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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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
The canker typically exhibits a few pink or coral fruiting structures of the fungus in mid-summer. Photo by S. Weikert.
Apple Disease - Nectria Twig Blight - Articles Articles

Apple Disease - Nectria Twig Blight

Kari A. Peter, Ph.D.

Nectria twig blight, caused by the fungus Nectria cinnabarina, is a minor disease that breaks out occasionally. More
The disorder is characterized by irregularly shaped necrotic blotches on the leaves, limited by the veins. Affected leaves turn yellow in about 4 days and subsequently fall off the tree. Photo by K. Peter.
Apple Physiological Disorder - Necrotic Leaf Blotch - Articles Articles
The cause of necrotic leaf blotch of apple is not known, and it is considered a physiological disorder. The disorder is most common on Golden Delicious worldwide. More
Source: Edward Beasley, University of Georgia, Bugwood.org
Blueberry Disease - Mummy Berry - Articles Articles
Mummy berry, Monilinia vaccinii-corymbosi, is the most serious and widespread disease of highbush, lowbush, and rabbiteye blueberries. It is most serious following moist, spring weather conditions. More
The fungus survives in the soil as spores. Populations of these spores in the soil increase one to two months after fruit have been harvested. Photo by K. Peter.
Apple and Pear Disease - Mucor Rot - Articles Articles

Apple and Pear Disease - Mucor Rot

Kari A. Peter, Ph.D.

Mucor rot is a fungal disease of apples and pears. The disease is a postharvest storage problem. More
The fungi enter the developing fruit through an opening in the calyx. Photo by K. Peter.
Apple Disease: Moldy Core - Articles Articles

Apple Disease: Moldy Core

Kari A. Peter, Ph.D.

Moldy core is caused by several different fungal pathogens. Many cultivars of apples are affected, including Delicious, which is very susceptible. More
Photo 1. Early symptom of orange rust. Photo: K. Demchak
Bramble Disease - Managing Orange Rust - Articles Articles

Bramble Disease - Managing Orange Rust

Kathy Demchak, mahfuzur rahman

Orange rust, Gymnoconia nitens, is a systemic disease, any plants propagated from infected plants will also be infected. More
Source: Frank Louws, NCSU.
Strawberry Disease - Leather Rot - Articles Articles
Leather, or crown rot, Phytophthora cactorum, infection is favored by warm, wet weather and poorly drained soil. The fungus attacks berries in the field at all stages of growth. More
Source: Edward Sikora, Auburn University, Bugwood.org
Strawberry Disease - Leaf Spots - Articles Articles
A wide array of leaf spots infect strawberries, including birds-eye leaf spot, black leaf spot, septoria leaf spot, cercospora leaf spot, alternaria leaf spot, red spot, and angular leaf spot. More
Source: B. Martin. USDA-ARS Horticulture Crops Research Unit
Bramble Disease - Leaf Curl Virus - Articles Articles
Raspberries are affected more severely by leaf curl than are blackberries. More
Protect your fruit: bitter rot on apple can wreak havoc in the orchard. (Photo: K. Peter)
Apple Disease - Rots, Keeping Apples Clean - Articles Articles
A review of managing pre- and postharvest apple fruit rots is discussed. Alternative rot management strategies are included. More
Late season fungicides needed to protect against fruit rot in storage. Photo: K. Peter, Penn State
Apple Disease, Pre- and Post-harvest - Keep Apples Free From Fruit Rot - Articles Articles
Management considerations are discussed for mitigating pome fruit rots before and after harvesting. More
Once established in the wound, the fungus can quickly spread from infected fruit to adjacent healthy fruit during storage. Photo by K. Peter.
Apple and Pear Disease - Gray Mold - Articles Articles

Apple and Pear Disease - Gray Mold

Kari A. Peter, Ph.D.

Gray mold, Botrytis cinerea, is the most important postharvest disease of pears and is second to blue mold in importance to apple. More
Photo by Kathy Demchak.
Strawberry Disease - Gray Mold - Articles Articles
Gray mold, or botrytis blight, Botrytis cinerea, causes a greater loss of strawberry flowers and fruit than any other disease. It is found on green as well as ripening and harvested fruit. More
Pear Disease - Fire Blight
Pear Disease - Fire Blight - Articles Articles
Fire blight is the most serious pear disease in the eastern United States. Caused by the bacterium Erwinia amylovora, the disease can attack some 75 species of plants of the rose family. More
A characteristic symptom of shoot blight is the bending of terminal growth into the shape of a shepherd’s crook. Photo by K. Peter.
Apple Disease - Fire Blight - Articles Articles

Apple Disease - Fire Blight

Kari A. Peter, Ph.D.

Fire blight, Erwinia amylovora, is a destructive disease that can attack some 75 species of plants of the rose family. More
Apple and Pear Disease - Fire Blight, Dormant Removal of Cankers
Apple and Pear Disease - Fire Blight, Dormant Removal of Cankers - Articles Articles
When it comes to managing fire blight, the first line of defense is good sanitation, which is removing the overwintering source for the bacteria: cankers. More
University of Georgia Plant Pathology, University of Georgia, Bugwood.org
Grape Disease - Eutypa Dieback - Articles Articles
Eutypa dieback, Eutypa lata, is a fungal disease appearing as cankers on trunks and arms of infected grapevines. It is one of the most destructive diseases on the woody tissue of grapes. More
Grape Disease - Downy Mildew
Grape Disease - Downy Mildew - Articles Articles
Downy mildew, Plasmopara viticola, can infect berries, leaves and young shoots. It occurs wherever it is wet and warm during the growing season. 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
Apple Disease Control Toolbox - Fungicide Timing
Apple Disease Control Toolbox - Fungicide 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
Apple Disease Control Toolbox - Fungicide and Antibiotic Efficacy
Apple Disease Control Toolbox - Fungicide and Antibiotic Efficacy - Articles Articles
Fungicides should be selected based on apple 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