Pine wilt disease is a devastating disease affecting coniferous trees, primarily those of the Pinus genus, in the state of Michigan. The causal agent is the plant parasitic nematode Bursaphelenchus xylophilus, commonly known as the pinewood nematode (PWN). This disease has been reported in Michigan since 1980, primarily affecting non-native pine species such as Scotch and Austrian pines.
What is the Definition of Pine Wilt Disease?
Pine wilt disease is a fatal disease that affects pine trees, caused by the pinewood nematode (Bursaphelenchus xylophilus). This nematode is a plant-parasitic roundworm that infects the vascular system of pine trees, leading to the rapid decline and death of the affected tree.
What are the Symptoms of Pine Wilt Disease?
The symptoms of pine wilt disease typically progress through the following stages:
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Initial Symptoms: The first visible symptom is the yellowing of needles on one or more branches. These branches die quickly, and needles remain attached as symptoms spread through the whole tree.
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Progression: The disease progresses from the top of the tree downward, distinguishing it from needle diseases. Needle discoloration changes from normal to grayish green and finally to tan or brown. Retention of dead needles on the branch is another diagnostic feature.
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Time Frame: Trees typically die within 3 to 4 months after the onset of symptoms.
What are the Preventative Measures for Pine Wilt Disease in Michigan?
To prevent and manage pine wilt disease in Michigan, the following measures can be taken:
- Cultural Practices:
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Maintain healthy trees by using mulch, fertilizing based on soil test results, and providing water during dry conditions.
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Avoid Non-Native Species:
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Refrain from planting non-native pine species in the future to reduce susceptibility to pine wilt disease.
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Timely Removal:
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Cut down and destroy infected trees before the beetles emerge in early summer to prevent further spread.
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Sample Submission:
- Submit samples from branches exhibiting early symptoms to the nematode lab at MSU’s Diagnostic Services for confirmation.
What are the Relevant Measurements for Pine Wilt Disease Samples?
When submitting samples for pine wilt disease diagnosis, the following measurements are relevant:
- Sample Size: Branches should be at least 1 inch in diameter and 6 to 8 inches long for submission.
- Time Frame for Sample Collection: Collect samples during early stages of infection, typically within 3 to 4 months of symptom onset.
References
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Pine Wilt Disease – American Phytopathological Society:
https://www.apsnet.org/edcenter/disandpath/nematode/pdlessons/Pages/PineWilt.aspx -
Loss of Exotic Pines in Michigan from Pine Wilt Disease:
https://www.canr.msu.edu/news/loss_of_exotic_pines_in_michigan_from_pine_wilt_disease -
Fungal Communities of the Pine Wilt Disease Complex – NCBI:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9257700/