Pinyon needle scale

What it is

Matsucoccus acalyptus, a sap-feeding scale insect

Trees affected

Pinyon pines; the extension write-up names Pinus edulis and related pines

Where in our area

Dry pinyon-juniper slopes and the yards built on them

Key sign

Black bean-like nymphs on needles; thin crowns with tufts at branch tips

Damage

Older needles brown and drop; weakened trees may attract bark beetles

Pinyon needle scale is a native pest of pinyon pines in the Southwest and Great Basin. The New Mexico State University write-up describes small black bumps on needles that look like tiny black beans. This page covers identification, which trees, what an arborist checks and when pruning or removal is the answer.

What does pinyon needle scale look like?

Pull a few needles from a thin-looking branch. The developing insects look like small black beans attached to the needles through the winter, and many are empty husks after they emerge. In early spring the insects move to the trunk and larger branches, where adults lay cottony egg masses in March and April, according to Colorado State Extension. Old, lower needles brown and fall.

Heavily infested trees look 'lion-tailed': thin, bare branches that end in small tufts of green. The pattern on a hillside is a patchy canopy that is mostly bare below. The New Mexico State University write-up uses that phrase.

• Black bean-like bumps on needles
• Cottony egg masses on bark in March or April
• Older needles brown and drop
• Thin, lion-tailed branches

Which trees and which elevations?

The scale feeds on pinyon. The New Mexico State University write-up names pinyon pine (Pinus edulis) and several related pine species, and Colorado State says pinyon is the host. Single-leaf pinyon is the pinyon of the Great Basin hills, so it is the tree to think of on lots in the dry hills above the valleys. The arborist, not this page, confirms the cause on the tree itself.

Pinyon is a tree of the dry slopes, so a lot on the valley floor at about 4,500 feet is less likely to have one than a hillside lot.

How does it relate to drought and bark beetles?

The New Mexico State write-up says the scale rarely kills trees directly, but that weakened trees become more vulnerable to bark beetles, and that populations rise and fall from year to year with drought and heat among the factors. Stressed pinyons with little green foliage are more likely to be attacked by beetles that can kill them.

A pinyon that is browning from the top down or turning fast is more likely to have beetles or another stress than scale alone. See bark beetles in pines and drought stress and dieback. The similar-sounding pine needle scale is a different insect with white scales on needles.

What does an arborist check?

The arborist checks how much green foliage remains, whether the thinning is old or sudden, the bark for beetle holes and pitch and the base for root problems. They also check what stands under the tree, and whether it is close to a house in a fire-prone area.

• Amount of live green foliage
• Beetle entry holes, pitch or boring dust
• Black nymphs or egg masses
• Roots and base
• Defensible-space and fall zone

When is pruning or removal the answer?

Dead lower branches can be pruned off, and for a pinyon near a house that is often a defensible-space step in itself; see ladder fuels. Pruning will not cure a scale outbreak, and cutting into green growth on a weakened pinyon does more harm.

Removal is the answer when the tree is dead or mostly dead, when beetles are in it or when it threatens a structure. Dead pinyon is fuel next to a house. Colorado State notes that pinyon needle scale outbreaks happen in native stands and ornamental plantings. See removing dead pines.

What does Battle Born Tree Service do about pinyon needle scale?

We look at the whole tree, not only the part that worries you, and the free estimate lays out pruning dead wood or removal. The crew is eight people, two of them ISA Certified Arborists, and the phone line is staffed seven days a week at 775.232.8243. We identify the problem, prune out dead or hazardous wood and remove trees that cannot be saved; we do not spray, inject, fertilize or apply products.