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Resources for Garden Plant Diseases

Title Available As Summary Date ID Author
Bacterial Leaf Scorch of Landscape Trees
Bacterial leaf scorch is an important and often lethal disease of many landscape trees, particularly in the southern and eastern U.S. In Virginia landscapes it is most often observed on oak, elm, and sycamore; however, many other landscape tree species are susceptible to this disease. The bacterium that causes bacterial leaf scorch colonizes the tree's water-conducting tissue (xylem), disrupting water movement and reducing water availability to the tree. The symptoms of bacterial leaf scorch are very similar to symptoms of other problems that limit water uptake. This is why marginal leaf scorch symptoms caused by other problems, such as drought stress or root disease, are often mistaken for symptoms of bacterial leaf scorch. Laboratory identification of the causal bacterium (Xylella fastidiosa) from affected petiole and leaf tissue is necessary for positive confirmation of the disease.
Feb 2, 2024 3001-1433 (SPES-568NP)
Diagnosing Plant Problems
Something is wrong with your plant. What’s the cause? You can begin to determine the cause of the problem by taking on the role of Sherlock Holmes – be a keen observer and ask many questions. Diagnosing plant problems is often a difficult task. There can be many different causes for a given symptom, not all of them related to insects or diseases. The health of a plant may be affected by soil nutrition and texture, weather conditions, quantity of light, other environmental and cultural conditions, and animals, including humans. Complicating this scenario is the fact that any two of the above factors can interact to give rise to a problem. For example, a prolonged period of drought may weaken plants so that they are more susceptible to pests; this is typically observed with boxwoods.
Nov 6, 2023 426-714
Angular Leaf Spot of Cucumber
Angular leaf spot of cucurbits is caused by the bacterium Pseudomonas syringae pv. lachrymans. The bacterium can attack a wide range of cucurbits including watermelon, melon, squash, cucumber, zucchini, and pumpkin.
Jan 22, 2024 450-700 (SPES-528P)
Late Blight of Tomato and Potato Jan 19, 2024 ANR-6 (SPES-567P)
Insect and Mite Pests of Boxwood
Three pests, the boxwood leafminer, mite and psyllid commonly attack American and English boxwood in Virginia and cause spotting, yellowing, and puckering of leaves.
Apr 3, 2019 ENTO-42NP (ENTO-314NP)
Food Safety For School and Community Gardens: A Handbook for Beginning and Veteran Garden Organizers
Creating and maintaining community and school gardens has been identified as an effective strategy to increase healthy food awareness and consumption. Unfortunately, fresh fruits and vegetables have been linked to hundreds of outbreaks of foodborne illness in the U.S. since 1990. This document outlines the recommended agricultural practices for food safety in gardens.
Feb 20, 2024 FST-60P (FST-470)
Mortality of Great Rhododendron (Rhododendron maximum) in Virginia
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.
Aug 21, 2019 SPES-151P
Fusarium Wilt of Mimosa (Albizia julibrissin) Aug 13, 2020 SPES-230NP
Virginia Cooperative Extension Gardener Handbook Jun 8, 2023 SPES-504NP