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Posted on July 31st, 2024 in Disease, Forestry, Plants, Wildlife | No Comments »

Purdue Landscape Report: Early June, we received a white pine sample at the Purdue University Plant and Pest Diagnostic Lab that showed early season needle loss lower in the tree canopy (Figure 1, 2). The majority of conifers hold onto their needles for multiple years, so loss of needles, even in the fall, can come as a shock to homeowners. In this particular case, we found multiple fungi that could be contributing to needle blight or needlecast.


Figure 1: Eastern white pine trees with early season needle loss.
Figure 1: Eastern white pine trees with early season needle loss.

Figure 2: Closeup images of white pine with needlecast. Multiple fungi were present: Lophodermium, Lecanosticta, and, Septorioides. Note, primarily the older needles have been affected. New needles appear green and healthy.
Figure 2: Closeup images of white pine with needlecast. Multiple fungi were present: Lophodermium, Lecanosticta, and, Septorioides. Note, primarily the older needles have been affected. New needles appear green and healthy.
The first two fungi were determined to be relatively common pathogens for Indiana: Lophodermium and Lecanosticta (brown spot). Symptoms appeared relatively typical for these pathogens where the needles turned brown over-time. However, there were other needles in the canopy and on the sample that had a lighter coloration. We found small black fungal structures dotted along the length of these needles producing light colored cirrhi (also called spore horns) (Figure 3).  After examining the fungal spores, isolating the fungus, and performing DNA testing, we determined this third fungus to be Septorioides strobi, the causal agent of Septoriorides needle blight of pines. This fungus has been determined to be a contributor to white pine needle damage/defoliation.
Figure 3: Black fungal structures developing on dead needles with white sporulation exuding from the top.

Figure 3: Black fungal structures developing on dead needles with white sporulation exuding from the top.

White pine needle damage/defoliation (WPND) was first observed in the state of Maine in 2010 and was attributed to three needle blight diseases, including Lecanosticta, and has since been observed throughout the Northeast US. However, researchers eventually determined that a new fungus, Septorioides strobi, was also found consistently in blighted needles and could be contributing to WPND.

This is the first time we have found this fungus in the state of Indiana, though it has been present for longer than a single season. We do not know how it will react to our climate nor if it will cause significant damage to affected trees. Like other needle blight pathogens, Septorioides has been observed to sporulate around the same time during humid, wet weather, but symptoms may not develop until the following year. White pines are the primary host for this needle cast disease, but it can also develop on 2, 3, and 5 needle pines. While we see white pine decline is a major problem, Septorioides will not likely be the final nail in the coffin for white pines in Indiana, though it certainly will not help us keep them healthy.

Original article posted: Septorioides Needle Blight of Pine.

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Resources:
ID That Tree: Virginia Pine
ID That Tree, Purdue Extension – FNR YouTube playlist
Borers of Pines and Other Needle Bearing Evergreens in Landscapes, The Education Store, Purdue Extension’s resource center
Tree Diseases: White Pine Decline in Indiana, The Education Store
Managing the Zimmerman Pine Moth, The Education Store
Purdue Arboretum Explorer
The Woody Plant Seed Manual, U.S. Forest Service
Native Trees of the Midwest, The Education Store
Root Rot in Landscape Plants, The Education Store, Purdue Extension resource center
Dead Man’s Fingers, Purdue Landscape Report
An Introduction to Trees of Indiana, The Education Store
Subscribe, Purdue Extension – FNR YouTube Channel
Tree Defect Identification, The Education Store
Tree Wound and Healing, Got Nature? Blog, Purdue Extension – FNR
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store
Ask an Expert: Tree Selection and Planting, Purdue Extension – FNR YouTube playlist
Invasive Species, Playlist, Purdue Extension – FNR YouTube Channel
Report Invasive Species, Purdue Invasive Species
Find an Arborist, International Society of Arboriculture

John Bonkowski, Lead Extension Administrator
Purdue Department of Botany and Plant Pathology

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