Hello Kirk,

Most likely cause: normal inner‑leaf shedding (seasonal needle drop)

The browning pattern in your photo is internal, uniform, and not tip‑dieback. On arborvitae, false cypress, and many cedars, the older interior foliage turns yellow → orange → brown in fall and spring as part of a natural renewal cycle.

Key indicators from your image:

Browning is on the interior scales, not the ends of the sprays

The outer shell of foliage is still green

No visible cankers, resin bleeding, or discrete lesions

No banding or spotting is typical of fungal pathogens

No “flagging” (random dead branch tips)

This is exactly how Thuja, Chamaecyparis, and Platycladus behave when shedding older foliage.

MSU Extension notes that this natural drop can look alarming, but it is not a health problem.

Other possibilities (less likely from your photo)

1. Drought stress from last season

You know how hard Michigan’s late‑summer dry spells can be. Conifers often show the effects the following spring.

Clues would include:

Browning on both interior and tips

Sparse canopy

Reduced new growth this spring

Your photo doesn’t show a tip injury, so drought is a secondary possibility.

2. Root stress or compaction

If this tree is in a wet spot, near construction, or has had grade changes, you might see:

Whole‑branch dieback

Yellowing progressing outward

Not visible here.

3. Fungal blights (very unlikely)

Kabatina or Phomopsis blight causes:

Tip dieback

Distinct lesions at the base of the dead tip

Browning starts at the ends, not the interior

Your tree does not show this pattern.

What you can do to help the tree

1. Do nothing if this is normal shedding

If the outer foliage stays green and new growth emerges in May–June, the tree is fine.

2. Water deeply during dry periods

For conifers in Michigan, aim for:

1 inch of water per week (rain + irrigation)

Deep watering at the dripline, not at the trunk

3. Mulch properly

2–3 inches of mulch

Keep mulch 3–6 inches away from the trunk

This stabilizes soil moisture and protects shallow conifer roots.

4. Prune only dead branchlets

If any interior twigs are fully brown and dry, you can remove them for appearance.

Avoid heavy pruning—most conifers do not regenerate from old wood.

5. Monitor for tip dieback in early summer

If you start seeing:

Browning at the tips

Sudden “flagging”

Resin or cankers

Then we’d reassess for blight or winter injury.

AFTER READING ALL OF THE ABOVE INFORMATION, I HIGHLY RECOMMEND THAT YOU GET A CONFIRMED DIAGNOSIS FROM THE MSU PLANT AND PEST DIAGNOSTIC LAB. PLEASE DO THE FOLLOWING:

What the MSU Plant and Pest Diagnostic Lab will need from you to confirm 100%

If you want a definitive diagnosis, send:

A photo of the entire tree

A close‑up of the branch tips

Any info on irrigation, winter exposure, or recent soil disturbance

But based on the image you shared, this appears to be a normal seasonal needle drop, not a disease.

I recommend you email all your images to the MSU Plant & Pest Diagnostics Lab to obtain a confirmed diagnosis of the problem.

Their email is <personal data hidden> - Please include your first and last name.

The experts there can also provide you with the best treatment options.

The lab will let you know if they need a sample sent.

The lab may also ask for additional images. So be prepared.

Their website is at this link:

Plant & Pest Diagnostics (msu.edu)

Their Contact Information is at this link:

Contact Us - Plant & Pest Diagnostics (msu.edu)

This link will explain the details on submitting a sample to the MSU Plant & Pest Diagnostics Lab:

Submit Samples - Plant & Pest Diagnostics (msu.edu)

I hope this helps!