Landscape and Nursery - Japanese Maple Scale Observations

Japanese Maple Scale is becoming a bigger problem in this region. The following is an article from the University of Maryland detailing observations on this pest in 2009.

Japanese Maple Scale (JMS) has been in MD for many years with records back to at least 1960. However, in the last 5 or so years the populations of this armored scale have increased to the point where it has become a key pest in nurseries (and landscapes) causing significant economic and aesthetic damage to a wide range of host trees. There are many challenges to monitoring and managing JMS: the life cycle (# of generations, timing of crawler activity) is not clear; wide host range of woody trees and shrubs; and very small size. Therefore, we (Stan Gill, Paula Shrewsbury, our technicians) with the help of growers and scouts have increased our efforts to learn more about JMS biology and management.

Here we provide a quick update on where the JMS populations are in their development this week (based on JMS populations we are monitoring in Frederick and Montgomery Counties MD) to help nursery managers and scouts make better management decisions.

Eggs of JMS from overwintering females began hatching the week of June 8th to start the 1st JMS generation of 2009. Many of you targeted JMS for control around mid-June. This week it appears that about ½ of the 1st generation JMS are immature 2nd instars; the other ½ consists of adult females (no eggs as of yet) and males that are close to emerging as adults (pre-pupal and pupal stages). We will let you know when the 1st generation females lay eggs and those eggs hatch to crawlers which will start the 2nd JMS generation of 2009. This will be the time to apply control measures targeting the 2nd generation crawlers. To our knowledge an application of an IGR (Talus or Distance) with a 0.5-1.0% oil targeting the crawlers should provide the best control. One “fly in the ointment” with JMS is that we have continued to find JMS adult females from the overwintering generation with viable eggs under their covers, although fewer and fewer over the weeks since initial egg hatch in mid-June. What this means is that we have been having continual egg hatch / 1st generation crawler activity since mid-June. It is likely that pesticide applications applied in mid-June may no longer be effective at killing a proportion of these “late emerging 1st generation crawlers”. This is why those of you fighting the battle of JMS should seriously consider a 2nd treatment application when the 2nd generation crawlers become active.

For more information on Japanese maple scale go to: http://ipmnet.umd.edu/09JapaneseMapleScale-UMD.pdf

Information from the current issue of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Jul31L.pdf