Diagnosing Plant Problems: Insects and Other Arthropods Hodges and Ellis. December 2006. Update, August 2008. NPDN Publication No. 0008

National Plant Diagnostic NetworkNational Plant Diagnostic Network

Diagnosing Plant Problems:Insects and Other Arthropods

Hodges and Ellis. December 2006.Hodges and Ellis. December 2006.Update, August 2008.Update, August 2008.NPDN Publication No. 0008NPDN Publication No. 0008

MODULE 4 – Diagnosing Plant Problems: Insects & Arthropods

Insect Diagnosis

Focuses on classic, morphology based taxonomy.

Often requires an expert taxonomist for species-level identification.

Limited resources for diagnosticians.

Quality of sample submitted is important!


How is an Insect Identified to Species?

First Detectors (County Extension Agents, Crop Consultants)

Extension Diagnostic Specialists (at Land

Grant Universities)

Taxonomic Specialists (usually federal, state, or university employees)

Species Identification Confirmed


Signs and Symptoms of Damage

• Over-development of tissues• Necrosis of tissue• Types of arthropod feeding damage

- Stippling- Chlorosis- Sooty Mold- Leafmining- Leaf Defoliaters- Spider Mites- Borers- Root Damage

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Photo 1: Paul Weston, Cornell University, www.forestryimages.orgPhoto 2: Jim Occi, BugPics, www.forestryimages.org Photo 3: Petr Kapitola, Forestry and Game Management Research Institute - Czechia, www.forestryimages.orgPhoto 4: Jerald E. Dewey, USDA Forest Service, www.forestryimages.org

http://www.forestryimages.org/images/768x512/9005050.jpg


Signs and Symptoms

Over-development of tissues

• Some insect and mite species can induce gall formation on a variety of host plant structures.

• Gall-makers are generally host plant specific.

A mite gall, Aculops laevigata on willow

Photo: William M. Ciesla, Forest Health Management International, www.forestryimages.org

Photo: Petr Kapitola, Forestry and Game Management Research Institute - Czechia, www.forestryimages.org

Gall Mite Damage

Eyespot Gall


Signs and SymptomsOver-development of

tissues• How do you know if an

insect has caused this damage?

• Closely examine plant deformation.

• Cut open gall.• Exit holes, frass, empty

larval chambers, etc.• Rear insects to adult

stage.

Photo: Ronald F. Billings, Texas Forest Service, www.forestryimages.org

cynipid gall wasps

Photo: Jerry A. Payne, USDA Agricultural Research Service, www.forestryimages.org

oriental chestnut gall wasp


Signs and SymptomsOver-development

of tissues• Can insect or mite galls

cause serious damage to host plants?

Yes, heavy infestations can negatively effect overall plant health and reduce the aesthetic value of ornamentalcrops.

ash flower gall mite damage Photo: A. Steven Munson, USDA Forest Service, www.forestryimages.org


Signs and SymptomsOver-development

of tissues Non-insect bacterial and fungal galls may resemble insect galls.

Crown gall bacterium causes galls on roots, crowns and stems.

Fungi can also form large galls that superficially resemble the crown gall bacterium.

Photo: USDA Forest Service - Ogden Archives, USDA Forest Service, www.forestryimages.org

bacterial gall on douglas-fir


Signs and SymptomsNecrosis of tissue

Dieback-insect damage• Feeding damage from

several types of insects can lead to limb dieback.

• Death of the host may result.

Loblolly pine killed by southern pine beetle

larch casebearer damage

Top Photo: Petr Kapitola, Forestry and Game Management Research Institute - Czechia, www.forestryimages.org

Bottom Photo: Ronald Billings. Texas Forest Service. http://www.forestryimages.org/.


Signs and Symptoms

Types of Insect Feeding Damage Insects with piercing- sucking mouthparts cause stippling and/or chlorosis on the host.

Example groups: aphids, true bugs, hoppers, scale insects, whiteflies, etc.

Azalea lace bug damage

Top Photo: Clemson University - USDA Cooperative Extension Slide Series, www.forestryimages.org

Bottom Photo: John A. Weidhass, Virginia Polytechnic Institute and State University, www.forestryimages.org

wax scale


Signs and SymptomsTypes of Insect Feeding

Damage• Presence of sooty mold

may suggest an infestation of honeydew producing insects such as scales, mealybugs, whiteflies, or aphids.

• Presence of ants may also be an indicator of these insects!

Photo: Scott Tunnock, USDA Forest Service, www.forestryimages.org

sooty mold on grand fir


Signs and Symptoms

Types of Insect Feeding Damage

Leafmining• Insects that produce

characteristic “mines” in leaves by feeding.

• Formed by various insects including flies, wasps, moths, and beetles.

Aspen blotchminer

Bottom Photo: Minnesota Department of Natural Resources Archives, Minnesota Department of Natural Resources. http://www.forestryimages.org/

columbine leafminer

Top Photo: Lisa Ames, UGA, www.forestryimages.org


Signs and SymptomsTypes of Insect Feeding

Damage

Leaf Defoliaters• Damage caused to a

plant by insect feeding.

• “Skeletonizing” results when the veins or the “skeleton” of the leaf is left behind.

Bottom Photo: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, www.forestryimages.org

maple trumpet skeletonizer

oak skeletonizer

Top Photo: James Solomon, USDA Forest Service, www.forestryimages.org


Signs and SymptomsTypes of Arthropod

Feeding Damage

Spider Mites

• Leaf damage includes flecking, bronzing, and/or scorching of leaves.

• Several natural enemies. Most problematic in heavy insecticide use areas.

gorse spider mite damage

Photo: Eric Coombs, Oregon Department of Agriculture, www.forestryimages.org

twospotted spider mite

Photo: Mississippi State University Archives, Mississippi State University, www.forestryimages.org


Signs and SymptomsTypes of Insect

Feeding DamageBorers• Insects that bore into a

host trunk, stem, or twig as part of their life cycle.

• Damage often results in weakening or killing the host.

A Lepidopteran stalk borer, Papaipema nebris, in silver maple Photo: James Solomon. USDA Forest Service.

http://www.forestryimages.org/


Signs and SymptomsTypes of Insect

Feeding Damage

Roots• Don’t forget to look

for potential insect damage on roots!

Aspen root girdler

Bottom Photo: Robert L. Anderson, USDA Forest Service, www.forestryimages.org

Scarab beetle larval feeding damage on root system of pine

Top Photo: Ostry, Mike. USDA Forest Service. http://www.forestryimages.org/


Insect IdentificationKnow Common Pest Arthropod Groups!• Numerous lepidopteran caterpillars (ex.

armyworms, cutworms)• Beetles (Order Coleoptera): numerous leaf-

feeding and wood-boring pests• Sawflies (Order Hymenoptera)• Various flies (Order Diptera)• Various insects with piercing-sucking

mouthparts including scales, mealybugs, whiteflies, aphids, psyllids, hoppers, various other members of the Order Hemiptera.

• Spider Mites


Insect Identification• Know the difference

between pests and beneficials!

• There are several predatory or parasitic beneficial insects!

Pest - southern green stink bug

Top Photo: David Cappaert, www.forestryimages.org

Beneficial-a predatory stink bug

Bottom Photo: Lawrence Abrahamson, State University of New York, www.forestryimages.org


• Amanda C. Hodges, Ph.D., [email protected]

SPDN Assistant Director, University of Florida

• Amanda M. Ellis, [email protected],

University of Florida, SPDN

Authors

mailto:[email protected]

mailto:[email protected]


• This publication can be used for non-profit, educational use only purposes. Photographers retain copyright to photographs or other images contained in this publication as cited. This material was developed as a core training module for NPDN First Detector Training. Authors and the website should be properly cited. Images or photographs should also be properly cited and credited to the original source.

• Publication Number: 0008• Publication Date: December 2006

Publication Details

Documents

Diagnosing Plant Problems: Insects and Other Arthropods Hodges and Ellis. December 2006. Update, August 2008. NPDN Publication No. 0008