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Extension Entomology

Tag: nymphs

Sorghum Update – (chinch bugs, corn leaf aphids, corn earworms)

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Chinch bugs continue to be very active in both corn and sorghum throughout north central Kansas.  Both nymphs and adults are present.

 

Many adults are still mating, which indicates that there are more eggs, nymphs, and adults yet to come.  One consolation relative to the numerous chinch bugs in sorghum fields is that the four spotted egg eater, Collops quadrimaculatas, seems to be plentiful as well.  They have been collected in samples while sweep sampling alfalfa and are also present in sorghum fields.  These little beetles are predacious on insect eggs, and it has even been reported that they feed on chinch bug eggs.  Not sure they will be able to provide a great deal of control on chinch bug populations but it sure can’t hurt!

 

Corn leaf aphids are also very plentiful throughout north central Kansas.  These aphids usually feed on developing corn tassels and silks, but probably are more commonly associated with, or at least noticed in, whorl stage sorghum.  These aphid colonies sometimes produce enough honeydew, and it is so sticky, that often the sorghum head gets bound up in the whorl and therefore doesn’t extend up properly.  These colonies are not usually dense enough on a field-wide basis to justify and insecticide application.  These plentiful aphids are also serving as a food source for many predators, i.e. lady beetles, green lacewings, etc.

 

 

Corn earworms are still plentiful in corn but as they mature, pupate, and become adults they most likely will migrate to sorghum to feed on developing kernels (between flowering and soft dough), and soybeans where they will feed on developing beans within the pods.

For more information on sorghum and soybean pest management, please consult the KSU Sorghum Insect Management guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

And the KSU Soybean Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf

 

 

“The Wheels On The Bus Go Round And Round” — A Rite Of The Fall Season — Wheel Bugs

–Dr. Bob Bauernfeind

This common musical refrain comes to mind each fall as BIG YELLOWS  roar back into action picking up and delivering kiddos to and from school.  Another commonly encountered fall harbinger is a large assassin bug which possesses a distinct dorsal thoracic crest:  the wheel bug.

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Actually, wheel bugs are frequently first noted in the beginning of summer.  However, they are not recognized as such due to their radically different appearance.  Wheel bug nymphs hatching from overwintered eggs are small, possess a red abdomen which is held in an elevated position, rapidly move about on long “spidery” black legs, and lack the adult’s characteristic “wheel”.  Wheel bug nymphs are the basis for reports of “small red biting spiders”.

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The proboscis is the “action end” of wheel bugs (both nymphs and adults).  Like the earlier described minute pirate bugs, wheel bugs are predators.  They use their piercing/sucking mouthpart to pierce through the integument of their prey.  During this probing process, they introduce a bit of paralytic saliva which immobilizes their prey as well as aiding in the liquefaction of internal elements which then are withdrawn.  Wheel bugs are opportunistic feeders and capable of rapid movement.  However, given the slooooow movement of caterpillars which are a known “favorite food” of wheel bugs, speed-of-capture would seem irrelevant.

Despite their reputation for inflicting a painful bite, they can be carefully handled.  It should be stated that wheel bugs are not aggressive in the sense of attacking people. If one offers a finger or a hand for a wheel bug to crawl onto, their first tendency is to shy away/hide.  However they may choose to lazily climb aboard.  Let them wander, and when tired of such, quickly flick them off.  Do not grab/hold onto them for that will invite a bite (actually, not a bite/chomp per se, but rather a defensive jab).

Just as a person can safely handle a snapping turtle by properly grasping onto the base of its tail, if one wishes to get a closer look at a wheel bug, while it is on a hard surface, use your index finger and thumb to properly grasp the wheel bug on the sides of its hardened thorax.  Use a toothpick or piece of straw to maneuver its proboscis forward, and you may see a small bubble produced at its tip —- this is the saliva which it uses to paralyze its prey (and that which causes the pain/sting on the receiving end of a defensive poke).

Another interesting feature has to do with the female wheel bug.  While in your finger-thumb grasp, as an expression of her annoyance, she may react by everting her reddish/orange anal glands which produce a substance with a distinctive odor.  This may be a defensive tactic.  It has also been suggested that it may act as a repellent offering protection to newly deposited egg masses.

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While the wheel bug is the most widely recognized assassin bug, there are many other species.

They vary in size and body shape.  While most are rather non-descript and dark-in-color (varying shades of brown or black), others can be brightly colored and patterned.  Although most prey upon insects, several species require blood meals for development and egg production.  The eastern bloodsucking conenose (Triatoma sanguisuga) is the representative species found in Kansas.  Typically feeding on a wide variety of mammalian wildlife, they have been known to also seek a blood meal from humans.  People may have heard about “kissing bugs” being responsible for transmitting Chagas Disease.  This is of significance in tropical countries where other Triatoma spp. are the major vectors.  Thus Kansans can be-at-ease.

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Grasshoppers

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

There continue to be numerous reports of grasshoppers coming in from all over the state.  Most are still nymphs and are mostly still in grassy/weedy areas adjacent to crops, but as they get larger, are starting to move into crops.  The best time to control these grasshoppers is before they become adults.  Most of the insecticides labeled for grasshoppers work quite well, especially while they are still nymphs.  So, if treatment is justified, applications should be made ASAP!

grasshopper nymphs

Leafhoppers in Alfalfa

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa can be kind of a forgotten crop during this very busy time of year.  Most growers are busy planting sorghum, soybeans, sunflowers, and/or harvesting wheat, working wheat ground, etc.  This year, so far, has been a rough one for swathing and baling alfalfa.  Now, there are substantial infestations of potato leafhoppers, both adults and nymphs.  Potato leafhoppers can be quite damaging from now until fall.

Leafhopper adult

Leafhopper nymph

 

Both nymphs and adults feed by sucking juice from the plant and in so doing inject a toxin into the plants.  This can cause serious yellowing of the leaves, and even stems, if it continues for very long.  Generally, swathing and hay removal will disrupt this feeding and remove the leafhoppers from the fields.  They rarely re-infest fields after this physical removal or after an insecticide application, if that is justified.  If swathing is possible within the next 7-10 days, that should take care of the potato leafhopper problem.  However, be sure to keep scouting these fields as the damage caused by potato leafhoppers usually occurs much before the yellowing is noticed.  This feeding damage is cumulative – the stressed plants don’t seem to regain their original vigor and therefore don’t ever yield as much tonnage as expected.

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