ENTM 340 Insect Pests of Trees Turf and Ornamentals�

C. Sadof� Purdue University

Insects that Discolor and Disfigure Leaves

I. Introduction to Insect Feeding Guilds

a. Herbivorous Guilds-� Insects that feed� on plants (to be covered in more detail later in the semester)

i. Insects that discolor or disfigure leaves� (leaf hoppers, plant bugs, lace bugs, spider mites.

ii. Producers of liquid excrement (honeydew), or wax (aphid, scales, plant hoppers.)

iii. Gall makers -� Those that live in specialized habitats (tumors) produced by plants.

iv. Defoliators � Insects that remove leaf tissue (Japanese beetles)

v. Leaf miners � Insects that live between the upper and lower surface of plants.

vi. Stem and trunk borers. � Insects that live inside plant stems and trunks. (Borers)

vii. Root feeders � Insects that feed in the soil on plant roots.

viii. Disease vectors� Insects that transmit disease (Elm bark beetles- Dutch Elm Disease, Elm Yellows, Ash Yellows, Bacterial leaf scorch)

b. Beneficial Guilds � Insects that feed on insects we consider to be pests.

i. Parasites- Insects complete their life inside a pests ( parasitic wasp)

ii. Predators � Insects that consume other insects ( lady beetles)

c. Decomposers� - Insects that feed on dead and decaying plant and animal matter.� ( termites, carpenter ants)

II.� Insects that Discolor or Disfigure Leaves

�� a. How are plant leaves discolored and disfigured by insects and mites?

� 1.� Discoloration � Chlorophyll is removed by insect or mite with piercing sucking mouthparts

� 2.� Disfigurement �

�� a.� Cells in damaged plant tissue fail to expand at same rate of other surrounding tissue.� This� can cause puckering or distortion.

�� b.� Cells in damaged tissue swell faster than other tissues.

b.� How does this damage affect plant health?

�� 1.� Simple distortion alters aesthetics.� Extensive distortion can kill shoot tips and deform plant shape.

2.� Piercing/sucking insects can transmit disease when they move between plants.� (more on this in later lectures)�

�� - Ash yellows, Pierce�s disease of grape is vectored by leaf hoppers and sharpshooter leafhoppers

III. Disfiguring pests

Who disfigures?

Leafhoppers, plant bugs, lacebugs, spider mites

�� A. Leafhoppers� ( Order Hemiptera, Suborder: Homoptera:� Family Cicadellidae)

�� 1.� Feed on vascular tissue and/or spongy mesophyll.

�� a.� Species feeding on vascular tissue of leaves cause distortion.

�� b.� Species feeding on mesophyll cause discoloration

�� 2.� Examples.

�� a. . Vascular feeder.� Potato leafhopper:� Empoasca fabae.

�� Hosts:� Succulent leaves of many species.� Big problem on red maples.�

�� Damage:� Leaf curl and reduced shoot elongation.

�� Biology:� Winters south near Gulf of Mexico. Migrates to green forages in �� April.� Moves to� trees in early June after hay is cut, or fields of tall weeds �� are mowed.

�� Control: �Apply insectides before injury is seen, and IF threshold is �� reached.� 3 hoppers / shoot/tree.�� Nurseries should spray before June � mowings. Pyrethroids are most effective.�

�� b.� Mesophyll feeders/egg layers:

�� Rose Leaf hopper:� Edwarsiana rosae

�� Host: �Rosaceae in spring, other species in summer

�� Damage:� Leaf stippling.� Excessive egg-laying and feeding can kill plant.

�� Biology:� Winter as eggs in canes of cultivated and wild rose. Pimple like dot indicates eggs are present.� Completes first generation on rose than moves to other hosts.

�� Control:� Early spring application of pyrethroid insecticide, or systemic application of imidacloprid in cultivated rose where infestation has been a problem.

�� c.� Other minor leafhoppers of note

�� White apple leaf hopper Typhlociba pomaria

�� Sharpshooter leaf hoppers� Graphocephala spp

�� Distinctive coloration,-� important in grapes.

Plant Bugs� :� Order Hemiptera� Suborder Heteroptera.

��

Four lined plant bug-� Poecilocapsus lineatus

�� Host:� 250 species of deciduous woody and perennial plants.

�� Damage:� Circular holes

�� Biology: Winter as egg clusters in slits of stems. 30 days from egg to adult. One generation per year.

�� Control:� 2% Insecticidal soap or oil to kill nymphs.

�� Insect growth regulators, neem

�� Conventional foliar insectides, pyrethroids effective.

�� Systemic:� imidacloprid in fall.

Honeylocust plant bug:� Diaphnocoris chlorionis

�� Damage:� Distortion as feeds on unfurling leaves

�� Biology: 1 generation per year.� Starts in May ends by June 30. Winters as eggs on plant twigs.

�� Control:� Use threshold of 1 plant bug per compound leaf. Early season use can cause spider mite outbreaks.�� Problematic 1 out of every 4 years.

�� Conventional foliar insectides, pyrethroids effective .

�� Systemic:� Imidacloprid in fall.

Eastern Ash plant bug. Tropidosteptes amoenus

�� Host: Green ash

�� Damage:� Discoloration and black tarspots on leaves. Reddish brown nymphs.

�� Biology.� 2 generations per year starting when leaves unfold in May and again in July.� Winter as eggs on loose bark.

��

Tarnished plant bug: Lygus lineaolaris:

�� Host: 385 spp of trees including conifers, perennials.�

�� Damage:� holes and distortion.

�� Biology: Eggs laid in stems of plants herbaceous plants flowering herbs.

�� 25 days from egg to adult.� 2-5 generations/ year.

�� Control same as Fourlined plant bug.

BoxElder Bugs-� Boisea trivittatus

� Host:� Boxelder��

� Damage:� Distortion, and nuisance.

�Arthropods Causing Discoloration (contd.)

Lacebugs:� Order Hemiptera� Suborder Heteroptera� Family Tingidae

�� Host:� Many species� See table 18 Johnson and Lyons.

�� Damage and Diagnosis:� Bleaching of leaf undersides.� Tarspot excrement.�

�� Eggs laid embedded in leaves.

�� Biology:� Winter as adults on or near hosts.� Eggs laid on leaves in spring. 2-5 generations per year depending on species and latitude.

Control:� Many natural enemies including favored by presence of floral resources and shade:� Work done on azalea lacebug (Kris Bremen-Georgia)� indicates that planting in appropriate habitat and allowing up to 20% discoloration will foster eventual decline of population due to biological control.

� predatory bugs

� lacewing

� spiders

� ground beetles

Chemical control: Use biorationals when possible.� 2% oil, soap, neem.

�� Imidacloprid works well when applied in fall to target spring generation.

Downside of imidacloprid use is potential mite outbreaks due to its impact on beneficial hemipteran predators minute pirate bugs that eat mites but take occasional drinks of plant sap. .� .

Mites:

Basic Biology of mites.�

Tetranychoid (spider) mite

Life cycle

Egg -> larva (six legs)->protonymph -> deuotonymph ->adult

�Deutogyne= resting stage�

Males pointy abdomen, Females rounded abdomen

Damage

Feeding causes stippled spots on leaf surface.� Eggs and webbing often present on leaf undersides.

Some Common spider mites

See http://www.entm.purdue.edu/entomology/ext/targets/e-series/EseriesPDF/E-42.htm� for details

Warm season� = Daytime T > 85 F

� Two spotted spider mite

� Honeylocust spider mite

� Oak red mite

� European Red mite

Cool season� = Daytime T < 85 F

� Spruce spider mites

� Southern Red mite

� Boxwood Mites

Rust Mites

Life cycle

Egg = Larva- protonymph- deutonymph->adult � cigar shaped mites.

Damage and Diagnosis

Feeding causes fine stippled spots on leaf surface, or leaf distortion (Gall formers are extreme destortors that will be discussed later.� Small, elongate, clear mites visible with 20x handlens.

Some Common Injurious Rust mites

� Privet rust mite

� Hemlock eriophyid

� Baldcypress rust mite

Managing Spider Mites

Biological control is critical

Reduce use of early season insecticides, via thresholds for other pests
When possible use selective insecticides against early season pests that kill spider mite predators
Refrain from using imidacloprid on plant species prone to mite problems (e.g. honeylocust) due to growing body of evidence that suggests predaceous plant bugs like minute pirate bugs, are killed when they drink plant sap)
Use selective miticides that do not kill predators or the rust mites that feed them.� (Apple literature)

Miticides

Rescue type � Kills all spider and rust mites and natural enemies in ornamental plantings.

Talstar,

Scimitar, Battle,

Avid (also labeled for interiorscape),

Sanmite (also labeled for interiorscape)

Short residuals that suffocate and disrupt membranes-

Oil, soap, cinnamite?, garlic oil? ( ?= marginal effectiveness)

Selective Easy on Beneficials� 3 types:

1.� Kills mobile stages of spider mites and clover mites, NOT rust mites, broad mites or flat mites that feed predators

� Floramite �Exterior Landscapes only

2. Kills eggs and newly hatched spider mites and clover mites, NOT rust mites or predators

� Ovation �Greenhouse, nursery , landscape

� Hexygon � All sites but interiorscapes

3. Kills mobile stage of� most mites, but less toxic on beneficials

Vendex� (48 hr REI)

Review Questions:

How do potato leafhoppers tend to damage red maples and why is this more of a problem in rural areas where alfalfa is grown, or in weedy nurseries?
What threshold can nursery producers use to guide their sprays against this pest?
Why is it important to use thresholds to manage honeylocust plant bugs in urban areas?
What is the relationship between early season applications of broad spectrum insecticides and outbreaks of honeylocust spider mites?
Which stages of the lacebug can killed by a contact insecticide?� ��
Although fall application of the systemic insecticide gives great control of lacebugs, it occaisionaly has been associated with spider mite outbreaks.� Why?
Distinguish between cool season and warm season spider mites.
Some rust mites are pests, others cause minor injury.� How does the presence of these rust mites early in the season foster the development of predators that reduce the more devastating spider mite injury later in the season.� Explain how this phenomenon works to make Floramite and Ovation a better miticide.