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Extension Entomology

Month: April 2016

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

Alfalfa – Weevils and Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevil feeding seems to be slowing as pupation has started, but there are quite a few larvae still active.

AW pupa

AW different sizes

The photo below is of our insecticide plots which were treated 8 days after the surrounding alfalfa field, thus the dramatic visual difference insecticide timing can make.

KSU plots 2016

Also, there are some aphids present in the alfalfa.  Dr. Stu Duncan, KSU Agronomist, reported some spotted alfalfa aphids from the AltaVista area and we have a few in our plots in Dickinson Co.  Pea aphids have been present since early March and continue to be found in relatively low numbers.

spotted aphid

spotted aphid

Wheat Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Wheat aphids, primarily bird cherry-oat and greenbugs, continue to migrate into Kansas on southern winds.

GB adult and nymphs

BCOA nymphs

The most common question this last week then is whether to add insecticide to a fungicide application to kill the aphids.  First of all, we do not recommend pesticide applications unless justified, and the mere presence of aphids in wheat does not justify an insecticide application.  Aphids need to be at densities of 20+ aphids/tiller when wheat is in the boot to heading stages before aphids begin to impact wheat simply due to their feeding.  Even then, their feeding is more impactful on plants that are already stressed by less than ideal growing conditions and when there are few beneficials present, i.e. lady beetles, lacewings, parasitic wasps, etc.  Recent rains seem to have really helped alleviate the previous dry conditions- so growing conditions are not stressing the wheat.  When an insecticide is added to a justified fungicide application, the insecticide will kill the aphids, as well as all the beneficials.  The aphids will continue to migrate into the state but the beneficials will be gone and much slower to re-populate.  Foliar insecticide applications made to control aphids with the aim of reducing the transmission of Barley yellow dwarf viruses has not been proven and thus is not recommended.  At the present time there seem to be good populations of lady beetles and parasitic wasps in wheat fields to help mitigate aphid populations.

lady beetle larva

aphid mummy

Ash/Lilac Borer: Do Not Get “W-holed” Down By This Borer

–by Dr. Raymond Cloyd

      We are receiving inquiries regarding the ash/lilac borer (Podosesia syringae). It is important to note that this is not the same insect pest as the Emerald ash borer (Agrilius planipennis). The Emerald ash borer is a wood-boring beetle whereas the ash/lilac is a wood-boring caterpillar. Ash/lilac borer adults are typically active from mid-to-late-April through early-May. The adults are brown, clearwing moths that resemble paper wasps. Peak moth activity usually occurs from May through June although this depends on temperature. Adult females lay tan-colored, oval-shaped eggs in cracks and crevices, or wounds at the base of plant stems. A single mated female may live about one week and lay up to 400 eggs. Below are the major biological and management parameters associated with this insect pest:

* Larvae cause plant damage by creating tunnels and feeding within the bark (cambium). The larvae may also bore further into the wood and feed within the sapwood and heartwood.

* Larval feeding restricts the flow of water and nutrients causing shoot or branch dieback. Ash/lilac borer typically feeds near the base of plant stems creating swollen areas or cracks at the base of plants, and where major branches attach to the trunk.

* Evidence of larval feeding includes the presence of light-colored sawdust that accumulates at the base of infected trees or shrubs. Clear-wing borer larvae expel sawdust from cracks in the bark that accumulate at the base of infested trees and shrubs while beetle borers (particularly flat-headed borers) pack their galleries with sawdust-like frass.

* Ash/lilac borer overwinters as late-instar larvae located in feeding tunnels or galleries.

* One way to determine if trees or shrubs are or have been infested with ash/lilac borers is the presence of brown papery pupal cases that protrude from the bark (Figure 1 and Figure 2) These pupal cases are where adults emerge from.

Figure1AshLilacBorerPupalCaseJPEG

Figure 1

Figure2AshLilacBorerPupalCaseJPEG

Figure 2

* In Kansas, there is one generation per year.

* The primary means of alleviating problems with ash/lilac borer is to avoid “plant stress” by properly implementing cultural practices such as irrigation (watering), fertility, pruning, and mulching. Stressed plants are more susceptible to attack than so called “healthy plants.” A two to three foot wide mulched area around the base of trees and shrubs will prevent injury from lawn mowers and weed-trimmers. Furthermore, avoid pruning plants in late spring through early summer (under usual weather conditions), because this time period is when moths are typically present.

* Insecticides containing the active ingredients, permethrin or bifenthrin may be applied to the bark, at least up to six feet from the base, in order to prevent ash/lilac borer larvae from entering plants. Clear-wing borer larvae crawl on the bark in search of entry points, which exposes them to insecticide residues.

* Pheromone traps are commercially available for capturing adult males, which helps to determine when females will be laying eggs. The use of pheromone traps helps in timing applications of insecticides. Insecticide spray applications should begin seven to 10 days after capturing the first moths. Also, be sure to check traps two to three times per week and record the number of newly captured males.

* For more information regarding ash/lilac borer management contact your county or state extension specialist.

I want to acknowledge Jeff Otto of Wichita, KS. Jeff keeps me abreast of the “bug situation” in south-central Kansas. Also, the images associated with Figures 1 and 2 are courtesy of Jeff. If anyone wants to act as a “bug scout” and provide me with information on what “bug” activity is going on in Kansas throughout the year, just like Jeff, please contact me at 785-532-4750 or rcloyd@ksu.edu.

 

European Pine Sawfly

–by Dr. Raymond Cloyd, Professor and Extension Specialist in Ornamental Entomology/Plant Protection

      European pine sawfly, Neodiprion sertifer larvae are out-and-about feeding on pine trees. Young larvae are 1/4 inch in length and olive-green in color with a black head (Figures 1 and 2).

Figure1

Figure 1

Figure2

Figure 2

Older larvae are >1.0 inch long with green stripes. The larvae are gregarious or feed in groups on the needles of a variety of pines, especially Scotch, red, and mugo pine. Larvae will strip the needles of mature foliage, leaving only the central core, which is white and then turns brown (Figure 3); eventually falling off.

Figure3

Figure 3

In general, larvae complete feeding by the time needles emerge from the candelabra. Therefore, those needles are not damaged. There really is only a minor threat of branch or tree death resulting from sawfly larval feeding. However, the loss of second- and third-year needles may be noticeable in landscape trees and ruin their appearance. In late spring, the larvae drop to the ground and pupate in brown, leathery cocoons at the base of trees. Wasp-like adults emerge in fall and lay eggs in the needles before winter. There is one generation per year in Kansas.

Although sawfly larvae look-like caterpillars; they are not caterpillars (Order: Lepidoptera) as they are related to ants, bees, and wasps (Order: Hymenoptera). The best way to tell a sawfly larva from a caterpillar is by the following: 1) sawfly larva have prolegs on every abdominal segment whereas caterpillars are missing prolegs on the abdomen and 2) caterpillar larva have hairs or crochets on their feet whereas sawfly larva do not have hairs or crochets on their feet.

Since sawfly larvae are not caterpillars, the bacterial insecticide, Bacillus thuringiensis subsp. kurstaki (sold as Dipel) will not directly kill sawfly larvae. Therefore, dealing with sawfly larvae involves hand-picking (you can wear gloves if you wish) or dislodging larvae from plants by using a forceful water spray. If necessary, there are a number of insecticides that may be applied to suppress populations of the European pine sawfly including acephate (Orthene), azadirachtin, carbaryl (Sevin), spinosad (Captain Jack’s DeadBug Brew and Conserve), and any pyrethroid-based insecticide with any of the following active ingredients: bifenthrin, cyfluthrin, and lambda-cyhalothrin). Be sure to read the insecticide label to make sure that sawflies are listed. For more information regarding European pine sawfly management contact your county or state extension specialist.

 

 

 

 

 

Wheat Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Received a report from north central Kansas about a small wheat field infested with ca. 20 aphids/tiller, but the aphids weren’t identified.  All wheat fields we visited in the last week had aphids, including bird cherry-oat, English grain, and/or greenbugs.  However, we were only finding about 1/10 plants or less and beneficials (lady beetles, lacewings, and parasitic wasp activity) were present in all of these fields.  Most wheat averaged Feekes 6-8 and no other pests really have been noted.

Alfalfa Weevil Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevils are still very active throughout north central Kansas.  They also range in development from small 1st instar larvae to relatively mature 3rd instars.

Aw life stages

We have also had reports of pupae in south central and north central Kansas.  Many fields are still showing signs of freeze damage.

freeze damaged field

The freeze did seem to affect the weevils by slowing their development but did not kill them.  However, most larvae in freeze-damaged fields are more yellow than the usual greenish color.  Whether that means they are getting the proper nourishment from the yellowed, freeze-damaged alfalfa tissue or not is unknown.

larvae color difference

Weevil larvae in untreated, non-freeze-damaged fields seem mostly about to pupate within 7-10 days if temperatures stay between 45-80°F.  No other pests have been noted in alfalfa fields we visited over the past week.

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