First, Conifers - pines, spruces and others - sometimes lose older needles during the fall. This is normal, and does not indicate a pest problem.

Pine needles live for two to seven years and then die and drop during the fall. These are the older needles toward the center of the tree. Needles that are going to drop start turning yellow as early as late August. By mid-September these needles turn brown and begin falling from the tree. Following are a few links to University Extension sites with more info:

https://byf.unl.edu/natural-needle-drop

https://extension.illinois.edu/blogs/rhonda-ferrees-ilriverhort/2015-10-09-white-pine-needle-dropgood-or-bad

Evergreen needles don’t last forever. Some needle loss toward the center of the tree during autumn is normal. Needle loss at other times of the year is not normal and may be due to an insect or fungal pest or the result of severe environmental stress.

Unfortunately, many white pines across are experiencing "white pine decline" due to a complex combination of stress factors. Inclement weather stresses a tree and can result in poor growth and/or the slow decline of white pines. Symptoms vary but generally include some pattern of needle yellowing or browning, small needle size, stunted growth, sparse foliage, shriveled bark on branches or trunk, sap exudate on branches, and in some cases death of the tree. Often trees with white pine decline do not recover. Watering helps (except in cases of flooding stress), as does the use of natural mulch (such as shredded bark) over the root system.

So how do you know if your white pine needle drop is normal or not? If older, inner needles turn yellow and drop uniformly across the entire tree in the autumn, it is probably normal needle drop. But, if needles turn yellow and drop in other times of the year, include the outer needles, or is sporadically arranged across the tree, it might be something more serious.

If the needle drop occurs at other times of the year there could be other causes to consider. Growing in heavy clay soils and high pH can contribute to needle drop. Periods of heavy rain saturate the soil inhibiting oxygen take up by the roots. We had a very rainy spring.

There are also a number of diseases that cause white pine needle drop: https://extension.psu.edu/eastern-white-pine-modern-disease-threats-to-a-historically-important-species

If your needle browning and drop occurred in other times of the year and not the fall, consider sending a sample to the OSU C. Wayne Ellet Plant and Pest Diagnostic Clinic for evaluation and diagnosis: https://ppdc.osu.edu/