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Introduction to Applied Entomology, Lab 10

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Introduction to Applied Entomology, Lab 10 Landscape Insects This laboratory session covers selected insects of trees, shrubs, and turf. To provide some structure for a very broad range of plants and insects, the specimens and materials provided in this lab session are arranged in broad categories -- defoliators, sap-sucking insects, gall-makers, wood borers and bark beetles, and turf insects. Within these groups a few common examples are presented as representatives of many, many more species with similar life histories. In the previous lab on field crop insects, specific sampling methods and thresholds were summarized because the damage and the economic impact of that damage are moderately well established for field crop pests. Well defined thresholds for control of landscape insects are much less common. Defoliators eastern tent caterpillar, Malacosoma americanum (Fabr.) (Lepidoptera: Lasiocampidae), and fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae) gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lasiocampidae) bagworm, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae) Sap-sucking insects leafhoppers, including potato leafhopper, Empoasca fabae (Harris) (Hemiptera: Cicadellidae) aphids (Hemiptera: Aphididae) scale insects, including cottony maple scale, Pulvinaria innumerabilis, (Rathvon) (Hemiptera: Coccidae), pine needle scale, Chionaspis pinifoliae (Fitch) (Hemiptera: Diaspididae), and oystershell scale, Lepidosaphes ulmi (Linnaeus) (Hemiptera: Diaspididae) Gall-makers hackberry psyllid, Pachypsylla celtidismamma (Riley) (Hemiptera: Psyllidae) horned oak gall wasp, Callirhytis cornigera (Osten Sacken) (Hymenoptera: Cynipidae) maple bladder gall and maple spindle gall mites, Vasates spp (Acari: Eriophyidae) Wood borers and bark beetles Longhorned beetles (Coleoptera: Cerambycidae): Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) and pine sawyers, Monochamus spp. Metallic wood boring beetles (Coleoptera: Buprestidae): emerald ash borer, Agrilus planipennis Fairmaire, and bronze birch borer, Agrilus anxius Gory ash/lilac borer, Podosesia syringae (Harris) (Lepidoptera: Sesiidae) bark beetles (Coleoptera: Curculionidae: Scolitinae): smaller European elm bark beetle, Scolytus multistriatus (Marsham), and mountain pine beetle, Dendroctonus ponderosae Hopkins Turf insects White grubs (Coleoptera: Scarabaeidae): annual white grub / masked chafer, Cyclocephala spp., and Japanese beetle, Popillia japonica Newman Sod webworms, Crambus spp. and others (Lepidoptera: Crambidae) In addition to these pest species, a few other insects of common interest are presented with this lab: Honey bees, bumble bees, carpenter bees, and sweat bees Yellow jackets and the bald-faced hornet 1 Defoliators 1. Eastern tent caterpillar and fall webworm Among the most common defoliators of trees and shrubs in Illinois are the eastern tent caterpillar, and the fall webworm. Tent caterpillars hatch in the spring from overwintered eggs, and larvae feed on trees as they first leaf out. Fall webworms overwinter as pupae, and moths emerge and lay eggs in early summer. Larval "nests" of the fall webworm become evident in late summer. Above left: Eastern tent caterpillar egg mass (Univ. of Illinois). Above center: tent caterpillars on webbing (Univ. of Wisconsin). Above right: Eastern (L) and forest tent caterpillar larvae (Ohio State Univ.). Below: Eastern tent caterpillar moth. Above: Fall webworm adult(left), larva (center), and webbing (right) (Oklahoma State University). For the eastern tent caterpillar, notice how egg masses surround a small twig and are covered with a shiny, dark brown coating. Eastern tent caterpillars secrete webbing or “tents” at the crotch of branches, and although the larvae rest within these tents, they leave them to feed on exposed foliage 2 anywhere on the host plant. In contrast, fall webworm larvae make nests at the tips of branches, and they feed on the foliage enclosed within their webbing. Outbreaks of tent caterpillars have been linked to mare reproductive loss syndrome in Kentucky. It appears that mares accidentally consume larvae and that the hairs on the larvae imbed in the lining of the alimentary canal and trigger bacterial infections that lead to miscarriages (http://www.ca.uky.edu/gluck/NewsMedAlertETC.asp). In most instances infestations of tent caterpillars or fall webworms are unsightly but not extremely harmful to the host trees. These insects can be controlled by removing nests (of fall webworm) or tents when larvae of tent caterpillars are resting on the webbing. Bacillus thuringiensis kurstaki (or aizawai) (Bt) is often recommended where insecticides must be used because sprays containing this bacteria are toxic only to caterpillars. References: Bessin, R. 2003. Eastern Tent Caterpillar. http://www.ca.uky.edu/entomology/entfacts/ef423.asp Mazzey, K., and M. Maziuk. Undated. Fall Webworm. http://woodypests.cas.psu.edu/FactSheets/InsectFactSheets/html/Fall_Webworm.html 2. Gypsy moth. Another well-known example of a Lepidopteran defoliator is the gypsy moth. This insect was introduced into North America in 1869 by a French naturalist trying to start a new silk industry. It has since spread to threaten a wide range of deciduous trees. It winters in the egg stage, and eggs may be laid on a variety of surfaces ... including travel trailers, moving vans, and other vehicles. As a result, its movement to new areas is aided by its hitch-hiking as well as its local dispersal. This hitch-hiking dispersal is especially important because adult females do not fly (even though they have wings). Left: Gypsy moth adult male (darker) and female (Penn State Univ.) Center: Female and egg mass (US Forest Service). Right: Gypsy moth larva (US Forest Service). Read the brief fact sheet provided at this station to understand more about this insect. The web site that presents this fact sheet (at http://www.fs.fed.us/ne/morgantown/4557/gmoth/) includes links with more information on its life history, its natural enemies, its management, and its historic and predicted spread. The maps presented here are taken from this web site. 3 Reference: Liebold, S. 2003 and updates. Gypsy Moth in North America. http://www.fs.fed.us/ne/morgantown/4557/gmoth/ 4 3. Bagworm. We usually think of Lepidopterans as butterflies or moths with well developed wings and as larvae that crawl around, quite visible on leaf surfaces. There are lots of exceptions to this generalization, however, and the bagworm is a common one. Bagworm larvae construct cases of foliar debris around themselves and feed from within this protective "bag". Females remain “larvaiform” and mate at the opening of their larval case, then they lay eggs (500 – 1,000 apiece) within it. In central Illinois, bagworms are most common on arborvitae and similar conifers, but they also may feed on several common broad-leafed trees as well. Left: bagworm larva and bag (University of Nebraska). Right: adult male (E.D. Cashatt, Illinois State Museum). Like many other arthropods that are wingless as adult females, bagworms still have a means of dispersal other than crawling. Young larvae, upon hatching from overwintered eggs, spin a silken thread and hang from it to attach to passing animals or to be windblown to new locations – this “ballooning” behavior is not unlike that seen in the twospotted spider mite. Hand-picking is often advised as a means of controlling bagworms on relatively small plants. Because larvae are concealed in a bag constructed of plant debris, they are not highly susceptible to conventional insecticides. Applications of insecticides that contain Bacillus thuringienis (kurstaki or aizawai) can be the most effective, as larvae consume spores and toxins when they feed on treated foliage. References: Mazzey, K., and M. Masiuk. Undated. Bagworm. http://woodypests.cas.psu.edu/FactSheets/InsectFactSheets/html/Bagworm.html 5 Sap-sucking Insects Below are a few examples of the many sap-sucking insects that infest trees and shrubs, but indeed only a very few. For the families presented here (Aphididae, Diaspididae, and Coccidae), there are dozens if not hundreds of species that feed on trees and shrubs. Moreover, there are several other families of sap- sucking insects not presented here at all – plant bugs, spittlebugs/froghoppers, tree hoppers, plant hoppers, psyllids, and more. The reference displayed in lab – Insects that Feed on Trees and Shrubs, by Johnson and Lyon – provides a good overview and excellent photos. 4. Leafhoppers, including potato leafhopper. Many leafhoppers feed on a wide range of trees and shrubs. As noted in the lab on field crop insects, when leafhoppers insert their stylets into plant foliage, they may injure plants in one of four ways: (1) direct removal of cell contents, reducing photosynthate availability; (2) transfer of plant pathogens (3) injection of salivary toxins that kill cells around feeding sites; and (4) secretion of honeydew that supports growth of sooty molds on plants surfaces. In trees and shrubs, a few examples include: Rose leafhopper and white apple leafhopper feed on roses, apples, and many other plants, removing chlorophyll and leaving white, stippled areas on leaves; their honeydew secretions also contribute to sooty mold on foliage. Leafhoppers known as sharpshooters in the genus Graphocephala (including rhododendron leafhopper) are known to carry pathogenic microorganisms. The potato leafhopper is a serious pest of several trees and shrubs, including maples, birch, and redbud. The salivary toxins it injects
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