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If you already know what diseases or insects are of concern to you, NEWA is a fantastic resource that enables you to select your location and learn what the pressure is on a specific date. This tool also provides treatment recommendations and images to assist with diagnostics.

Cornell Scaffolds is a wonderful source of disease and insect information with yearly archives dating back to 1995. Many orchardists consider this an orchard management bible.

Below you will find our own disease and pest descriptions. The first list is our dirty dozen, the twelve that are seen most often. This is followed by a second list of orchard problems that are less prevalent but by no means uncommon.

Most Common Diseases and Insects

Click on the disease/insect name to see a full description with prevention and treatments.

Name	Affected Fruits	Symptoms (in brief)
Powdery Mildew	all fruit	White powder-like mold on leaves.
Any of the borers: American Plum Borer and Dogwood Borer, Peach Tree Borer and Lesser Peach Borer	all fruit	Visible holes or damaged areas in tree bark that ooze gum.
Plum Curculio	all fruit	Scarred, malformed, rotted fruit; crescent-shaped punctures on fruit skin; larvae in fruit.
Fireblight	apple and pear	Wilted shoots; well-defined areas of burnt-looking, dead foliage or bark; sticky amber ooze.
Woolly Apple Aphid	apple and pear	Cottony masses at the base of leaves; galls on shoots; general decline in tree health.
Apple Scab	apple	Spots on leaves; brown-black spots on fruit.
Cedar-Apple Rust	apple	Red-black spots and visible spores on undersides of leaves; defoliation.
Codling Moth	apple (and sometimes other fruit)	Puncture marks on fruit and holes in fruit surrounded by waste; larvae in fruit, rotted fruit.
Brown Rot AKA Blossom Blight	all stone fruit (cherry, peach, plum, apricot)	Brown, rotted bloom; water-soaked, sunken lesions on twigs; brown or grey mold on fruit.
Perennial Canker	peach (and sometimes other stone fruit)	An area of darkened and sunken bark that expands every year; amber ooze coming from this area.
Peach Leaf Curl	peach	Malformed, puckered and “bubbly” leaves that turn red; defoliation.
Black Knot	plum	Wartlike fungal growth that starts green and matures to black over several seasons.

Other Diseases and Insects

Name	Affected Fruits	Symptoms (in brief)
Alternaria Leaf Blotch	Apple	Purple-brown leaf spots, defoliation.
Anthracnose Canker and Bullseye Rot	Apple	Cankers on wood; spotted leaves; circular areas of rot on fruit.
Apple Blister Spot	Apple	Black freckles on fruit skin.
Apple Maggot	Apple	Pocked and rotted fruit, maggots in fruit.
Bitter Pit	Apple	Circular blemishes on fruit surface that develop during storage.
Pear Psylla	Pear	Tiny cicadalike insects; sooty mold and russetting on fruit surface; defoliation and stunting.
Pear Scab	Pear	Spots on leaves; fruit malformation and spots on fruit that develop into dark cracked areas.
Pseudomonas	Pear	Darkening and die-back of blossom clusters.
Bitter Rot	Apple, Pear	Circular brown lesions on fruit with rot developing into the fruit.
Black Rot or Blossom End Rot or Frogeye Leaf Spot	Apple, Pear	Frog-eye leaf spots, defoliation; branch cankers; red-black lesions on fruit.
Brown Marmorated Stink Bug	Apple, Pear	Stippling on leaves; pitted, scarred, or rotted fruit.
Quince Rust	Apple, Pear	Deformed fruit and purple lesions on fruit; visible spore sacs on fruit.
Bacterial Canker of Stone Fruit	Peach, Plum, Nectarine, Cherry, Apricot	Spotted or shot-holed leaves; darkened areas of wood, sappy ooze.
Bacterial Spot	Peach, Plum, Nectarine, Cherry, Apricot	Spotted or shot-holed leaves; dark spots on fruit.
Cherry Leaf Spot	Cherry	Spotted or shot-holed leaves, defoliation; small, flavorless fruits.
Crown Gall	Apple, Peach, Plum, Pear, Nectarine, Cherry, Apricot	Gall (warty growth) on roots or lower trunk.
Phytophthora (Collar Rot, Crown Rot, Root Rot)	Apple, Peach, Plum, Pear, Nectarine, Cherry, Apricot	General sickly tree; discolored cambium toward the roots and discolored roots.
Replant Disease	Apple, Peach, Plum, Pear, Nectarine, Cherry, Apricot	Sickly, stunted trees with shortened internodes; necrotic, discolored and stunted roots.
San Jose Scale	Apple, Peach, Plum, Pear, Nectarine, Cherry, Apricot	Bark that is grey, crusted, or scaly; reddened tissue beneath the bark; loss of vigor.

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Fruit Tree Diseases & Insects: Diagnostics

Most Common Diseases and Insects

Other Diseases and Insects

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