Preliminary winter canola variety trials results

Canola harvest is in full swing with the end right around the corner for much of Oklahoma.  This has been a trying year for many across canola growing regions in the state.  This has been no different for the Oklahoma State variety testing program.  Yields from both Kingfisher and Fairview were relatively disappointing due to high winter loss, poor conditions during early reproductive, and some hail damage during reproduction.  However, Pond Creek, Chickasha, and Fort Cobb yielded relatively well.  The other four locations will be harvested within the next week to 10 days depending on weather.  Keep checking back for other locations.

Canola_yields_1

Sorghum Update: Finally getting going and questions about stands, watch the horizon for aphids

 

This spring has been a challenging one for many producers throughout the state.  Most crops have struggled at some point during the spring.  To date the Oklahoma sorghum crop this year can be fit into three categories, with some growers dealing with all three.  Oklahoma sorghum producers are not immune to this and their seasons can probably be fit into three general categories.  First are that growers were able to get the crop in a timely manner, had good conditions, and the crop is up and growing.  While we would like to see this on most acres, this has not been the case.  Most of the sorghum fell into the other two categories.  Either growers have not been able to get into their fields and still have sorghum in bags waiting to be planted or were able to be planted but have marginal stands.  For growers that have yet to plant, the question has become whether or not to continue with grain sorghum planting.  While most growers have to work through the financials on their individual farms, growers still have the ability to establish fields and be quite productive.  Historically, we have advised growers at this stage to hold off planting until late-season in order to minimize the impact of traditionally challenging environmental conditions experience in late-June and early-July.  However, sugarcane aphids have made the success of late season crop more dependent on insecticide applications.  Therefore, if growers are willing to budget 2 insecticide applications and be proactive on scouting and applications, this is still a potential option.  Other growers that have stands in the field and question on whether to maintain stands or terminate and replant.  This can be a difficult discussion and there can be quite a few things growers must consider before making this decision.  As a general rule, if growers have between 18k-20k active plants per acre, adequate yields can still be achieved without an additional seeds planted, especially this late in the season and if the plants still have a reasonably even stands.  If stands are spotty or skipping, growers can decide to plant certain areas of the field, while maintaining others.  If growers have less than 18k active plants per acre and growers decide that replanting must occur, several times growers can get away with over-seeding the crop over the current stands as opposed to completely terminating and completely replanting.  If growers over-seed, it is recommended that growers look at planting around half of the initial seeding rate.   

 

The validity of this critical 18k plant population to maintain a crop depends on several factors.  As previously mentioned stand distribution is a critical component.  An even stand can maintain high enough canopy coverage to cover the soil surface in order to help maintain soil moisture and help compete against weeds.  Another critical aspect is the hybrid that was planted.  Hybrids that have lower tillering potential would require higher populations to achieve adequate yields.  Without these tillers there just might not be enough heads/acre in order to maintain yields.  However, hybrids with better tillering potential can sustain these lower populations while still maintaining adequate yields. 

 

When growers have achieved stands, both weed control and fertility issues start to emerge.  If growers have made a large application on fertilizer preplant, especially N, with the current weather patterns we have experienced in the las several weeks, a good portion of this may have already been denitrified or leached deep into the soil profile.  This means growers need to be proactive with side-dress applications.  To trigger these, growers best option is to make sure to have N-rich strips throughout their fields.  If not, growers need to look for overly pale, stunted sorghum and be timely with an application.  Nitrogen fertilizer is not the only thing influenced by the moisture in these fields.  High levels of moisture and decrease the efficacy of many preplant herbicide programs.  Growers many need to make subsequent herbicide applications.  This becomes very critical as several chemicals need to be applied prior to the sorghum plant reaches ~30 inches tall. 

Sorghum stands with uneven stands (left) of even (right), those on the right still might produce adequate yields.

The challenges that this summer will hold for sorghum producers is still in question.  However, it must be noted that sugarcane aphid numbers are growing and moving north through Texas.  MyField website numbers as of May 25th, indicate the shift from populations solely in the Gulf Coast to several populations moving into south-central Texas.  While there is little need for Oklahoma producers to be concerned at this point, growers need to make sure they are aware of the moving population.  If growers are active on their scouting management plans and timely with insecticide applications, most growers in recent years have noted minimal impact of the pest on overall yields.  However, if growers get behind, sugarcane aphids will be a challenge for them throughout the season.  Currently OSU recommendation for applications are an average of 100 aphids per leaf blade.  To scout for aphids, growers need to identify 4 to 5 locations that are representative of the field and collect 5 to 6 plants at each location.  For each plant, growers need to look at the underside of the lowest most fully green leaf and the high most fully developed leaf.  If the plant is at flag leaf or later in reproductive stages, growers should scout the leaf under the flag leaf.  While counting aphids in-field on leaves can be a challenge, a good rule of thumb is 100 aphids per leaf is approximately the size of a quarter to half dollar.  As populations tend to congregate on the leaves, growers should also look for multiple smaller populations. 

 

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/