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Sorghum Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Chinch bugs are very active in double cropped sorghum in north central Kansas.  They are also numerous in corn but the field corn is mature enough that chinch bug feeding should be of little consequence.  However, young sorghum plants, especially under less than ideal growing conditions may be seriously stressed.

For more information on chinch bug biology, management decisions, and insecticides registered to control chinch bugs please see the Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

and Chinch Bugs: https://www.bookstore.ksre.ksu.edu/pubs/MF3107.pdf

 

 

Japanese Beetles

— by Dr. Jeff Whitworth and Dr. Holly Schwarting

Adult Japanese beetles have been detected around north central Kansas in the last 7-10 days.  These adults may feed on corn, sorghum, and soybean leaves, as far as field crops are concerned, and may cause some “window paneing” much like the leaf feeding of adult corn rootworms.  However, this leaf feeding usually is of little consequence.  In corn, these beetles will be attracted to the silks and, as they can be very veracious feeders, may clip these silks at a pretty good rate.  Fortunately, they are usually localized to small “hot spots” in some fields and thus do not really justify any insecticide application.  These adult Japanese beetles may be active for another couple of weeks, after which only eggs and larvae will be present, and these life stages are not a threat to these crops.

 

Carpenter Bees

–By Dr. Jeff Whitworth and Dr. Holly Schwarting

Carpenter Bees have been very active all across the state for the preceding 7-10 days and the noticeable activity may continue for another week or two.  These large (3/4 to 7/8 inch) black and yellow bees are most often mistaken for bumble bees.  However, carpenter bees, even though around the same size and flying at about the same speed, have bare abdomens while bumble bees have hairy abdomens.  Carpenter bees thus have shiny, dark blue to black abdomens while most bumble bees have hairy yellow abdomens.

Most folks do not want to get close enough to any large bee to make these distinctions, and they are even more difficult to distinguish when they are flying.  But, if you have large black and yellow bees hovering around any wooden structures and they are ‘dive bombing’ or buzzing around intruders into their area, i.e. you, neighbors, pets, etc. they are most likely carpenter bees.  It is the males that are buzzing intruders and they can be distinguished by their ‘bald faces’ which appear to have a yellow triangle in the middle of a black face.

These males cannot sting; they are just very territorial because they are waiting for a female bee to emerge from one of the holes in the wood so they can mate with her. This dive bombing behavior will continue until all the new females have mated, then the males will die and the noticeable activity will cease.  These females will then excavate new holes or extend established ones located in older, untreated, unpainted wood where they provision cells with nectar and pollen and then deposit eggs.  The larvae feed on these provisions throughout the summer, and then pupate.  The next generation of adults typically does not become active until the following spring.  While carpenter bees are not social bees, populations may build up in favorable locations and over years of repeated excavating, can weaken even structural wood.  For more information on carpenter bee biology and management, please visit: https://www.bookstore.ksre.ksu.edu/pubs/MF2946.pdf

European Elm Flea Weevil

–by Dr. Raymond Cloyd

   

We are seeing damage on elm (Ulmus spp.) trees caused by the larval stage of the European elm flea weevil (Orchestes alni). Larvae are cream-colored, legless (Figure 1),

Figure 1. European elm flea weevil larva

and found in the mines of leaves. Adults are 3.0 mm in length, red-brown in color with black spots or markings on the abdomen or wing covers (Figure 2).

Figure 2. Adult European elm flea weevil.

 

The mouthpart is shaped-like a snout (Figure 3)

 

Figure 3. European elm flea weevil adult (note the snout-like mouth)

since they are weevils and the hind legs are thickened and enlarged, which allows the adults to jump when disturbed. Adults are initially active in May, and after mating, females lay eggs in the large mid-veins of new leaves. Eggs hatch into larvae that tunnel through the leaf as they feed (which is occurring now), creating serpentine-like mines that enlarge as larvae mature (Figure 4).

Figure 4. Serpentine mines created by European elm flea weevil larvae.

Larvae eventually transition into a pupal stage, and then adults emerge in May and June. Adults primarily feed on leaf undersides creating small holes on young leaves (Figure 5).

Figure 5. Feeding damage caused by European elm flea weevil adult.

 

The feeding damage caused by both the larvae and adults will not kill an elm tree; however, extensive feeding may ruin the aesthetic appearance. Adults overwinter under loose bark and in leaf litter under previously infested trees. There is one generation per year in Kansas. Nearly all elm species are susceptible to feeding by the European elm flea weevil especially Siberian elms (Ulmus pumila) and certain elm hybrids with Asian parentage.

Management of European elm flea weevil involves maintaining proper tree health by means of watering, mulching, pruning, and fertilizing. Insecticides may be used to minimize damage; however, insecticides may be difficult to apply to large trees. Insecticides must be applied in May and June in order to suppress adult populations. A number of insecticides may be used including: acephate (Orthene), imidacloprid (Merit), or carbaryl (Sevin). However, if damage is not extensive, especially on large trees, then there be no rationale for using insecticides. For more information regarding European elm flea weevil management contact your county or state extension specialist.

 

 

 

 

 

Alfalfa

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa pests are still causing concern among alfalfa producers.  In north central Kansas the alfalfa has yet to become dormant, at least as of 29 Nov.  Also, in these slowly growing fields the pea aphids seem to be doing very well and no beneficials, which might help to control them, were detected.  Also, alfalfa weevil larvae are still actively feeding on leaf tissue.  One potato leafhopper was also picked up in sweep net samples.  Hopefully, the colder winter weather will eliminate the pea aphids and alfalfa weevil larvae!

pea-aphid-29-nov

aw-29-nov

aw-single-29-nov

Twospotted Spider Mites: “Hot and Ready”

— by Dr. Raymond Cloyd

The extreme heat we are experiencing throughout Kansas and the fact that plants are “stressed” due to a lack of moisture means you need to be on the look-out for the twospotted spider mite, Tetranychus urticae (Figures 1 and 2). Twospotted spider mite is a warm-weather mite because, in general, populations are active from late spring through early fall. Summer temperatures allow twospotted spider mites to reproduce rapidly, which helps them to overwhelm natural enemy populations. This article discusses the plant protection strategies that homeowners and professionals can implement in order to alleviate or avoid problems with twospotted spider mite populations.

TwospottedSpiderMitesSeptember2008

Fig 1: Twospotted spider mite adults and eggs (spherical shape objects).

IMG_4108

Fig 2: Twospotted spider mite feeding damage.

Twospotted spider mite management involves maintaining plant health, implementing sanitation practices, and/or using pesticides with miticidal activity (miticides/acaricides). First of all, avoid exposing plants to any type of “stress” by maintaining proper watering, fertilizer, and mulching practices so as to reduce potential problems with twospotted spider mite populations. For example, inadequate moisture or overfertilizing plants, particularly with nitrogen-based fertilizers, can enhance development and reproduction of twospotted spider mites. Also, be sure to monitor for twospotted spider mite populations regularly by shaking branches or twigs onto a white sheet of paper, and looking for the mites crawling around. You can crush the mites on the white sheet of paper to determine if they are a pest or not. For instance, plant-feeding spider mites typically leave a green streak when crushed whereas predatory mites leave a red streak. A quick method of dealing with twospotted spider mite populations is applying a forceful water spray throughout the plant canopy at least twice per week during the season. Forceful water sprays will dislodge eggs and the motile life stages (larvae, nymphs, and adults). Be sure to direct forceful water sprays toward the leaf undersides where all life stages (eggs, nymphs, larvae, and adults) of the twospotted spider mite are located. The removal of plant debris and weeds eliminates alternative hosts and overwintering sites.

There are many pesticides with miticidal activity available to professionals for suppression of twospotted spider mite populations outdoors, including: abamectin (Avid), acequinocyl (Shuttle), bifenazate (Floramite), etoxazole (TetraSan), hexythiazox (Hexygon), potassium salts of fatty acids (M-Pede), and horticultural oils (petroleum, mineral, or neem-based). Homeowners do not have many options in regards to miticides. The only “true miticide” still available is hexakis or fenbutatin-oxide, however, this active ingredient cannot be purchased by itself as the active ingredient is usually formulated with acephate (Orthene). Always read the label and apply miticides before twospotted spider mite populations are extensive and causing aesthetic damage. Furthermore, be sure to rotate miticides with different modes of action in order to avoid twospotted spider mite populations developing resistance. If possible, try to target “hot spots” or localized infestations of twospotted spider mites, which will reduce the potential for resistance developing. Be sure to thoroughly cover all plant parts with spray applications; especially when using pesticides with contact activity. Some miticides such as abamectin (Avid) and etoxazole (TetraSan) have translaminar activity, which means that the material penetrates into leaf tissues and forms a reservoir of active ingredient within the leaf. This provides residual activity even after spray residues have dried. Mites that feed on leaves will ingest a lethal concentration of the active ingredient and be killed.

It is important to note that many pesticides used to suppress other insect pests encountered on plants in landscapes and gardens may be harmful to the natural enemies of twospotted spider mite; consequently, resulting in an inadvertent increase in twospotted spider mite populations or secondary pest outbreaks.

 

European Fruit Lecanium Scale: Adding a “Decorative Touch” to Bald Cypress

–by Dr. Raymond Cloyd

The European fruit lecanium scale (Parthenolecanium cornii) is quite noticeable on bald cypress (Taxodium distichum) twigs and branches. The damage associated with this scale, which depends on the extensiveness of the infestation, includes plant stunting and wilting. The European fruit lecanium scale is a soft scale, so honeydew (a sticky, clear liquid) will be produced during feeding. The honeydew serves as a substrate for black sooty mold and attracts ants. In addition, honeydew can drip onto vehicles parked underneath infested trees leaving unsightly residue.

The scales are dark brown, 1/8 to 1/4 inches in diameter (Figures 1 and 2). Some scales may have white markings on the body. European fruit lecanium scale overwinters as an immature on twigs and branches with maturing occurring in spring. In May and June, females lay many eggs underneath their bodies. In June eggs hatch into small tan-colored crawlers. The duration of an egg hatch can last several days depending on the temperature. Crawlers migrate to leaf undersides and subsequently feed on plant fluids until late summer. At that point, the crawlers migrate back onto twigs and branches to complete their development the following spring. There is one generation per year in Kansas.

Figure 2. MatureEuropeanFruitLecaniumScaleonBaldCypressMay2016 Figure 1. MatureEuropeanFruitLecaniumScalesonBaldCypressMay2016
Figure 1 & 2: Mature European Fruit Lecanium Scale on Bald Cypress

Management of European fruit lecanium scale primarily involves timely applications of insecticides. Applications should be made when crawlers are present because the crawlers are most vulnerable life stage to insecticide sprays. Mature scales possess a shell-like covering that protects them from exposure to insecticides. Repeat applications will be required as the eggs do not all hatch simultaneously but may hatch over a three to four-week period. The most appropriate time to apply insecticides is in late June to early July when the crawlers are feeding on leaves; thus enhancing their exposure to any spray residues. There are a number of insecticides, with contact activity that are effective in suppressing populations of the European fruit lecanium scale. However, many have broad-spectrum activity and will kill many natural enemies including: parasitoids and predators. In fact, most out-breaks of scale insects are caused by the indiscriminate use of pesticides (insecticides and miticides). Therefore, always read the label and exercise caution when applying any pesticide. In the winter, dormant oils can be applied to kill overwintering scales by means of suffocation.

I need to acknowledge Jeff Otto of Wichita, KS for bringing to my attention that European fruit lecanium scale was active. I have also observed infestations in Manhattan, KS.

Wheat Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Last week wheat aphid populations were active and had increased considerably from the previous couple of weeks in north central Kansas.  Populations of bird cherry-oat aphids, English grain aphids, and greenbugs were all reproducing and still migrating in.  This week however, in fields we sampled in north central Kansas, the aphid populations had decreased drastically and the beneficials, especially lady beetles, had increased greatly.

Lady beetle larva 2

lady beetle adult

Last week these English grain aphids were inadvertently identified as greenbugs.

English grain aphids

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.

Wheat Pests

–by Dr. Jeff Whitworth, Dr. Holly Schwarting and JR Ewing

Worms (fall armyworms and armyworms) are still active in wheat and can be for another month, depending upon the weather.  If growing conditions are good, the wheat should be able to outgrow feeding caused by small worms.  Large worms have probably caused most of their feeding damage already, and hopefully, won’t be able to pupate, emerge as adults, lay eggs and have those eggs hatch again this fall.  Winter grain mites may cause some concern in the next month or so, especially under dry conditions. However, insecticide applications are rarely warranted or impact next year’s yield.  Again, good growing conditions will mitigate winter grain mite feeding damage.

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