Woody ornamental insect and non-insect arthropod pests to consider, a selected few:
- A Beneficial Sighting: the larvae of many Coccinellidae (ladybird beetles, ladybugs) are great predators of pest insects such as aphids, mites, and thrips. Although some species (such as the multicolored Asian lady beetle, Harmonia axyridis) may overwinter in homes in large, obnoxious numbers, the adults and larvae of many lady beetle species can be quite voracious predators and help us to manage some pest insects.
- Gypsy Moth: Lymantria dispar caterpillar dispersal via ballooning may be at an end, in most locations. (See previous Landscape Messages and the “Insects” section for more information regarding prior 2017 observations.) To be sure, monitor local gypsy moth caterpillars and look for tattered host plant foliage with young, still small gypsy moth caterpillars feeding beneath. If you find a host plant leaf with tattered holes in it, flip the leaf over and you may find a small, roughly ¼- ½-inch long gypsy moth caterpillar feeding on the leaf underside. These caterpillars are dark in color and hairy. Based on observations at a single location in Amherst, caterpillars are mostly still in the 2nd instar stage (at that location), but some 3rd instar individuals were seen with more defined, raised “wart-like” spots on the dorsal side of the insect. In Amherst, the “warts” of some of the gypsy moth caterpillars are developing to include the characteristic blue coloration. The color development of these spots will continue as caterpillars develop into the 4th instar, when blue and red spots/warts will be visible, along with a head capsule that is yellow mottled with black markings. Larval instars seen locally will vary depending upon how warm or cool the site is. See the Regional Reports above for more information about gypsy moth activity. Over the past few weeks, gypsy moth caterpillars have unfortunately been observed on the UMass Amherst campus, despite an apparent lack of readily visible egg masses. Research suggests that young gypsy moth caterpillars can balloon into an area from at least a mile away. For more information about gypsy moth egg hatch, please visit: https://ag.umass.edu/landscape/news/gypsy-moth-egg-hatch-has-begun-in-massachusetts.
To treat individual, landscape ornamental and shade trees using the active ingredient Btk (Bacillus thuringiensis Kurstaki) for gypsy moth, be sure that the newly hatched caterpillars have settled to feed on fully expanded foliage and are roughly between ¼ - ¾ inch in length. Larger caterpillars are less susceptible to Btk. These applications should be made when very young caterpillars are actively feeding on host plant leaves, as it must be ingested to be effective. Multiple applications of Btk may be necessary. Spinosad is effective on younger and older gypsy moth caterpillars (over ¾ inch in length) but should not be applied to plants while they are in bloom due to the risk toward pollinators.
Gypsy moth host plants include but are not limited to oak (favored), maple, birch, poplar, and many others. Caterpillars will feed on conifers (such as eastern white pine, hemlock, and spruce) when favored resources have been exhausted. (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.) Caterpillar dispersal occurs by crawling to the canopy of their host plant, where they can scatter 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.
We need the more “normal” rainfall amounts (non-drought conditions) that we have been experiencing to continue through the rest of May and June, to help facilitate the successful infection of younger gypsy moth caterpillars with the insect-killing fungus Entomophaga maimaiga. However, at this time, it is too early to know what impact this fungus will have on the 2017 gypsy moth population. It is also important to note that even with fungal infection in the caterpillars, we may still see significant defoliation in certain areas of Massachusetts this year due to this insect. 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 continue to see more normal rainfall amounts this season. Only time will tell. So far, according to reports from the Northeast Regional Climate Center, last month (April) showed most (not all) of Massachusetts at or above normal precipitation amounts for that month. As a region, they report from the U.S. Drought Monitor that the Northeast became free of severe drought for the first time since late June 2016 (reported on 4/27/17). See: http://www.nrcc.cornell.edu/regional/drought/drought.html.
We can also hope areas in Massachusetts that 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 southern central and eastern Massachusetts. However, due to the ballooning ability of the young caterpillars, where egg masses may exist nearby, previously unaffected host plants may be found to have gypsy moth caterpillars present on them this year. 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.
Reports continue to indicate that in most areas this year, winter moth caterpillar numbers are reduced. See Regional Reports above for updates regarding current winter moth activity. Dr. Joseph Elkinton and his lab team at the University of Massachusetts reported earlier in the season that when sampling for winter moth in host plant buds, at most of their research sites they were observing greatly reduced winter moth numbers this year. Dr. Elkinton reports that in past similar surveys, it was not uncommon to find 20+ winter moth caterpillars per host plant bud sampled. Earlier in the 2017 season, at most of their research sites, the Elkinton lab reports finding roughly 1-2 caterpillars every other bud or so that was sampled. Please see the Regional Reports above for local information regarding this insect. As of Friday, 5/26/17, the Elkinton Lab reported that winter moth caterpillars (at the sites they are monitoring) are mostly in the 3rd instar at that time, with a few 4th instar larvae present. As of Thursday, 5/25/17, the Elkinton Lab reports that more 4th and 5th instar winter moth larvae have been found at the majority of the sites they are monitoring, but that caterpillar development is variable across the landscape.
For individuals managing winter moth in ornamental plants, spinosad is 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). For more in-depth information regarding winter moth management, see the Identification and Management Fact Sheet above.
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.
- Azalea Bark Scale: Eriococcus azaleae was discovered in CT in 1917 and has since been reported in other states. It is found on the bark of twigs and stems and commonly settles in branch crotches. It has been reported on azalea, rhododendron, andromeda, and others. Female scales are approximately 2-3 mm. in length and covered in a white, waxy coating. The females are purple in color and may resemble a mealybug, although they are a soft or felt scale. These females have overwintered and are going to lay eggs which will hatch into crawlers toward the end of June through mid-July. Crawlers will settle into branch crotches, bark crevices, or on the axils of leaves. There is a parasitic wasp that will attack these insects. When high in number, these scales can cause yellowing of the foliage and their sugary excrement can lead to the promotion of sooty mold. Because these are soft scales, they may be targeted with horticultural oils or insecticidal soaps while observing label instructions to prevent phytotoxicity.
- Black Vine Weevil: Otiorhynchus sulcatus damage is apparent on rhododendron and taxus, but can also be seen on azalea, mountain laurel, and Euonymus. Adult weevils feed along the leaf/needle margins and create rounded notches. Inspect foliage of these plants for notching from last season’s feeding. Larvae, which dwell in the soil, are conducting their heaviest feeding on plant roots at this time. Pupation will occur by the end of this month. Adults will emerge in June and create new damage to leaves for this season. All individuals are females and reproduce asexually. This insect has developed resistance to many chemical insecticides. Entomopathogenic nematodes such as Steinernema carpocapsae, S. feltiae, and Heterorhabditis bacterio-phora work well against this insect, particularly on containerized plants. Results in the landscape vary. Wetting the soil thoroughly prior to application and keeping it wet for at least 5 days following application can help increase the efficacy of the nematodes. Burlap laid around the base of plants during the time adults are active, by the end of May through August, can be inspected weekly for adult weevils which can be killed before egg laying.
- Boxwood Psyllid: Psylla buxi is feeding on boxwood foliage with its piercing-sucking mouthparts. This feeding may not cause yellowing or loss of foliage, but will lead to the cupping of new leaves which can be an aesthetic issue for some. If population numbers are low, management of this pest may not be necessary. Nymphs of this insect may be managed between 290-440 GDD’s.
- Eastern Tent Caterpillar: Malacosoma americanum (ETC) tents continue to grow in size and are increasingly noticeable in certain areas of the state. Scout for, remove, and destroy any eastern tent caterpillar tents in the crotches of branches on susceptible hosts such as cherry and crabapple. If the tents and the growing 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. Pupation of this insect will begin in June and last for a few weeks. For a photo demonstration on how to mechanically manage ETC, please visit the following Buckeye Yard & Garden onLine report from Joe Boggs of the Ohio State University Extension. Warning, reader discretion is advised: http://bygl.osu.edu/node/733.
- Elongate Hemlock Scale: Fiorinia externa is found on eastern, Carolina, and Japanese hemlock, as well as yew, spruce, and fir. Crawlers will be present this month and throughout the growing season and the overlap of many developmental stages at any given time can be observed.
- European Pine Sawfly: Neodiprion sertifer caterpillars or sawflies are active. Reports of this insect on Mugo pine were made on 4/27/17 in Framingham. At that time, the tiny, newly hatched sawflies were still located on the very needles from which they emerged. For other locations, see the Regional Reports above. 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. By June, these caterpillars will drop to the ground to pupate. Adults are typically active in early September through the fall.
- Forest Tent Caterpillar: Malacosoma disstria (FTC) caterpillars continue to feed on maple and oak and were observed on 5/17/17 to be approximately 1 inch in length in Amherst. Other susceptible hosts such as birch, ash, elm, poplar, and basswood may also be fed upon by these caterpillars. These native caterpillars can defoliate their host plants, but are not currently in large populations in all areas in the state. In 2016, certain forested locations in Berkshire County supported ample numbers of these caterpillars. Neighboring states also reported some increased activity by this native insect such as in Vermont (http://bit.ly/2qAoxkR) and New Hampshire (https://nhbugs.org/forest-tent-caterpillar). It will be interesting to keep an eye on the Massachusetts population.
- Hemlock Looper: Two species of geometrid moths in the genus Lambdina are native insects capable of defoliating eastern hemlock, balsam fir, and white spruce. Adult moths lay their eggs on the trunk and limbs of hosts in September and October, and eggs will hatch by late May or early June. Monitor susceptible hosts for small, inch-worm like caterpillars. Where populations are low, no management is necessary. Anecdotal reports of increasing hemlock looper populations in certain areas of western Massachusetts (Berkshire County) have been made this season.
- Lily Leaf Beetle: Lilioceris lilii adult beetles were observed causing feeding damage, mating, and eggs were laid on plants in Amherst. As of 5/24/17, frass or excrement-covered larvae of this insect were found feeding in Amherst. For the most part, adults are easily visible and still mating and laying more eggs. See Regional Reports for local activity of this insect. Management can be achieved by hand-picking and removing adults and larvae. 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/
- Roseslugs: Two species of sawfly can be found on the leaves of roses at this time. These small, caterpillar-like larvae will skeletonize the upper leaf surface and leave a “window-pane” like pattern behind. When present in large numbers, these insects are capable of defoliating their entire host. Management options include an insecticidal soap spray or a product containing spinosad.
- Two-marked Tree Hopper: The Enchenopa binotata species complex is now thought to be made up of very closely related Enchenopa spp. that are morphologically very similar but separated by the different host plants that they are found on. These particular treehoppers are found on black walnut, wafer ash (Ptelea trifoliata), and viburnum. These insects will feed on the host plants with piercing-sucking mouthparts and drink plant juices from the leaves and petioles. Leaves will become shiny and sticky with their excrement. Tiny nymphs have been observed on wafer ash in Amherst. Eggs are laid by adult females using saw-like ovipositors to insert them into plant stems. Eggs are then covered with a vivid white, sticky, frothy material that protects them but can easily be mistaken for a scale insect. Eggs have hatched and the tiny, young nymphs can be seen feeding at this time. These treehoppers, whether by their feeding activity or egg laying behavior into plant stems, are not considered to be damaging pests (even when high in numbers) and therefore management is generally not required.
- Viburnum Leaf Beetle: Pyrrhalta viburni is a beetle in the family Chrysomelidae that is native to Europe, but was found in Massachusetts in 2004. See the Regional Reports regarding areas where this insect has been noted to be active thus far this season. This beetle feeds exclusively on many different species of viburnum including but not limited to susceptible plants such as V. dentatum, V. nudum, V. opulus, V. propinquum, and V. rafinesquianum. Larvae may be treated with a product containing spinosad. 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/.
- White Spotted Pine Sawyer (WSPS): Monochamus scutellatus adults have been reported from Middlesex and Worcester counties at this time. Adults are typically active at this time of year, through July, depending upon local temperatures.This is a native insect in Massachusetts and is usually not a pest. Larvae develop in weakened or recently dead conifers, particularly eastern white pine (Pinus strobus). However, the white spotted pine sawyer looks very similar to the invasive Asian Longhorned Beetle, Anoplophora glabripennis, ALB. ALB adults do not emerge in Massachusetts until July and August. Beginning in July, look for the key difference between WSPS and ALB adults, which is a white spot in the top center of the wing covers (the scutellum) on the back of the beetle. White spotted pine sawyer will have this white spot, whereas Asian longhorned beetle will not. Both insects can have other white spots on the rest of their wing covers; however, the difference in the color of the scutellum is a key characteristic. See the Asian longhorned beetle entry below for more information about that non-native insect.
- 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. 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 be emerging this season around 450 GDD’s (see Environmental Data above). 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.
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.
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.
For information about managing ticks in landscapes, among other topics, please visit the following publication from the Connecticut Agricultural Experiment Station: “Tick Management Handbook”: http://www.ct.gov/caes/lib/caes/documents/publications/bulletins/b1010.pdf.
Report by Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program