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Extension Entomology

Month: August 2015

Old “Defoliated” Friends Revisited

–by Dr. Bob Bauernfeind

One of my favorite most succinct introductory slides simply says:

#1

While attentiveness, care and pampering are especially important in the early years after newly transplanted trees first become “family members”, there does come a point-in-time when they become “Big Boys and Girls”.  Look at mature trees lining city streets, in park and recreation areas and in the countryside —- all thriving on their own.  This despite having to contend with different insect pests.

Most alarming for homeowners is the compromised appearance of trees when foliar feeding species come-to-town.  The situation is such that their presence first becomes apparent (after-the-fact) when the offending species are approaching the end of their feeding phase-of-development — a time at which they are of such size that they ravenously feed on and rapidly deplete available foliage thus drawing attention to their presence.

Defoliations may vary in intensity from a few bare branches to the entire canopy.  As alarming as a complete defoliation might appear, it should be regarded as but a cosmetic issue.  Probably more objectionable is the visible and audible “rain-of-frass”, as well as streams of descended mature larvae roaming about in search of pupation sites.  Early-season defoliations are of temporary duration because trees rapidly produce a new flush of growth restoring normalcy.  On the other hand, new foliage production is scant late in the season at a time when leaf abscission is imminent after the cessation of seasonal photosynthetic activities.  Come springtime, trees again will fully leaf out — seemingly none the worse-for-wear.

People may ask, “What did I do wrong?  Couldn’t I have prevented this?”, to which I would respond, “You did nothing wrong.  Outbreaks are unpredictable!”. As mentioned earlier, a person is unaware of the presence of specific pests which (as “wee ones”) scrape and nibble away not producing any noticeable foliar damage to give away their presence.

Come the questions, (1) “Well, once I notice the damage, shouldn’t I spray?”, to which there is not an absolute response.  Consider the size (and possibly) number of trees, and the unlikely capability of an individual to apply/achieve thorough spray coverage. (2)  “Well couldn’t I hire a service to spray for me?”, to which the response might be, “If the service provider is “booked” and unable to get to your tree(s) in a timely fashion, by the time they do arrive, caterpillars/larvae may have already completed and ceased feeding —- little point in spraying at that point.

Balancing the cost of hiring a spray service against what-is-to-be-gained by spraying at a time that tree appearance has already been compromised may make the decision to be to simply allow the situation to run its course.

“Is there a need to “kill-them-now” to prevent a repeat?”  While this seems to be a logical thought, in reality, we really have little control over future events.  Nature sort of has its own checks-and-balances.  Whether unfavorable environmental conditions or biological entities (diseases, predators, parasites) reduce or eliminate potential future “seed” for pest populations, or, if pests themselves naturally disperse, one may never again experience a repeat situation.  Individuals who have experienced defoliations and who have seen their trees recover are convinced of the need to let nature run-its-course.                            

Defoliations:  before and after

Greenstriped Mapleworms on silver maples

#2

 

Yellownecked Caterpillars on oak 

#3

 

             Walnut Caterpillars on black walnut (red arrow = limb pruned out in 2011)

#4

 

Foliar Dessication:  Before and After

Some foliar-feeders are relatively small in size and therefore incapable of skelotinizing and defoliating tree hosts.  Rather, their feeding activities are reduced to nibbling/consuming the epidermal tissues of leaves.  Both the upper and lower epidermis (with their thicker “waxy” cuticles) protect the more delicate inbetween high-in-moisture-content internal cellular layers. Deprived of their protective outer layer, leaf dessication leads to leaf death — the resultant being the unsightly browned/burnt appearance of trees.

Mimosa Webworms on honey locust

#5

 

Elm Leaf Beetles on elm

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In this incidence, I do not have a current image of the trees above.  They no longer exist.  However, not due to to the depredations of elm leaf beetles.  Rather, simply, they were in the way of progress.  A highway expansion project necessitated their removal.  They were no match against “man”.  Soooo painful to watch trees ripped out roots-and-all by powerful excavating equipment.  But again, the lesson being that the asthetically unacceptable foliar appearances resulting from insect activities are but an occasional temporary fleeting occurrences …. leading to the following:

On a return trip to Manhattan Monday, I noted the presence of fall webworms along the roadway — sometimes one or two in an occasional tree here and there, or  (in this instance) numerous web masses.

#8

 

#7

 

These did not develop “overnight”  Judging by their size, these colonies likely were initiated 4-5 weeks earlier.  Again under the banner of defoliators, people may worry about the impact of feeding depredations.  Minimal!  Probably a more verbally expressed concern is the unsightlyness created by the webbing, as well  “creepy” clumps of caterpillars within.

#9

 

A common recommendation is to prune out webbed branches.  One must consider the accessibility of web masses — those beyond reach simply allowed to remain.

#10

Pruning might be doable if just a branch or two —- but possibly unacceptable and disfiguring when trees are heavily infested with web masses.

If within reach, consider an implement (of sorts) to “rake out”/remove  webbing.  And what implement could be more handy (yes, pun intended) than one’s own hand.  There is no need to fear the dry webbing and/or dried fecal deposits and squirmy caterpillers within.  As webbing is removed, also removed will be the objectionable dead/dry foliage and the fallwebworms.  Simply dispose of the gathered material.  All that is left behind is the leafless (but still living) branch and it’s intact buds which will produce the ensuing year’s foliage.

#11

 

 

Alfalfa Aphids

–by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing

Cowpea and spotted aphids continue to maintain their populations in most alfalfa fields throughout north central Kansas.  Lady beetles and other beneficials still appear to be helping control both species, but these fields need to be periodically examined to ensure these aphid populations stay at low levels.

cowpea aphids

 

Spotted alf aphid

 

 

Sorghum Pests

–by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing

Sorghum fields checked in north central Kansas this week indicated a variety of very active pests.  Fields were anywhere from whorl-stage to flowering.  Regardless of the stage of plant development, 100% of the plants sampled were infested with chinch bugs.  Most are still small reddish to brown or black nymphs, but there are still mating adults as well.  These bugs are feeding mainly around the base of the plants.

Chinch bug nymps many stages

 

 

Some plants in the boot stage have populations of corn leaf aphids feeding right at the top of the about-to-emerge heads.  Occasionally, these aphids are so numerous at the point of head extension that their honeydew interferes with the head’s emergence.  Fortunately, aphid populations were not found frequently enough to potentially impact yield, just an occasional plant here and there.

CLA on sorghum

 

Most of the whorl-stage sorghum (90%) is infested with a “ragworm”.  These are a combination of corn earworms, armyworms, and fall armyworms, Mr. Tom Maxwell, Extension Agent in Saline County, even found a cattail caterpillar.  They are in all larval stages, but mainly smaller, from 1st to 3rd instars.  Thus, they will be feeding in the whorls for another 10-21 days, and then will pupate in the soil.  In approximately 7-10 days, moths will emerge and start ovipositing in sorghum, which is vulnerable from flowering to soft dough, and/or soybeans.  Some early flowering plants already had “headworms” feeding in the just emerging heads.

Ragworm feeding sorghum

 

Sorghum headworm

 

ELM LEAF BEETLE

–by Dr. Raymond Cloyd

Now is the time to be on the lookout for the elm leaf beetle, Pyrrhalta luteola, which may feed on all elms; however, elm leaf beetle prefers Siberian and American elm, with Chinese elm being less susceptible. Adults are about 1/4-inch long, slender, and yellow-green in color, with black stripes extending down the entire length of the abdomen. Furthermore, there are distinct black spots on the head and thorax. Adults appear in spring and eat small holes in leaves. Females lay yellow-orange eggs in clusters on leaf undersides. A single female can lay between 600 to 800 eggs during her lifetime. Eggs hatch in 5 to 6 days into green larvae that look-like grubs. Larvae are approximately 3/8 to 1/2 inches in length. Initially, they are black, and then turn yellow in color with two black lateral stripes along the sides of the body. Larval feeding causes leaves to appear skeletonized because they scrape the leaf tissue from the upper surface with their chewing mouthparts; leaving the veins intact. The tissue between the veins eventually turns brown. Larvae, which are the major source of damage to plants, feed for about 3 weeks.

ElmLeafBeetleAdultWC2012abc

 

ElmLeafBeetleEgg

 

The last larval instar crawls down tree trunks, where they pupate at the base of trees in and on the ground. They may also pupate in the cracks and crevices of the trunk or in large branches. In about two-weeks, adults emerge and start feeding on plant leaves. They normally feed on the same trees that larvae fed upon. Adults may be a nuisance pest in late summer and early fall when they migrate from trees and enter homes to overwinter. They will also overwinter in protected places outdoors. It is interesting to note that both adults and larvae may be present simultaneously. There are two generations per year in Kansas with the second generation causing the most damage.

ElmLeafBeetle2008

 

Insecticides should be applied at the first appearance of both adults and larvae, and routinely throughout the summer and early fall in order to protect elm trees. This is especially the case if extensive feeding by elm leaf beetles will impact the aesthetic appearance of elm trees. When using contact insecticides, it is important to obtain thorough coverage of both the underside and upper side of plant leaves. However, avoid applying acephate (Orthene) on American elms as this may cause plant injury. If elm leaf beetle populations are minimal, then insecticide applications may not be warranted. Always read the insecticide label prior to making any applications.

Update on the sugarcane aphid in Kansas

In 2013 some sugarcane aphid (SCA) populations made a switch from preferring sugarcane as a host to preferring sorghum. The sorghum-loving sugarcane aphid populations now overwinter in Texas and are passively swept northward when the weather warms.

sca map aug 15 2015

Current map of US counties with sugarcane aphids.

In 2014, the SCA made it to Sedgwick and Sumner counties with only minor infestations in a few fields. However this summer, SCA populations have come further north than ever before. Currently, they have been reported in Sedgwick, Butler, Cowley, Sumner and Pawnee counties. Populations in most places, except Pawnee county, have been over threshold and many fields have been treated this season already. Treatment options are limited this year to Silvanto and Transform (temporary section 18 use for 2015). With these chemicals be sure to consult the label for pre-harvest intervals. More info on the insecticide options for SCA can be found here.

Scout early and often for the sugarcane aphid in sorghum

Sugarcane aphids are found on the undersides of sorghum leaves. Leaves below infested ones will be covered in honey dew (aphid excretion) and will have a shiny appearance which become colonized with a sooty mold after a period of time (see photos below).

IMG_0858 (2)

sca leaf

There are several similar species on sorghum that could be confused with the sugarcane aphids especially when the aphids are young. The SCA has a smooth body with a light colored head and light colored legs with dark feet. They have dark colored, short cornicles (tail pipes) with no shading at the base of them as on the corn leaf aphid.

sca lookalikes1. sugarcane aphid

2. corn leaf aphid nymph

3. english grain aphid nymph

4. english grain aphid

5. sugarcane aphid

6. yellow sugarcane aphid

 

Timing effective control for SCA in sorghum depends on the size of the populations. To estimate the number of SCA and determine if management is needed in a field, follow the guidelines in our new Scouting Sugarcane Aphid guide.

Download our new scouting guide here!

Screenshot 2015-08-18 21.38.37

-Sarah Zukoff and Brian McCornack

Uninvited Guests – Crickets

–by Dr. Bob Bauernfeind

While I certainly do not want to create any hysteria as did Henny Penny when she ran around the town shouting, “The sky is falling.  The sky is falling”, it may be that we are in store for impending cricket invasions, at least based upon what I am currently seeing (for the first time ever that I can recall) in-and-around my yard and home: crickets, crickets and more crickets.  Actually thinking back earlier this year, I recall saying to myself, “Huh, look at these little crickets!”  While I cannot account for their observed numbers (no official counts per se), perhaps this year’s adequate moisture may have been favorable for their survival and development.

 

Crickets subsist on a wide range of food sources.  As generalist omnivores, they are opportunistic feeders deriving nourishment wherever on whatever is available including plant, dead organic plant and animal matter, algal, fungal and bacterial sources.

 

The mere presence of crickets can be annoying.  In addition, while the chirping of male insects may be considered beautiful music-in-the-night out-of-doors, indoors it may be regarded as noisy and disruptive.  Although not bona fide fabric pests, being what they are (insects with chewing mouthparts) and doing what many insects do (test/taste-their-surroundings), crickets may be responsible for creating holes in and leaving stains on light-colored fabrics (curtains/sheers the oft-cited areas showing damage).

 

When people think about crickets in the home, logically the name house crickets comes to mind.  And there are crickets officially called “house crickets”.  House crickets are brown in color and about an inch in length. Whereas they naturally occur in the warmer climates of southwestern Asia, they have no special overwintering stage as would be required for surviving winters in temperate regions where they are commercially reared and marketed as food for amphibians, birds, reptiles and other arthropods.  While they now have become established worldwide, survival of escaped adults is minimal (but possible) in and around heated areas.  It is unlikely that “house crickets” will be paying you a visit.

#1

 

Rather, the crickets which enter homes will likely be “field crickets”.  Mature field crickets approach an inch in length.  The female, is easily identifiable by the presence of her prominent ovipositor measuring another ¾-inch.  Most field crickets are all black in color, but some may have a lighter appearance due to their coppery-colored wings.

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A third type of cricket is a smaller-in-size “ground cricket” commonly called the striped ground cricket.  These are the small “summer crickets” that occasionally are attracted to commercial districts and businesses illuminated by high intensity lighting which acts as a beacon to these crickets capable of flying to the distant glow of city lights and business-lit areas.  Their life cycle differs in that they attain adulthood during mid-late summer.  Eggs are already deposited and most adults died before the onset of cooler fall weather.

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With regard to seasonal life history, field crickets overwinter as eggs deposited in the soil.  Currently, field crickets are now in their mid-development stages, and for the most part go unnoticed.  By the time cooler fall weather moves in, field crickets will have reached their adult stages.  Before and after mating and depositing eggs, crickets move towards sources of heat such as homes and buildings whose exteriors “soak up” the sunlight/heat.  Crickets are capable of detecting heat gradients and thus are drawn in.  Once on-the-doorstep, they are a hop away from secretly moving in through any available crack/crevice/opening.

 

How does one go about attempting to prevent cricket “visitors” in homes and possibly business establishments?  The first thought might be the outdoors use of insecticides to kill crickets.  When cricket populations are large and there is the likelihood of impending invasions, reduction of their numbers may be achieved with insecticide applications as barrier treatments applied to a 6- to12-foot band around the perimeters of homes and businesses.  Once inside, insecticides registered for indoor use against crickets or (in general) indoor invasive species can be applied per labeled instructions.  Indoor applications may be general surface, spot, mist or crack and crevice treatments.

 

According to NPIRS (National Pesticide Information Retrieval System, currently in Kansas, individually clicking onto striped ground crickets, house crickets, field crickets and crickets, there are 4, 44, 84, 1392 products, respectively.  Collectively clicking onto all of the mentioned categories, there are 1,410 products.  So there are plenty of insecticide options.  However, even if a person sprays, sprays, sprays outdoor areas until they glow that does not guarantee against eliminating all potential invaders.

 

Perhaps a more successful approach for preventing cricket “guests” is to EXCLUDE THEM!  Again, as previously mentioned, crickets (as well as any other commonly named “fall guests” such as boxelder bugs, elm leaf beetles, multicolored Asian lady beetles, spiders) gain entrance via any  available crack/crevice/hole/gap.  Thus sealing these portals of entry is a recommended method of exclusion.  Attempt to insect-proof houses and buildings by thoroughly inspecting and identifying entry points. Check for cracks and gaps in structure foundations, ill-fitting doorways and garage doors, overhang louvers, chimney vents, roof ducts, soffits, air conditioner connections, outdoor faucets and siding. Use caulk to seal cracks and crevices, weather stripping to make doorways and garage doors tightfitting, and metal screening over/under/behind other entry points.  Such simple words.  Yet, in all practicality when looking at my home (which I consider sound-and-sealed), I know that there are (still remaining) untended access points.  I expect that like many other people, I will have “fall visitors”.  Sort of a fact-of-life that one must accept.

Potato Leafhoppers

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

A few potato leafhoppers are still present in alfalfa fields.  Swathing seems to be doing a good job of controlling their numbers and thus, damage.  They also seem to be relatively numerous in soybeans.  Again, they do not appear to be causing any problems.  Field sampling in northcentral Kansas had very few defoliators yet and most beans were just starting to flower.

Cowpea Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

We have started finding a few cowpea aphids on alfalfa stems in north central Kansas (see photo).  However, there are also many lady beetles, lacewings, and mummies, which indicate parasitoid activity, present (see photos).  Aphid populations can increase rapidly and swathing will remove many aphids, but not all of them.  So fields should be rechecked weekly.  For more information on cowpea aphids, please visit: http://www.bookstore.ksre.ksu.edu/pubs/MF2865.pdf

cowpea aphids

 

cowpea aphid mummies

 

lady beetle

Chinch Bugs

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Chinch bug populations are increasing dramatically in north central Kansas.  Sampling plants from the boot stage to flowering revealed approximately 25-60 chinch bugs of all stages per plant (see photo).  Growing conditions have been good so far in central KS, thus plants have grown well and chinch bug feeding around the base of the plants (see photo) has not caused any concern, yet.  However, with these chinch bug populations still increasing (we are even still finding mating adults!) if growing conditions become less favorable,  the added stress caused by all these chinch bugs feeding around the base of these plants may substantially weaken the stalks and cause lodging prior to harvest.

chinch bug immatures2

 

chinch bug feeding

 

chinch bug mating

 

 

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