Woody ornamental insect and non-insect arthropod pests to consider, a selected few:
- Gypsy Moth: Lymantria dispar caterpillars are dying across Massachusetts! Reports had been trickling in throughout most of June, and from earlier Landscape Message’s you know that Dr. Joseph Elkinton’s Lab at the University of Massachusetts has been documenting fungal (Entomophaga maimaiga) activity for a couple of weeks now. E. maimaiga is of course an insect-killing fungus that is quite specific to gypsy moths. Any gypsy moth caterpillars that have not become diseased are mostly 6th instar females at this point, and others have begun to pupate. The feeding period for gypsy moth is nearly over for 2017, so management at this time is not necessary.
Particularly at the end of last week and through the weekend (6/24 and 6/25), reports of caterpillar mortality (with photographic evidence) have flooded in to UMass Extension from various locations. This includes but is not limited to the following areas of Massachusetts: Amherst, Belchertown, Bernardston, Boylston, Brewster, Brookfield, Cotuit, Eastham, Falmouth, Hanson, Hingham, Marlborough, Marstons Mills (Barnstable), Milford, Monson, North Attleborough, Pelham, Plymouth, Sturbridge, Wellfleet, West Bridgewater, West Brookfield, Yarmouth, and much of Cape Cod and the South Shore. The spores of the fungus (Entomophaga maimaiga) have been confirmed from samples taken from many of those areas and the NPV virus was confirmed active in Hanson, MA and is likely active in other areas as well.
For example, a population of gypsy moth caterpillars was observed to be “otherwise healthy” and feeding on a crabapple at a location in Amherst, MA on Sunday, 6/18/2017. (They had already done a number on nearby oaks in the area.) By Friday, 6/23/17, the caterpillars were either shriveled up and hanging vertically from the trunk and branches of the tree (may be indicative of Entomophaga maimaiga) or juicy and drooping in this location in an inverted-V shape, which may be mortality caused by the NPV virus that kills gypsy moth. (The only way to truly tell which pathogen is responsible is to look at samples from the dead caterpillars under a microscope.) If you have gypsy moth caterpillars hanging off of your trees in this manner, there is no need to "clean them off" in any way. They will eventually be washed off by rains, etc. Leave them where they are so that the fungal spores or NPV viral particles can disperse in a natural manner.
Unfortunately, gypsy moth caterpillars are still responsible for some widespread defoliation in certain areas of the state this year, as seen in these photos from Ware, MA (taken on 6/24/17). Many caterpillars survived long enough to reach the size where they are able to partially or completely strip the leaves from their host trees. Partial or complete defoliation of trees due to gypsy moth can be seen on either sides of the MA Turnpike (I-90), particularly from Wilbraham to the Charlton Plaza. More updates about estimated total acreage defoliated by gypsy moth in 2017 will become available once the Massachusetts Department of Conservation and Recreation is able to complete their aerial survey of the state. This survey began only recently, in order to most accurately capture the defoliation caused by these caterpillars (those not killed by the fungus are still feeding, particularly the female caterpillars who undergo an additional instar (6th), or developmental stage, than the males (5th)). Some are still reporting caterpillar feeding activity in areas such as Brimfield, Southborough, and Westborough, MA. The Elkinton Lab reports that many have successfully pupated in the Hopkinton, MA area. This should be noted, as although the mortality of these caterpillars has been very impressive in many areas, we should remind ourselves that it is not occurring in 100% of the population.
Residents in Massachusetts, particularly in southern central MA and the southeastern portions of Franklin, Hampshire, and Hampden counties still experienced high populations of this insect in 2017, many dealing with caterpillars dropping in driveways along with shredded leaves. Caterpillar frass (excrement) could be heard raining down from tree canopies at various locations, often covering patios and lawn furniture. The recent wave of mortality sweeping gypsy moth caterpillars is a welcome sight for many.
Just as we may be able to credit (mostly) the drought conditions experienced in 2015 and 2016 with the recent increase in the gypsy moth population (through the impediment of Entomophaga maimaiga activity), we can credit the rainfall events seen in May and June of 2017 for the success of the fungus this year. Although we have been waiting for this with much anticipation and wish the caterpillar collapse occurred sooner, it is certainly better than the alternative. Hopefully, this outbreak of these pathogens in this year’s gypsy moth population will mean a reprieve for many from this insect in 2018. The Elkinton Lab reports that fungal activity was particularly pronounced on Cape Cod and the South Shore, and it seems that in many other areas across the state, the fungus has kicked in just in time.
Gypsy moth caterpillars (those that survived), as mentioned previously, have begun to pupate in many locations. (The pupae, or “resting stage”, do not feed and neither do the adults, so management is no longer necessary this season.) Those that successfully pupate will become adults, which will mate (particularly in July) and the females will lay their fuzzy, tannish-brown egg masses, which will overwinter and provide caterpillars for 2018. Our hope is that we will see fewer males (brown moths that fly) and perhaps most importantly fewer females (white colored moths that, although they have wings, do not fly) which will lead to fewer egg masses to hatch in 2018. Fewer: that is not to say that these insects will 100% disappear from the landscape next year. However, the hope is that the population will drop below nuisance levels at least in some locations. The Elkinton Lab reports as of 6/28/17, with the exception of one of their research sites in Massachusetts, 80-90% of their sampled caterpillars have perished. This is certainly excellent news; however, we should keep this in perspective, given that each female moth can potentially lay, according to Dr. Elkinton, approximately 300 female eggs. Even if 298 of those individuals die before maturity in 2018, the population could still theoretically increase.
Therefore, we rejoice in the fact that the fungus and virus are finally active in the gypsy moth population this year as compared to recent years, but remain cautious. We will continue to watch the number of caterpillars that make it to pupation in the next week, and keep an eye on the adults and the number of egg masses the females lay. Overall, having these grotesque caterpillars stuck to the sides of our trees is a great thing. In many areas, they are full of the hardy, long-lived resting spores of Entomophaga maimaiga, which are capable of overwintering and providing continued infection of this insect’s population for many years to come.
- 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. By the time the next Landscape Message is released, adults of this insect could be active in the regulated area in Massachusetts.
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.
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.
- 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. Now is the time to 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 (ALB’s is black). See the Asian longhorned beetle entry above for more information about that non-native insect.
- Asiatic Garden Beetle: Maladera castanea adults are active and are typically most abundant in July and August. These rusty-red colored beetles are bullet-shaped and active at night. They are often attracted to porch lights. They feed on a number of ornamental plants, defoliating leaves by giving the edges a ragged appearance and also feeding on blossoms. Butterfly bush, rose, dahlia, aster, and chrysanthemum can be favored hosts. When levels of damage reach a management threshold, pyrethroid- based insecticides may be necessary. Read and follow label instructions and avoid harming non-target organisms. Certain neem oil products are also labelled for use against adult beetles. Observe label instructions to minimize the potential for leaf injury.
- 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.
- 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 active. 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, 6/14/17, and 6/28/17 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 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. Crawlers were observed on a small sample of elm leaves at a location being monitored in Amherst on 6/28/17. 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. Crawlers were observed beneath a single desiccated female sampled on 6/29/17 from Taxus in Amherst, MA. 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.
- 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.
- Lace Bugs: Corythucha spp. and Stephanitis spp. lace bugs are active. Corythucha spp. utilize many hosts such as: hawthorn, cotoneaster, amelanchier, quince, pyracantha, various oaks, birch, maple, mountain ash, sycamore, hackberry, elm, walnut, butternut, basswood, etc. By the time we reach 1266-1544 GDD’s, management of Corythuca spp. may be necessary again if these insects were problematic earlier this season. Stephanitis spp. lacebugs such as S. pyriodes can cause severe injury to azalea foliage. S. rhododendri can be common on rhododendron and mountain laurel. S. takeyai has been found developing on Japanese andromeda, leucothoe, styrax, and willow. Stephanitis spp. lace bugs should be monitored through September. Before populations become too large, treat with a summer rate horticultural oil spray as needed. Be sure to target the undersides of the foliage in order to get proper coverage of the insects. Fall or early spring soil treatment with imidacloprid has been effective, but be aware of the implications this may have on pollinators attracted to these flowering plants when making management decisions. Certain azalea and andromeda cultivars may be less preferred by lace bugs.
- Lily Leaf Beetle: Lilioceris lilii adult beetles were still present and mating when observed on 6/28/17. Frass-covered larvae were difficult to find on this particular scouting mission to a location that has been continuously monitored in Amherst this season. 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.) Larvae can feed for 16-24 days and then drop to the soil to pupate. Adults will emerge 16-22 days later and are then seen feeding throughout the remainder of the growing season. Adults will overwinter.
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 passes typically by mid-June.
- Taxus Mealybug: Dysmicoccus wistariae was spotted on taxus in Amherst on 5/31/17, 6/8/17, 6/14/17, and 6/29/17. 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. What a difference a week can make! Much larger nymphs and adults have now been observed on wafer ash in Amherst on 6/28/17. Eggs will be laid by adult females using saw-like ovipositors to insert them into plant stems. (This has not yet been observed at this location.) Eggs are then covered with a vivid white, sticky, frothy material that protects them but can easily be mistaken for a scale insect. 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 soon be present in most locations where they exist 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. 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 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.
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:
there are important things to consider if outdoors while celebrating the 4th of July. 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. For extensive information and resources, see our Information Regarding Ticks and Tick-Borne Diseases
Report by Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program