BRIAN PAIGE
Pest RECEIVES Update BEACON AWARD
BRIAN PAIGE
Pest RECEIVES Update BEACON AWARD
Invasive Insect Updates for Massachusetts
By Tawny Simisky , Extension Entomologist , UMass Extension Landscape , Nursery & Urban Forestry Program
Box tree moth , elm zigzag sawfly , and the spotted lanternfly have all been active in our state in 2024 . Public reports of box tree moth , elm zigzag sawfly and spotted lanternfly are on the rise . This article will provide short updates for the 2024 growing season .
Box Tree Moth Hosts & Damage
moths were reported in Yarmouth , and Plymouth , MA ( also Barnstable County ).
Elm Zigzag Sawfly Hosts & Damage As the common name suggests , the caterpillars of the elm zigzag sawfly feed on elm ( Ulmus spp .). They may commonly feed on slippery elm ( Ulmus rubra ), winged elm ( Ulmus alata ), American elm ( Ulmus americana ), Siberian elm ( Ulmus pumila ), English elm ( Ulmus minor ' Atinia '), lacebark elm ( Ulmus parvifolia ), and hybrid elms ( Ulmus spp .). ( Hybrids found to be impacted in Virginia include : Ulmus ‘ Cathedral ’ Japanese x Siberian hybrid .) Elms in both natural / forested areas as well as managed landscapes are fed upon by this insect .
Females cause a tiny amount of damage to the edges of host plant leaves as they lay their eggs . Tiny scars are formed because of female egg laying . Eggs hatch , and young sawfly caterpillars begin their characteristic zig-zag patterned feeding . These zigzag shaped notches in the leaf can extend 5-10 mm into the leaf from the edge . Multiple caterpillars can feed on a single leaf . Entire leaves can be completely defoliated , leaving only veins behind . Heavily infested trees can suffer partial or complete defoliation .
As the common name would suggest , the primary hosts of the box tree moth are boxwood ( Buxus spp .). Heavy defoliation of ornamental boxwoods can occur if this insect is not managed . Defoliation of existing or new growth can eventually lead to plant death . Once the caterpillars have eaten all the host plant leaves , some have been observed to strip bark from branches or main stems , which may also lead to host plant mortality . This damage may be difficult to see in the beginning of an infestation . Young , tiny larvae are good at hiding among host plant leaves and branches . Eventually , defoliation , webbing , and green-black frass pellets may be noticed because of box tree moth infestation . Defoliated leaves may appear “ peeled ” or with only a midrib remaining . Severely infested plants look brown or scorched . New Detections in MA in 2024
Box tree moths have been detected previously ( August of 2023 ) in Barnstable County in the communities of Bourne , Sandwich , and Barnstable , MA . In 2024 , box tree
It is currently thought that elms can recover from periodic defoliation by this pest , however individual elm trees may be weakened and predisposed to other pests and stressors by elm zigzag sawfly feeding . If several years of complete defoliation occur in a row , tree mortality could possibly occur , however this has not yet been
( continued on page 21 )
MALP Newsline | Winter 2025 15