Pear
Symptom Cause  
Leaves curled/discolored; honeydew on undersides of leaves, sooty mold forms
Aphids
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Beak marks penetrate skin, fruit eaten
Birds
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Many holes in trunk and branches; small limbs girdled sawdust at holes
Borers
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Skeletonized leaves
Cankerworms
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Much foliage is eaten starting from top of tree down
Caterpillar of Tussock Moth
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Ends of twigs die and fall off
Cicadas
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Roots, stems and/or crowns develop tumors (galls); outer layer turns brown and corky.
Crown Gall
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Fruit falls, crescent –shaped cuts in skin of fruit
Curculios
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Foliage and fruit disappears below ten feet
Deer
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Blossoms turn brown, die; young twigs wilt and are blackened in color, tips die.
Fireblight
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Leaves riddled with shot holes; plant weakens
Flea Beetles
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Small misshapen fruits
Fruit Fly Larvae
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Small hole in fruit; sawdust-material around hole; interior of fruit dark, rotted.
Larvae of Codling Moth
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Tip of leaves brown, internal larvae trails visible.
Leaf Miners
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Holes in flowers; leaves rolled up
Leafrollers
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Cottony white masses on roots, stems, branches leaves; reduced plant vigor
Mealybugs
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Deformed or dwarf flowers
Plant Bugs
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Young tree seedling wilt, roots gnawed, plant dies
Pocket Gophers
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Leaves yellowed and may drop
Psyllids
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Orange or brown pustules on leaves
Rust (on plants)
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Weaken plant, stunting growth, fewer blooms and fruit.
Sawflies
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Leaves yellow, drop; bumps on leaves and stems; sometimes sticky material on leaves
Scale
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Black mold on leaves and stems of plant.
Sooty Mold
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Leaves stippled, yellow, dirty; webbing on interior stems of plant
Spider Mites
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Webbed nest in branches filled with caterpillars
Tent Caterpillars
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Leaves discolored; black fecal spots on underside of leaf.
Thrips
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