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Entomology 462 Ornamentals Pests: Sucking Pests. David J. Shetlar, Ph.D. The “BugDoc”. The Ohio State University, OARDC & OSU Extension Columbus, OH. © October, 2004, D.J. Shetlar, all rights reserved. Woody Ornamental Pest Groups Sucking Pests. Thrips (Thysanoptera)

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slide1

Entomology 462

Ornamentals Pests:

Sucking Pests

David J. Shetlar, Ph.D.

The “BugDoc”

The Ohio State University,

OARDC & OSU Extension

Columbus, OH

© October, 2004, D.J. Shetlar, all rights reserved

slide2

Woody Ornamental Pest Groups

Sucking Pests

Thrips (Thysanoptera)

True Bugs (Hemiptera)

Plant/Leaf bugs, Lace Bugs

Bug-like Insects (Hemiptera)

Leaf/Plant/Tree hoppers, Psyllids, Aphids,

Whiteflies, Mealybugs, Scales

Mites (Acarina)

Spider mites, Eriophyid mites

slide3

Woody Ornamental Pest Groups

Sucking Pests - Signs

Plant Distortion -

Leaf & stem twisting & curling

Dead spots

Excrement Deposits -Tar spots - true bugs, lace bugs, thrips

Honeydew & Sooty Mold

Foliage Discoloration -

Spots & Stipples

Yellowing & Bronzing

slide4

Cuban Laurel (Ficus) thrips leaf distortion.

Honeylocust leaflet distorted.

Tarspots from lace bugs.

Sooty mold from scale honeydew.

slide5

Woody Ornamental Pest Groups

Sucking Pests - Thrips

  • Cause streaking of flowers or spotting of foliage.
  • Occasionally cause foliage distortion.
  • Usually produce tiny tar spots.
  • Have complicated life cycle with non-feeding “prepupa” and “pupal” stages.

eggs  nymph 1  nymph 2  “prepupa”  “pupa”  adult

(larva) (larva)

(Thrips specialists often call the nymphal stages “larvae” which should really be used with insects that have a complete life cycle!)

slide6

There are actually few thrips that are common pests of ornamental plants. The pear thrips occasionally attacks sugar maple in the spring. In this case, overwintered adults insert eggs in the veins of expanding maple leaves. The damage causes the leaves to distort and ragged holes may be formed.

Several species of flower thrips cause streaking and spotting of flower petals. These are most noticeable in roses and some perennials.

The greenhouse thrips commonly damages a variety of broadleaf evergreens in southern states. Attacks result in bronzed foliage. Upon close inspection, the leaves will be covered with tiny tarspots and numerous speckles where cell contents were removed by the thrips.

The privet thrips causes similar damage to privet in northern states. Leaves first appear yellowed and then turn bronze or brown.

The Cuban laural thrips causes severe stunting, discoloration and folding of ornamental figs.

slide7

Pear thrips on maple leaf.

Flower thrips on leaf. Note small tarspots and blanching due to cell contents being removed.

slide8

Woody Ornamental Pest Groups

Sucking Pests – Plant/Leaf Bugs

  • Usually feed by injecting salivary digestive juices into leaf tissues which cause round to irregular necrotic spots.
  • Adults form “tar spots” with excrement.
  • Heavy feeding by adults or nymphs on young foliage can cause severe foliar distortion.
  • Most overwinter as eggs inserted into host plant tissues though some overwinter as adults.
  • Adults have typical “bug” look.
slide9

Ash plant bug adult.

Fourlined plant bug, note damage below.

Tarnished plant bug, a general plant pest.

Tarnished plant bug damage & nymph.

slide10

Plant bugs are commonly called leaf bugs and almost all have the typical bug shape with a pentagonal pronotum, a triangular mesonotum, and a diamond shaped area where the membrane areas of both forewings cross.

Almost every plant has its own species of plant bug, but there are several species that are generalists feeders. The tarnished plant bug is common on a variety of woody shrubs, perennials and even annual flowers. The fourlined plant bug is common on smaller shrubs and perennials.

Most plant bugs produce irregular damage spots by liquefying leaf tissues with their salivary secretions during feeding. When damage occurs to young, expanding leaves, the leaves can be severely distorted and stunted.

The plant bugs produce tarspots rather than honeydew.

Controls are rarely necessary, and if needed, applications of contact pesticides should be made before the young nymphs have had sufficient time to cause extensive leaf damage.

slide11

Woody Ornamental Pest Groups

Sucking Pests – Lace Bugs

  • Pronotum and wings modified into highly reticulated (lacy) surface.
  • Nymphs usually spiny.
  • Produce “tar spot” excrement.
  • Usually remain in groups on leaf undersurfaces.
  • Feeding produces yellow speckles on leaf surfaces.
slide12

Azalea lace bug damage. Note conspicuous leaf speckling.

Typical lace bug adult. Note tar spots.

slide13

Lace bug nymphs.

Lace bugs that attack deciduous plants overwinter as adults. Those that attack broadleaf evergreens overwinter as eggs.

Sassafras lace bug adults. Most lace bug females attach their eggs to leaves with their excrement.

slide14

There are many species of lace bugs which attack a variety of deciduous and evergreen broadleaf trees and shrubs. Several species (e.g., the hawthorn lacebug) infest a large number of plants, but most species have rather limited host preferences.

Lace bugs that attack deciduous plants generally overwinter as adults under flaps of bark or in the leaf litter around their hosts. Lace bugs that attack broadleaf evergreens overwinter as eggs glued to host leaves with excrement (a tarspot like material).

Most species have several generations each season.

Almost all lace bugs live on leaf undersurfaces where they feed by removing the cell contents of several cells in any given area. This usually results in a small yellow to white spot appearing on the upper surface. Heavy feeding can cause general yellowing or blanching of host foliage.

Control can be achieved by using contact pesticides, including insecticidal soaps and oils, but these need to be directed to leaf undersurfaces.

slide15

Woody Ornamental Pest Groups

Sucking Pests - Aphids

  • Pear-shaped insects with long antennae and diagnostic cornicles on abdomen.
  • Most alternate between sexual and asexual forms.
  • Most alternate between spring hosts (usually woody plants) and summer hosts (usually annuals or herbaceous plants).
  • Asexual form females are parthenogenic (don’t mate) and ovoviviparous (give live birth).
slide16

Goldenrod aphids, winged and wingless forms.

Milkweed aphids. Note paired cornicles (black “tailpipes”) which produce an alarm pheromone not the honeydew.

slide17

White pine aphids.

Aphid eggs on pine needle.

Cinera pine aphids.

slide18

Birch leaf aphids. Note honeydew on leaf tip which is being eaten by carpenter ants. Ants often protect and move aphids around in order to “harvest” the honeydew. Aphids are often called “ant cows”!

Black bean aphids on winged euonymus leaves which they distort.

slide19

Generalized diagram of an aphid life cycle showing a species that alternates asexual and sexual forms along with alternation of hosts.

slide20

Woody Ornamental Pest Groups

Sucking Pests - Psyllids

  • Sometimes called jumping plantlice.
  • Adults look like miniature cicadas which jump.
  • Nymphs may look like flat scales.
  • Produce honeydew.

Acacia psyllid adults.

slide21

Boxwood psyllid nymph. The nymphs feed on expanding leaves, causing them to cup. The nymphs produce wax rather than honeydew.

Boxwood psyllid adults actively jump and fly when disturbed. They are known to occasionally bite when they land on human skin. Adults insert eggs into buds and die by mid-summer.

slide22

Woody Ornamental Pest Groups

Sucking Pests - Cicadas

  • Cicadas are commonly called “locusts” because our European forefathers believed them to be singing tree grasshoppers.
  • Cicada nymphs feed on the roots of plants.
  • Periodical cicadas take 13 or 17 years to develop, depending on the species.
  • Dog-day or annual cicadas take one to two years to develop.
  • Females damage small branches by inserting eggs.
slide23

Annual cicada adult.

Periodical cicada adult.

slide24

Cicada “shell” (actually the cast nymphal skin).

Periodical cicada adult emerging from nymphal skin.

Tree branches flagged by cicada egg laying.

slide25

Woody Ornamental Pest Groups

Sucking Pests - Leafhoppers

  • Wedge-shaped insects that run sideways and readily jump.
  • Nymphs and adults produce small white to yellow spots on leaves.
  • Produce honeydew, some “shoot” the honeydew some distance (these are often called sharpshooters).
  • A few transmit plant diseases.
  • Some cause stunting of plant growth – hopperburn.
slide26

Typical leaf speckling from rose leafhoppers.

Rose leafhopper nymph.

Rose leafhopper adult.

slide27

Phlox plants with puckered leaves, caused by leafhopper feeding.

Phlox leafhopper nymphs on leaf undersurface.

slide28

Woody Ornamental Pest Groups

Sucking Pests - Planthoppers

  • Usually wedge-shaped insects that are larger than most leafhoppers and jump when disturbed.
  • Nymphs and adults usually feed on stems and produce waxy threads.
  • Produce honeydew which is usually thrown some some distance from the insect(s).
  • Rarely cause damage.
slide29

A planthopper nymph among waxy filaments.

Cluster of planthopper adults.

slide30

Woody Ornamental Pest Groups

Sucking Pests - Spittlebugs

  • Nymphs excrete thick honeydew-like material in which bubbles are formed and the nymphs hide.
  • Adults are boat-shaped and can jump.
  • “Spittle” can drip onto foliage and encourage growth of sooty mold.
  • Instructor states that these insects should be called “anal-bubble-bugs” because they blow the bubbles in the spittle mass using a chamber in the anus!
  • Feeding punctures and moisture may assist diseases.
slide31

Pine spittlebug mass on Scotch pine branch.

Pine spittlebug adult emerging from nymphal skin.

slide32

Woody Ornamental Pest Groups

Sucking Pests - Mealybugs

  • Mealybugs are common on tropical and subtropical plants, but a few can survive temperate climates.
  • Adults and nymphs produce honeydew.
  • Many are parthenogenic but most produce eggs in waxy filamentous masses called ovisacs.

eggs in ovisac  nymph  “pupa”  winged adult male

 nymphlike female

slide33

Woody Ornamental Pest Groups

Sucking Pests - Scales

  • Scale insects are highly modified, often having lost all features that would identify them as insects. Adult females usually have no wings, functional legs or obvious segmentation.
  • Though there are about five families of scales, most divide them into soft scale or armored scale groups.
  • Many are parthenogenic and ovoviviparous but most produce eggs and have winged males.
slide35

Fletcher scale adults on arborvitae. Note characteristic shape.

Spruce bud scales which are commonly mistaken for branch buds.

slide36

Pine needle scale second instar nymphs and male “pupae” on needles.

Pine tortoise scale mature females on stem.

Pine needle scale winged male in search of an unmated female.

slide37

Cactus scale.

Black pine leaf scales.

Hemlock fiorinia scales.

Rose scales

slide38

Pine needle scale females. Note pinkish eggs at end of scale test (shell) and a settled crawler at upper left.

Group of pine needle scale settled crawlers (tan) and a couple of fresh crawlers (pinkish) in color.

slide39

Woody Ornamental Pest Groups

Mites

Spider Mites - Tetranychidae

Upper surface/ lower surface/ both

Warm-season & Cool-season

Eriophyid Mites - Eriophyidae

Rust Mites

Gall Mites

False Spider Mites - Tenuipalpidae

Privet mite - Citrus flat mites

slide40

Most spider mites can be grouped as “warm-season” or “cool-season” mites. Warm-season mites seem to perform best when temperatures are above 70°F, rainfall is sparse, but humidity is moderate. Cool-season mites do best when temperatures range between 45°F and 75°F. Warm-season mites generally build populations between mid-May through September while cool-season mites are most active between mid-March and mid-June and again between late September and early December.

Warm-season mites usually overwinter as dormant eggs (though the twospotted spider mite overwinters as females), while cool-season mites oversummer (aestivates) as eggs and also overwinter when daily temperatures generally go below freezing.

Each species can usually produce silk, but some produce more silk than others. Some species inhabit leaf upper surfaces while others inhabit the lower surface.

These mites feed by tearing small holes into cells and removing the contents. This produces tiny yellow to white speckles. Extensive feeding results in yellowing and eventually browning (=bronzing) of the foliage.

Most spider mites are controlled naturally by predators, but chemical controls are occasionally necessary to keep damage to acceptable levels. Thorough coverage is essential to success due to the small size of mites.

slide41

Honeylocust spider mites inhabit leaf undersurfaces.

Oak mites inhabit the upper leaf surface.

European red mites clustering to balloon to new plants.

European red mite overwintering eggs

slide42

The twospotted spider mite is a generalist feeder that also produces considerable webbing.

Twospotted spider mites prefer leaf undersurfaces. Note the small round eggs and small oval nymphs.

slide43

Spruce spider mite eggs and “trash” from silk, cast skins and old egg shells.

Spruce spider mites are typical cool-season mites. Note the small yellow speckles resulting from feeding. Affected trees turn yellow and bronze color.

slide44

Spruce spider mite populations (thick line) over the 1993 season in Columbus, OH. Note that the population of active mites disappears in early July due to several days with temperatures above 29°C (=86°F), a characteristic of a cool-season mite.

slide45

Hemlock rust mites are microscopic eriophyids that cause the foliage to appear yellowish or rust colored.

slide46

Woody Ornamental Pest Groups

Gall Makers

Open Galls -

Bladder, Spindle, Erineum

Vein, Petiole, Pocket

Closed Galls -

Bud, Vein, Leaf, Petiole

Apple, Spangle, Bulls-eye,

Bullet, Gouty, etc.

slide47

Open galls are produced by insects and mites that have sucking mouthparts. The galls have a natural opening through which the pests escape when it is time to leave the gall. This witch-hazel nipplegall has been cut down the middle. The aphids that live inside are visible as is the small hole at the bottom of the gall. This hole opens when the gall dries.

Closed galls are produced by insects that have chewing mothparts as larvae and/or adults. The galls are generally solid masses of host plant tissue in which the gall insect larva develops by eating some of the tissues or absorbing nutrients secreted by the tissues. The larva or adult gall insect has to chew an emergence hole through the gall tissues in order to emerge.

This oak apple gall has been cut in half to expose the wasp pupa inside the tissues.

slide48

Elm cockscomb galls are a type of bladder or purse gall produced by an aphid.

The Cooley spruce gall adelgid produces a pinecone shaped gall that is formed by swollen bases of needles. The young gall is on the left and the opened gall is on the right.

slide49

Oaks have over 300 different kinds of galls! This is a small sample – oak apple galls (upper left), oak bullet galls (above) and oak spangle galls (left). These are produced by gall wasps.

slide50

Woody Ornamental Pest Groups

Nuisance Pests

Stinging Pests –

bees, wasps, ants, caterpillars

Biting Pests -

thrips, plant/leaf bugs, psyllids

Household Invaders -

leaf-footed bugs, boxelder bugs, psyllids

carpenter ants & other ants

Mammals & Birds -

squirrels, raccoons, black birds

slide51

There are a number of pests that do little or no damage to their host plants, but they can occur in such numbers that they cause concern. Others may bite, sting or invade homes. These are considered to be nuisance pests.

The boxelder bug (above) and the pine leaffooted bug (right) are occasional house invaders and can be considerable nuisances in and around some homes.