghum to help with sugarcane aphids

With warming temperatures and March upon us, many growers are looking toward their summer crops and starting to think about acreage and planting decisions.  While there has been much concern over the last several years about the increased presence of the sugarcane aphid, growers should know there are several things that they can do now and in the next several weeks to maximum sorghum growth and productivity while minimize the impact of these pests. 

Hybrid Selection:

Hybrid selection is probably the most effective and cheapest way to help manage against sugarcane aphids.  Through the last several years, many hybrids have been identified to have varying degrees of tolerance to sugarcane aphid pressure.  Below is the current up-to-date list of tolerant sorghum hybrids that have been both proven in university trials and are currently commercially available. 

Resistant_hybrids
Tolerant sorghum hybrids.

It should be noted that these hybrids are resistant or tolerant in the truest sense.  With increased number of resistant weeds, we have denoted resistances either the inability to control or complete insensitivity.  Using this mentality, a resistant hybrid would no longer be affected by the sugarcane aphids.  Unfortunately, this is not the case.  These hybrids are resistant in that they provide some level of resistance to these pests not complete elimination of the treat.  This is why many people will refer to these hybrids are tolerant or susceptible. 

Planting:

While selecting a tolerant hybrid is increasingly important, it is only the first step.  Timely planting can be argued to be the most important step into a successful grain sorghum crop in Oklahoma.  Timely planting will greatly improve sorghum yields.  The major contributing factor to this is trying to avoid having critical sorghum growth stages during sub-optimal times of the year (i.e. sorghum flowering and grain fill during the end of July and the first of August).  Outside of the panhandle, the optimum time for planting sorghum is typically from early April through early May.  The further into May growers plant, the risk is increased that they will be pairing flowering or grain fill during hot, dry conditions.  It must be stated that this is only a guideline and some years May plantings will produce suitable yields; however, the risk associated is typically much higher compared to earlier planting.  Recent work at Oklahoma State University (multiple locations across northwest Oklahoma) documented at nearly 30% decrease in crop yield associated with Mid-May plantings compared to Mid-April. 

Yield by date
Percent of total yield associated with planting date.  Data is averaged from multiple locations in northwestern Oklahoma.

The benefits of earlier planting are more evident in current production systems due to the sugarcane aphids.  With earlier plantings, growers should be looking for the crop to reach the later stages of soft dough or hard dough prior to infestation.  This makes these pests only a minor yield limitation, compared to earlier infestations.  These pests will still have to be managed at harvest but yield in field is less impacted. 

Historically, if growers could not plant during the month of April, it was advised to delay planting until June.  However, with increased presence of sugarcane aphids, this will not always successfully save the crop.  Additionally, compared to years ago, double-crop planting has become a riskier practice.  This is because by the time the crop has reached the critical reproductive stages, sugarcane aphids will have built up on full-season sorghum and heavy infestations will be more impactful on these younger (already highly stressed) plants.  This does not mean double-crop production is not worth considering, but other critical management practices (i.e. tolerant hybrids and timely chemical applications) become more critical than with full-season production systems. 

Overall, proper agronomic management can help a sorghum crop that would otherwise not provide suitable or profitable production.  These, however, are not silver bullets and will solely help growers minimize potential risks associated with sorghum production and sugarcane aphids. 

Chemical options for aphid management in canola

With recent indication of aphids starting to building in some canola acres in southern Oklahoma, it is important to not only when and how to manage these pests but what are our chemical options.  An updated list of these can be found at: 

http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-3045/CR-7667web2016.pdf

It is not clear if these pests will continue to build or even move into more canola growing areas of the state; however, growers need to make sure to start scouting fields to not let these pests build this early during the green-up and spring develop.  As always, if you are mixing insecticides and herbicides/fertilizers when making these application, check the labels for detailed mixing restrictions and instructions.  

Aphid management in Oklahoma Canola Fields

Tom A. Royer, Extension Entomologist

Heath Sanders and Josh Lofton provided me with some pictures of a canola field that appeared to have significant winterkill (Figure 1) but it turned out that it had a severe aphid infestation. It looked like they were a mixture of green peach and turnip aphids (Figure 2). Canola fields need to be scouted regularly starting NOW.

Green peach aphids are pale green to yellow (and sometimes pink) with long cornicles and antennae and measure 0.08 inch. They occur in winter and spring on leaves and cause stunting and defoliation as they feed and build numbers. They can also transmit plant disease-causing viruses such as cauliflower mosaic and turnip mosaic viruses.

Turnip aphids are small, pale gray-green aphids that measure 0.06 inches with dark bars along the top of their abdomen, and very shortened cornicles with black tips.

Look for aphids on the underside of the leaves. Later, when plants have bolted, they will be on leaves and racemes.

Research at OSU found that and average of one green peach aphid per plant can reduce seed yield by about 0.5 lb. per acre. Latest quote for June Futures for canola at Fargo, ND USDA is canola can be contracted for about $0.18 per lb. https://www.ams.usda.gov/mnreports/ms_gr111.txt. Dr. Sholar says that a more realistic price is $0.14 per lb. Let’s assume application costs are $10.00 per acre. A simple calculation shows that an infestation of 143 aphids per plant X 0.5 lb. loss per aphid (71.5 lb.), x $0.14 per lb. would result in a loss of about $10.00 per acre, equal to the cost of the application. This is the ECONOMIC INJURY LEVEL (EIL). We typically set the ECONOMIC THRESHOLD (ET) below the EIL, in this case at 80% of the EIL (143 aphids x 0.8) = 114 aphids per plant) to give time to schedule an application before the EIL is reached. Table 1 is a set of suggested ECONOMIC THRESHOLDS, based on the cost of the application and a price of $0.14 per pound of canola.

aphidthresholdcost

Australian research suggests that a treatment threshold for turnip and cabbage aphids on racemes is 20% infested racemes.

CR-7667, Management of Insect and Mite Pests in Canola, contains current aphid control recommendations and is available online at http://pods.dasnr.okstate.edu/docushare/dsweb/HomePage. Remember, green peach aphid is known to develop resistance to pyrethroids, which are the primary registered insecticides for use in canola. Consider rotating with another non-pyrethroid (Carbine before or after petal fall, or Transform after petal fall) if another application is required. Thorough coverage of an insecticide application is necessary to obtain optimal control.

In 2015, Transform® insecticide registrations were canceled due to concerns about honeybee exposure. Transform was re-registered for use in canola on October 14, 2016, but can be applied only AFTER petal fall. With all pesticides, review label restrictions for applications during bloom, to avoid exposure to foraging honeybees. The Oklahoma Department of Agriculture Food and Forestry has a Managed Pollinator Protection Plan and a website that can assist growers and beekeepers to keep in good communication with each other if pesticide applications are required http://www.ag.ok.gov/

Decisions on late planted canola

With October underway, planters will be running through the field on a daily basis.  For canola fields, planting should be nearing completion.  While planting conditions have been great for many others have not had as good of luck.  Additionally, even growers that have had good planting conditions, these have not lasted for long in a lot of locations.  Good conditions have quickly changed into heavy pounding rains, good moisture followed by rapid drying and crusting, armyworm feeding, or more recent flooded conditions.  With this, many growers have been left with a decision of whether it is too late to plant, either initially or with replants.   

There are quite a few factors that need to go on when making this decision.  The first is, if growers are replanting, what kind of stand do they currently have.  For canola, often a descent stand with good fall growth is a good stand.  The hardest part of growing canola in Oklahoma seems to be getting a good stand after winter.  Marginal stands with good growth will be a lower risk and potentially higher reward than better stands and less growth.  Canola does not need a lot of individual plants to make a good to descent crop.  It has the potential to branch and utilize space in a thinner stand to develop more yield per plant later in the season.  However, grower should make sure they there is at least enough canola to make a stand in the spring even if winter kill reaches nearly 30-50% of current stands.  If growers decide to terminate their current stand, they need to evaluate both time and conditions on whether a replant will be successful.  With the critical time for canola planting closing in on us, growers will need to make planting a top priority in the coming week.  With descent soil moisture and forecasted mild conditions, growers should have until the end of the week (October 15th) to get canola in the ground and growing to still have a good chance at getting a good crop.  Without soil moisture, “dusting in” this late will be a major risk.  With cooler conditions on the horizon, canola growth will be severely restricted and lag behind the potential it had a couple weeks ago.  Planting after the 15th should not be advised, except for in very specific situations.  Planting this late in the fall could heavily rely on the first major freeze event occur well into the month of December for the crop to be very successful.  An early- to mid-November freeze could do in a later planted crop. 

The second thing a grower needs to evaluate is the planting conditions.  This will be true for both initial and replanted canola.  Good moisture, with limited drying could allow the grower to plant a little shallower than they would have in the last week or two.  This shallower planting will allow the canola to emerge quick and get better growth compared to planting near 1”.  Three quarters to a half inch is a good depth for canola into good soil conditions.  Without this good soil moisture at or near the surface, growers will have to plant much deeper. This deeper planting will make getting a quick stand in these late conditions more difficult. 

The final thing growers need to be thinking about, especially planting late, is other management practices.  These will include weed management, fertility, and pest management.  With late planting, crop stresses should be minimized to allow for unimpeded growth.  Therefore, growers need to make sure they are starting with a clean system, making sure they have optimum fertility, and making sure to scout and spray early for vegetative feeders (particularly foliar feeding worms).  

If growers can get canola planted timely and make sure to minimize other stress, many should still be able to have a great canola year this year.  With potentially better costs on the horizon, it is looking like a good canola crop will be a great cash crop for Oklahoma this year. 

Canola update: Planting and beyond

With recent rains, planting should be well underway or will start shortly.  Many growers have been concerned with not being able to get any canola planted in recent weeks due to too much or too little soil moisture.  While production system issues may exist, canola planted within the next couple of days to weeks is well within the recommended window and those planted in the next couple of days is right in the prime planting time.  While most research has shown September 20th through the 25th as the best time for planting.  However, these are working on averages and the conditions of last week (hot temperatures with excessive drying conditions right before a projected major rain) was not optimum for canola planting.  With regional soil moisture and cooler temperatures forecasted for the current week, this week may be the best time to get canola into the ground.  With the cooling conditions, however, we need to make sure to be timely with planting as canola will need time and growing days to get enough growth prior to the first frost to optimize winter survival.  The good news is there is plenty of time for growers to get seed into the ground and current 10-day forecast look to be prime for drying but not quick drying resulting in crusting and poor emergence and more reasonable temperatures. 

When canola has been planted, we cannot completely leave canola in order to do other fall activities.  Two major activities should be at the front of growers’ minds following planting.  First need to be N management.  While all nutrients need to be managed in canola in accordance to a soil sample collected, most other nutrients will have already been applied or applied with an in-furrow application.  However, planting is the time to make sure there are N-rich strips in all fields.  Many growers will think putting these strips in all production fields, especially in canola, is excessive but we are coming off a year were getting enough N for optimum production was challenging.  Additionally, high amounts of rainfall in late-spring, summer, and early fall could make N management in the spring challenging again.  Therefore, it is critical that growers make placing N-rich strips in the field to make spring N applications more manageable a priority this fall.  For further information on N-rich strips and setting up N management practices, please visit: osunpk.com or a short 101 video on N-rich strips can be found at https://www.youtube.com/watch?v=kJ3DSwWYgE8.

The other thing that needs to be a primary concern for growers in scouting and controlling foliage feeding worms in their planted canola.  These can be diamondback moth larvae or fall army worms or a combination of the two.  This was a major issue last fall and these pests were found in such high numbers that they were able to completely destroy entire fields.  While these were only in a couple of fields, it could be any field so growers need to make sure to scout throughout the early stages of the fall.  If last year is any sign, these pests can go from non-detected to catastrophic within a couple of days, therefore, growers need to be in their fields as often as possible (remember this is a major issue with both canola and wheat fields).  The critical limit to target an application is one worm per square foot and most pyrethroids can be used as a control measure or more advanced insecticides.  For further information check the most updated insect management in canola at: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-3045/CR-7667web2015.pdf.

worm_damage_canola
Early season worm damage on canola seedling.

While planting conditions throughout the last several weeks might not have been optimum for many growers, things are starting to look better for getting the crop in the ground in a timely manner and off to a good start.  While it is easy to do with planting, harvesting, and cattle to manage, growers cannot plant and walk after from their canola crop.  With the good yields from last year still fresh in everyone’s mind, it is critical that the crop be managed properly in order to get the most out of this crop.  For further information on canola management, N-rich strips, or fall worm management, feel free to contact your local county educator, district agronomist, or specialist directly.