Page 26 - Free State Summer 2022

TOTAL PLANT MANAGEMENT (Continued) minute cypress scale on them.

Both of these armored scales have one generation per
to the general public. Since they aren’t readily identified as
insects, they have been mistaken for a fungus. Upon closer year, and you should begin scouting for crawlers at 530
examination, a little horn is visible protruding from the degree-days. I prefer using an insect growth regulator as
teste- the wax covering the scale. my first choice. Horticulture oils can be used to suppress
the population.
The crawler stage for these is between 854-985 degree-
days with one generation per year. In most years this falls Japanese maple scale
between late June and early July. Horticulture oils are not The Japanese maple scale is dangerous scale. It is the
effective for the Indian wax scale because the oils will nastiest scale we have dealt with and most prevalent
not stick to their waxy coating. Systemic insecticides or in nurseries and the landscape in the last decade. In a
neonicotinoids are effective, as are the IGRs in controlling normal season the first crawler stage is six to seven weeks
Indian wax scale. We are presently testing a new systemic long. This is very long compared to the typical two to
insecticide called Altus for soft scale control and should three weeks for most scale insects. Because they produce
have results by early 2018. crawlers over a longer period of time, they have a greater
Juniper scale and minute cypress scale survival rate – and there are two generations per year.
The second generation can crawler periods lasting up to
Both of these are armored scales and are difficult to 7 – 8 weeks.
distinguish in the field. The treatment is for both species
is similar. The two species have slightly different crawler Chemical controls may breakdown before the crawler
periods. The Leyland cypress has been the major host for period ends; in some cases two applications might
the minute cypress scale in Maryland. Green giant cypress be necessary. Most standard pesticides are not
is gaining popularity and although we haven’t seen minute effective against this pest. We were not successful with
cypress scale on these yet, I suspect that as the population pyrethroids, neonicotinoids or most systemics. Control
of green giant cypress increases, we will begin finding was achieved when the plants were treated with the
insect growth regulators in our trials. Over the years we
have found that the IGR Distance does it a good job.
In heavy populations it may take up to two years of
application to bring the scale under control.

Part of our research grant from the Maryland Nursery,
Landscape, and Greenhouse Association was used to
monitor these insects for two years. The first generation
of Japanese maple scale begins crawling at 806 degree-
days and ends at 1,144. The second generation starts at
2,200 degree-days and ends at 3,037. There is a longer
crawler period for the second generation. The insects
finish crawling and overwinter in their second instar on
the bark in late fall. A

Stanton Gill, Extension Specialist in
IPM for Greenhouses and Nurseries,
University of Maryland Extension
And Professor, Montgomery College,
Germantown Campus, Landscape
Technology Program

sgill@umd.edu
On bottlebrsuh plant indian wax scale https://go.umd.edu/ipmnet
Photo: Jamie Weisner

26 SUMMER 2022 • Free State News