Woody ornamental insect and non-insect arthropod pests to consider, a selected few:
- Gypsy Moth: Lymantria dispar caterpillars are in various sizes or developmental stages (instars) depending upon the location in Massachusetts. However, observations indicate that in many locations, these larvae are mostly in the 4th instar stage, however some 5th instars have been spotted. Male gypsy moth caterpillars go through 5 instars and female gypsy moth caterpillars have 6 instars. These caterpillars will continue to feed for the next couple of weeks, until they pupate, typically at the end of June. Male caterpillars will pupate just prior to the female caterpillars; pupation, like the transformation between the previous stages, does not happen all at once.
At this time and until the end of June, the defoliation they cause will be most noticeable. Reports made on 6/6/17 indicate that tree canopy thinning and complete defoliation were observed along I-90, approximately 4 miles east of Palmer, MA. On 6/15/17, a “55-65 MPH Survey” (driving along the MA Pike, I-90, on the way to a previously scheduled training) was conducted from the Westfield Exit (#3) to Exit 14 toward 95 south. Gypsy moth defoliation was highly visible beginning in Wilbraham while headed east through Palmer. On either side of the MA Pike, partial or complete defoliation (mostly oaks) could be seen. At mile marker 66.5 (just before) when headed downhill in the eastbound direction over the Quaboag River, there is a certain vantage point where you are at a higher elevation than the surrounding hillsides on either side of the highway. From that point of view, the defoliation was incredible. Large swaths on either side of the surrounding hills were covered in bare trees. When continuing east down I-90, the defoliation on either side of the highway continues through Sturbridge and roughly to the Charlton Plaza. From that point on, the defoliation was significantly less, at least on the trees visible from the highway. This trend continued roughly through Worcester, with any defoliation remaining in patches and certainly not to the extent of what was seen west of there. It seemed to not pick up again until roughly mile marker 98 and then was sporadic and relatively light (again, when thinking about the previously described areas) until you reach Hopkinton and Exit 11A to 495. Defoliation in that area seemed again analogous to what was seen from Wilbraham to the Charlton plaza. By mile marker 108.7, defoliation dropped to sporadic, light patches again. This limited, quick survey ended at Exit 14 and no samples of caterpillars were taken at that time due to safety concerns and time limits. However, it will be interesting to see what the 2017 aerial survey maps from the MA Department of Conservation and Recreation look like for defoliation this year.
Caterpillars are actively crawling up and down tree trunks, a behavior which makes them more likely to be exposed to pathogens, including the fungus, Entomophaga maimaiga. Reports of the sound of frass (excrement) dropping from the canopy where these caterpillars are feeding have been made. (The sound of frass dropping could be heard in Belchertown on 6/9/17 and Hanson on 6/15/17.) Roughly, 1- 1.5-inch long gypsy moth caterpillars have been observed resting or crawling on tree trunks and branches in Amherst as of 6/14/17. These caterpillars are dark in color, hairy, and the “warts” have developed to include the characteristic blue and red coloration, along with a head capsule that is yellow and mottled with black markings. In areas where gypsy moth caterpillars are abundant, citizens are dealing with caterpillars crawling all over the sides of homes, sheds, lawn furniture, and dropping from these locations and nearby trees. Caterpillars may be found on driveways, along with shredded sections of leaves due to their feeding, which are easily visible against that background. In Amherst on 6/12/17, caterpillars were found in a cluster, hidden behind a sign that was leaned up against a Norway maple. The sign was moved from the shaded area beneath the tree to a location in full sun, in order to inspect the cluster of caterpillars on the tree. In moments, the sun heated the sign and 50+ caterpillars came crawling down from where they were hidden along the edges of said sign. See the Regional Reports above for more information about gypsy moth activity.
According to prior reports from the Elkinton Lab, successful infection of gypsy moth caterpillars with the insect-killing fungus Entomophaga maimaiga, has begun. It is 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. Dr. Joseph Elkinton and his lab group, along with other local cooperators, are conducting a study that he is referring to as the “Cloud of Death Experiment”! What Dr. Elkinton means by this is that the research will aim to detect the amount of air-borne spores of the Entomophaga maimaiga fungus in certain locations of Massachusetts throughout the rest of the 2017 caterpillar activity (roughly through June). He and his lab hope to compare this to a measurement of the caterpillars killed at these various locations while determining if the fungus (or virus) is responsible. The Elkinton Lab has sites in Amherst, Belchertown, Brewster, Eastham, Hanson, and West Bridgewater to conduct these observations. To date, they have reported fungal activity at some of these sites, now with approximately 30% mortality due to Entomophaga maimaiga observed in caterpillars being reared on artificial diets (in the lab) collected from these sites. Anecdotally in the field, however, some reports of gypsy moth caterpillars “disappearing in large numbers” have been made at various locations across the state. This may be, in part, due to the behavior change that occurs when caterpillars reach the 4th instar. If an observer is used to seeing the caterpillars actively feeding on foliage during the day, they may be surprised to find them missing. The 4th instar caterpillars will change their behavior such that they feed at night, while hiding during the day. That being said, in high populations, even 4th instar caterpillars will feed at any time, daytime included. Fungal spores were isolated from a caterpillar collected from Belchertown on 6/9/17; however, the majority of the (many) caterpillars observed on that date were healthy and actively feeding (even during the day) at that location. Reports of caterpillar dieback at a location in Marlborough were also made on 6/15/17. The Elkinton Lab expects the percentage of caterpillars killed by the fungus will increase, but unfortunately, we cannot determine at this time how large of an impact the fungus will have on gypsy moth this year. Look to the Landscape Message for continued updates about Dr. Elkinton’s research as well as reports concerning the activity of Entomophaga maimaiga in Massachusetts.
To treat individual, landscape ornamental and shade trees, 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. Gypsy moth damage has also been reported on blueberry crops in Massachusetts this year.
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 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
- 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. Adults 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, through August, can be inspected weekly for adult weevils which can be killed before egg laying.
- Cottony Taxus Scale: Chloropulvinaria floccifera, also referred to as the cottony camellia scale, utilizes such hosts as taxus, camellia, holly, hydrangea, Japanese maple, euonymus, magnolia, jasmine, and Callicarpa americana. This insect was observed on taxus in Amherst on 5/31/17. Females are laying the long, narrow, white colored egg sac that makes them much more noticeable. This was observed again on 6/8/17 and 6/14/17. Eggs will hatch over an extended period of 6 weeks and crawlers may be treated between 802-1388 GDD’s. This insect can cause the host to appear off-color. They also produce honeydew which promotes sooty mold growth. Target the underside of the foliage. Horticultural oil, neem oil, and insecticidal soaps may be used to manage these soft scales. They may also be washed from plants with a strong jet of water.
- Eastern Tent Caterpillar: Malacosoma americanum (ETC) impacts cherry, crabapple, apple, ash, birch, willow, maple, oak, poplar, and witch-hazel. Pupation of this insect will begin in June and last for a few weeks. Adults are typically seen in late June - early July. At a site being monitored in Westfield, MA, the tents of ETC are vacant and the caterpillars are nowhere to be found. Due to the amount of poison ivy at the site, closer inspection for pupae was not possible; however, it is suspected that the caterpillars at that location have begun to pupate.
- Elongate Hemlock Scale: Fiorinia externa is found on eastern, Carolina, and Japanese hemlock, as well as yew, spruce, and fir. Crawlers will be present throughout the growing season and the overlap of many developmental stages at any given time can be observed.
- 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) and most recently, cultivated olive (Olea europaea). (See: https://academic.oup.com/jee/article-lookup/doi/10.1093/jee/tox139.) Adult insects of this species are emerging at this time, as we have surpassed in most areas of the state 450-550 GDD’s (see Environmental Data above). Anyone monitoring for emerald ash borer using traps and lures should have them deployed at this time (if they have not already), otherwise they risk missing adult beetle activity. Signs of an EAB infested tree may include D-shaped exit holes in the bark, “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/upon peeling 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 report it at the Massachusetts Introduced Pests Outreach Project: http://massnrc.org/pests/pestreports.htm
- European Elm Scale: Gossyparia spuria is a type of felt scale and was observed on an elm on 6/7/17 and 6/14/17 in Amherst. First noted in New York in 1884, this non-native scale is now widespread in North America and is found on native and European elms, but also rarely on hackberry and Zelkova. This insect can cause yellowing of foliage, premature leaf drop, and eventually dieback on its host. Honeydew and thus sooty mold are produced. The females observed in Amherst have produced a ring of white fibers around their black, oval bodies. By the end of June, these females will lay eggs that hatch into bright yellow crawlers, which will disperse to the midrib and leaf veins on the underside of elm leaves where they will remain to feed. Crawlers are tiny and magnification is necessary to observe. Natural enemies such as parasitic wasps and predatory insects have been reported as successful in managing this insect.
- Fletcher Scale: Parthenolecanium fletcheri (soft scale) was observed on taxus (yew) in Amherst on 6/8/17 and 6/14/17. Several effective parasites will impact these scale populations and any management decisions should seek to preserve them. Dead, desiccated female scales appear at this time as covers (test) that one might expect from an armored scale and should not be confused for one. When removed, it is easy to find hundreds of tiny, white colored eggs beneath the female (you will need a hand lens to observe). This scale is commonly found on yew and arborvitae (but has also been reported on juniper and hemlock). It may be confused with the European fruit lecanium (P. corni), which has a much broader host range. Depending upon the host plant, crawlers of the fletcher scale will hatch by the end of June and management may be targeted between 1029-1388 GDD’s, base 50°F. Large populations of this scale may lead to host plant yellowing, premature needle drop, and production of honeydew giving way for sooty mold. Each female produces on average 500-600 eggs. The degree of impact this insect may have depends on the host. Some hosts, such as yew, are reportedly more heavily impacted by this scale as when compared to arborvitae, where visible damage may be seldom. Horticultural oil, insecticidal soap, or neem oil may be used according to label instructions in order to preserve natural enemies.
- Forest Tent Caterpillar: Malacosoma disstria (FTC) caterpillars continue to feed on maple and oak. Other susceptible hosts such as birch, ash, elm, poplar, and basswood may also be fed upon by these caterpillars. These native insects can defoliate their host plants, but are not currently in large populations in all areas in the state. At a location in Amherst, FTC’s were observed to have perished due to a fungus (different species of Entomophaga affect these native caterpillars than the one found in gypsy moth). At a location in Belchertown on 6/9/2017, many large FTC’s were observed feeding alongside gypsy moth caterpillars. Pupation of forest tent caterpillars will begin soon, but they are still actively feeding at this time.
- 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 hatched in 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 still causing feeding damage, mating, and eggs were laid on plants in Amherst on 6/14/17. More frass or excrement-covered larvae of this insect were also found feeding in Amherst at this time. These larvae are growing ever-larger and are completely devouring leaves; whereas their smaller counterparts are still skeletonizing. 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. (Although when many plants are involved, mechanical management may not be practical.)
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: These small, caterpillar-like sawfly 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. One species, Allantus cinctus, may require management again in mid-August; otherwise the window for management will pass typically by mid-June.
- Taxus Mealybug: Dysmicoccus wistariae was spotted on taxus in Amherst on 5/31/17, 6/8/17, and 6/14/17. This insect will produce honeydew and lead to sooty mold growth, yellowing of needles, and sparsely foliated plants. Eventual dieback may be possible. This species is commonly associated with taxus in New England, but can be occasionally found on dogwood, rhododendron, Prunus spp., maple, andromeda, and crabapple. These mealybugs are found on stems and branches and particularly like to congregate at branch crotches. Management may be targeted between 246-618 GDD’s. Horticultural oil and neem oil may be used.
- 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. (This was observed for the first time in Amherst on 6/14/17, although the nymphs have been active for quite some time now this season.) Still small 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 this season. At this time, larvae have dropped to the soil to pupate and adult beetles will be present in late-June through roughly October, or when the first frost hits. Adult beetles will create their own feeding damage, but will also mate and females will lay eggs in the stems of the viburnums, typically beginning in late-June to mid-July until October. 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 previously reported from Middlesex, Plymouth, and Worcester counties in MA. (One was also observed in Jaffrey, NH while hiking in Monadnock State Park on Saturday, June 3.) Adults will continue to be active through July. 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.
- Woolly Elm Aphid: Eriosoma americanum is most likely the species responsible for the distorted and curled leaves observed on a plant in Amherst on 6/7/17 and again on 6/14/17. This particular aphid is known to have alternate hosts that it utilizes on a yearly basis. Elm is the overwintering and spring-time host, and by the end of June the winged, migrating generation leaves the elm in search of the roots of Amelanchier. The best time to manage for this aphid has passed (121-246 GDD, base 50°F) and although abundant, the individuals are well protected within the curled and distorted leaves at this time. This particular plant was also highly attractive to adult multicolored Asian lady beetles who were seen mating and scurrying along branches.
- 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 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 until July.
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.
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