Aphids on the upswing but make they are present before you spray

There has been a recent uptick in the amount of calls and reports we have been getting on the increasing presence of sugarcane aphids in the western grain sorghum production regions of Oklahoma, Kansas, and Texas.  This is particularly in the panhandle region where sorghum is just now reaching the reproductive stages of growth.  This has not only resulted in concern for these pests presence early in reproductive growth but has also increased the number of fields that have been sprayed or intend to be sprayed in the coming week.  This has been meet some indication that applications are being made premature or when sugarcane aphids are not even present in the fields.

Proper identification:

Probably the most challenging thing for consultants and producers working to manage grain sorghum in sorghum production is proper identification of sugarcane aphids in the field.  This is due to the fact that in small populations or with immature nymphs, many of the distinguishing features are difficult to see with the naked eye.  A hand-lens or magnifying glass should be used to allow for proper identification.  These can typically be purchased at a local store or purchased online at a reasonable price.

Many in-field indicators can aid growers in the identification of sugarcane aphids in the field.  Honeydew on the top side of the leaves is one of the most telling signs of a sugarcane aphid infestation.  However, two issues typically exist with using honeydew for identification or make recommendations on chemical control.  Firstly, when noticeable honeydew is present in the field, especially enough that can be seen during quick field checks, often the population has grown large enough to create serious losses to the sorghum crop.  Furthermore, several other insects in sorghum can create honeydew.  One of these in-particular is corn-leaf aphids.  These aphids are typically found in the whorl during vegetative growth or in the collar region of sorghum during reproductive growth stages.  While these can create a large amount of honeydew, they typically cause little to no yield reduction of the sorghum plant and application is rarely ever recommended.  These corn-leaf aphids also aid in the sustenance of predators that can be helpful in controlling sugarcane aphids if communities establish.  Therefore, making an application to control these pests are frequently cost adverse and can negatively impact natural predator populations.

Corn leaf aphid at flowering in sorghum (Photo courtesy of Jason Warren).

There has also been increased reports of sugarcane aphids in the sorghum head during early flowering.  While this is always within the realm of possibilities, these aphid pests do not like sunlight and will typically not be in the head at these early stages due to the high amount of sunlight that is present.  We can see sugarcane aphids in the heads but often much later in the season during grain fill or ripening when there is much less exposure to sun.  Sugarcane aphids, for the bulk majority of the season, will be found on the underside of the sorghum leaf.  Aphids can be present on the upper side of the leaf, but these will typically be yellow sugarcane aphids not the white sugarcane aphids we are concerned with.

While honeydew and location are good indicators that sugarcane aphids could be present, physical identification needs to be done prior to making an application.  This is the only true way to positively identify these pests as well as know the magnitude of populations growers will have to manage around.

When to make an application:

When to pull the trigger on a chemical application is very challenging and several factors (including population, stage of the crop, and environment) come into play in this decision.  Furthermore, based on the potential growth patterns of these pests, the line between under threshold and exceeding threshold is very narrow.  Growers do not want to become overwhelmed with aphids prior to making an application.  Not only could this drastically effect yields but incomplete coverage applications could allow for lower efficacy of applications resulting in not achieving a complete kill.  However, growers do not want to apply before the economic threshold.  These applications can be costly, especially when applying high gallons.  Early application do not use the potential predators in the field to help control these pests and may result in an application that was unwarranted.

Growers should make an application when a minimum of 50% of plants have between 50-100 aphids per leaf.  To visualize, 50-100 aphids will result of being able to be completely covered by a quarter.  Higher populations would be considered over threshold.

Should I treat aphids in forage sorghum/BRM sorghum/Sorghum-Sudan:

This is a difficult question to answer.  While there has been some indication that aphids do impact these forage-type sorghums in-season, whether or not to spend money on an application is more difficult.  The challenge with application is two-fold, both return on investment and application efficacy.  Determining the return on investment is difficult as we do not fully understand or know the amount of impact sugarcane aphids can have on tonnage or quality.  Initial indication from Texas A&M has indicated that quality did decrease in forage-type sorghums that were infested by sugarcane aphids but not to the level that was expected.  The second challenge come with application.  As the current chemistries used to manage sugarcane aphids do not have true systemic nature, coverage is critical.  On forage-type sorghums, this can be very challenging, especially later as the crop nears cuttings.  Therefore, control of the upper canopy may be achieved but mid- to lower canopy would only be marginal.

So what should I do?

One of the best management for sugarcane aphids in more maturity forage-sorghums is to harvest.  Cutting and baling will remove or minimize the impact these pests can have on the crop.  However, there has been reports that aphids on the cut and windrowed hay have caused issues in the baling process.  There current is not solid answer for what to do if aphids persist on the cut hay.  Both chemicals have harvest and grazing restrictions that growers will have to adhere.  However, the return on investment and efficacy still come into question and unfortunately there is no solid answer to this currently.

Managing aphids late-season:

Outside of the far west regions, sorghum producers have begun to finish up the growing season, with several fields being harvested prior to recent rains.  However, with increased aphid pressure, questions arise on how to manage a crop that is infested with aphids at or near harvest.  Discussions were had last year that growers could use desiccants to management sugarcane aphids at harvest.  The results on the success of this practice have been highly variable.  A rapid dry-down of the plant may dissuade the pests from those plants and active populations could deplete food stores and die out, resulting in success of this practice.  However, it has been shown that more gradual dry-down of sorghum can result in the aphids moving into the head of the sorghum plant and causing greater harvest issues there.  It should be noted that sugarcane aphids present after black-layer will no longer effect grain yield but may decrease the harvest efficiency and lead to lower yields realized on a per acre basis through increased honeydew.  This should be evaluated on a case-by-case basis.  Low populations down within the canopy of the plant should result in little to not issue at planting and a desiccant may be sufficient to control these pest at harvest.  However, if populations are high, particularly higher in the plant canopy or in the head of the plant, the application of a desiccant and insecticide (Transform® or Sivanto®) may be warranted.  Be cautious as there are harvest restrictions on both of these chemicals.

Overall, this is a good crop in front of much of Oklahoma.  Grower should make sure to take steps to ensure that yields and profits are optimized on each field individually because with insect management, fields can change across the road.  Sugarcane aphids have been a minimal pest up until now throughout the region.  However, now is the time to get out into sorghum fields to be scouting for sugarcane aphids.  For further questions please visit your local Oklahoma County Extension office for additional information and management details.


Sorghum progressing well through many areas of the state but sugarcane aphids are looming

What does the crop look like?

Throughout the state, the crop could be considered average to above-average.  However, similar to wheat, canola, corn, soybean, and cotton crops this year, it is highly variable.  Certain areas that have received moisture have taken advantage of the warmer temperatures and look quite well.  The areas that have not receive rains or only portions of the overall rainfall have more evident stressed plants.

Above average sorghum crop planted early near Chickasha.  This area has received numerous rains since planting.

What will happen to these stressed plants?

This will depend on what happens in the next several days to weeks.  Areas of the state that have failed to receive many of the recent rains, the crop is starting to struggle.  This has resulted in a majority of leaves beginning to roll earlier in the day.  Even under these stressful conditions, many earlier maturity sorghum hybrids are beginning to push reproductive growth.  Moisture stress during booting and early flowering stage quickly reduces yield be decreasing the total number of seeds set for each head and decreasing overall seed size.  If water stress continues, it will decrease seed weight in addition to the other factors.  This will result in many of these hybrids yield potential, that could be achieve later in the year, decreasing.  However, we cannot forget that the tillering nature of sorghum can allow the plant to recover from these conditions a lot better than most other crops, as long as adequate conditions return shortly.

Can these recover?

Yes, the crop can still recover, especially if the crop was planted into decent moisture and had any degree of moisture within the soil profile.  Yield have begun to become to be limiting.  However, this is only after moisture stress.  Grain sorghum leaves will inherently begin to roll when humidity is low and temperatures are high.  Growers should evaluate moisture stress between 9-10am.  If leaves are already rolled or have started to roll, the plant are under moisture stress.  If leaves do not begin to roll until later in the afternoon, this is a natural reaction to the environment around the plant.  If hot, dry conditions persist, moisture stress will get more severe and the physiological response will occur earlier in the day.

Moisture stressed sorghum.  Leaves were rolled by 10am

What about sugarcane aphids?

There has been increasing reports of sugarcane aphids being found throughout the state.  The best place to keep up to date with sugarcane aphid activity is the MyFields website (https://www.myfields.info/pests/sugarcane-aphid).  This will keep you up to date with where sugarcane aphids have been identified by sorghum specialists from around the state and nation.  It must be noted that this is done on a county by county basis and your county being on this list solely means sugarcane aphids have been found in your county on sorghum.  Furthermore, this does not indicate that sugarcane aphids have even been found at a treatable level in the county but they have just been found.  Seeing your county on this list should solely be an indication that extra care and scouting should be done and not that action is warranted.  This should be used as another tool at producer’s disposal to help with management of sugarcane aphids.

What will the temperature do with sugarcane aphid populations?

Overall, general thought is that hot and dry conditions cause an increase in population to sugarcane aphids.  The mechanism for this is a little less known.  Some have indicated that sugarcane aphids thrive in these environments and can quickly overwhelm the grain sorghum plants due to not only population increases but the added stress on the plants from the environmental conditions.  Other indicate that sugarcane aphid population growth is not directly influenced by hot and dry weather but rather beneficial insects that would typically help keep aphid populations in check and negative impacted by these conditions.  Decrease in beneficial populations allows the aphids to grow unchecked and result in a drastic increase in population.  Indifferent of the mechanism, under hot, dry conditions, aphid populations will likely continue to increase and extra scouting should be done in order to catch populations low prior to any needed application.

When should I make an application for aphids?

Target threshold for aphid applications is the same as it has been the last several years.  We are looking for 100 aphids per leaf.  However, the way we distinguish this threshold has changed from previous years.  This season, when scouting for aphids, we will need to evaluate a minimum of 20 plants.  It is better if 40-50 plants are evaluated but 20 gives a decent indication.  Once a plant has been identified, growers will need look at two leaves.  This will make a total of 40-100 leaves being evaluated depending on how many plants are selected.  If over 50% of these leaves surpass the 100 aphid per leaf threshold an application is warranted.  We have shifted to this newer evaluation method to ensure applications are being made when aphids are present throughout the field and not just in isolated hotspots.  If hotspots are identified, there may be a validity in spot spraying these areas, especially if they are areas of the field prone to aphid movement and buildup (i.e. edges of fields near ditches with Johnsongrass or tree lines).


Overall, similar to other crops in the state, this year’s crop will be plagued by spottiness, where some areas of the state will have a great to average crop while other portions will be meet with challenges.  However, most of this is due to challenges with Mother Nature.  As far as aphids are concerned with this year, we have had several reports of aphids; however, number have been low.  This does not mean the applications are imminent or that populations will crash, solely that growers in these regions should be more proactive in their scouting patterns and visit the site an addition time or two during a week to scout.

Winter canola and recent freezes

With recent freezes across the region, there will probably be several questions over the next couple of days and weeks regarding the status of the canola crop.  It has been said and it could not be any truer, no two freeze events are the same.  This is definitely true for the freeze event that was experienced nearly statewide over the weekend.  Many factors play into the severity of a freeze event, these will include: how cold were the temperatures, length of the freeze event, and stage of the crop.  For the most part, this last freeze did not play nicely with any of these factors.  Quite a bit of the crop was nearly flowering or at beginning flower.  Most folks experienced with canola will tell you that the bottom third of the canola raceme hold a fair amount of total yield (in a typical season).  For those with fields flowering, the temperatures were cold enough for a prolonged period of time that we could see some decent loss of flowers on these primary stems.  This is because all the flower exposed to this freeze event will typically go sterile and not produce a viable pod.  Those producers that were at bolting or at late rosette, the canola should be in a much better place.  Most of the canola that I found today presented with crooked stems that did not bend beyond half-way down the plant.  Plants should have adequate time to correct this and produce and adequate main stem.  Furthermore, most buds that were not quite at the flowering stage looked good and should have been protected against the cold weather and still should produce flowers.

Canola plant with stem bending typically associated with freeze damage, 2014 freeze (Josh Bushong, Oklahoma State University).

As with most crops following a freeze event, the conditions over the next several days and weeks will determine how much yield was lost.  If the weather cooperates over this period, even the most severely damaged canola should put on further axillary buds and be able to put on additional flowers.  This indeterminate nature is a value of canola during these later freeze events.  As opposed to wheat, where if the head of a tiller is killed that tiller is no longer productive, canola can still produce yields from that primary stem.  If good growing conditions present, the canola plant may still produce but will likely be delayed.  The fear from the delayed maturity of the plant will be the plant maturing into less favorable conditions.  This is especially true regarding flowering during months that typically have much higher average temperatures.  This could result in poor pollination which in turn will result in poor pod set. 

Several other questions have arisen, particularly regarding the impact the drought conditions will have on the canola plant heading into a major freeze.  This should have little to maybe a slightly positive effect.  A more stressed plant will produce physiological features to handle this stress, this could result in less impact on the plant due to the freeze.  The primary concern regarding the dry conditions prior to this freeze will be on the limited vegetative growth following green-up that much of the state has experienced.  This lack of vegetation could leave more limited reserves for the plant to catch up and the plant will be more reliant on cool, moisture conditions over the next several days to weeks. 

To evaluate the damage of the canola, most will have to wait for adequate growing conditions to return.  Based on the 10-day forecast, this could be the end of next week or the week following.  If the reproductive structures continue to progress, whether that be continue to grow or to produce flowers, the plant should be able to adequately yield.  If sub-optimal conditions come over the next several days, the yield potential could be damaged.  With a freeze of this magnitude, growers should expect to see some gaps in the flowering structure and potential stem splitting when they return to the fields next week.  This stem splits have less an impact on yield but a higher potential impact on stalk strength and standability later in the season.  Higher amounts of split stems will result in higher amount of lodging and potential decreased harvest efficiency. 

Split stem following a major freeze event.  This may cause issues with stem strength and potentially increased lodging (Photo used with permission from Dr. Mike Stamm, Kansas State University).

With growers assessing the damage over the next several days for both wheat and canola, growers can take solace in that canola has very good resilience and can rebound from these events.  As of now, we must take time to let both plants try to rebound and produce adequate yields for these two critical winter crops.   

Grain sorghum summary from down-state sorghum trials

These are the preliminary results from the Oklahoma State University grain sorghum hybrid trials.  Complete summaries will be provided following harvest.  Data from the hybrid trials in the panhandle will be provided following harvest.  These trials should be harvested near the end of October.  If there are any questions or comments please feel free to contact your local extension educator or myself directly.







Canola planting update: What can growers be doing to help improve upcoming canola crop

Canola planting is right around the corner.  While last season’s canola crop had mixed results with many growers not achieving the yields they expected, there are several things growers can do prior to planting that can pay off later in the season and promote crop productivity and success. 

Weed management:

Weed control is vital for canola production.  Successful use of herbicides can help control problematic grassy weeds, which is one of the primary benefits of integrating canola in Oklahoma production systems.  Within the canola production season, most canola yield losses associated with weed competition is early in the growing season.  Once the crop is established, it can typically outcompete most weeds.  However, this is only true if the crop was maintained weed-free up until this point.  Therefore, preplant herbicide programs are essential to make sure the crop established into weed-free conditions.  While there are a limited number of herbicide active ingredients that are labeled for preplant use in canola, those labeled are typically quite effective at managing weeds within the crop.  Most growers would benefit from a preplant program that integrated a residual herbicide to delay in-season applications until the crop has been established.  This is why one of the better preplant herbicides options is Trifluralin.  Trifluralin can help manage most fall weed species as long as the seedbed is relatively clean and the herbicide is incorporated into the soil within 24-hours of application.  This is why Trifluralin is a good option for producers that integrate tillage practices, as tillage can both clean the seedbed and incorporate the herbicide after application. 

Fewer options are available for no-till canola producers.  Glyphosate is really the primary option for pre-plant herbicide application, since incorporation cannot be done.  Glyphosate can still be used with using conventional canola cultivars, as long as the application is made prior to emergence.  Additionally, glyphosate can only control weeds that have already emerged and does not have any residual control.  This results in the need for further applications in-season.  Oklahoma State University is currently evaluating several other preplant herbicide options but as of this time these are all off label and considered illegal applications. 

Nutrient management:

Soil nutrient management is also a practice that can help canola establish and achieve good early season growth.  While we are very close to planting, soil testing and fertilizer applications are still a management practice growers can do to help the crop.  Soil test results should help guide fertilizer applications but enough P and K are needed at planting and early in the fall.  However, higher rates of both P and K are frequently associated with products that contain relatively high amounts of N.  While canola does need N in the fall, too high of N fertilizer applications can lead to excessive fall growth and in-turn potentially higher winterkills. Enough N should be applied to ensure the crop does not stress but limit fall growth.  Most growers should be able to utilize the 1/3 and 2/3 method, where only up to a third of the N is applied in the fall and higher rates are applied at green-up in the spring.    

One application that has shown benefit in canola has been an application of N and P with the seed at planting.  While these applications do not always translate to increased crop yields, especially if fields are not low pH or low STP, but can promote early season growth and increased root growth.  These applications can either be applied in-furrow or beside the row.  However, it must be cautioned that, due to the salt sensitivity of winter canola, in-furrow fertilizer applications cannot be made at rates as high as in wheat crop.  This application provides both N and P to the canola crop early in the crop cycle and allows it to achieve good growth early in the season. 


in-furrow_non in-furrow
Difference between in-furrow 10-34-0 and not. Low pH soils and low available P soils typically show greater benefit of in-furrow applications. (Photo courtesy of Josh Bushong)



Probably the most important management considerations are the decisions grower make around planting.  While other practices discussed can alter early season growth, these considerations will directly influence the growth of the crop. 

Cultivar selection:

There are several cultivars that are well adapted to Oklahoma systems.  These include both conventional and glyphosate-tolerant cultivars.  While there is a good amount of flexibility in the glyphosate-resistant cultivars, as they can utilize glyphosate to clean up weedy spots in the fields, yields from the conventional varieties have been competitive if not slightly higher when compared side-by-side in the Oklahoma State Variety trials.  Challenges with conventional cultivars, i.e. limited broadleaf weed control, can typically be overcome with adequate early season weed control and adequate plant populations.  These conventional varieties have value when growers will double-crop, especially soybean, behind canola as the conventional canola cultivars can be easily controlled with glyphosate.  However, with increasing glyphosate-resistant summer weeds and the availability of auxin resistant summer crops, these glyphosate resistant canola cultivars can be a viable option in double crop systems. 

Planting date:

Traditional planting dates range from September 10th through October 10th.  However, optimum planting usually is during the last 10 days of September for the northern part of the state and the end of September through the first of October for the southern part of the state.  When planting early, many producers just want to ensure that enough growth has been achieved before the first killing freeze to store enough reserves in the plant and rooting system to survive the winter.  This is a good thought to always have during planting but canola only needs around 6 weeks of growth to increase the likelihood of winter survival.  Planting on September 6th would result in 8 weeks before the first average light frost (November 2nd, NOAA), 10 weeks before the first freeze (28F, November 14th, NOAA), and 12 weeks before the first killing freeze (24F, November 25th, NOAA).  If a large amount of growth was the only factor in achieving high winter survival and good stands in the spring, then planting into good conditions as early as possible would be the best practices.  However, with increased vegetative material, high amount of water and nutrients will be needed to sustain the plant in later winter and early spring.  This increased stress can result in diminished winter survival and spring stands.  Pushing these planting dates back into late-September into early October can greatly increase winter survival chances in most years. 

Several factors go into a successful canola crop.  While many of these factors are associated with environmental conditions, proper management of planting will help with early season growth and over-winter survival, allowing growers their best chance at a successful crop in both good and poorer years.    

We at Oklahoma State University wish all producers a safe and productive planting time.  If any further guidance is needed regarding planting issues feel free to contract your local county extension office, regional agronomist, or myself. 


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.