Landscape Message: April 29, 2016

April 29, 2016
Issue: 
6

Happy Arbor Day!

UMass Extension's Landscape Message is an educational newsletter intended to inform and guide Green Industry professionals in the management of our collective landscape. Scouts compile and record environmental and phenological data for locations throughout Massachusetts to aid in the monitoring of plant and pest development, the planning of management strategies, and the creation of site-specific records for future reference.  Detailed reports from Extension specialists on growing conditions, pest activity, and cultural practices for the management of woody ornamentals, trees, and turf are regular features. UMass Extension has updated the following issue to provide timely management information and the latest regional news and environmental data.

The Landscape Message will be updated weekly April through June. The next message will be available on May 6. To receive immediate notification when the next Landscape Message update is posted, be sure to join our e-mail list.

NEW! To read individual sections of the message, click on the section headings below to expand the content:

Scouting Information by Region

Environmental Data

The following growing-degree-day (GDD) and precipitation data was collected for an approximately one week period, April 21 through April 27. Soil temperatures and phenological indicators were observed on or about April 27. Total accumulated growing degree days (GDD) represent the heating units above a 50° F baseline temperature collected via our instruments for the 2016 calendar year. This information is intended for use as a guide for monitoring the developmental stages of pests in your location and planning management strategies accordingly.

Region/Location

GDD

Soil Temp
(°F at 4" depth)

Precipitation
(1-Week Gain)

Time/Date of Readings

1-Week Gain

2016 Total

Sun

Shade

Cape Cod

26

81

60

48

0.49

4:00 PM 4/27

Southeast

26

86

59

52

0.50

4:19 PM 4/27

North Shore

22

72

44

41

0.25

10:15 AM 4/27

East

35.5

96.5

58

55

0.37

3:30 PM 4/27

Metro West

30.5

77.5

41

39

0.60

5:45 AM 4/27

Central

38

115

44

41

0.66

9:38 AM 4/27

Pioneer Valley

28

87

51

47

0.76

10:00 AM 4/27

Berkshires

24

74

47

45

0.48

9:30 AM 4/27

AVERAGE

29

86

51

46

0.51

-

n/a = information not available

Phenology

Phenological indicators are a visual tool for correlating plant development with pest development. The following are indicator plants and the stages of bloom observed for this period:

Indicator Plants - Stages of Flowering (BEGIN, BEGIN/FULL, FULL, FULL/END, END)
PLANT NAME (Botanic/ Common) CAPE S.E. N.S. EAST METRO W. CENT. P.V. BERK.
Rhododendron spp. (Early Azaleas) * Begin Begin/Full Begin * * Begin *
Cornus florida (Flowering Dogwood) * Begin Begin Begin * Begin Begin *
Malus spp. (Crabapple) * * Begin Begin Begin Begin Begin/Full *
Cercis canadensis (Redbud) Begin * Begin Begin Begin Begin Full Begin
Amelanchier spp. (Shadbush, Serviceberry) * Full Full Full Begin/ Full Full Full Full
Pyrus calleryana (Callery Pear) Begin Begin/Full Full * Full Full Full Full
Chaenomeles speciosa (Common Flowering quince) Begin/Full Full Full Full Full   Full Full
Magnolia soulangeana (Saucer Magnolia) Full Full Full Begin/Full Full Full Full *
Rhododendron 'P. J. M.' Full Full Full End Full Begin Begin/Full *
Prunus serrulata (Japanese Flowering Cherry) Full/End Full Full * Full * Full *
Forsythia x intermedia (Border Forsythia) Full/End Full/End Full/End End Full/End Full/End End Full/End
* = no activity to report/information not available

Regional Notes

Cape Cod Region (Barnstable)

General Conditions: This has been another week of up and down weather. After closing the week with a high temperature of 73° F on Friday, April 22, the temperatures seemed unable to climb out of the 50s for most of the week. Saturday the 23rd brought scattered showers that only gave the Cape 0.22”. Tuesday the 26th was a cold, windy, and wet day. Temperatures topped off in the low 40s and the Cape received 0.27” of rain. Overall, precipitation is below average for the State as a whole for 2016 and April will go down as generally being below average temperature. That being said, plant development is progressing, albeit slowly. Lawns are green and actively growing and mowing season is well under way. Dandelions are in full bloom and bittercress is starting to go to seed. Early daffodils have gone by but late season daffodils are blooming. Early tulips and Creeping Phlox are providing some bright spots of color in the landscape.

Pests/Problems: Winter moths are actively feeding in flower buds of fruit trees as well as in leaf buds of deciduous trees. Leaves of the Full Moon maple (Acer shirasawanum) are emerging with tiny holes in the leaves. Small holes can be seen in the flowers buds of Asian pear (Pyrus pyrifolia) and the foliage is also damaged. Lily leaf beetle adults are actively feeding on true lilies. Eastern tent caterpillar webs are still quite small and can easily be pruned out if found on ornamentals such as crabapple. Cutworms are active in turf and in the vegetable garden. Pollinators such as carpenter bees and solitary bumble bees are active, as are honey bees. Ants are active. Rabbits are browsing on hosta and other early season perennials. Both deer tick adults and dog tick adults are active. Do thorough tick checks after working in brushy areas and be sure to use either DEET or permethrin labeled for use on clothing.

Cedar apple galls are quite visible after a few damp days.

Southeast Region (Hanson)

Southeast Region (Hanson)

General Conditions: It has been a cooler than usual April with little rain. Hanson did receive 0.50 inchesof rain on April 26th but soils are still dry and could use more rain. The cool temperatures continue to slow plant development, and Magnolia x loebneri ‘Leonard Messel’, Magnolia ‘Wada’s Memory’, still in bloom, are just now starting to end bloom; after a dubious start due to cold weather, these magnolias have, surprisingly, been in flower for almost 3 weeks! Forsythia is still in bloom in some areas and ending bloom in others. Magnolia soulangiana (Saucer Magnolia), Magnolia ‘Elizabeth’, Cherry 'Holly Jolivette', Rhododendron ‘Olga Mezitt’, PJM Rhododendron, Pieris 'Brouwer's Beauty', Pieris floribunda (Mountain Pieris), Pieris japonica, Chaenomeles speciosa (Common Floweringquince), Vaccinium corymbosum (highbush blueberry), Spiraea prunifolia f. simplicifolia (Bridlewreath Spirea), Spiraea thunbergii ‘Ogon’, Helleborus foetidus, Helleborus x hybridus, Glaucidium palmatum, Vinca, Pulmonaria, Trillium, Anemones, Lamium, Primula, Corydalis scouleri, Brunnera macrophylla, Ajuga, Lunaria, Sanguinaria canadensis ‘Multiplex’ (Double Bloodroot), daffodils,hyacinths, Muscari botryoides Grape Hyacinth), Chionodoxa luciliae, Stylophorum diphyllum (Wood Poppy), Phlox subulata, Pachysandra terminalis, Dicentra cucullaria (Dutchman’s Breeches), Erythronium americanum (Trout Lily), Lathyrus vernus, Dwarf Bearded Iris, Violets and Tulips are in full bloom. With all these plants in bloom, we should be seeing a very colorful spring, but due to all the previously discussed cold damage to plants, this spring is decidedly lacking in spring color. Exochorda racemosa (Pearlbush), Epimedium sp., Saruma henryi, Corydalis lutea, and Arisaema (Jack-in-the-pulpit) are beginning bloom. Lonicera fragrantissima (Winter honeysuckle) which is just now ending bloom, began blooming in January, was injured by the cold in February, started blooming again February - March, was injured by the early April freeze and resumed flowering and is still in bloom. Strange spring. Lawns are green and mowing and cleanups are well underway.

Pests/Problems: As plants slowly start to develop, cold damage to them is becoming more visible. Flower bud damage was observed on: cherries, rhododendrons, peaches, apples, Corylopsis, Norway maple, blueberries, Arisaema, etc. Some branch dieback was also observed on Japanese maple, and some cherries. Butterfly bush and many cultivars of Hydrangea macrophylla are showing dieback to the ground with new foliage emerging from the base. The cool weather is delaying leaf expansion, providing a nice, safe, environs for winter moth caterpillars to develop and feed unnoticed (base 40 growing degree days are at 361). Look for leaves, Japanese maples for example, webbed together by the silk the caterpillars produce and find the tiny caterpillars (1st & 2nd instar) feeding within. Although the caterpillars are very small, they can cause damage, especially in this cool weather where the leaves are not expanding very quickly. In many areas, oak and red maple buds have not expanded but winter moth caterpillars were found down in the buds. Continue to monitor oak, tree lilac, birch, crabapple, apple, American beech, maples, and other susceptible plants, for winter moth caterpillars and manage as needed. Amelanchier (shadbush) is a good indicator plant for monitoring gypsy moth hatch and Amelanchier is now in full bloom. Bright red lily leaf beetle is active on true lilies; monitor and manage as needed. Black flies have emerged and are annoyingly very active. Monitor for European pine sawfly on pines, especially hard-needled pines, like Mugo pine, and manage when found, as these sawflies can devour the new pine foliage very quickly, if not treated. Bacillus thuringiensis (Bt) does not work on sawfly larvae. Monitor crabapples, cherries, etc. for Eastern tent caterpillars and their webs, and remove and destroy webs and caterpillars. Continue to monitor for Hemlock woolly adelgid, mosquitoes, deer ticks, wasps, carpenter bees, bumblebees, ants, honeybees, solitary bee, boxelder bugs and snowball aphids on viburnum. The following weeds are in bloom: veronica, ground ivy, Ranunculus ficaria, violet, dandelion and chickweed. Vole damage to the crowns of Hosta and Epimedium continue to show up; look for thinning crowns. With the recent rain, the orange, jelly-like galls of cedar-apple rust (Gymnosporangium) were found on Eastern red cedar. Hummingbirds have returned to the Plymouth County with a report from Kingston on April 27th; time to put out the feeders.

North Shore Region (Beverly)

General Conditions: Temperatures during this reporting period has been very variable. Day temperatures have ranged from the low 50s to low 70s. However the night temperatures have been in the 30s except on the weekend when the night temperatures climbed into mid 50s. There has been very little precipitation during this reporting period and relative humidity has been mostly very low. Due to the warm temperatures during the weekend, we gained 22 growing degree days at Long Hill. Woody plants still in bloom since the last reporting period include: Leonard Messel Magnolia (Magnolia x loebneri), Merrill Magnolia (Magnolia x loebneri ‘Merrill’), andstar magnolia (Magnolia stellata).New woody plants seen in include Shadblow serviceberry (Amelanchier canadensis), Burkwood viburnum (Viburnum x burkwoodii), Japanese rock forsythia (Forsythia japonica), Mountain andromeda (Pieris floribunda) and yellow root (Xanthorhiza simplicissima). Non-woody plants seen in bloom include: Bloodroot (Sanguinaria canadensis), Glory of the snow (Chionodoxa sp.), Vinca vine (Vinca minor), Daffodil (Narcissus spp.) Japanese wood poppy (Glaucidium palmatum), forget me not (Myosotis sylvatica) and tulips (Tulipa sp).

Pests/Problems: Because of very low relative humidity, fire danger weather warnings were posted for several days this week. Ticks are active and people should be careful to protect themselves when working outdoors. Some weeds seen in bloom include: Dandelion (Taraxacum officinale), Fig buttercup (Ranunculus ficaria), Ground Ivy (Glechoma hederacea) and Purple Deadnettle (Lamium purpureum). Norway maple (Acer platanoides) is still in full bloom. A douglas fir tree (Pseudotsuga menziesii) was seenin decline due to needlecast disease. Weeping Higan Cherry trees (Prunus subhirtella var. pendula) flowered heavily last year but they have little or no flowers this year. It seems like the cold temperatures at the beginning of April may have affected their flowering.

East Region (Boston)

General Conditions: It seemed as if spring had arrived before summer-like temperatures moved in; high temperatures ranged from 54° F to a high of 80° F averaging 64° F while low temperatures averaged 44° F, ranging from 37° F to 50° F. The 21st and 22nd saw temperatures reach 77° F and 80° F respectively, accumulating the majority of the GDDs for this week. We gained 35.5 GDDs, bringing us to 96.5 GDDs for the year. A cold front came through on the 24th bringing more seasonal temperatures. We received 0.37 inches of rain over two rain events, one during the early morning hours of the 23rd and the second during midday on the 26th. Several later flowering magnolias unaffected by the early spring frost are in bloom: Magnolia ‘Elizabeth’, cultivars of M. x loebneri (Loebner magnolia) including ‘Leonard Messel’, and cultivars of M. soulangeana (saucer magnolia). Other plants in bloom include: Epimedium sp. (barrenwort), Exochorda sp. (pearlbush), Fothergilla major (large fothergilla), Malus mandshurica (Manchurian crab apple), Oemleria cerasiformis (osoberry or Indian plum), Prinsepia sinensis (cherry prinsepia), Prunus alleghaniensis (Allegheny plum), P. depressa (sand cherry), P. padus var. glauca (European bird cherry), P. x cistena (purpleleaf sand cherry), Rhododendron schlippenbachii (royal azalea), many Ribes sp. (currant), early flowering lilacs Syringa oblata (early lilac), S. x diversifolia (varileaf lilac) cultivars, S. x hyacinthiflora hyacinth lilac) cultivars, and the earliest viburnums V. bitchiuense (Bitchiu viburnum) and V. furcatum (forked viburnum). Snapping turtles have been active travelling between ponds; painted turtles have also been observed in abundance, sunning themselves on pond edges.

Pests/Problems: Winter moth (Operophtera brumata) is feeding heavily on plants that have leafed out, especially on birches (Betula sp.), buckeyes (Aesculus sp.), and crabapples (Malus sp.). Pine bark adelgid (Pineus strobi) are visible on white pine. Gypsy moth (Lymantria dispar) has hatched. Garlic mustard (Alliaria petiolata) is flowering. Dandelions (Taraxacum sp.) are flowering profusely in turf and planting beds.

Metro West (Acton)

General Conditions: Happy Arbor Day! Lawns are greening up and growing especially with the recent rain; leaves and flower buds are expanding; and day length is increasing by 2 or so minutes daily and will be at 14 hours and 5 minutes come May 1st. The total rainfall recorded for the month of April thus far is at was 2.33", significantly less than the monthly average of 4.16". Much is in bloom for this time of the year, including the following woody plants: Amelanchier spp. (Shadbush, Serviceberry), Cercis canadensis (Redbud), Chaenomeles speciosa (Common Flowering Quince), Forsythia spp. (Forsythia), Lindera benzoin (Common Spicebush), Magnolia x loebneri 'Merrill', M. x soulangeana (Saucer Magnolia), Malus spp. (Crabapples) including M. ‘Dolgo’, M. ‘Snowdrift’, and M. x zumi, Pieris japonica (Japanese Pieris), Prunus spp. (Cherry), Pyrus spp. (Pear), Rhododendron 'P. J. M.' (PJM Rhododendron) Spirea thunbergii (Thunberg Spirea), Vaccinium angustifolium (Lowbush Blueberry), V. corymbosum (Highbush Blueberry), and Viburnum x burkwoodii (Burkwood Viburnum). Contributing even more color and interest to the landscape are some flowering herbaceous plants and spring ephemerals including: Anemone nemorosa (Wood Anemone), Asarum europaeum (European Ginger), Aurinia saxatilis (Basket of Gold), Caltha palustris (Marsh Marigold), Chionodoxa luciliae (Glory of the Snow), Claytonia virginica (Virginia Spring Beauty), Dicentra canadensis (Squirrel Corn), D. cucullaria (Dutchman's Breeches), D. eximia (Fringed Bleeding Heart), Epimedium x versicolor 'Niveum' (White Flowering Barrenwort), E. x versicolor 'Roseuem' (Pink Flowering Barrenwort), E. versicolor 'Sulphureum' (Yellow Flowering Barrenwort), Erythronium americanum (Yellow Trout-Lily), Helleborus niger (Christmas Rose), Hyacinthus spp. (Hyacinth), Lunaria annua (money Plant), Mertensia virginica (Virginia Bluebells), Muscari sp. (Grape Hyacinth), Narcissus spp. (Daffodil), Omphalodes verna (Blue-eyed Mary), Pachysandra procumbens (Allegheny Spurge), P. terminalis (Japanese Pachysandra), Phlox subulata (Moss Phlox), Primula spp. (Primrose), Pulmonaria longifolia (Lungwort), P. rubra (Salmon colored Lungwort), Puschkinia libanotica (Striped Squill), Sanguinaria canadensis (Bloodroot), S. canadensis 'Multiplex' (Double Bloodroot), Scilla siberica (Siberian Squill), Stylophorum diphyllum (Wood Poppy), Tiarella cordifolia (Foam Flower), Trillium erectum (Red Flowering Trillium), T. sessile (Toadshade), Tulipa spp. (Tulip), Vinca minor (Periwinkle), Viola spp. (Violet), Waldsteinia ternata (Barren Strawberry) and Zizia aptera (Heart-Leaved Alexander).

Pests/Problems: Acer platanoides (Norway Maple) is in full bloom. This invasive tree is hard to miss now that it is in bloom and its flowers are yellowish-green and it is found growing most everywhere. Also in bloom and hard to miss is Alliaria petiolata (Garlic Mustard). This biennial can also be found growing most anywhere and is in bloom right now and it is hard to miss its white flowers. Black flies and ticks are active as well as Eastern tent caterpillar as reported by a colleague hiking along the Mid State Trail near Mt. Wachusett.

Central Region (Boylston)

General Conditions: Blooming in the landscape: Lindera benzoin, Hybrid Tulips, Phlox subulata, Mertensia viginica, Asarum canadense, Narcissus cultivars, Pieris ‘Brouwer’s Beauty’, Pieris floribunda, Corylopsis pauciflora, Bergenia cordifolia, Magnolia ‘Elizabeth’, Adonis vernalis, Prunus ‘Hally Jolivette’, Trillium luteum, Pulsatilla vulgaris, Corydalis lutea, Iberis sempervirens.

Pests/Problems: Eastern Tent caterpillar, ticks, blackflies. Cherry & many early Magnolia blossoms were damaged by the cold. Dandelions, Gill-Over-The-Ground, Senecio vulgaris, Yellow Rocket, Hairy Bittercress and other winter annuals are blooming or now beginning to go to seed.

Pioneer Valley Region (Amherst)

General Conditions: Overall, the Pioneer valley experienced pleasant spring weather during this past reporting period. Highs reached the upper 70s on Thursday, 4/21 and aside from the brief cold front on 4/26 (highs reached only the mid-40s), temperatures hovered in the 60s to low 70s. While a bit below average, the spring winds were not as relentless as they often are this time of year in the valley. Nights continue to be cool, with lows in the mid-30s to low 40s. Pockets of frost were reported on the morning of Wednesday, 4/27 with heavy fog along the river bottoms. However, after the deep freeze in early April, most landscape ornamentals appear unfazed by marginally freezing temperatures at this point. Much needed rainfall occurred on Friday, 4/23 in the form of afternoon thunderstorms. Accumulations were spotty, with the heaviest totals in the Northampton area at upwards of 0.7″ while portions of the eastern valley (e.g. Belchertown) saw less than 0.1″. Additional rain was recorded on Tuesday, 4/27 although accumulations were minor, mostly in the 0.3″ throughout the valley. While these two rain events were good for turfgrass, which is vibrant green in most locations right now, we need a thorough soaking of 1″ or more to provide ample moisture for trees and shrubs. Continue to monitor soils and irrigate recently transplanted trees and shrubs, especially when considering the low humidity and drying winds. The rain and cool nights caused soil temperatures to drop somewhat over the past week, particularly in shaded settings. Leaf out continues for many trees and shrubs and slowly the landscape is approaching peak spring color. Yews and balsam fir buds are breaking, Douglas-fir buds are very swollen but are not flushing yet and hard and soft pine candles continue to elongate. Spruce buds are slowly swelling but none have been observed flushing just yet.

Pests/Problems: Scout rhododendrons for winter injury and prune out these blighted shoots and leaves. If left in the canopy, they will become colonized by one or several fungal pathogens that will further the dieback. Apple scab and cedar apple rust spores are abundant right now after the rains on 4/22 and 4/26. However, temperatures were so cool on 4/26 that spore germination likely did not take place on leaf surfaces. Continue to monitor and destroy eastern tent caterpillars on crabapple and cherry, among other known hosts. If pine bark adelgid is abundant on eastern white pine, treat with oil or insecticidal soap to eliminate this pest before needles flush in late May to early June. We are entering the time frame for dogwood anthracnose management on flowering dogwood (Cornus florida). Once the foliage emerges, it should be treated with a registered fungicide. To avoid the disease, flowering dogwoods must be treated both culturally and chemically, otherwise they will become infected with this destructive disease. Flowering dogwoods should be planted in full sun with no surrounding plantings to maximize airflow and reduce free moisture on lower canopy foliage. Many trees on the UMass campus are only passively managed (e.g. discarded foliage is raked up and removed in the fall) but numerous cankered stems in the canopy harbor the fungus and it readily spreads the following season. Prune and discard cankered twigs and branches and scout for epicormic sprouts that develop near large, perennial cankers. Kousa dogwoods are highly resistant to the disease and should be utilized over flowering dogwood in situations where shade is unavoidable. The dry weather and cool temperatures in April have kept most anthracnose fungi suppressed but this situation can change quickly during the month of May when leaves are still tender and more mild conditions typically occur. Scout for the presences of elongate hemlock scale on eastern hemlock and true firs (balsam, Canaan, white, etc.). This non-native pest can be very destructive to landscape firs and symptoms may be cryptic until the infestation is severe on lower canopy branches. Crawler emergence for this armored scale is staggered over the growing season but the first round will begin emerging in mid-May. Applications of horticultural oil can be made now or over the next several weeks with a systemic insecticide (dinotefuran).

Berkshire Region (Great Barrington)

General Conditions: Plant development continues to proceed slowly. Except for April 22, temperatures have been at or below normal for this time of year. Despite rain on April 26, the rainfall deficit for Berkshire County is between 2 and 2.5 inches depending upon locale. Soil moisture is moderate after the current rain and with a prospect for rain early next week, planting conditions look very good. Pieris japonica remains in full bloom. Norway maple is also in full bloom. A few flowering tree and shrubs which appear to have had significant damage to flower buds are now belatedly showing some bloom. These include Magnolia stellata, Forsythia, and ornamental cherry species. However, flowering is sparse. Magnolia soulangeana show no signs of flowering and many flower buds are dropping without opening.

Pests/Problems: Deer ticks continue to be a major problem. Eriophyid mites on hemlock are active. Lily leaf beetles are now feeding on emerging true lilies. Winter kill of rose stems appears to be quite severe. Rabbit, deer, and vole browsing continue. Still no sign of emergence of Eastern tent caterpillar. Crabapples hard hit by the extreme cold events of the past winter and early spring are showing signs of recovery as new leaves are expanding where earlier leaves were killed. However, some twigs on the most severely affected crabapples have died back.

Regional Scouting Credits

  • CAPE COD REGION - Roberta Clark, UMass Extension Horticulturist for Barnstable County - Retired, reporting from Barnstable.
  • SOUTHEAST REGION - Deborah Swanson, UMass Extension Horticulturist for Plymouth County - Retired, reporting from Hanson.
  • NORTH SHORE REGION - Geoffrey Njue, Green Industry Specialist, UMass Extension, reporting from the Long Hill Reservation, Beverly.
  • EAST REGION - Kit Ganshaw & Sue Pfeiffer, Horticulturists, reporting from the Arnold Arboretum, Jamaica Plain.
  • METRO WEST REGION – Julie Coop, Forester, Massachusetts Department of Conservation & Recreation, reporting from Acton.
  • CENTRAL REGION  -  Joann Vieira, Superintendent of Horticulture, reporting from the Tower Hill Botanic Garden, Boylston.
  • PIONEER VALLEY REGION - Nick Brazee, Plant Pathologist, UMass Extension Plant Diagnostic Lab, reporting from UMass Amherst.
  • BERKSHIRE REGION - Ron Kujawski, Horticultural Consultant, reporting from Great Barrington.

Woody Ornamentals

Diseases

Recent pathogens of interest seen in the UMass Extension Plant Diagnostic Lab:

Marginal leaf blight on Rhododendron caused by Pestalotiopsis, Pseudocercospora and Phomopsis. 20-year-old shrub that has been present at the site for 15 years. This spring, leaf margins became brown and curled, eventually turning ash-gray. The shrub exists in a shady, woodland garden and likely receives excessive irrigation. Of the three foliar pathogens, Pestalotiopsis is most common and can also attack small-diameter stems.

Foliar blight of common cherry laurel (Prunus laurocerasus ‘Schipkaensis’) caused by Phyllosticta and Colletotrichum. Several trees, 10-years-old, in a bed planting to screen out an air conditioning compound. Trees have been present at the site for eight years and are planted very close together with south-facing aspect. Deer repellent and an anti-desiccant were applied in autumn of 2015. During the late winter weeks, spots and blotches developed on the foliage. Colletotrichum is an anthracnose fungus that has a very broad host range, causing a foliar blight and depending on the host, stem cankers.

Blue spruce (Picea pungens) decline caused by needlecast (Rhizosphaera and Stigmina) and spruce needle rust (Chrysomyxa). Tree is 20-years-old and has been present at the site for nearly as long. Typical decline symptoms have developed in recent years and include: browning and premature shedding of interior branch needles and dieback of lower branches that is spreading upward. In many cases, weakened stems become colonized by cankering pathogens like Phomopsis, which only exacerbates the dieback.

Stem cankering on blue haven juniper (Juniperus scopulorum ‘Blue Haven’) caused by the quince rust fungus Gymnosporangium claviceps. Tree is approximately 6′ tall and was transplanted in late March of this year to a south-facing site with ¾ sun. After the rainstorm on Friday, 4/22 brick red, eruptive pads of spores present on twigs and branches gelatinized into swollen, orange masses so that spores could become wind-dispersed (pictured below). On Saturday, 4/23 the tree was treated with Phosphorous acid (Agri-Fos) as a lower bole drench with the carrier Pentra-Bark in an attempt to promote compartmentalization and healing of the stem cankers.

Mature telia of the quince rust pathogen (Gymnosporangium claviceps) on eastern redcedar (Juniperus virginiana). These brick red pads of fungal tissue swell in April to release spores via wind. These swollen cankers often girdle small stems but some will live on and become perennial sources of the rust pathogen.      Blue haven juniper (Juniperus scopulorum 'Blue Haven') with a quince rust infection. Following the afternoon rain on 4/22 mature telia of Gymnosporangium claviceps gelatinized so that spores could become wind-dispersed. This branch at the base of the tree has been a harboring the rust fungus for many years, as the pathogen failed to girdle the infected stem.      Virus-like symptoms on lilac (Syringa). Aphids and leafhoppers are the primary vectors of viruses on lilac and this particular plant is suffering additional stress from lilac borer.

For more detailed management information for woody plant diseases in the landscape, refer to UMass Extension's Professional Management Guide for Diseases of Trees and Shrubs.

Report by Nick Brazee, Plant Pathologist, UMass Extension Plant Diagnostic Lab, UMass Amherst.

Insects

Woody ornamental insect and non-insect arthropod pests to consider, a selected few:

  • Azalea Sawfly: Amauronematus azalae is active on deciduous azaleas as soon as new foliage emerges. Monitor for the feeding damage of this caterpillar as soon as new foliage appears and continue monitoring for 3-4 weeks after. In that amount of time, this insect could completely defoliate the plant if present in large numbers. Spinosad based products are effective on this hymenopteran pest, while Bacillus thuringiensis Kurstaki is not.

  • Balsam Twig Aphid: Mindarus abietinus is active at this time. Inspect the needles of fir for “stem mothers” that will soon be reproducing. Young aphid feeding will lead to distorted foliage. Excessive amounts of honeydew are produced and cause needles to stick together. Monitor for the presence of reproducing females and treat with an oil application as weather permits.

  • 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 in late May. 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.

  • Birch Leafminer: Fenusa pusilla will be active in areas approaching 100 GDD’s, base 50°F, or when newly emerged leaves are approximately the size of a dime. The adult female sawfly wasps are small and dark and can be observed visually on host plant foliage. Eggs are laid within the newly emerging leaves. The use of yellow-sticky cards (1 per tree) works extremely well for monitoring for this pest. Once the adult sawflies have emerged, the tree can then be treated with a chemical insecticide, such as a pyrethroid, to prevent egg-laying within the foliage. Bacillus thuringiensis Kurstaki is not effective against sawflies.

  • Cooley Spruce Gall Adelgid: Adelges cooleyi is active at this time. This insect can be found in the crevices of bark on terminal twigs and bases of buds of blue spruce, Norway spruce, and Douglas fir.

  • Eastern Tent Caterpillar: (Continued monitoring) Eastern tent caterpillar eggs have hatched and larvae are active at this time. Young caterpillars are found in small tents in the crotches of branches. Remove small tents by pruning (when possible, without removing too much foliage) or destroy with a stick or other object. Do not set the tents on fire, as this can do more damage to the plant and surrounding area than the caterpillars ever could. Remove Forest Tent Caterpillar egg masses before we reach 192 GDD, base 50°F, when hatch will occur.

  • Euonymus caterpillar: Yponomeuta cagnagella will be active soon, in areas above 95 GDD’s, base 50°F. These small yellow caterpillars with black spots feed throughout the host plant and are capable of creating vast amounts of unsightly silk while feeding on the leaves. By early summer, entire viburnum can be covered with silk and leafless. Inspect for the presence of this pest and treat with a product that contains Spinosad if deemed necessary. Handpick and destroy if caterpillars are small in number.

  • European Pine Sawfly: Neodiprion sertifer caterpillar will be active soon. 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.

  • Gypsy Moth: (Continued monitoring) Eggs of the gypsy moth have begun to hatch in the Brimfield area. Tiny caterpillars can be observed resting on their egg masses. Serviceberry (shadbush) is blooming and is the phenological indicator for the eggs to hatch of this insect. Let’s hope for a wet and rainy month of May so that the entomopathogenic fungus, Entomophaga maimaiga, can get well established in the gypsy moth population and help reduce the amount of young caterpillars. In areas of the state where multitudes of egg masses have been seen, such as towns around the Quabbin Reservoir and points further east, Bacillus thuringiensis Kurstaki can be used on small caterpillars.

  • Hemlock Eriophyid Mite: Nalepella tsugifoliae (also known as the hemlock rust mite) is currently active and should be monitored for on eastern hemlock, spruce, fir, and yew.

  • Honeylocust Plantbug: Diaphnocoris chlorionis generally appears at the same time as bud-break of the host plant. It immediately begins to feed on the foliage with its piercing-sucking mouth. If numbers are low and the foliage expands quickly then damage is insignificant. Damage in this case will appear as scattered patches of fine yellow stippling on parts of the leaflets. However, if this pest is present in large numbers or foliage expands slowly, damage may warrant management. Monitor for numbers of this pest by gently shaking branches over a white piece of paper. Examine carefully with a hand lens for the tiny pale green nymphs. Young nymphs can be treated with a spray of insecticidal soap.

  • Lily Leaf Beetle: Lilioceris lilii should be monitored for at this time. 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. Pyrethroids can be used against adult beetles, whereas spinosad products are most effective against the larvae.

  • Pine Bark Adelgid: Pineus strobi has been observed in the Amherst area actively feeding at this time and secreting large amounts of waxy-white wool over their bodies (on white pine). This insect can be found on the trunk, twigs, and branches of white, Scotch, and Austrian pines. These cottony masses can even be seen on the bases of needles. On healthy trees, this insect has not warranted management as they appear unaffected by its feeding. If aesthetically unpleasant, adelgids and wool may be washed off with a strong stream of water from a garden hose on smaller plants.

  • Snowball Aphid: Neoceruraphis viburnicola is now being seen on certain species of viburnum. This insect is particularly noticeable on V. opulus, V. prunifolium, and V. acerifolia. Stem mothers, appearing blueish-white, can be found in curled up and distorted foliage and have been observed to be active in Amherst, MA. This pest is mostly aesthetically damaging; however, if chemical management options are deemed necessary, foliar applications of products containing active ingredients such as permethrin can be made at this time.

  • Viburnum Leaf Beetle: Pyrrhalta virburni, now is the time to inspect susceptible plants (viburnum) for over-wintering eggs on stems toward branch tips. Removal and destruction of infested stems, if small in number, can be effective. If management this way is not possible, larvae may be treated with a product containing spinosad once they appear soon after bud break.

  • Winter Moth: (Continued monitoring) Operophtera brumata egg hatch is complete and 1st and 2nd instar caterpillars are being found in host plants such as maple, apple, and blueberry. Silk and frass (excrement) may be seen on newly emerged leaves of hosts and tiny caterpillars seen with a hand lens. Continue to monitor susceptible hosts for the presence of caterpillars. With the cooler weather, bud development and leaf expansion is at varying degrees with the different hosts. For green industry professionals looking to manage winter moth in the landscape wait until leaves have opened to treat with insecticides. By waiting until the leaf expands, it is easier for the insecticide to reach the caterpillar than when it is protected inside the bud. Products containing active ingredients such as spinosad and pyrethroids are available. Apples, crabapples, and other flowering plants should not be sprayed with these products while in bloom to avoid unintended impacts to pollinators.

A note about Deer 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. Adults and nymphs can be active when temperatures are above freezing and 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 Laboratory of Medical Zoology (www.tickdiseases.org) and click on the red 'Test a Tick' button for more information.

Report by Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program

Management Practices

Plant of the Week: Malus hybrids (crabapples)

Malus hybrids are small to medium sized trees with various forms and branching structures ranging from spreading to pendulous to upright. Flower colors range from white to pinks to reds. Single flowers have 5 petals; with semi-double and double flowered forms also available. Flowers can also vary by flower size and fragrance. The fruit is a pome ranging in color from red to yellow to green and can range from ¼” to 2” in size. Plants should be planted in full sun, in well-drained, moist, acidic soil (pH 5.0-6.5) for best results. Pruning should be done in early June as most crabapples begin developing the next season’s flower buds in late June to early July. Crabapples can suffer from a variety of disease and insects problems with fireblight, cedar apple rust, and apple scab all being problems. When choosing cultivars, disease resistant cultivars are the best options. Malus spp. are frequented by pollinators when in bloom.

Malus hybrids (crabapple)      Malus hybrids (crabapple)      Malus hybrids (crabapple)      Malus hybrids (crabapple)

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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.

Ticks are active at this time! Remember to take appropriate precautions when working and playing outdoors, and conduct daily tick checks. UMass tests ticks for the presence of Lyme disease and other disease pathogens. Learn more