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Extension Entomology

Author: Sarah Zukoff

Sorghum Hybrids with Resistance to Sugarcane Aphid

A number of sorghum hybrids have now been identified which express variable, but quite significant, levels of resistance to sugarcane aphids (SCA).  Below is a list of those which are potentially suitable for planting in Kansas, based on having early to med-early maturity.

Growers are encouraged to contact their seed suppliers for more detailed information on the agronomic characteristics of these lines.  All of these hybrids express fortuitous resistance to SCA; that is, they happen to have traits that greatly reduce their suitability as a host plant for the aphid.

Conventionally, a source of aphid resistance is first identified in some odd land race of the crop and then intentionally bred into commercially acceptable parental lines, resulting in a wide range of hybrids that all express the same trait.  Success with this approach is usually only temporary because reliance on a single trait exerts strong selection on the aphid population to evolve virulence; often only a small genetic change in the aphid is required and the trait is no longer effective.

In contrast, every example of fortuitous resistance is most likely due to completely different traits that have a similar end result for the aphids, albeit via different mechanisms: reduced immature survival combined with slower rates of growth and reproduction.  The use of multiple resistance traits will dilute the strength of selection acting on the aphids because a single genetic change is no longer likely to confer virulence to all these different traits.  Thus, the outlook going forward is very positive as we would expect these traits to remain effective for some time.

The use of resistant hybrids is encouraged because they serve to synergize the impact of natural enemies and reduce the need for spraying.  Slower aphid population growth means more time for predators to arrive in sufficient numbers and consume all the aphids before they can reach densities sufficient to escape biological control.  It also means that management decisions are not quite so urgent as aphids approach threshold numbers that may require an insecticide application.  But do not expect resistant plants to be aphid-free; they will still get infested, but the aphids will not thrive. Some hybrids may even need to be sprayed once, so be sure to scout early and scout often.

-J.P. Michaud and Sarah Zukoff

Be on the lookout for this new wheat pest…

SSipha-maydis-216797ipha maydis is a new invasive aphid that was recently found in Colorado and could potentially be found in Kansas.

“Wheat and barley are this aphid’s preferred hosts, although it can feed on many weedy grasses, corn and sorghum. It is a particular concern in wheat and barley since it can kill leaves and transmit barley yellow dwarf virus.”

Read more about this potential threat here:

http://wci.colostate.edu/shtml/Sipha.maydis.shtml

https://smallgrains.ces.ncsu.edu/2016/04/new-invasive-aphid-of-wheat-now-in-south-carolina/

-Sarah Zukoff

Preplant considerations for the sorghum sugarcane aphid

sca bowlingA new report from Robert Bowling (TAMU) revealed that sugarcane aphids (SCA) are building in southern Texas volunteer sorghum and may soon start to move into Central Texas. What this means for Kansas and Oklahoma sorghum is still unknown at this point, but it is worth noting the aphid got a much slower start last year. In preparing for possible SCA aphid infestations, there are a few important things farmers should consider prior to planting sorghum this season:

  • Plant as early as possible to give plants a head start on the aphids, which tend to arrive later in the growing season.
  • Currently, the insecticide Sivanto (Bayer) is the only chemical labeled for Kansas sorghum for managing sugarcane aphid infestations. Last season in 2015, Kansas had a Section 18 approval for the insecticide Transform (Dow), and although a 2016 Section 18 has been requested, this has yet to be approved for Oklahoma or Kansas.
  • Efforts are underway to screen hybrids for resistance to SCA, but few are being sold as resistant so far. However, data collected so far suggests that a number of varieties rated as resistant to greenbugs also express resistance to SCA – but not all of them.
  • Farmers can expect SCA to arrive in Kansas as early as July, depending on weather conditions and wind direction. Be sure to monitor the spread of the aphids northward migration via updates from this blog, county agent updates, and twitter.

Read Dr. Bowlings full article here: https://drive.google.com/file/d/0B4lb0hWyS3iMaGV5dVVIcUd1YUE/view?usp=sharing

-Sarah Zukoff and JP Michaud

Hessian fly in wheat-check your fields now

Recent visits to Edwards county wheat fields revealed spotty but heavy infestations of hessian fly. One field (LCS Mint variety) in particular was planted on Sept. 25th which was just a few days shy of the “fly-free” date of October 1st in Edwards county.  In this field the adults likely emerged from the adjacent wheat stubble and then infested the nearby wheat seedlings in mid-late October. If the farmer would have planted after Oct. 1st, some egg laying would still have occurred in this field because many of the adults emerged later than the fly-free date. Although this is still a good rule of thumb, the term “Hessian fly-free date” is not completely correct anymore since hessian fly adults can be caught flying up until December in some places in Kansas now. This infestation is likely not limited to Edwards county since large populations of hessian flies were detected in many areas in south-central Kansas last spring. The adults were detected by sweeping wheat fields that were located near wheat stubble or in continuous wheat. Farmers should check now for the puparia or ‘flaxseed’ stage (see below) and will need to weigh further input costs if infested fields are found.

hessian finalhessian fly total

Hessian fly maggot feeding on seedlings in the fall can cause severe injury to plants. Infested wheat is stunted, dark green, and its leaves are broader than normal. Such injured plants will never grow past the four-leaf stage and will generally die during the winter. If tillering has begun, then only infested tillers may die.  To scout for the hessian fly in the winter months, peel back the leaf sheaths to uncover the puparia. Flies in the flaxseed stage will usually emerge in March-April as adults and will fly to nearby areas to deposit their eggs onto wheat leaves. There are no chemical management options for hessian fly maggots or those in the flaxseed stage. Managing adult hessian flies is not recommended either because emergence can be staggered over a period of several weeks yet adults live for only a few days. The best way to prevent further infestation is to plant varieties of wheat that have greater resistance to hessian flies and plant after the fly-free dates for their county.

mikes hessian flaxseed pic mikes hessian fly

For more detailed information on the Hessian fly in Kansas visit: https://www.bookstore.ksre.ksu.edu/pubs/MF2866.pdf

https://webapp.agron.ksu.edu/agr_social/eu_article.throck?article_id=691

-Sarah Zukoff

New proposed Pesticide Applicator rules-comment period open for a limited time

7ea3d39439d55ffd4ffffa294bad9d14The EPA has proposed new rules for those getting Private and Commercial Pesticide Applicators licenses.  The final set of rules will likely not take affect for some time, however the time to comment on the proposed rules is now until November 23, 2015. To read the full document and leave comments go here.

Among the proposed changes, a few to note are:

  • Establishes a first time-ever nation-wide minimum age of 18 for certified applicators and persons working under their direct supervision.
    • currently there is no age limit for private applicators in KS
  • Requires all applicators to renew certifications every 3 years.
    • currently this is every 5 years for private applicators in KS
  • Requires additional specialized certifications for private applicators using high-risk application methods (fumigation and aerial).
    • currently there is no specialized certification for this in KS
  • Requires first time annual safety training and increased oversight for persons working under the direct supervision of a certified applicator.
  • Private applicators will be required to pass a written, closed book-proctored exam for certification
    • currently private applicators exams are open book in KS
  • The credit hours or CEU’s  required for applicators will increase:
    • Private applicators-6 general core CEU’s + 3 CEU’s per category of certification (currently no training is required for Private applicators in KS)
    • Commercial applicators-6 general core CEU’s + 6 CEU’s per category of certification  (currently 1 core hour is required +7 per category for most categories in KS)

To read more go to http://www2.epa.gov/pesticide-worker-safety/epa-proposes-stronger-standards-people-applying-riskiest-pesticides

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-Sarah Zukoff and Frannie Miller

The sugarcane aphids are slowing down…for now

The sugarcane aphid (SCA) movement in Kansas has slowed down for the moment with the sorghum crop maturing and drying down. South-central Kansas seemed to be the “hot zone” this year, but many counties further north and west got to see populations of these aphids as well. Some chemical rep’s have suggested spraying sorghum fields as soon as  SCA populations of any size are found, however finding a few SCA does not necessarily warrant immediate treatment. Using our new thresholds (found here), many farmers outside of the “hot zone” in Kansas did not have to spray their sorghum fields for SCA. sca map updated 9_21

Next season it will be important to monitor the progression of the SCA northward from TX and OK and observe thresholds before treating. This is especially important because populations of SCA can be swept into the same fields multiple times depending on the weather, and the chemical options for treating the SCA will be even more limited next year. A federal judge recently ruled against the sale of Sulfoxaflor which is the active ingredient in one of our best tools against SCA, Transform insecticide (Article here). Our SCA Task Force is currently working on what this means for SCA control next season, but it will likely mean that Transform will not be sold anymore. We will keep you posted on this issue.

sept 18 usa sca map

This map shows the states where sugarcane aphids were found in sorghum as of Sept. 18th this year.  So far, several new state records have been recorded including Virginia, Tennessee, New Mexico, Colorado, and Illinois.

Temperature affects efficacy of Transform and Sivanto for sugarcane aphids control

Mississippi State just released some very good preliminary data on the efficacy of Transform and Sivanto for sugarcane aphid control during cool temperatures. Cooler temps (<60F) slow the aphids activity down and they do not feed as much and are not taking the product up as fast. For maximum efficacy, apply these two chemicals during the hottest part of the day especially during cooler days.

http://www.mississippi-crops.com/2015/08/24/sugarcane-aphid-control-with-falling-temperatures/

-Sarah Zukoff

 

Discovery of Rusty Plum Aphid in Southwestern Kansas

Discovery of Rusty Plum Aphid, Hysteroneura setariae (Thomas), in Southwestern Kansas

As if cereal farmers didn’t have enough to worry about with the explosion of sugarcane aphid in sorghum and recent reports of the hedgehog grain aphid, Sipha maydis, New Mexico, Colorado and Missouri. Last week, samples of a reddish-brown aphid were collected from sorghum in mixed infestations of sugarcane aphid, Melanaphis sacchari, and corn leaf aphid, Rhopalosiphum maidis.  Specimens were identified by Dr. Susan Halbert (Dept. of Plant Industry, Florida) as rusty plum aphid, Hysteroneura setariae (Thomas).  The aphids were discovered in a dryland sorghum field just north of a grassy pasture in Stevens county.

The host range of this aphid is quite broad and includes grasses in the genera Cynodon, Eragrotis, Eleusine, Hordeum, Oryza, Panicum, Pennisetum, Saccharum, Setaria, Sorghum and Triticum.  Thus, it has the potential to infest wheat, sorghum, barley, millet and sugarcane; it is a recognized pest of rice in Asia and Africa. Plants in the family Cyperaceae (sedges), cocconut seedlings, peanut and papaya have also been reported as hosts. Direct feeding damage to plants appears limited to sap removal, and it may have greater economic importance as a vector of many plant viruses including sugarcane mosaic potyvirus, cucumber mosaic, watermelon mosaic 2, papaya ringspot, and zucchini yellow mosaic.

rusty plum aphid ks

The rusty plum aphid is capable of sexual reproduction (and thus overwintering in the egg stage) wherever trees of the genus Prunus are present, although it can also remain asexual on cereals year-round in warm climates.  It has been found in North America for many years, primarily in California and Florida, and as far north as Minnesota and several northeast states, but very little is known about its biology or its potential to attain pest status the High Plains cereal crops.

rusty plum aphid ks 2

The key features for identifying rusty plum aphid are the first 3 antennal segments that, along with the tibia (lower leg), are very pale, almost colorless, with the distal segments of these appendages shading to black.  The cornicles (‘tailpipes’) are long and uniformly dark and the cauda (tail) is pale.

-Sarah Zukoff and J.P. Michaud

Sugarcane aphid is on the move

The sugarcane aphid continues to spread in Kansas sorghum and has now reached as far west as Haskell county and as far north as Dickinson county. In addition to these counties, the SCA was discovered in Edwards county today. Populations are low in these counties so far, but fields in these areas should be monitored closely. Contact your local extension agent if you discover the SCA or if you need help identifying aphids in your sorghum.

dusty sca sca map ks 2015-Sarah Zukoff

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