Kansas State University


Extension Entomology

Tag: larvae

Nuisance Moths = “Miller Moths” = Army cutworm Moths

–by Dr. Bob Bauernfeind

Recent questions have been received inquiring about the annoying “miller moths”.  Also, numbers of moth captures in my (at home) blacklight trap have picked up

What are they?  Why so many?  What can I do about them?


“Miller moth” is an all-inclusive umbrella term used to describe any plain brown drab moth.  Because virtually all moth species have wings covered with scales, those scales are fluffed off like dust-in-the-air (as dust associated with flour milling plants).  At this time of year, the “miller moths” of note are army cutworm moths, Euxoa auxillaris.

Upon close examination, army cutworm moths definitely are not plain, brown or drab.  There are 5 morphological forms (called varieties) of army cutworm moths.  Each possesses its own intricate and distinctive wing pattern.  Adding more to the visual array, brown forms of each variety are males, whereas grayish individuals are females.


The seasonal life history begins in the fall of the year when moths deposit eggs in the soil in fields of fall-seeded wheat, alfalfa stands and weedy fields/patches.  Eggs may hatch within several days of being deposited, but may be delayed under unfavorable/dry conditions.  Larvae preferably feed during the dark of night, and seek shelter in the soil during daytime hours.  Army cutworms overwinter as partially grown larvae (red rectangle).


Each year in the central plains states, overwintered army cutworm larvae resume their feeding as temperatures moderate/become warmer.  They complete their development towards the beginning of May, after which they burrow into the ground where they create protective earthen cocoons inside of which they pupate.


Moth emergence usually begins by late May.  Although moths are the mature form of the army cutworm, at this point in time, they are not sexually mature.  For a period of time, moths remain near areas where they emerged.  Then an undefined stimulus (likely photoperiod driven) signals moths across the central plains states to migrate westward to the higher elevations in the Rockies. There in the cool-of-summer, they feed, accumulate body fat and attain sexual maturity.  In mid- to late September, they migrate back to the central plains where they deposit eggs (as previously described) to initiate the next generation of army cutworms.

The current complaints revolve around the moths.  Again, because moths are active during evening hours, they shun daylight.  That is, with the approach of daylight, army cutworm moths seek shelter/cover in any conceivable space.  Excluding moths is difficult because they will exploit very small openings.  Because garage doors seldom are tight fitting, when one opens the garage door, a flurry of moths may rush out.   A car window left open overnight provides an attractive entry point – and when one gets ready to drive to work, he/she will be greeted by a flurry of excited moths.  Open a polycart to deposit a trash bag and you may be greeted by a rush of moths.  Take an early morning walk and as you pass a line of shrubs, you may be startled by hundreds of excited moths darting out.  And so on.  In homes, catch or swat a moth on your wall or curtains/sheers and you will find a coating of “dust” (wing scales) left behind.

An example of the “dust” produced by army cutworm moths can be seen where moths gathered from a single blacklight trap are dumped out of a garbage can.  Talk about being up-to-your-neck in army cutworm moths!


Another interesting tidbit about army cutworm moths:  food for grizzly bears. During summer months, bears move to the higher elevations to feast on army cutworm moths.  It was determined that single moth possesses ½ calorie of fat content.  It was further estimated that a bear obtains 20,000 calories of fat on a daily basis by consuming 40,000 moths per day.


Rose Sawflies

–by Raymond Cloyd

There are at least two species of sawflies that attack roses during this time of year; the rose slug (Endelomyia aethiops) and bristly rose slug (Cladius difformis). Rose slugs are the immature (larval) stage of sawflies, which are black to yellow-colored wasps.

Rose sawfly females make pockets or slits along the edges of rose leaves using their saw-like ovipositor (egg-laying devise), and insert individual eggs. Eggs hatch into larvae that look-like a slug. Larvae are 1.2 cm in length when fully grown and yellow-green in color, with an orange head (Figure 1). The larvae eventually fall on the soil surface to


pupate. Rose slugs overwinter as pupae in earthen cells created by the larvae. There is usually one generation per year in Kansas. Bristly rose slug larvae are pale-green in color and 1.5 to nearly 2.0 cm long. The body is covered with numerous bristle-like hairs (Figure 2). There is generally one generation per year in Kansas.



Rose slug larvae feed on the underside of the leaf resulting in the leaves having a skeletonized appearance (Figure 3), eventually they create notches or holes on the leaf margins. Bristly rose slug larvae feed on the leaf undersides and also cause leaves to appear skeletonized (Figure 4). However, the larvae may chew larger holes than the rose slug.


Small infestations of either the rose sawfly or bristly rose slug can be removed by hand and subsequently placed into a container of soapy water. A forceful water spray will quickly dislodge sawfly larvae from rose plants; consequently, sawfly larvae are not able to crawl back onto rose plants. A number of contact insecticides (various active ingredients) may be effective in suppressing populations of both sawflies. However, the bacterium, Bacillus thuringiensis subsp. kurstaki (sold as Dipel or Thuricide) will have no activity on sawflies as this compound only works on caterpillars.




Brownheaded Ash Sawfly

–Dr. Raymond Cloyd

We continue to receive inquires throughout the state regarding green ash (Fraxinus pennsylvanica) trees being fed upon by populations of the brownheaded ash sawfly, Tomostethus multicinctus. This is a sporadic, early season, defoliating insect pest that appeared in Manhattan, KS in 2013. Populations feed extensively causing noticeable foliar damage and producing lots of frass (sawfly poop).

Brownheaded ash sawfly larvae, which resemble caterpillars, are 15 to 20 mm long and yellow-green in color with white and green stripes extending the length of the abdomen or back (Figures 1 and 2). They possess a brown head, and have prolegs on every abdominal

figure 1 cloyd

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segment with no crochets or hairs on the feet, which distinguishes them from caterpillars. Brownheaded ash sawfly larvae feed primarily on ash trees (green and white) (Figure 3).

figure 3 cloyd


Brownheaded ash sawfly pupates in the spring, with adults, which are wasp-like in appearance, emerging and females laying eggs inside leaves. Eggs hatch into larvae that congregate into massive groups at the base of trees (Figures 4 through 6), and feed from May through June. The larvae create shot-hole or pin-hole damage on leaves when young (Figure 7), but as they increase in size, the larvae consume entire leaves, especially terminal leaves (except the main veins), resulting in almost complete defoliation. The larvae are full-grown by June and shed a paper-like skin that is attached to the leaf (Figure 8). Larvae then migrate toward the base of the tree, enter the soil, and form a protective cocoon. Brownheaded ash sawfly overwinters as a full-grown larvae or pre-pupae within silken-lined cells located in the top portion of the soil at the base of previously infested trees. High numbers may congregate at the base of trees. There is one generation per year.

figure 4 cloyd

figure 5 cloyd

figure 6 cloyd

figure 7 cloyd

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In general, it is not warranted to spray an insecticide unless populations of brownheaded ash sawfly larvae are excessive and causing substantial damage to ash trees, which is contingent on the size or age of the tree. It is interesting to note that rainfall will quickly remove larvae from trees. In fact, a forceful water spray will dislodge larvae, which fall to the ground, and then are subsequently consumed by birds. If necessary, insecticides may be applied that contain the following active ingredients: acephate, bifenthrin, carbaryl, cyfluthrin, lambda-cyhalothrin, permethrin, petroleum oil (horticultural oil), potassium salts of fatty acids (insecticidal soap), and pyrethrins. These are all contact insecticides so thorough coverage of the tree canopy is important. Since this insect is a sawfly, insecticides such as Dipel or Thuricide that contain the active ingredient, Bacillus thuringiensis subsp. kurstaki will not be effective (refer to the previous issue of the newsletter). Be sure to assess the numbers of larvae present in order to determine if sufficient damage is occurring to justify the application of an insecticide.





Caterpillars and Sawflies

—Dr. Raymond Cloyd

Caterpillars are the larval stage of butterflies and moths; whereas the larval stage of sawflies is greasy looking and slug-like with the adults resembling wasps. Remember, caterpillars are in the insect order Lepidoptera (butterflies and moths) whereas sawflies are in the order Hymenoptera (ants, bees, and wasps). There are a number of caterpillars and sawflies that feed on horticultural crops. Common caterpillar pests include bagworms, eastern tent caterpillar, fall webworm, mimosa webworm, yellownecked caterpillar, walnut caterpillar, cutworms, European corn borer, and tomato/tobacco hornworms. Sawflies that feed on plants include the European pine sawfly, brownheaded ash sawfly, rose sawfly, and scarlet oak sawfly. Sawfly larvae resemble caterpillars; however, there is a difference.


There are two ways to distinguish between caterpillars and sawflies. First, sawfly larvae have prolegs (stubby-looking legs) on every segment of the abdomen whereas caterpillars are typically missing prolegs. In Figure 1, a caterpillar is on the top and sawfly on the bottom. Second, caterpillar larvae have hairs or crochets on their feet while sawfly larva do not have hairs or crochets on their feet, which is shown in Figure 2, with the caterpillar prolegs on the top and sawfly prolegs on the bottom. Why is it important to know the difference between caterpillars and sawflies? Well, one of the common insecticides recommended for use against young caterpillars is Bacillus thuringiensis subsp. kurstaki that is sold under many trade names including Dipel and Thuricide. This is a bacterium that must be ingested or consumed by the target insect pest, in this case, caterpillars, in order for death to occur. However, the insecticide has no direct effect on sawfly larvae. Therefore, it is important to correctly identify the “caterpillar-like” insect before selecting an insecticide. Specimens may be sent to Kansas State University, Department of Entomology (Manhattan, KS) or the Kansas State University Diagnostic Clinic in the Department of Plant Pathology (Manhattan, KS).


Alfalfa – Weevils and Aphids

—by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevils continue to be very active in north central Kansas. The recent cooler weather has slowed down development a little but they are still feeding. We determined development from larvae collected on 20 and 22 April. Here is what the population breakdown looks like:

20 AprilNo. larvae   23 April No. larvae
12 1st Instars 4
25 2nd Instars 16
15 3rd Instars 30
   numerous Pupae numerous

alfalfa weevil

So what does this mean? Alfalfa weevil larval feeding will continue for another 7-10 days, depending on the weather. Egg hatch and consequent larval feeding has been going on since 13 March in north central KS. Insecticides applied since that time have provided adequate protection, for the most part.

field trial

This photo shows KSU chemical efficacy trials with many different products being tested, and the obvious untreated plots plus the border around the plots. The rest of the field was treated with Stallion® by MKC in Abilene, KS and, as illustrated here seemed to work relatively well with 1 application. Remember, feeding will continue for at least another week and therefore treatment (or re-treatment) may still be appropriate.

Alfalfa aphids, mainly pea aphids, are becoming more numerous throughout north central Kansas. Treating for alfalfa weevils probably pretty much decimated the natural enemies/beneficials and they will not repopulate as quickly as the aphids migrate in to infest fields.