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
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: Bruce Watt, University of Maine, Bugwood.org
Stone Fruit Disease - Powdery Mildew of Cherry and Plum - Articles Articles
The disease is caused by Podosphaeria oxyacanthae, one of the common species of the powdery mildew group of fungi. 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
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
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
The disease first emerges on upper sides of leaves as tiny, red to purple, circular spots. After the leaves become infected, they turn yellow and fall. Photo by K. Peter.
Cherry Disease - Cherry Leaf Spot - Articles Articles
Cherry leaf spot, caused by the fungus Blumeriella jaapii (formerly Coccomyces hiemali), attacks the leaves, leaf stems, fruit, and fruit stems of tart, sweet, and English Morello 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
Photo by G. Moorman
Plum Disease - Black Knot - Articles Articles

Plum Disease - Black Knot

Kari A. Peter, Ph.D.

Black knot of plum, caused by the fungus Dibotryon morbosum, is well-named because of the characteristic black, warty knots it forms on branches of infected trees. 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
Gumming is frequent in the spring and fall, when the disease is most active. Photo by K. Peter.
Cherry Disease - Bacterial Canker - Articles Articles

Cherry Disease - Bacterial Canker

Kari A. Peter, Ph.D.

While bacterial canker, Pseudomonas syringae, can occur on all stone fruit trees and on apple and pear blossoms, it is only important in the Northeast on sweet and ornamental cherry trees. 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
Watch out for brown rot on sweet cherries. Photo: K. Peter, Penn State
Protecting Cherries From Brown Rot - News News
As the sweet cherry harvest commences, there are concerns about brown rot. Management options are discussed. More
Dormant copper sprays are encouraged to help keep diseases in check. (Photo: K. Peter)
Disease Management Strategies For The Grower Radar - News News
Consider applying dormant sprays soon to manage fungal and bacterial diseases this season. More
Protect any trees still in bloom: Fire blight conditions ideal April 29 through May 2. (Photo: K. Peter)
Fire Blight, Apple Scab, Rust, Plus Others: Be On Alert! - News News
Conditions are optimal for fire blight, apple scab, and rust infections. Growers are encouraged to keep trees protected. Other diseases for the fruit grower radar are also discussed. More
Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org
Home Orchards: Table 2.4. Plant Protection Materials - Articles Articles
Informational table showing pesticides available for home garden use on various fruit crops. More
Home Orchard: Table 2.3. Pesticide Application Amounts
Home Orchard: Table 2.3. Pesticide Application Amounts - Articles Articles
Informational table showing pesticide application amounts on fruit. More
Black Knot of Plum in the Home Fruit Planting
Black Knot of Plum in the Home Fruit Planting - Articles Articles
Black knot of plum, caused by the fungus Apiosporina mobosa, is well-named because of the characteristic black, warty knots it forms on the branches of infected trees. More
Brown Rot of Stone Fruit in the Home Fruit Planting
Brown Rot of Stone Fruit in the Home Fruit Planting - Articles Articles
Brown rot can cause a blossom and twig blight, a canker, a leaf infection, and a fruit rot. More
Cherry Leaf Spot in Home Fruit Plantings
Cherry Leaf Spot in Home Fruit Plantings - Articles Articles
Cherry leaf spot, caused by the fungus Blumeriella jaapii, attacks the leaves, leaf stems, fruit, and fruit stems of tart, sweet, and English Morello cherries. More
Cytospora Canker of Stone Fruits in the Home Fruit Planting
Cytospora Canker of Stone Fruits in the Home Fruit Planting - Articles Articles
Cytospora canker, also known as perennial canker, peach canker, Valsa canker, and Leucostoma canker, can cause trees in young orchards to die. Infected trees in older orchards slowly decline. More
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