Shothole in Transition: From Nursery to the Planted Landscape
Cherry shot-hole disease
Photo by Guilhem Vellut from Annecy, France, licensed under Creative Commons Attribution 2.0.
Introduction
Shothole—a condition characterized by small, round lesions or “holes” in the leaves—often appears in plants grown in nursery settings. While it’s a common issue in high-density production environments, it can raise questions for homeowners, landscapers, and property managers once plants are installed in the landscape. Understanding why shothole develops and why it usually subsides after planting can ease concerns and provide confidence in the long-term health of new plants.
What Causes Shothole in Nursery Production?
Shothole is a condition affecting plants in the Prunus family—such as cherries, plums, and laurels—caused by both fungal and bacterial pathogens. This condition results in small, round leaf lesions, which may dry out and fall away, leaving distinctive holes. Although often mistaken for insect damage, shothole is a minor, temporary symptom stemming from the plant’s exposure to specific pathogens. These pathogens thrive in moist conditions and are common in nursery production due to frequent overhead watering and the high density of plants.
Fungus: The fungal pathogen Wilsonomyces carpophilus is a primary cause of shothole disease. This fungus can infect various parts of the plant, including buds, twigs, branches, blossoms, leaves, and even fruit, especially in nursery environments with high moisture levels. It thrives in the humid conditions typical of dense nursery settings, spreading via water splashes from overhead irrigation.
Bacterium: In addition to the fungal cause, a bacterium known as Pseudomonas syringae can also lead to shothole, particularly on cherry and laurel trees. This bacterial canker affects the leaves, causing similar round lesions that may fall out and create a “shotholed” appearance. Like the fungus, Pseudomonas syringae spreads through water and flourishes in moist environments.
Understanding these two causes helps clarify why shothole appears primarily on nursery-grown plants and tends to diminish once plants are moved to a landscape setting with better airflow and root-zone watering practices.
Why Shothole Persists in Nursery Plants but Often Disappears After Planting
Plants grown in nurseries receive frequent irrigation to support vigorous growth, which creates a humid environment ideal for fungal pathogens. When these plants transition to a landscape, the change in growing conditions can help prevent further spread of the fungi responsible for shothole. Here’s why:
Improved Air Circulation: Plants are typically spaced more widely in the landscape, allowing for better airflow. This natural circulation dries foliage more quickly after rain or watering, reducing the likelihood of fungal development.
Different Watering Practices: Overhead watering in nurseries keeps foliage wet, but in a landscape setting, irrigation often targets the root zone, maintaining dry leaves and making the plant less hospitable to fungal pathogens.
Seasonal Leaf Drop: Fall brings a natural leaf drop for deciduous plants, including cherry trees. Any leaves showing shothole will soon fall off, leaving the tree free of visible symptoms. In spring, fresh foliage emerges without the damage seen in nursery leaves.
Managing Shothole in Newly Planted Trees
If a shothole is visible when a tree is planted, there’s generally no need for concern. The condition is almost always cosmetic, especially as plants transition to a drier, more open landscape environment. Here’s how to support plants as they adjust:
Water at the Root Zone: Focus irrigation at the base of the plant, minimizing water on the foliage to reduce the likelihood of fungal growth.
Keep Mulch Off Foliage: Leave a few inches of space around the trunk and branches when mulching. Mulch too close to foliage can trap moisture, promoting fungal growth.
Prune Wisely: If severe shothole is present, you can prune affected branches in winter, which will further help prevent fungi from overwintering on the tree. However, extensive pruning is rarely necessary, as seasonal leaf drop usually resolves the symptoms.
Why Shothole Shouldn’t Affect Plant Health Long-Term
Shothole, while noticeable, is a condition that almost always improves as plants settle into their landscape environment. Once established, trees and shrubs have greater resilience to minor fungal issues. The enhanced airflow, targeted watering, and seasonal leaf drop allow the plant to grow fresh, healthy foliage each season, free from the shothole seen in the nursery.
Addressing Concerns for Homeowners and Landscapers
Seeing shothole on newly planted trees can be surprising. Still, it’s helpful to remember that these marks are temporary and unlikely to impact the plant’s vigor. Over time, the plant will shed any leaves showing signs of shothole and produce a fresh canopy of healthy foliage. This reassurance can help homeowners and landscapers confidently care for newly planted trees, knowing that shothole is just a transitional issue from the nursery.
Conclusion
While shothole may look concerning at first, it’s a minor condition that often fades after plants transition from the nursery to the landscape. With proper watering and a healthy environment, trees and shrubs will thrive in their new setting, leaving shothole behind as a temporary mark of their nursery origins. For landscapers and homeowners, knowing how and why shothole appears—and why it won’t last—offers peace of mind and the knowledge that the plants will continue to grow beautifully for years to come.