Fusarium wilt is a common and lethal disease of mimosa (Albizia julibrissin)1, also commonly known as silktree. In the United States this disease occurs in the east from New York southward and also in Louisiana, Arkansas and California. Fusarium wilt is caused by the fungus Fusarium oxysporum forma specialis perniciosum. Albizia spp. are the only known host of F. oxysporum'' f.sp. ''perniciosum''. Fusarium oxysporum f. sp. perniciosum colonizes and clogs the tree’s vascular (water-conducting) tissue, and interferes with the movement of plant sap. This results in relatively rapid tree death.

Fusarium head blight (FHB), or scab, continues to impact small grain crops grown in Virginia. Caused primarily by the fungus Fusarium graminearum (also known as Gibberella zeae), this disease can negatively impact yield and grain quality.

Plant Disease Diagnostic Form

The most effective form of plant disease control in the landscape is prevention. Disease prevention can be as simple as choosing the right plant for the right place at planting time. This fact sheet was developed as a guide to shrubs that generally experience few problems in Virginia landscapes. Using these species for new plantings should help you avoid troublesome disease and insect problems in your landscape.

Many of the tree species commonly planted in Virginia landscapes suffer from disease problems. Although some diseases can be cured, most must be controlled on a preventative basis. The best option for new plantings is to choose species that have a low risk of developing disease. Listed below, in alphabetical order, are some choices of problem-free trees for Virginia landscapes.

Iris leaf spot (also called Heterosporium leaf spot) is the most common disease of iris in Virginia. It is caused by the fungus Cladosporium iridis (syn. Heterosporium iridis). Leaf spotting is most conspicuous on the upper half of the leaf following bloom. Although this pathogen is most common on bulbous iris, it can also cause severe damage to rhizomatous iris, and has also been reported on Gladiolus, Freesia and Narcissus species.

Botrytis blight is a common fungal disease that confronts the peony grower each spring. The fungus Botrytis cinerea blights stems, buds, and leaves and can cause plants to look unsightly, especially in wet springs. This fungus causes disease on a wide variety of herbaceous and woody ornamentals, as well as vegetables and small fruits. It is sometimes referred to as “gray mold” because of the conspicuous, fluffy, gray fungal growth that forms on infected plant parts.

Powdery mildew fungi attack a variety of ornamental plants grown in Virginia.

Leaf and flower gall is a disease that is common on azaleas and camellias in the spring. The disease has also been reported on other members of the plant family Ericaceae. It occurs in home landscapes and nurseries, and is often seen on flame azaleas in the forest in the spring. The disease is caused by species of the fungus Exobasidium.

Photinia, a shrub belonging to the plant family Rosaceae, is a popular landscape shrub in the southeastern U.S. Several species are grown, but the most popular is the hybrid Photinia ×fraseri, or “redtip”, so named for its bright red, immature foliage. The biggest drawback to growing photinia is a leaf spot disease caused by the fungus Diplocarpon mespili (syn. Entomosporium mespili) to which redtip is highly susceptible.

Gray leaf spot disease of corn caused by the fungus Cercospora zeae-maydis, poses a serious threat to corn production in many areas of the eastern United States, including Virginia, and more recently in large areas of the U. S. Corn Belt

English boxwood, are susceptible to several diseases that can decrease their effectiveness in established plantings. The major diseases of boxwood are discussed

Rose rosette disease (RRD), a disease believed to be caused by the recently identified Rose rosette virus, has been spreading through much of the wild rose population of the Midwestern, Southern, and Eastern United States for years.

Common smut of corn is caused by the fungus Ustilago maydis. The fungus causes gall formation on all aboveground parts of corn plant

Anthracnose is a major disease of the common snap bean (Phaseolus vulgaris) and can occur on other legumes. It is caused by the fungus Colletotrichum lindemuthianum. When environmental conditions are favorable, crop losses can be as high as 100 percent on susceptible cultivars of snap beans.

Brown rot is one of the most destructive diseases of peach and nectarine in Virginia, and also occurs on other stone fruits such as apricot, cherry, and plum. When environmental conditions favor this disease, crop loss can be devastating.

Pesticide use affects the quality of human health, the environment, and nontarget organisms in the ecosystem. Therefore, any pesticide application warrants a careful assessment of the expected benefits and risks. Too often, however, homeowners use pesticides inappropriately or without careful consideration of alternatives. This fact sheet outlines general pest control tactics that can easily be implemented for home lawns and gardens, along with other information that home owners can use to make sound pest management decisions. The intent is to ensure that homeowners are aware of alternative control tactics and pesticide characteristics, and that pesticides are used properly and only when necessary.

Most trees and shrubs are susceptible to dieback and cankers caused by several species of the fungal genus Botryosphaeria. Botryosphaeria fungi are typically opportunistic pathogens. Opportunistic pathogens only cause disease on plants that are stressed. Therefore, avoiding plant stress, which predisposes plant tissue to infection and colonization by this fungal group, is the best strategy to prevent Botryosphaeria disease problems.

Plants can be defined as multicellular, photosynthetic organisms with reproductive structures that are more complex than single cells. By this definition, algae are not considered plants because they are either unicellular or their reproductive structures are essentially unicellular. Fungi, too, are excluded because they are not photosynthetic. At least 400 million years of diversification have resulted in a wide diversity of taxonomically distinct major groups of plants. Some of the most important groups of plants found in Virginia are described below.

Plants can be defined as multicellular photosynthetic organisms with reproductive structures that are more complex than single cells. By this definition, algae are not considered plants because they are either unicellular or their reproductive structures are essentially unicellular, and fungi, too, are excluded because they are not photosynthetic.

Tree fruits are important to the agricultural economy in Virginia. The commonwealth ranks sixth in the nation in apple production, with a crop valued at more than $68 million, and 20th in peach production, with a crop valued at $4.5 million. Although smaller in acreage, cherries, pears, and plums also play an important role in some areas of Virginia. These fruit crops are susceptible to an everchanging array of insects, plant diseases, and weeds, and pest management programs are complex and knowledge-intensive.

Galls are abnormal growths of plant tissue induced by insects and other organisms. Gall-making parasites release growth-regulating chemicals as they feed, causing adjacent plant tissues to form a gall. The parasite then develops within the relative security of the gall. Galls come in an endless variety of forms. Many are strikingly colored or curiously shaped. Each gall-making species causes a gall structurally different from all others. By noting the type of host plant and the structure of the gall, one can identify the gall-making mite without actually seeing it.

This Best Management Practice document is a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.

To provide leadership in safeguarding and protecting the ornamental horticulture industry, historical gardens and landscape plantings from boxwood blight.

This Best Management Practice document is a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.

This Best Management Practice document is a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.

This Best Management Practice document is a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.

This Best Management Practice document is a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.

Best management practices for boxwood blight (also called “box blight”) for greenery producers are practices recommended to avoid the introduction and spread of boxwood blight, caused by the fungus Calonectria pseudonaviculata (syn. Cylindrocladium pseudonaviculatum). The recommendations in this document are designed to avoid spread of boxwood blight within a planting or to new locations when pruned tips are collected, sold and/or used for holiday greenery1. These recommendations are relevant to anyone involved in the greenery (“tipping”) industry, including small and large-scale greenery producers, home growers who sell boxwood tips, and people who tip-prune boxwood on other people’s property. Care must be taken at all levels of greenery production to prevent the spread of the boxwood blight pathogen and avoid economic losses associated with this disease.

Boxwood blight is caused by the fungal pathogen Calonectria pseudonaviculata (syn. Cylindrocladium buxicola). Boxwood blight was first described in the United Kingdom in the mid-1990’s and by 2002 was found in several other European countries and New Zealand. In September 2011 boxwood blight was discovered in North America. Symptoms of the disease include leaf spotting (Fig. 1), elongate, dark cankers on stems (Fig. 2), defoliation, and dieback (Fig. 3). The primary means by which the disease spreads is the inadvertent introduction of infected boxwood to existing plantings. The pathogen can also spread by spores, which readily adhere to equipment and work clothes, and by microsclerotia, which survive in infested soil and plant debris. This document outlines best management practices for landscapers and property managers to reduce the risk of spreading boxwood blight to landscapes and public and historic gardens, and to manage the disease if it is introduced.

Since 2015, Extension specialists from Virginia Tech (VT) have visited and collected plant and soil samples from several large areas of dying great rhododendron (Rhododendron maximum) in Virginia’s mountainous regions. In 2016 VT specialists met with Virginia Department of Forestry, US Forest Service personnel, and other experts to revisit some of these sites. No consistent cause of this mortality has yet been identified. It is possible that a variety of factors are stressing the rhododendrons in these areas to a point where opportunistic pathogens or insects can successfully attack and kill them. The following information summarizes our observations and diagnostic results from four separate great rhododendron mortality sites in Virginia. This information is not equivalent to a research study, which would also include samples taken from healthy great rhododendron for comparison; however, we are confident that we have ruled out two diseases that are frequently mentioned both online and anecdotally as a cause of this mortality, specifically Phytophthora root rot and Botryosphaeria dieback.