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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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
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
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
Rusty spot is recognized only on the fruit. The earliest symptoms on young green fruit appear as small, orange-tan spots. K. Peter.
Peach Disease - Rusty Spot - Articles Articles

Peach Disease - Rusty Spot

Kari A. Peter, Ph.D.

Minor issue in Pennsylvania and is caused by the same fungus as apple powdery mildew. Loring is a susceptible variety. More
Plum Pox Virus - Replanting Stone Fruit in Sites Previously Affected by PPV
Plum Pox Virus - Replanting Stone Fruit in Sites Previously Affected by PPV - Articles Articles
Lifting the PPV quarantine in Pennsylvania offered the opportunity for a “fresh start” and growers must plan carefully to get the most from their investment. More
Stone Fruit Disease - Prunus Stem Pitting
Stone Fruit Disease - Prunus Stem Pitting - Articles Articles
Prunus stem pitting, caused by the tomato ringspot virus, is an important disease of all stone fruits. It is also called prune brownline and constriction disease. More
A thermometer that records the maximum and minimum temperature is extremely useful for determining degree hours.
Tree Fruit Diseases - Predicting Infection Periods to Apply Protection - Articles Articles
This article will help you manually determine infection periods for certain diseases. Also included is a table listing coppers available to manage bacterial spot during cover sprays. More
Source: William M. Brown Jr., Bugwood.org
Peach Disease - Powdery Mildew of Peach, Nectarine, and Apricot - Articles Articles
Powdery mildew, Sphaerotheca pannosa, sometimes called rose mildew (it affects some woody ornamentals), is not often serious. More
Source: Bugwood.org
Tree Fruit Disease - Phytophthora Collar, Crown and Root Rots - Articles Articles
Phytophthora collar, crown, and root rots, Phytophthora cactorum, continue to be a major cause of tree death in Pennsylvania orchards. These rots can affect both pome and stone fruit. More
Although the fruits remain susceptible through harvest, it is usually only infections that occur during the shuck split to pit hardening stage of development that have an opportunity to show symptoms at harvest. Photo by K. Peter.
Peach Disease - Scab - Articles Articles

Peach Disease - Scab

Kari A. Peter, Ph.D.

Peach scab, Cladosporium carpophilum, is an important disease in warm, humid peach-producing areas of the world. More
Infected leaves, which begin appearing in mid-May, are easily distinguished from healthy leaves in that they are puckered and thicker than normal. Deformed areas are red to yellow at first and then turn brown. Photo by K. Peter.
Peach Disease - Peach Leaf Curl - Articles Articles

Peach Disease - Peach Leaf Curl

Kari A. Peter, Ph.D.

The peach leaf curl fungus, Taphrina deformans, destroys early peach leaves. More
In recognition of their work in eradicating Plum Pox Virus, research and industry partners received a USDA award. Pictured is Jim Lerew, one of the local growers recognized in the ceremony.
Plum Pox Eradication in PA - A Blueprint for Future Plant Disease Outbreaks - Articles Articles
In an increasingly global society, the transmission of viruses and various diseases has been facilitated through our own technologies. More
Stone Fruit Disease Control Toolbox - Fungicide and Antibiotic Timing
Stone Fruit Disease Control Toolbox - Fungicide and Antibiotic Timing - Articles Articles
Timing of a fungicide application in relation to disease development is important for achieving the best results. More
Stone Fruit Disease Control Toolbox - Fungicide and Antibiotic Efficacy
Stone Fruit Disease Control Toolbox - Fungicide and Antibiotic Efficacy - Articles Articles
Fungicides should be selected based on stone fruit diseases to be controlled and product efficacy for each. Growers can prevent resistance to fungicides by alternating chemicals by FRAC code group. More
Bacterial spot on peach fruit. Photo by S. Bardsley.
Peach Disease - Bacterial Spot Differentiation from Copper Injury - Articles Articles
It can be confusing to discern between bacterial spot disease and copper injury. This article describes offers guidance to avoid the pitfalls of using copper for disease control. More
The Cytospora canker fungus attacks the woody parts of stone fruit trees through bark injuries and pruning cuts, and through dead shoots and buds. Photo by K. Peter.
Stone Fruit Disease - Cytospora Canker - Articles Articles
Cytospora canker is one of the most destructive diseases of peaches, nectarines, apricots, sweet cherries, and plums in Pennsylvania. More
Young galls are light in color and with age become dark and hard, ½ inch to 3 or 4 inches in diameter. Photo by B. Butler.
Tree Fruit Disease - Crown Gall - Articles Articles

Tree Fruit Disease - Crown Gall

Kari A. Peter, Ph.D.

Crown gall is caused by a bacterium, Agrobacterium tumefaciens, and affects apples, pears, quince, peaches, nectarines, apricots, plums, and cherries. More
Fruit infections begin as small brown spots, and under wet and humid conditions, ash-gray to brown tufts of fungus develop over the surface of the infected area. Photo by S. Bardsley.
Stone Fruit Disease - Brown Rot - Articles Articles

Stone Fruit Disease - Brown Rot

Kari A. Peter, Ph.D.

Brown rot is caused by the fungus Monilinia fructicola. It affects peaches, apricots, nectarines, plums, and cherries. More
Infected leaves have angular spots, most numerous at the tip ends and along midribs. Photo by K. Peter.
Stone Fruit Disease - Bacterial Spot - Articles Articles
Bacterial spot, caused by the bacterium Xanthomonas arboricola pv. pruni (formerly Xanthomonas campestris pv. pruni), occurs in most countries where stone fruit are grown. More
Bacterial spot on peach fruit. Photo by S. Bardsley.
Stone Fruit Disease - Bacterial Spot, Refining Disease Management - Articles Articles
Bacterial spot, Xanthomonas arboricola pv. pruni, is a difficult disease to manage. More
Source: University of Georgia Plant Pathology, University of Georgia, Bugwood.org
Peach Disease - Anthracnose - Articles Articles

Peach Disease - Anthracnose

Kari A. Peter, Ph.D.

Most years, anthracnose, caused by two Colletotrichum species, is considered a minor disease of peach. If left unchecked, this disease that attacks peach fruit can cause serious fruit rot infection. More
If ripe fruit are not kept cold, Rhizopus rot can take over very quickly. (Photo: K. Peter)
Peach Disease - Rhizopus Rot - Articles Articles

Peach Disease - Rhizopus Rot

Kari A. Peter, Ph.D.

Management strategies are discussed for mitigating the postharvest disease Rhizopus rot on peaches and nectarines. More
Postharvest fungicide sprays are necessary to prevent defoliation from cherry leaf spot. Photo: K. Peter, Penn State
Getting the Upper Hand on Tree Fruit Diseases in July - News News
Conditions may be optimal for several fungal and bacterial pome and stone fruit diseases in July. More
Be vigilant and scout for apple scab! Photo: K. Peter, Penn State
June Diseases for the Grower Radar - News News
Diseases for the fruit grower radar and their management strategies are discussed as we wrap up May and begin June. More
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