Landscape and Nursery - Scale Pests of Leyland Cypress, Arborvitae, Cryptomeria, and Junipers

There are two scale insects showing up on Leyland Cypress, Arborvitae, Cryptomeria, and Junipers called the Maskell scale and the minute cypress scale. The following is information on these pests from the University of Maryland.

If you are growing Leyland Cypress, Arborvitae, Cryptomeria, or Junipers at your nursery or your customers have these plants in their landscapes you need to look carefully for Maskell scale and minute cypress scale on the foliage.

We have received samples from a number of sites in the last couple of weeks with Maskell scale. This armored scale appears to be showing up more frequently on Leyland cypress and Cryptomeria. We have also received samples of Leyland cypress from several sites with minute cypress scale present in abundant numbers. In some cases Maskell scale and minute cypress scale have been found on the same plants. In 1991, Hodgson and Hilburn reported Bermuda cedar that was infested with both Maskell scale and minute cypress scale killed entire trees and almost eliminated the Bermuda cedar on Bermuda.

There is concern with the increase in frequency of samples in Maryland infested with Maskell scale and minute cypress scale. We do not have much information on these pests and the exact number of generations per year is not clear for Maskell scale. Davidson and Miller (2006) reported that in Maryland, adult males are present in late September into October along with all stages including eggs, crawlers, 2nd instar and adult females. If you have infested plants please let us know when you see crawlers so we can alert others in the state.

Minute Cypress Scale on Arborvitae

Maskell Scale on Cryptomeria

Information adapted from the April 18, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/08Apr18L.pdf