Plant Disease Identification and Control

Information on plant disease identification and control, including rot, freeze damage, rust, blight, mold, scales, bacteria, viruses, fungus, wilt, mildew, gall, mites, moths and cankers. Tips on integrated pest management and herbicide summaries.

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Hail damaged fruit need protection from fruit rots. Photo: T. Ford, Penn State
Managing Fruit Rots This Season - News News

Managing Fruit Rots This Season

07/26/2018

Fungicide re-applications are necessary since several inches of rain have fallen the last few days. Management considerations are discussed for mitigating pome and stone fruit rots. More
Tree Fruit Disease Toolbox - Fungicide Resistance Management
Tree Fruit Disease Toolbox - Fungicide Resistance Management - Articles Articles
Resistance has sometimes resulted in pest-management-program failures. Below are presented tactics to help delay resistance to fungicides. More
Tiny, black, spherical structures are produced on stalks above the white mold. Each of these contains thousands of spores that are released to float in the air. Photo by K. Peter.
Stone Fruit Disease - Rhizopus Rot - Articles Articles

Stone Fruit Disease - Rhizopus Rot

Kari A. Peter, Ph.D.

Rhizopus rot, caused by Rhizopus nigricans, can be very destructive to harvested fruit. More
Source: Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org
Apple Disease - Blossom End Rot - Articles Articles

Apple Disease - Blossom End Rot

Kari A. Peter, Ph.D.

Blossom end rot of apple, is caused by various fungi (Sclerotinia sclerotiorum, Botrytis cinerea, Botrysphaeria obtusa) just before or during petal fall. More
Stay Alert for Oak Wilt!
Stay Alert for Oak Wilt! - Articles Articles

Stay Alert for Oak Wilt!

Sandy Feather

Oak wilt was not known in New York before 2008, but foresters and arborists are managing it there now. More
Scales on new growth and fruit produce deep purplish-red coloration in the tissue. Photo by G. Krawczyk.
Tree Fruit Insect Pest - San Jose Scale - Articles Articles

Tree Fruit Insect Pest - San Jose Scale

Grzegorz (Greg) Krawczyk, Ph.D.

The San Jose scale, Quadraspidiotus perniciosus, is a pest of fruit trees, but it attacks many other trees as well as shrubs. More
Source: Steve L. Brown, University of Georgia, Bugwood.org
Tree Fruit Insect Pest - Potato Leafhopper - Articles Articles
Potato leafhopper, Empoasca fabae, is a migratory pest of many crops. It feeds on leaves of rapidly growing apple terminals and may aid in spread of fire blight. More
Apple rust mites. Photo: David Biddinger
Tree Fruit Mite Pest - Apple Rust Mite - Articles Articles

Tree Fruit Mite Pest - Apple Rust Mite

Grzegorz (Greg) Krawczyk, Ph.D.

Apple rust mite, Aculus schlechtendali, is commonly found, but is rarely an important pest of apple in Pennsylvania. More
Protect tart cherries during bloom to prevent cherry leaf spot infection.
Tree Fruit Diseases - Spring Control Strategies - Articles Articles
May is the battleground month for disease management: be on alert for apple scab, fire blight, powdery mildew, rust, cherry leaf spot, brown rot, and bacterial spot infection conditions. More
Blister mites become active at bud break, migrate to the tender, new leaves, and burrow beneath the epidermis of the undersides of leaves to feed. This results in a gall, or blister, in which the eggs are laid. Photo by G. Krawczyk.
Tree Fruit Mite Pests - Pear Blister Mite and Pear Rust Mite - Articles Articles
Pearleaf blister mite, Phytoptus pyri, and pear rust mite, Epitrimerus pyri, are similar species, virtually invisible to the naked eye, that often are common on unsprayed trees. More
Be sure to protect your fruit from rots: bitter rot on Red Delicious. (Photo credit: K. Peter)
Tree Fruit Diseases - Managing Pre- and Postharvest Rots - Articles Articles
A big disease concern is keeping fruit free of rots as they are nearing the home stretch of the season. More
Symptoms typical of severe anthracnose infection on blackberry.
Blackberry Fruit Disorders - Effects on Fruit Quality - Articles Articles
This article discusses some common blackberry fruit issues, including whitening of drupelets, drupelet reddening, insect feeding injury, canker diseases and spotted wing drosophila. More
External rot is first visible as small, slightly sunken, brown spots that may be surrounded by a red halo. As the decayed area expands, the core becomes rotten and eventually the entire fruit. Photo by K. Peter.
Apple Disease - White Rot - Articles Articles

Apple Disease - White Rot

Kari A. Peter, Ph.D.

The white rot fungus, Botryosphaeria dothidea, often referred to as “Bot rot” or Botryosphaeria rot, is most important on apple trees, but it also attacks crabapple, pear, grape, and chestnut. More
Source: SCRI-Dundee , Scottish Crop Research Institute, Bugwood.org
Bramble Diseases - Viruses - Articles Articles
Virus diseases can seriously damage brambles, especially raspberries, and can affect the lifetime of a planting. More
Raspberry Mosaic Virus. Photo by K. Demchak.
Bramble Diseases - Virus Control - Articles Articles
Control measures for virus diseases in brambles are aimed mainly at removing sources of the virus from within and around the planting. More
Strawberry Disease - Verticillium Wilt
Strawberry Disease - Verticillium Wilt - Articles Articles
Verticillium wilt of strawberry, caused by the soilborne fungus Verticillium albo-atrum, infects more than 300 kinds of cultivated plants. More
Bramble Disease - Verticillium Wilt
Bramble Disease - Verticillium Wilt - Articles Articles
Verticillium wilt is caused by two common soilborne fungi (Verticillium dahliae and Verticillium albo-atrum) that have a wide host range and attack more than 300 woody and herbaceous plants. More
Plum Pox Virus Success Story
Plum Pox Virus Success Story - Articles Articles

Plum Pox Virus Success Story

John Halbrendt, Ph.D.

The successful eradication of PPV could not have been achieved without the cooperation of fruit growers, PDA, USDA/APHIS, USDA/ARS, Penn State, and homeowners. More
Necrotic leaf blotch, which is a physiological disorder and not a disease, has been manifesting throughout the area and is predominantly seen on the leaves of Golden Delicious, as well as those cultivars with Golden Delicious as a parent.
Tree Fruit Diseases - Preharvest - Articles Articles

Tree Fruit Diseases - Preharvest

Kari A. Peter, Ph.D.

Management is discussed for controlling the physiological disorder necrotic leaf blotch on apple and for pre-harvest peach diseases. More
Left: gray mold; right: anthracnose fruit rot.
Strawberry Disease - Fruit Rot Protection Begins at Bloom - Articles Articles
Our two main targets for bloom time protection of strawberries are gray mold/ Botrytis fruit rot, and, if you are growing susceptible varieties like Chandler, anthracnose fruit rot. More
Strawberry Disease Photos - Angular Leaf Spot Bacterium
Strawberry Disease Photos - Angular Leaf Spot Bacterium - Articles Articles
Angular leaf spot is caused by the bacterium Xanthomonas fragariae. More
Pear Disease - Stony Pit
Pear Disease - Stony Pit - Articles Articles

Pear Disease - Stony Pit

Kari A. Peter, Ph.D.

Stony pit of pear is presumed to be caused by a destructive virus, but the virus has not been isolated. Affected fruit are unsightly and unmarketable. More
Source: Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org
Bramble Disease - Spur Blight - Articles Articles
Red and purple raspberries are more affected by spur blight, Didymella applanata, than black raspberries. Blackberries appear to be immune. More
Photo by K. Peter.
Pear Disease - Sooty Mold - Articles Articles

Pear Disease - Sooty Mold

Kari A. Peter, Ph.D.

Sooty mold fungi of the genus Capnodium cause an unsightly blackening over the surface of fruit and leaves. More
Spores of the fungi are windblown into and throughout the orchard; fruit infection can occur any time after petal fall but is most prevalent in mid- to late summer. Photo by K. Peter.
Apple Diseases - Sooty Blotch and Flyspeck - Articles Articles
Affecting apple, crabapple, and pear trees, sooty blotch and flyspeck of apple are separate diseases, but both are normally present on the same fruit. More
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