A monthly e-newsletter from UMass Extension for landscapers, arborists, and other Green Industry professionals.
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Hot Topics
UMass Garden Calendar Photo Contest
Ever take a great garden photo and think “this would be perfect for the UMass Garden Calendar?” We are pleased to announce that we are now accepting photos submitted by the public. Submissions will be judged by the calendar team at UMass Extension and may earn a spot in the 2019 Garden Calendar. For more information visit the Garden Calendar page.
Ticks are active at this time!
Remember to take precautions when working outdoors and to conduct daily tick checks. The UMass Amherst Laboratory of Medical Zoology tests ticks for Lyme Disease and other tick-borne pathogens. Visit the Tick Report website for more information.
Questions & Answers
Q: A magnolia on this property is covered in sooty mold, has small/stunted leaves, and the occasional dead twig. What might be going on here?
A: When sooty mold is involved, one of the first thoughts you should have is: could there be a honeydew-producing insect on this plant? Honeydew is the sugary, watery secretion (excrement) from certain insects with piercing-sucking mouthparts that feed on plant juices. Such insects include but are not limited to most of the soft scales (armored scales typically do not produce honeydew), aphids, and others. Many of these insects are “tapping into” the plant phloem, or the vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves. Sugar is in much larger abundance in these particular plant fluids than other essential materials for life, including amino acids (organic compounds) that these types of insects need in order to build proteins. Therefore, these insects must imbibe great quantities of these plant liquids, excreting extra sugar and water in the form of honeydew, in order to absorb enough amino acids. This excreted honeydew encourages the growth of sooty mold (the common name given to many species of fungi that grow on these secretions) and can also be attractive to sugar-loving insects such as ants, wasps, and hornets. Because of this excessive feeding on the plant fluids, leaf yellowing/discoloration and even stunting may occur on the host plant. Eventually, small twigs and entire branches on certain magnolias may perish due to heavy infestations of either the magnolia scale (Neolecanium cornuparvum; the largest scale insect found in the USA) or the tuliptree scale (Toumeyella liriodendri; a close second for the title of one of the largest scale insects in the United States).
Q: What is the life cycle of the magnolia scale, Neolecanium cornuparvum? What hosts are primarily impacted by this insect?
A: The magnolia scale is a species of soft scale insect (Family: Coccidae) that is native to the United States and found throughout the eastern US. It is the largest scale insect found in this country. Adult female magnolia scales can measure up to ½ inch or more in length. Host plants include Magnolia stellata (star magnolia), M. acuminata (cucumber magnolia), M. lilliflora ‘Nigra’ (lily magnolia; formerly M. quinquepeta), and M. soulangeana (saucer magnolia). Other species may be hosts for this scale, but attacked to a lesser degree. M. grandiflora (southern magnolia) may be such an example. This scale overwinters as a young nymph (immature stage) which are elliptical in shape, mostly a dark-slate gray, except for a median ridge that is red/brown in color. These overwintering nymphs may be found on the undersides of 1st and 2nd year old twigs. The first molt (shedding of the exoskeleton to allow growth) can occur by late-April or May in parts of this insect’s range, and the second molt will occur in early June. At this time, the immature scales have turned a deep purple color. Stems of the host plant may appear purple in color and thickened – but this is a coating of nymphal magnolia scales, not the stem itself. Eventually, these immature scales secrete a white layer of wax over their bodies, looking as if they have been rolled in powdered sugar. By August, the adult female scale is fully developed, elliptical and convex in shape and ranging from a pinkish-orange to a dark brown in color. Adult females may also be covered in a white, waxy coating. By that time, the females produce nymphs (living young; eggs are not “laid”) that wander the host before settling on the newest twigs to overwinter. In the Northeastern United States, this scale insect has a single generation per year.
Q: What is the life cycle of the tuliptree scale, Toumeyella liriodendri? What hosts are primarily impacted by this insect?
A: The tuliptree scale is a species of soft scale insect (Family: Coccidae) that is native to the United States and also found in much of the eastern US, but also has been recorded in California. It appears to be present wherever host trees are found. It is another one of the larger scale insects found in the United States, a close second in size to the magnolia scale discussed above. Adult female tuliptree scales can measure up to ¼ to just under ½ inch in length. Host plants include Liriodendron tulipifera (tuliptree or yellow poplar), Magnolia stellata (star magnolia), and M. soulangeana (saucer magnolia). This insect has also been recorded on M. grandiflora (southern magnolia) and Tilia spp. (linden). The tuliptree scale has also, to a lesser extent, been reported on other ornamental trees and shrubs. When this insect is present on magnolias, such as those mentioned above, it is often confused for the magnolia scale (Neolecanium cornuparvum). The two may be similar in size and have similar life cycles. The mature female tuliptree scale is hemispherical in shape. Color of the mature female varies in this species as well, a grayish-green to pink-orange insect mottled with black. Adult males emerge sometime in June and mate with the females. Like the magnolia scale, eggs develop within the body of the female tuliptree scale, leading to the “live birth” of immatures (crawlers) in late August and September. In the Northeast, one generation of tuliptree scales occurs per year. (However, in the southern-most portions of its range, this insect has been found in all stages of development during the winter, suggesting multiple generations per year.) A single female tuliptree scale may produce 3,000+ crawlers in one season. These crawlers are tiny (approximately the size of the head of a pin) and settle on host plant twigs in September. Past studies have shown that in addition to moving on their own with fully functional legs, the crawlers can be blown to new hosts on the wind, up to 100 feet away. (Being wind-blown to a new host, however, is a haphazard method of travel through which some less than 20% of these crawlers successfully make contact with a host plant, and fewer still attach to a suitable site on the plant.) The immature, crawler stage molts once prior to overwintering.
Q: What are my options for management?
A: As two native scale insects in North America, the magnolia and tuliptree scales are hosts themselves for natural enemies that can impact their populations. Solitary parasitoid larvae have been collected from magnolia scales and have been identified as a syrphid fly species, Ocyptamus costatus. The natural enemies of the tuliptree scale have been studied to a greater degree, including certain lady beetle species (Hyperaspis signata, Adalia (formerly Hyperaspis) bipunctata, and Chilocorus stigma) which feed on nymphal scales, a number of parasitic wasps, and even an insect-feeding moth caterpillar (Laetilia coccidivora). This particular moth species, also referred to as a type of snout moth, will consume the tuliptree scale underneath the protection of a silken web it spins over them! (The specific epithet coccidivora can be translated as “ones that eat soft scales” or Coccidae.) Unfortunately, in a landscape setting, it often seems that although these natural enemies may be common within the scale populations, they are seldom able to reduce the scale insect numbers below damaging levels. That being said, our management options should seek to preserve these natural enemies.
Management options for the magnolia scale (Neolecanium cornuparvum) include mechanical removal (by hand; by July) of the adult females prior to crawler emergence in August. Severely infested branches may also be pruned from the host plant where possible, then destroyed. Many chemical management options are available for the magnolia scale, however few offer reduced impacts toward natural enemies and pollinators. Some reduced-risk options include dormant horticultural oil applications roughly between 7-35 Growing Degree Days, Base 50°F, while avoiding sprays on opening buds or blooms. Foliar applications in October can target magnolia scale crawlers present on branches but severe infestations may require two treatments. Insecticidal soap or neem oil products can be reduced-risk options for fall foliar applications. Systemic insecticides applied via soil application are made in the late fall or early spring.
Management options for the tuliptree scale (Touymeyella liriodendri) include mechanical management by removing scales by hand or pruning and destroying infested plant material when practical/possible. High-pressure water sprays can at times dislodge scale insects from smaller host plants, yet care must be taken to avoid plant damage. Although this is a soft scale, foliar applications of insecticides should still target the crawler or immature stages of this insect, as the tuliptree scale is covered with a protective waxy layer for most of its life cycle. Many active ingredients are also available for use against the tuliptree scale, but reduced risk products may include horticultural oil, insecticidal soap, and neem oil. Dormant oils may be applied between 12-121 Growing Degree Days, Base 50°F, for this pest. Foliar insecticides may be applied between 2032-2629 Growing Degree Days, Base 50°F, or roughly in late August through mid-September.
As always, if choosing chemical management options, please read, understand, and follow all label instructions for use and safety of the applicator and the environment.
For both of these insects, reduction of host plant stress through proper plant installation, irrigation, and maintenance can go a long way toward maximizing plant tolerance to insect pests. In general, plant stress is associated with greater scale insect abundance on landscape ornamental plants.
For information on how you can use Growing Degree Days to time management decisions for insect pests in landscape settings, please visit the Growing Degree Days for Management of Insect Pests in the Landscape Fact Sheet
Q: Why do scale insects suck so much? (Pardon the poorly planned pun.)
A: Scale insects have piercing-sucking mouthparts that are used to drink host plant fluids. Many of these insects are “tapping into” the plant phloem, or the vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves. Sugar is in much larger abundance in these particular plant fluids than other essential materials for life, including amino acids (organic compounds) that these types of insects need in order to build proteins. Therefore, these insects must imbibe great quantities of these plant liquids, excreting extra sugar and water as honeydew, in order to absorb enough amino acids.
This type of feeding may lead to host plant leaf yellowing, premature leaf drop, and can also lead to twig and branch dieback. These insects can be difficult to manage at times, due to their relatively small size (especially the immatures) which can allow them to go unnoticed until large populations are either A) producing excessive amounts of honeydew or B) causing noticeable plant damage. They are also extremely fecund, as mentioned with the tuliptree scale example, which are capable of producing 3,000+ young in a single season. Finally, although these are soft scales and do not have the armor-like “tests” or hardened coverings of their armored scale counterparts, they do secrete a protective, waxy covering over themselves which can protect them from certain contact insecticides.
Q: Where can I find more information?
A: Look to the Landscape Message for seasonal updates about insect pest activity throughout the remainder of 2017. Please also “Like” and “Follow” us on Facebook @UMassExtLandscape to receive updates and notifications.
Please also visit the following Fact Sheets regarding insect and mite pests in Massachusetts: https://ag.umass.edu/landscape/fact-sheets/insects-mites.
Have an insect pest on a tree or shrub and need it identified? Send a sample to the UMass Plant Diagnostics Laboratory.
Sources:
Burns, D. P., & Donley, D. E. (1970). Biology of the tuliptree scale, Toumeyella liriodendri
(Homoptera: Coccidae). Annals of the Entomological Society of America, 63(1), 228-235.
Cranshaw. Whitney. Garden Insects of North America: The Ultimate Guide to Backyard Bugs.
Princeton University Press, 2004.
Johnson, Warren T., and Howard H. Lyon. Insects That Feed on Trees and Shrubs. 2nd, Revised
Ed., Comstock Pub. Associates, 1991.
Vanek, S. J., & Potter, D. A. (2010). An interesting case of ant-created enemy-free space for
magnolia scale (Hemiptera: Coccidae). Journal of insect behavior, 23(5), 389-395.
Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program
Trouble Maker of the Month
Invasive Oriental Bittersweet, Celastrus orbiculatus
Species overview
Oriental bittersweet is an invasive, deciduous vine found throughout New England. This woody perennial reproduces sexually by seed and asexually by creeping roots that sprout to form new stems. Oriental bittersweet can be observed growing as a brushy groundcover to a height of a few feet or as a climbing vine on tall trees where the vines may reach 40 to 60 feet. Climbing vines can negatively impact the health of native trees and shrubs. Stems of climbing vines can reach 3 to 4 inches in diameter. Alternate leaves are round with crenate margins. Five-petaled, greenish-white flowers grow in clusters and are somewhat inconspicuous. These clusters are produced axillary along the stem. Flowering occurs in late spring and early summer. Oriental Bittersweet is almost always dioecious, producing male (staminate) and female (pistillate) flowers on separate plants. This can readily be observed in the fall as the female plants will produce fruit and male plants will be fruitless. Individual fruits are about 1/3", globoid-ovoid in shape, and glabrous. At maturity, the outer husk of each fruit turns yellow and splits open into 3 parts to reveal a bright red, fleshy fruit that contains 1-2 seeds. Fruits are readily consumed by various birds and other small animals. Consumption of fruit by animals is known to aid in the spread of this invasive plant. Oriental bittersweet is rarely affected by insect pests and disease organisms which allows populations to grow unchecked in both landscapes and wild habitats. Humans can play a role in the spread of this invasive when they decide unwisely to use it as an ornamental plant in landscaping or collect branches of the colorful fruits for ornamental purposes.
Management
Physical/Mechanical: Oriental bittersweet is a prolific seed producer and seedlings/small plants are very common. As part of an ongoing maintenance program, these seedlings/small plants should be pulled by hand as they appear. After Oriental bittersweet is controlled with an herbicide, physical removal should be used as part of an ongoing management program to prevent regrowth.
Herbicides: Foliar applications of glyphosate will not control Oriental bittersweet. These applications will only cause temporary yellowing and the plant will recover in a short period of time. Foliar applications of triclopyr are a better postemergence choice. Alternatively, glyphosate and triclopyr can be used as a cut stem/cut stump treatment. Selection of foliar versus cut stem/cut stump treatments will be determined by the growth habit of the oriental bittersweet. In other words, is it growing as a groundcover (low growing brush) or a tree-climbing vine? Triclopyr can also be applied a basal bark treatment.
Final management note: Often home gardeners face a large population of Oriental bittersweet where both ground-sprawling and tree-climbing growth habits are present. In this situation, a home gardener may want to consider contacting a landscape or invasive plant management contractor.
Randy Prostak, UMass Extension Weed Specialist
Plant of the Month
Cornus kousa, kousa dogwood
Cornus kousa (kousa dogwood) is one, of a few, terrific landscape plants that have multi-seasonal appeal. It could be Plant of the Month for June, when it flowers. The white, to creamy-white, inflorescence, or “flower”, held above deep green 2-2 ½ inch leaves, is comprised of four white bracts that many people think are the “petals”. Each individual bract is about 1-2 inches long and approximately ¼ to ¾ wide. The four bracts surround the “true” small, almost inconspicuous, green – yellow flowers produced in an umbel in the center of the four white bracts, which usually persist for six weeks, and sometimes even longer. Pollinators, like bees and butterflies, are attracted to the small flowers and after pollinating them, a round green fruit (drupe) begins to form on a 2-2 ½ inch long pendulous stalk.
The round green fruit develops into a round, spherical raspberry-like, deep pink- red fruit that begins to color up in late August – early September and often persists into October. The fruit, while mealy and not very palatable, is edible and is also attractive to wildlife (birds, squirrels, etc.). A showy display of these pink-red fruits dangling from the branches on the kousa dogwood adds color and decorative visual interest to the September landscape, making it a good choice for Plant of the Month for September.
In autumn, the medium-dark green foliage of kousa dogwood gives way to a deep red-burgundy fall color, and on older, more mature trees, after the leaves fall, a beautiful, mottled, exfoliating bark of tans, browns and grays can be seen, adding interest to the late fall, winter and early spring landscapes.
Cornus kousa is a small to medium (20-35 feet high with equal width), vase- shaped deciduous tree, native to China, Korea and Japan. It is a tree with no significant insect or disease problems. It is resistant to dogwood borer and dogwood anthracnose and for those reasons; it is often planted as alternative to Cornus florida, of which it is also more drought tolerant of. Kousa dogwood may be planted in small groups, used as a specimen plant, or as a lawn plant, in a mixed shrub border, etc. However, be aware that it will drop its’ decorative fruit, so avoid planting it near a driveway or other areas where the fruit would be construed as messy, or become a maintenance problem.
Kousa dogwood grows best in an organic, well-drained moistures-retentive soil, in full sun (6 or more hours), but will tolerate some light shade. It is winter hardy to Zone 5 and is an excellent low-maintenance, sustainable tree that provides landscape interest throughout the year.
There are numerous, maybe 100 or more, Cornus kousa cultivars available including some like ‘Benji Fuji’ or ‘Satomi’ with bright pink bracts. There are cultivars with green and white variegated foliage like ‘Wolf Eyes’ and ‘Samzan’ (Samaritan®); or cultivars with green foliage with a gold center (‘Gold Star’). There are Cornus kousa weeping forms like ‘Elizabeth Lustgarten, ‘Lustgarten Weeping’ and ‘Weaver’s Weeping’, which may grow to a height of twelve - fifteen feet and display downward arching branches covered in cascading white flowers in June.
Cornus kousa – a great plant for September as well as many other months; so many cultivars, so little time.
Deborah C. Swanson, Horticulturist
Upcoming Events
Featured Event: Fall Interest Tree and Shrub ID Walk
Studying for the MCH, MCLP, or MCA exam? Want some hand's on experience identifying significant landscape plants to either prepare for one of the exams or to expand your palette of offerings for your clients, while also scouting for potential insect problems? Join Tawny Simisky, Extension Entomologist, and Mandy Bayer, Extension Assistant Professor at UMass-Amherst, for a walk around the grounds of the Tower Hill Botanical Garden. This will be the perfect time of year to focus on trees and shrubs with particular fall interest as well as insects active during the fall. Dress for walking; held outdoors rain or shine. 1 Pesticide contact hour for category 36 and Applicator's License.
Event Location: Tower Hill Botanic Garden, Boylston, MA
Other Upcoming Events:
- 9/23: Landscape and Forest Tree and Shrub Disease Workshop (filled)
- 10/4: Fall Intrest Tree and Shrub ID Walk
- 11/29-12/1: New England Grows
- 1/8-2/16: UMass Winter School for Turf Managers
For more information and registration for any of these events visit the UMass Extension Landscape, Nursery, and Urban Forestry Program Upcoming Events Page.
Additional Resources
For detailed reports on growing conditions and pest activity – Check out the Landscape Message
For commercial growers of greenhouse crops and flowers - Check out the New England Greenhouse Update website
For professional turf managers - Check out Turf Management Updates
For home gardeners and garden retailers - Check out home lawn and garden resources. UMass Extension also has a Twitter feed that provides timely, daily gardening tips, sunrise and sunset times to home gardeners, see https://twitter.com/UMassGardenClip
Diagnostic Services
A UMass Laboratory Diagnoses Landscape and Turf Problems - The UMass Extension Plant Diagnostic Lab is available to serve commercial landscape contractors, turf managers, arborists, nurseries and other green industry professionals. It provides woody plant and turf disease analysis, woody plant and turf insect identification, turfgrass identification, weed identification, and offers a report of pest management strategies that are research based, economically sound and environmentally appropriate for the situation. Accurate diagnosis for a turf or landscape problem can often eliminate or reduce the need for pesticide use. For sampling procedures, detailed submission instructions and a list of fees, see Plant Diagnostics Laboratory
Soil and Plant Nutrient Testing - The University of Massachusetts Soil and Plant Nutrient Testing Laboratory is located on the campus of The University of Massachusetts at Amherst. Testing services are available to all. The function of the Soil and Plant Nutrient Testing Laboratory is to provide test results and recommendations that lead to the wise and economical use of soils and soil amendments. For complete information, visit the UMass Soil and Plant Nutrient Testing Laboratory web site. Alternatively, call the lab at (413) 545-2311.
