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Extension Entomology

Euonymus Scale: What Can You Do?

Posted on by Sharon Schroll

by–Dr. Raymond Cloyd

      This is the time of year when euonymus scale (Unaspis euonymi) becomes noticeable in landscapes on evergreen euonymus (Euonymus japonica) and Japanese pachysandra (Pachysandra terminalis). Euonymus scale typically overwinters as a mated female, primarily on plant stems. Eggs develop and mature underneath the scale, and then hatch over a two to three week period. The newly hatched crawlers migrate along the stem and start feeding near the base of host plants. Crawlers can also infect adjacent plants by being blown around on air currents, resulting in infestations often not being detected until populations are extensive and damage is noticeable—like right now. Leaves eventually become spotted with yellow or white areas. Plants located near structures such as foundations (Figure 1), walls or in parking areas are more susceptible to euonymus scale than plants growing in open areas that receive sunlight and air movement. In addition, the variegated forms of euonymus are more susceptible to euonymus scale than the green forms.

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Figure 1:  Euonymus Plants Near Foundation infested with Euonymus Scale.

Heavy infestations of euonymus scale can ruin the aesthetic appearance of plants, causing complete defoliation or even plant death. Females are dark brown, flattened, and resemble an oyster shell. Males, however, are elongated, ridged, and white in color (Figure 2). Males tend to be located on leaves along leaf veins whereas females reside on the stems. There may be up to three generations per year.

newFigure2CloseupofEuonymusScaleFemalesandMales

 

Figure 2: Close up of Euonymus Scale Females and Males.

Cultural practices such as pruning out heavily infested branches—without ruining the aesthetic quality of the plant—is extremely effective in quickly reducing euonymus scale populations; especially this time of year. Be sure to immediately discard pruned branches away from the area. If feasible, avoid planting Euonymus japonica in landscapes since this species is highly susceptible to euonymus scale. Winged euonymus (Euonymus alata) is less susceptible to euonymus scale, even when adjacent plants are infested. Applications of insecticides in May through June, which is when the crawlers are most active, will help to alleviate problems with euonymus scale later in the season. Insecticides recommended for suppression of euonymus scale populations, primarily targeting the crawlers, include acephate (Orthene); pyrethroid-based insecticides such as bifenthrin (Talstar), cyfluthrin (Tempo), and lambda-cyhalothrin (Scimitar); potassium salts of fatty acids (insecticidal soap); and horticultural (petroleum or mineral-based) and neem (clarified hydrophobic extract of neem oil) oils. Always regularly check plants for the presence of crawlers, which will help time insecticide applications. In general, three to four applications performed at seven to 10-day intervals may be required; however, this is dependent on the level of the infestation. Euonymus scale is a hard or armored scale, so, in most cases, soil or drench applications of systemic insecticides such as imidacloprid (Merit) are not effective in suppressing euonymus scale populations; however, the systemic insecticide dinotefuran (Safari), due to its high-water solubility (39,000 ppm), may provide suppression of euonymus scale populations when applied as a drench to the soil. Dormant oil applications can be conducted in winter to kill the overwintering mated females on stems. However, thorough coverage of all plant parts is important in order to obtain sufficient mortality.

Euonymus scale is susceptible to a variety of natural enemies (e.g. parasitoids and predators). These include braconid and ichneumonid wasps, ladybird beetles, green lacewings, and minute pirate bugs. However, natural enemies may fail to provide enough mortality (‘killing power’) to significantly impact “high” populations of euonymus scale. Furthermore, insecticides such as acephate (Orthene), and many of the pyrethroid-based insecticides, including bifenthrin (Talstar), cyfluthrin (Tempo), and lambda-cyhalothrin (Scimitar) are very harmful to most natural enemies, so applications of these materials may disrupt any natural regulation or suppression.

Emerald Ash Borer In Kansas: Another Quarantined County

Posted on by Sharon Schroll

by–Dr. Raymond Cloyd

If you have not heard, on September 30, 2015 an Emerald ash borer (Agrilius planipennis) larva was found in a girdled trap tree in Eudora, KS (Douglas County) by the Kansas Department of Agriculture. This means that Kansas has four counties in which Emerald ash borer has been detected, and subsequently quarantined, including Wyandotte, Johnson, Leavenworth, and Douglas. First detected in 2002 in Michigan, the Emerald ash borer has been found in 23 states throughout the USA (Figure 1), and is responsible for causing the death of over 30 million ash trees. For more information regarding Emerald ash borer, contact the Kansas Department of Agriculture or the Department of Entomology at Kanas State University (Manhattan, KS).

Figure1DistributionMayofEmeraldAshBorerAugust32015

 

Figure 1: Distribution May of Emerald Ash Borer August 3, 2015

Sugarcane Aphids

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Sugarcane aphids (SCA) colonies have rapidly declined in some fields in north central Kansas, slowly declined in others, but actually increased somewhat in other fields.  In one field, approximately 90% of all previous SCA’s are gone and enormous numbers of lacewing adults remain (see pics).  However, prior to the latest cold front, most top leaves had winged aphids with nymphs.  This means, evidently, that they are still migrating in and trying to establish colonies.  However, with huge numbers of beneficials now present, it seems unlikely that they will be successful, especially with the recent cooler weather.  Everywhere that SCA colonies became established, they produced honeydew, which coated the sorghum leaves, and was then covered with a dark sooty mold.  However, when the colonies are eliminated the honeydew is no longer sticky and the black mold becomes dry and washes off (see pic).

brown lacewing

green lacewing

 

old honeydew

Armyworms and Army cutworms in Wheat

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Several planted fields have already been sprayed to control worms.  What we have been seeing in south central and north central Kansas are a combination of armyworms (see pic) and fall armyworms (see pic).  Both of these species will do a similar type of damage.  When they are small they will feed on one side of the wheat leaf causing what is commonly called ‘window paning’.  As the larvae grow they devour more and more tissue until it may become quite noticeable and, under unfavorable growing conditions, may even severely reduce the stand (see pic).  Armyworm larvae will feed, probably for a couple more weeks, depending upon temperatures, and then pupate. If we haven’t yet had a hard freeze, they may emerge as moths and lay eggs in other wheat fields.  The first hard freeze will terminate armyworms.  Army cutworms, on the other hand, will not be terminated by the first hard freeze but will continue to develop all winter, feeding anytime temperatures are over about 45°F and will complete their development in the spring (see pic).  So, it is important to make proper identification of armyworms feeding in wheat as armyworms and fall armyworms will not be feeding throughout the winter and early spring but army cutworms will.

armyworm

 

fall armyworm

 

armyworm damage wheat

 

 

army cutworm

Not so mysterious “Itching” (Oak Leaf Itch Mite)

Posted on by Sharon Schroll

–by Dr. Bob Bauernfeind

Whereas scratching an itch sometimes provides satisfying (almost pleasurable) relief, at other times scratching an itch can be painful and distressing.  The latter situation is attributable to the mite, Pyemotes herfsi (Oudeman).

Unlike chiggers which have been long-recognized for producing annoying but fleeting bouts of itchiness, mysterious “bites” causing raised quarter-sized reddened areas each with a centralized pinhead-size blister were of widespread occurrence in 2004 in various Midwestern states.

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Through investigative studies, the aforementioned Pyemotes herfsi mites were identified as being responsible for the mysterious bites.  Although the existence of these mites had been well known for multiple decades, the correlation between them and reported widespread occurrences of human discomfort was unknown.  The severity of the 2004 outbreaks resulted in cooperative efforts between K-State and the University of Nebraska entomologists, the resultant being the identification of Pyemotes herfsi as responsible for the stressful skin disorders.

Pyemotes herfsi were recovered from marginal fold galls on (primarily) pin oak leaves.  Marginal galls are associated with the larvae/maggots of tiny midges.  That is, Pyemotes herfsi prey upon the midge larvae.  The following side-by-side close-up images show an intact marginal gall, and a dissected gall revealing female Pyemotes herfsi.  Despite their small size, they become readily visible due to their bulbous abdomens which can contain up to 200 offspring.

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Due to their minuscule size compared to that of midge larvae, Pyemotes herfsi possess a potent neurotoxin used to paralyze their maggot hosts.  This toxin is that which is responsible for initiating the skin irritations which cause discomfort in individuals upon which Pyemotes herfsi happen to come in contact with.  Because Pyemotes herfsi are associated with the midge larvae responsible for marginal galls on oak leaves, Pyemotes herfsi have been given the common name, Oak Leaf Itch Mite.  It is believed that oak leaf itch mites also prey upon the larvae of another closely related midge species responsible for the formation of vein pocket galls on the undersides of oak leaves.  A full description of the oak leaf itch mite life cycle is available online by accessing Kansas State University Extension Publication MF2806.

The good news is that oak leaf itch mite populations may be extremely low or absent for years-on-end —— people can enjoy the outdoors without having to contend with oak leaf itch mite encounters.  The bad news is that the reappearance/resurgence of oak leaf itch mite populations is unpredictable. There are various unknown factors as to the whys-and-where their populations are and when they will surge.  Undoubtedly there are ever-present reservoir populations of oak leaf itch mites, but, where are they?  Possibly a major factor for population explosions is contingent on fluctuating populations of the appropriate gall midges responsible for the formation of  marginal galls and/or vein pocket galls.  An intriguing question then would be, “How do the tiny mites detect and move to the galls up in tree canopies?”  

More bad news:  Each female oak leaf itch mite produces many progeny.  And the developmental cycle is reported to be just 7 days.  The resultant is the production of uncountable numbers of oak leaf itch mites which ultimately leave the confines of leaf galls. Passive dispersal via air currents is the bane to people, especially those in neighborhoods where pin oaks constitute the main trees species.

The bad news continues: There is a wide time frame during which encounters with oak leaf itch mite might occur.  It is not only the initial late summer encounters, but the presence of oak leaf itch mites extending well into the fall when people are raking leaves and kids having fun playing in leaf piles.

And if this is not enough negativity regarding oak leaf itch mites, there is little to be done (well, actually nothing to be done) in treating and reducing/eliminating their populations.  THEY WILL HAVE THEIR WAY!

 The people who are most likely to encounter oak leaf itch mites will be those in living in areas/neighborhoods where oaks (again, especially pin oaks) are the dominant tree species.  When oak leaf itch mite populations are excessive, restricting outdoor activities is one method of reducing the risk of exposure.  While the use of repellents may work against annoying insect species which actively seek a host, repellents have little effect against oak leaf itch mites which are passively dispersed, and lack the ability to alter their course/direction.  It has been suggested that susceptible individuals (yes, some people do not have negative reactions to oak leaf itch mite bites) spend as little outdoor time as possible.  And showers immediately upon returning indoors might eliminate/wash off mites before they bite and cause reactions.

Individuals experiencing oak leaf itch mite encounters might utilize medications and lotions so designed to provide relief from itching discomfort as well as secondary infections of excoriated areas.  Seek advice and recommendations from appropriate personnel.

 

“Float like a butterfly, sting like a bee!” “They’re here”. —- Monarch Butterflies

Posted on by Sharon Schroll

–by Dr. Bob Bauernfeind

Pushing the envelope (as I often do), how does one use Muhammad Ali’s  “Float like a butterfly, sting like a bee”, epitomized boxing style, and  the movie Poltergeist tagline, “They’re here”, as an introduction to a Kansas Insect Newsletter article?  I spent time on Saturday and Sunday doing yardwork.  It was Sunday afternoon that (out of the corner of my eye) I frequently glimpsed monarch butterflies lazily/lightly floating by.  I had noticed none the day before.  So, “They’re here” refers to their arrival in Kansas (well, Manhattan) on Sunday as they were on their southward migration to their overwintering grounds in Mexico.

There are individuals with passionate interests in the status of monarch butterfly populations and activities.  Avid monarch-watchers access websites which better document the current presence/movements of migrating monarchs.  My sighting certainly has no official status in terms of documentation —- just a “casual” observation on my part.

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Sorghum Pest Update

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

The majority of the double cropped sorghum seems to be past flowering and almost to the soft dough stage.  This means much of this crop is almost past the susceptible stage relative to corn earworms (a.k.a. sorghum headworms), which is about soft dough.  Later planted sorghum still needs to be monitored though as earworm moths are still ovipositing in sorghum heads.  Sugarcane aphids (SCA) are still very active in north central Kansas, as are their natural enemies, and thus these populations should also continue to be monitored.  The insecticides registered for sugarcane aphids have performed really well at controlling these aphids, as have the products used for controlling headworms.  Just remember, gallonage is extremely important for SCA applications.