Woody ornamental insect and non-insect arthropod pests to consider, a selected few:
New Pollinator Protection Resource Online: The Massachusetts Department of Agricultural Resources has developed a Massachusetts Pollinator Protection Plan. It is a set of voluntary guidelines that discuss best management practices for stakeholders seeking to promote the health of the European honeybee and other pollinators. This document includes information for beekeepers, pesticide applicators, land managers and farmers, nurseries and landscapers, and homeowners and gardeners. Please locate the MA Pollinator Protection Plan for more information here: http://www.mass.gov/eea/docs/agr/farmproducts/apiary/pollinator-plan.pdf.
- Gypsy Moth: Lymantria dispar overwintered egg masses laid by female moths in 2016 can be seen at this time and egg hatch is just beginning in some locations of the state. Gypsy moth egg hatch was observed in Massachusetts on 4/26/17 at a location in Belchertown and on 4/27/17 at a location in Hingham. As of 4/26/17, scouts monitoring egg masses at locations in Acton, Boston, Boylston, Cape Cod, and Hanson report that hatch has not yet occurred in those areas. For more information about gypsy moth egg hatch, please visit: https://ag.umass.edu/landscape/news/gypsy-moth-egg-hatch-has-begun-in-massachusetts. At this point in time, it is too early to treat individual, landscape ornamental and shade trees using the active ingredient Btk (Bacillus thuringiensis Kurstaki) for gypsy moth. These applications should be made when very young caterpillars (roughly ¼-¾ inch in length) are actively feeding on host plant leaves, as it must be ingested to be effective. Gypsy moth caterpillars are tiny and resting on top of their egg masses at this time, at locations where egg hatch has begun. Btk would not be effective on these very newly hatched caterpillars as they are not yet feeding.
Egg masses are “fuzzy” or hairy and brownish-tan in color. Each egg mass can hold up to 500-1000 eggs. Gypsy moth egg hatch typically occurs between 90-100 growing degree-days, using a base of 50°F, average temperatures, and a March 1st start date. This is usually around the first week in May in Massachusetts, but variations in temperature may lead to early egg hatch in the last week in April as has been observed this year in certain areas. This can also coincide with serviceberry (Amelanchier) bloom. Amelanchier bloom has begun or is in full activity in certain portions of the state.
These masses may be found on host plant trunks and branches such as oak (favored), maple, birch, poplar, and many others, but are also laid on inanimate objects including the surfaces of homes, outdoor furniture, camping equipment, firewood piles, etc. This may make the accidental movement of gypsy moth egg masses possible. (Note: winter moth and gypsy moth share some common host plants. Therefore, where populations of these two insects overlap in Massachusetts, the same tree may be defoliated by winter moth and then again by gypsy moth following in the same season.) After egg hatch occurs, groups of tiny gypsy moth caterpillars may remain on their egg mass (as seen in the photos included in the above link) just before crawling to the canopy of their host plant, where they can disperse using a technique known as “ballooning”. Ballooning occurs when very young caterpillars spin a silken thread and catch the wind to blow onto a new host plant once the thread breaks. This method of dispersal can lead to host plants becoming defoliated that previously did not have egg masses directly on them, however egg masses may be present on nearby oaks, for example, and provide a local population of caterpillars.
Patchy areas across mostly central and eastern Massachusetts experienced elevated populations of gypsy moth and significant amounts of defoliation in 2016 (see the Insects section of the archived 2016 Landscape Messages between April 29 and July 29). The Massachusetts Department of Conservation and Recreation aerially mapped approximately 350,000 acres of defoliation across Massachusetts last year, attributed to gypsy moth. State officials warn the public about another year of defoliation from gypsy moth as predicted for 2017: http://www.mass.gov/eea/agencies/dcr/pr-2017/another-year-of-defoliation-from-gypsy-moth-in-2017.html. That web page also links to a map of the 2016 defoliation from gypsy moth, which may provide a reference regarding areas that may be impacted by this insect again in 2017. To prepare for this insect, now is a great time to scout the landscape and count the number of gypsy moth egg masses present not only on valuable landscape specimens that are hosts for this insect, but on nearby forested hosts such as oak which might provide sources of ballooning caterpillars. At this time, check to see if a few of the egg masses have begun to hatch. Tiny, hairy caterpillars may be seen resting on top of the mass. Egg mass counts can help us make decisions regarding whether or not to manage for this insect. Some individuals also use this opportunity to scrape egg masses into a container of soapy water, although this is time consuming and some egg masses will be missed. Once eggs have completely hatched, scraping them into a container of soapy water is no longer effective (the caterpillars have left the eggs).
We can hope for elevated rainfall in the months of May and June, which helps facilitate the successful infection of younger gypsy moth caterpillars with the insect-killing fungus Entomophaga maimaiga. This fungus overwinters in the soil litter in tough, protected asexual resting spores, which can survive in this state for years. Having lacked much precipitation most recently during the springs of 2015 and 2016, it is thought that our current expanding populations of gypsy moth are at least in part a result of a lack of infection in the caterpillar population by this fungus. Hopefully Massachusetts will see more normal rainfall amounts this season. Only time will tell.
We can also hope areas in Massachusetts that do not have large numbers of gypsy moth egg masses present at this time and did not experience much gypsy moth defoliation last year (areas such as most of Berkshire County) will be mostly spared in 2017 in comparison to those areas who suffered last year in central and eastern Massachusetts. At this time, monitoring susceptible hosts for hatching gypsy moth egg masses and educating and reminding ourselves about this invasive insect that has a long history in the state is the best way to plan for management this season. For more information about gypsy moth, please visit: http://ag.umass.edu/landscape/fact-sheets/gypsy-moth and return to the Landscape Message for timely updates about this pest and others throughout the season. An excellent article written by Dr. Joseph Elkinton and Jeff Boettner of the University of Massachusetts about the 2016 outbreak and the history of this insect in Massachusetts may be found here: http://www.mass.gov/eea/agencies/dfg/dfw/publications/gypsy-moth-outbreak-of-2016.html .
Winter moth egg hatch is complete in the areas of eastern Massachusetts that suffer from this defoliating caterpillar. Tiny caterpillars are now feeding within the newly expanding and developing foliage of their host plants. Please see the Regional Reports above for local information regarding this insect.
For individuals managing winter moth in ornamental plants, depending on the active ingredient being used, waiting until host plant leaves open completely may be important for management, particularly if Bacillus thuringiensis Kurstaki (Btk) is the active ingredient of choice. Btk must be ingested by actively feeding, young caterpillars to be effective. Applying Btk to partially open buds for winter moth management will not have the desired effect. Spinosad is also effective through ingestion and contact on winter moth (including older caterpillars) once ornamental plant leaves have fully expanded, however it should not be applied to plants in flower as it is toxic to pollinators until it has dried (which can take 1-3 hours depending upon local environmental conditions). The Elkinton Lab has reported that the number of pupating winter moth in 2016 (at their study sites) was much lower than what has been observed in previous years. Reports from Hanson, MA indicate fewer winter moth eggs were present on monitored trees than in previous years. Hopefully this will translate into fewer caterpillars at least for some areas in Massachusetts this year, however one should not expect them (or the damage they cause) to completely disappear in 2017.
Winter moth is a non-native insect that was identified in Massachusetts for the first time in 2003 following persistent reports of defoliation in eastern areas of the state such as Cape Anne and on the North Shore near Cohasset, Hingham, and Rockland on the South Shore in the late 1990’s. For more detailed information about the history of this insect pest in North America and Massachusetts, please visit the newly updated (March, 2017) fact sheet: Winter Moth in Massachusetts: History and Biological Control (https://ag.umass.edu/landscape/fact-sheets/winter-moth-in-massachusetts-history-biological-control ).
This fact sheet also includes updates regarding the progress of the work of Dr. Joseph Elkinton’s laboratory group at the University of Massachusetts and their efforts towards the biological control of winter moth using Cyzenis albicans, a tachinid fly. The fly parasitizes the caterpillars of winter moth specifically. In other areas, such as Nova Scotia where winter moth was also problematic, this fly used for biological control has been successful in reducing winter moth to a non-pest. C. albicans has been released across 41 sites in Massachusetts and has been established in at least 17 of those sites as evidenced through the recovery of flies in winter moth in subsequent years. In one site in Wellesley, these flies have been observed to be spreading from the initial release location and their populations have increased alongside an observed decrease in the winter moth population there. For more information, please visit the above mentioned fact sheet.
- Balsam Twig Aphid: Mindarus abietinus is active between 30-120 GDD’s, base 50°F. Inspect the needles of fir for “stem mothers” that will soon be reproducing. Young aphid feeding will lead to distorted foliage. Excessive amounts of honeydew are produced and cause needles to stick together. Monitor for the presence of reproducing females and treat with an oil application as weather permits.
- Eastern Tent Caterpillar: Malacosoma americanum eggs have hatched and tiny, newly hatched caterpillars are forming their tents as they feed on tender, new plant foliage. Egg masses of Malacosoma americanum vary from those of Malacosoma disstria, the forest tent caterpillar, as they have a rounded edge whereas M. disstria egg masses have square edges. Scout for, remove, and destroy the small, newly forming eastern tent caterpillar tents in the crotches of branches on susceptible hosts such as cherry and crabapple. If the tents and the tiny caterpillars within are found early enough, this is a great way of removing these insects without the use of chemicals. Other host plants impacted by this native insect can include apple, ash, birch, willow, maple, oak, poplar, and witch-hazel.
- European Pine Sawfly: Neodiprion sertifer caterpillar will be active soon, between 78-220 GDD, base 50°F. The primary host in MA is Mugo pine but it can be found on Scots, red, jack, and Japanese red pine, but is also found on white, Austrian, ponderosa, shortleaf, and pitch pine when near the aforementioned species. This dark colored caterpillar feeds in tight groups and small numbers can be pruned away and destroyed. Larger numbers can be treated with an insecticidal soap spray when the caterpillars are still small. Spinosad products can be used whenever the caterpillars are actively feeding, usually by mid-May and when caterpillars are still small. Bacillus thuringiensis Kurstaki is not effective against sawflies.
- Forest Tent Caterpillar: Malacosoma disstria egg hatch will occur between 192-400 GDD’s, base 50°F. Scout for and prune out or otherwise remove any reachable forest tent caterpillar egg masses, which can hold 100’s of eggs, on susceptible hosts such as oak, birch, ash, maple, elm, poplar, and basswood at this time. Once these egg masses hatch, these native caterpillars can defoliate their host plants.
- Lily Leaf Beetle: Lilioceris lilii should be monitored for at this time. Management can be achieved by hand-picking and removing adults and larvae. Adult activity of this beetle has been reported in Berkshire County (see Regional Report above). Some chemical management options are available for this insect, but if caught early mechanical management may be effective.
The University of Rhode Island Biological Control Lab is researching ways to find a natural method to combat these beetles. Small parasitic insects have been established in lily plots in Cumberland, RI and Wellesley, MA in hopes that these insects will disperse naturally to reduce the effects of the lily leaf beetle. If you have larvae in your yard (or a customer’s yard), please send to URI, following the instructions on the URI Biocontrol Lab website: http://web.uri.edu/biocontrol/home/lily-leaf-beetle-larval-collections-2016-mailing-instructions/
- Viburnum Leaf Beetle: Pyrrhalta viburni is a beetle in the family Chrysomelidae that is native to Europe, but was found in Massachusetts in 2004. This beetle feeds exclusively on many different species of viburnum. This insect overwinters in the twigs of the host plant as eggs, which hatch soon after bud break. Inspect susceptible plants (including but not limited to viburnum such as V. dentatum, V. nudum, V. opulus, V. propinquum, and V. rafinesquianum) for over-wintering eggs on stems toward branch tips. Inspect branches for egg laying sites created by female viburnum leaf beetles last season. These will appear as small holes approximately 1 mm. in diameter that have been capped with a lid made of chewed bark and excrement, which may appear raised above the surface of the twig. Removal and destruction of infested stems, if small in number, can help reduce populations of this insect pest. If management this way is not possible, larvae may be treated with a product containing spinosad once they appear soon after bud break. Some viburnum have been observed to have varying levels of resistance to this insect, including but not limited to V. bodnantense, V. carlesii, V. davidii, V. plicatum, V. rhytidophyllum, V. setigerum, and V. sieboldii. More information about viburnum leaf beetle may be found at http://www.hort.cornell.edu/vlb/.
- Chilli Thrips: *A non-native insect has been confirmed in Massachusetts for the first time.* The non-native, exotic chilli thrips (Scirtothrips dorsalis) has been recently confirmed from two samples of damaged Hydrangea spp. foliage from two residential landscapes located in Barnstable County, MA submitted to the UMass Plant Diagnostics Laboratory. At this time, this pest has not been confirmed in nurseries or greenhouses in Massachusetts or on any other host plants. Due to the limited number of samples, the significance of chilli thrips in Massachusetts is not yet known. This species of thrips is a significant global pest of economically important ornamental, vegetable, and fruit crops in southern and eastern Asia, Oceania, and parts of Africa. It was first determined to be established in the United States in 2005 in Florida, although previous interceptions of this pest were detected. It is reportedly a pest of over 100 host plants belonging to over 40 plant families, including, but not limited to, pepper, strawberry, blueberry, cotton, rose, peanut, Japanese privet, Rhododendron spp., Viburnum spp., eggplant, grapes, melon, tobacco, and tomato. For more information, please visit this Chilli Thrips Fact Sheet (https://ag.umass.edu/landscape/fact-sheets/chilli-thrips) available on the UMass Extension Landscape, Nursery, and Urban Forestry Program web page.
- Asian Longhorned Beetle, Anoplophora glabripennis, ALB: Look for signs of an ALB infestation which include perfectly round exit holes (about the size of a dime), shallow oval or round scars in the bark where a female has chewed an egg site, or sawdust-like frass (excrement) on the ground nearby host trees or caught in between branches. These particular signs of damage from the beetle may be more visible at this time of year, when host trees such as maples are leafless. Be advised that other, native insects may create perfectly round exit holes or sawdust-like frass, which can be confused with signs of ALB activity.
The regulated area for Asian longhorned beetle is 110 miles2 encompassing Worcester, Shrewsbury, Boylston, West Boylston, and parts of Holden and Auburn. If you believe you have seen damage caused by this insect, such as exit holes or egg sites, on susceptible host trees like maple, please call the Asian Longhorned Beetle Eradication Program office in Worcester, MA at 508-852-8090 or toll free at 1-866-702-9938. Adult insects of this species will not be present at this time of year.
To report an Asian longhorned beetle find online or compare it to common insect look-alikes, visit: http://massnrc.org/pests/albreport.aspx or https://www.aphis.usda.gov/pests-diseases/alb/report.
- Emerald Ash Borer (EAB): Agrilus planipennis readily attacks ash (Fraxinus spp.) including white, green, and black ash and has also been found developing in white fringe tree (Chionanthus virginicus). Adult insects of this species will not be present at this time of year. Signs of an EAB infested tree may include (at this time) D-shaped exit holes in the bark (from adult emergence in previous years), “blonding” or lighter coloration of the ash bark from woodpecker feeding (chipping away of the bark as they search for larvae beneath), and serpentine galleries visible through splits in the bark, from larval feeding beneath. Positive identification of an EAB-infested tree may not be possible with these signs individually on their own.
For a map of the known locations of emerald ash borer in the state, as well as further information about this insect, please visit: https://ag.umass.edu/fact-sheets/emerald-ash-borer. If you believe you have located EAB-infested ash trees, particularly in an area of Massachusetts not identified on the map provided, please follow the instructions below.
Concerned that you may have found an invasive insect or suspicious damage caused by one? Need to report a pest sighting? If so, please visit the Massachusetts Introduced Pests Outreach Project: http://massnrc.org/pests/pestreports.htm.
A note about Tick Awareness: deer ticks (Ixodes scapularis), the American dog tick (Dermacentor variabilis), and the lone star tick (Amblyomma americanum) are all found throughout Massachusetts. Each can carry their own complement of diseases. Anyone working in tick habitats (wood-line areas, forested areas, and landscaped areas with ground cover) should check themselves regularly for ticks while practicing preventative measures. Have a tick and need it tested? Visit the web page of the UMass Laboratory of Medical Zoology (www.tickdiseases.org) and click on the red Test a Tick button for more information.
Report by Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program