Hi Daniel,

Thank you for reaching out to the UNH Extension Infoline regarding your white pine trees.

We have received many inquiries over the summer (June-July) regarding white pine tree issues - specifically that pine needles were turning yellow/brown and shedding prematurely. I will be sharing lots of information that we shared with other clients over the summer months, which may also be impacting your white pines:

What you are observing in your landscape is most likely known to as: white pine needle disease (WPND;) also referred to as needle blight or needle cast disease. 

The dieback in needles is caused by fungal pathogens that favor moist, humid environments. Last summer, we received a significant increase in precipitation during the months of May - July, the same time when white pines are flushing new growth. A combination of increased rainfall and warming temperatures promotes an environment for disease development and spread. The fungal pathogens that primarily cause WPND are: Lecanosticta acicola (formerly Mycosphaerella dearnesii), Septorioides strobi, Bifusella linearis and Lophophacidium dooksii (formerly Canavirgella banfieldii). These pathogens rarely kill the pine trees themselves, but if the cycle of infection and other environmental stresses persist in consecutive years, trees can severely weaken over time.

White pine needles typically have a three-year cycle and seasonally shed their 2- and 3-year-old needles in late summer/early fall. The browning and premature drop of diseased needles that you are observing now are of one-year-old needles emerged from last year (NOT emerging needles this year,) with the peak occurring around mid-June. If your tree(s) show any other signs of stress or have experienced needle blight frequently, their overall health could be impacted. If this is the first exposure to this disease, the tree should be able to counter the effects of WPND this year and recover.

Here are a few resources to read more:
UNH Extension - White Pine
NH Bugs - Native Insects and Diseases
Society for the Protection of NH Forests - White Pine
UMass Extension - Dieback of Eastern White Pine

To address your white pine tree issue and to get to the root of the matter, we also recommend sending a sample into the plant diagnostic lab at UNH Extension for a positive diagnosis. The link below provides the homepage, including the address to send the sample. The submission form link provides best practices for submitting the plant sample as well as other resources.

Link to homepage: Plant Diagnostic Lab Homepage

Link to the submission form for a plant diagnostic sample: UNH Plant Diagnostic Lab

You may also consider reporting your observations to NH Bugs: Reporting Form

To assess the overall health of your pine trees and/or possible removal, we also recommend reaching out to a NH certified arborist: NHAA List of Certified Arborists. An arborist can come to your property to assess the health of your trees and determine whether removal is needed. I do think having an arborist visit for a second look to access possible causes would be extremely helpful! 

We hope this information is helpful. Best of luck with your trees!