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Extension Entomology

Month: May 2017

Rose Sawflies

–by Dr. Raymond Cloyd

 

There have been numerous inquiries regarding insects feeding, and completely devouring rose plants. These are sawflies, and there are at least two species that attack roses this time of year: the rose slug (Endelomyia aethiops) and bristly rose slug (Cladius difformis). Rose slugs are the immature or larval stage of sawflies, which are black to yellow-colored wasps.

Rose sawfly females create pockets or slits along the edges of rose leaves with their saw-like ovipositor (egg-laying devise), and insert eggs. Larvae hatch from eggs and resemble small slugs. Larvae are 1.2 cm long when full-grown and yellow-green, with an orange head (Figure 1). Larvae eventually fall onto the soil surface and pupate. Rose slugs overwinter as pupae in earthen cells created by the larvae. Bristly rose slug larvae are pale-green and 1.5 to 2.0 cm in length. The body is covered with numerous bristle-like hairs (Figure 2). There is generally one generation per year in Kansas for both species.

Figure 1. Rose Sawfly Larvae Feeding on Rose Leaf (Author-Raymond Cloyd, Kansas State University)

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

 

Figure 2. Bristly Rose Slug Larva Feeding On Leaf Underside of Rose (Author-Raymond Cloyd, Kansas State University)

Figure 3. Damage on Rose Plant Caused By Rose Slug Larvae Feeding (Author-Raymond Cloyd, Kansas State University)

Figure 4. Damage on Rose Leaf Caused By Rose Slug Larvae Feeding (Author-Raymond Cloyd, Kansas State University)

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

 

 

 

 

European Fruit Lecanium Scale

–by Dr. Raymond Cloyd

European fruit lecanium scale (Parthenolecanium cornii) is noticeable on the twigs and branches of certain trees and shrubs in landscapes. Damage associated with this scale, which depends on the extent 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. Honeydew attracts ants and serves as a substrate for black sooty mold. Moreover, honeydew can drip onto vehicles parked underneath infested trees leaving unsightly residues.

 

Figure 1. Close-Up of European Fruit Lecanium Scale (Author-Dan Potter, University of Kentucky).

 

Figure 2. European Fruit Lecanium Scale on Branch (Author-Dan Potter, University of Kentucky).

European fruit lecanium scales are dark brown and 1/8 to 1/4 inches in diameter when mature (Figures 1 and 2). Some scales may have white or dark markings on the body. European fruit lecanium scale overwinters as an immature on twigs and branches with maturation occurring in spring. Females lay eggs underneath her body from May through June. Eggs hatch into small tan-colored crawlers. The duration of egg hatch can last several days depending on temperature. Crawlers migrate to leaf undersides and 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.

European fruit lecanium scale management involves timely applications of insecticides. Applications need to be made when crawlers are present because the crawlers are the most vulnerable life stage to insecticide sprays. Mature scales possess a shell-like covering, which protects them from exposure to insecticides. Repeat applications will be required because the eggs do not all hatch simultaneously with eggs hatching over a three to four-week period. The best time to apply insecticides is late June through early July when crawlers are feeding on leaves, which enhances their exposure to any spray residues. There are a number of insecticides, with contact activity, that may suppress populations of the European fruit lecanium scale. However, many have broad-spectrum activity and consequently will kill many natural enemies (parasitoids and predators). In general, 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 and Matthew McKernan of Wichita, KS for bringing to my attention that European fruit lecanium scale was active.

 

 

Euonymus Scale

–by Dr. Raymond Cloyd

We are receiving inquiries regarding euonymus scale (Unaspis euonymi) crawlers on landscape plants such as evergreen euonymus (Euonymus japonica) and Japanese pachysandra (Pachysandra terminalis). Euonymus scale overwinters as a mated female on plant stems. Eggs develop and mature underneath the scale, and then hatch over a two- to three-week period. The newly hatched crawlers, noticeable migrating along the stem, start feeding near the base of host plants. Crawlers can also infect adjacent plants by being blown around on air currents, resulting in infestations not being detected until populations are extensive and damage is noticeable later on in the season. Leaves eventually become spotted with yellow or white areas. Plants located near foundations, walls or parking areas are more susceptible to euonymus scale than plants growing in open areas that receive sunlight and air movement. Moreover, the variegated forms of euonymus are more susceptible to euonymus scale than the green forms.

 

 

Figure 1. Euonymus Shrub Heavily-Infested with EuonymusScale (Author-Raymond Cloyd, Kansas State University)

Heavy infestations of euonymus scale can ruin the aesthetic appearance of plants (Figure 1) resulting in complete defoliation or even plant death. Females are dark brown, flattened, and resemble an oystershell whereas males are elongated, ridged, and white in color (Figures 2 and 3).

 

Figure 2. Female and Male Euonymus Scale on Leaf (Author-Raymond Cloyd, Kansas State University)

 

 

Figure 3. Female and Male Euonymus Scale on Leaf (Author-Raymond Cloyd, Kansas State University)

Males are typically located on leaves along leaf veins and females reside on the stems. There may be up to three generations per year in Kansas.

Cultural practices such as pruning-out heavily infested branches—without ruining the aesthetic quality of the plant—is effective in quickly reducing euonymus scale populations. Be sure to immediately discard pruned branches away from the area. If feasible, avoid planting Euonymus japonica in landscapes since this species is very susceptible to euonymus scale. Winged euonymus (Euonymus alata) is less susceptible to euonymus scale, even when adjacent plants are infested. Insecticide applications conducted from May through June, when the crawlers are most active, will help alleviate problems with euonymus scale later on in the season. Insecticides recommended for suppression of euonymus scale populations include: acephate (Orthene); pyrethroid-based insecticides [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) oil. Check plants routinely for the presence of crawlers, which will help time insecticide applications. Three to four applications, in general, should be performed at seven to 10-day intervals although this is contingent on the level of an 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® or Zylam®) may provide suppression of euonymus scale populations when applied as a drench to the soil due to the high water solubility (39,000 ppm) of this systemic insecticide.

Euonymus scale is susceptible to many natural enemies (e.g. parasitoids and predators) including: braconid and ichneumonid wasps, ladybird beetles, green lacewings, and minute pirate bugs. However, natural enemies may not provide enough mortality (‘killing power’) to substantially impact “high” populations of euonymus scale. Furthermore, insecticides such as acephate (Orthene®), and many of the pyrethroid-based insecticides, such as; bifenthrin (Talstar®), cyfluthrin (Tempo®), and lambda-cyhalothrin (Scimitar®) are directly harmful to natural enemies, so applications of these pesticides may disrupt any natural regulation.

 

I need to acknowledge Jeff Otto of Wichita, KS for informing me that euonymus scale was active in South-Central KS.

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

Beneficial Insects – Instructional Videos

— Dr. J.P. Michaud – Hays, KS

We have produced a series of short, instructional videos on the various beneficial insects contributing to biological control of sugarcane aphid.

These videos describe how to identify various life stages of the important groups of predators and provide information about their basic biology, ecology and life history.

 

Lady beetles: https://youtu.be/3kz2OcF76pU

Hoverflies: https://youtu.be/9GxUWy1Rk2E

Lacewings: https://youtu.be/q0R6D-PX8-k

The interplay between host plant resistance to aphids and biological control: https://youtu.be/KxI7CQ7DYt0

 

Termites vs Ants

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Termite and ant colonies have been very active over the past week or so and are producing reproductives or ‘swarmers’.  We have seen flying/fluttering individuals every place we have stopped throughout north central Kansas, as long as it was between about 10am and 4pm.  Thus, we have received many calls regarding the differences between reproductive ants versus reproductive termites, in both cases often just referred to as ‘swarmers’.  This swarming behavior seems to be initiated about the same time each year for both ants and termites as the same type of warm, wet weather evidently triggers both.  Thus, it is imperative to be able to distinguish the two as they do very different kinds of damage and consequently require different management plans.

Termite reproductives, or swarmers, are dark brown to black, with transparent or translucent wings of equal size, and the dark body is cigar shaped, having no noticeable body divisions or waist.  Termite antennae are straight and lack a club on the end.  Ant reproductives, or swarmers, are also dark brown to black with transparent or translucent wings, but the fore or front wings are a little longer than the bottom or back wings.  Ant antennae are elbowed, coming out perpendicular to the head then bending forward at a 90 degree angle.

For more information on ant identification, biology, and control, please visit:  https://www.bookstore.ksre.ksu.edu/pubs/MF2887.pdf

For more information on termite identification, biology, and control, please visit: http://www.bookstore.ksre.ksu.edu/pubs/mf722.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.

 

 

 

 

 

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