Woody Plant Pests

Table of Contents

1. Terminology/Definitions
2. Molt and Instar
3. Scale Insects
4. Mealybugs
5. Beetles
6. Plant Bugs
7. Leafhoppers/Planthoppers
8. Aphids/Plantlice
9. Fungus
10. Bacteria
11. Nematodes
12. Disease
13. Pathogen
14. Disease Cycle
15. Integrated Pest Management
16. Monitoring
17. Indicator Plants
18. Cultural Pest Control
19. Biological Pest Control
20. Plant Phenology Species
21. Ornamental Plant Pest Diagram

Terminology/Definitions:

Insect: a small animal without a backbone

a) with a hardened, external skeleton (cuticle)
b) distinct body regions (b1- head, b2- thorax, b3- abdomen)
c) one pair of segmented antennae
d) one pair of compound eyes
e) 3 pairs of segmented legs
f) 1 or 2 pairs of wings on thorax (some adults wingless: ants, aphids)

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Egg

Moth larva and beetle larva

Pupa

Adult moth and adult beetle

Egg mass

Aphid nymph and plant bug nymph

Aphid adult and plant bug adult

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Molt and Instar:

Insects grow by periodically shedding their external cuticle and expanding their newly produced tissues before the new hardens. "Molting" is the process of loosening/shedding the old cuticle and producing a larger replacement. "Instar" is the period of time between molts (about 4-8).

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Description of Pest			Picture of Representative Pest
Scale Insects: round, very sluggish/immobile insect covered in waxy secretion or hard covering, reduced antennae, sucking mouthparts found below, adult females most common; feeding causes accumulation of honeydew and sooty mold. (e.g. Magnolia scale).
Mealybugs: oblong shaped, slow-moving, whitish covering of wax, margins often adorned with waxy filaments; sucking mouthparts, feeding causes accumulation of honeydew and sooty mold (e.g. Taxus mealybug)
Beetles: largest group of insects, thickened front wings (elytra) cover the larger membranous hind wings (flying), chewing mouthparts, larval stage, (e.g. viburnum leaf beetle, weevils)
Plant Bugs: small, base of front wing is thickened while tips are membranous, sucking mouthparts feed on plant sap, feeding causes stipuling and bronzing of foliage; includes Lygus bugs and Fleahoppers (e.g. Four-lined plant bug)
Leafhoppers/Planthoppers: small, front wings uniformly membranous, wings held rooflike over body during resting, sucking mouthparts feed on plant sap causing stipuling on leaves, carry viruses, includes spittlebugs, cicadas (e.g. Rose leafhopper)
Aphids/Plantlice: small, winged and wingless, pear-shaped, cluster on stems or leaves, pair of tubes (cornicles) at end of abdomen, sucking insects that produce honeydew, cause leaves to curl, shrivel and yellow, may transmit viruses (e.g. Rose aphid)
Fungus: non-photosynthesizing organism that produces enzymes and absorbs its food; produces branched tubes called hyphae (vegetative growth) and spores (reproductive growth, I.D.)

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Bacteria:

microscopic, unicellular organisms, some reproduce with spores, most are non-photosynthesizing and must absorb food, only 100 species of bacteria incite diseases in plants (e.g. Bacterial canker of Lilac; Fireblight, Black knot)

Nematodes:

microscopic, worm-like animals, infest root tissue causing lesions, nodules; may also infest shoots (e.g. leaf nematodes cause black streaks between veins on many herbaceous ornamentals)

Disease:

any malfunctioning of host cells and tissues that results from irritation by a pathogen or environmental factor and leads to the development of symptoms. (e.g. leaf blight….fungus; leaf scorch….drought)

Pathogen:

an organism/entity that causes disease. (e.g. fungus, bacteria, virus, nematodes)

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Disease Cycle:

the chain of events involved in disease development. (e.g. peach leaf curl)

(Agriose, G.N. 1997. Plant Pathology. 4th Edition. California. USA.)

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Integrated Pest Management:

A decision-making process that integrates all available tools to reduce pest populations to an acceptable level in a cost-effective, environmentally rational manner. These tools include: Monitoring, Cultural Control (sanitation, weed control, cultivar resistance, irrigation i.e. good crop management), Physical Control (quarantine new plants, mechanical cultivation), Biological Control (parasites and predators), and Chemical Control (based on monitoring data, biorational products).

Monitoring:

Monitoring is the most important part of IPM. Walk around your production facility or landscape and inspect your plants for any signs of pests or symptoms of poor health. Lift up branches and inspect the underside of leaves, stems and twigs for disease symptoms (insects often hide out of site). Where foliage is wilting or yellowing, dig around the lower stem and roots for signs of chewing damage by soil inhabiting insects or root disease problems. Monitoring should be carried out on a weekly basis.

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Indicator Plants:

Indicator plants are those ornamentals which seem to attract specific pests first (i.e. Leafhoppers and Caragana sp.). These plants should be examined at the beginning if each monitoring cycle. By knowing your indicator plants, you can detect pest problems before they reach economically damaging levels.

Cultural Pest Control:

Remove infested plant material/pests from your plants and destroy, keep plants healthy (regular watering, fertilizer, mulching); use resistant varieties (e.g. powdery mildew and phlox)

Biological Pest Control:

Natural predators and parasites in the landscape; ladybird beetle (larvae and adults feed on aphids, mites, scale insects); lacewing (larvae feed on aphids and mites); hover flies, minute pirate bugs, assassin bugs, parasitic wasps and many more! Remember - when you spray an insecticide, you are also killing natural predators!

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Plant Phenology Species:

Calendar dates not useful since too much variation in seasonal temperatures; we use flowering and fruiting characteristics of common plants* in the landscape to indicate timing of insect life stages (e.g. when the saucer magnolia are in pink bud…. Cooley and Eastern spruce gall adelgids are vulnerable to insecticides)

*Norway maple, saucer magnolia, bridal wreath spiraea, common lilac, common horsechestnut, northern catalpa, Adam’s needle, Queen Anne’s lace, goldenrod

Ornamental Plant Pest Diagram

(Johnson, W.T. & H.H. Lyon. 1991. Insects that Feed on Trees and Shrubs. New York. USA)

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