UMass Extension's Landscape Message #17
June 26, 2008

The LANDSCAPE MESSAGE is an educational newsletter intended to guide landscape, nursery and urban forestry professionals in identifying pests in the landscape, monitoring their development, planning management strategies and creating site-specific records for future management reference. This issue has been updated to provide timely pest management information and the latest regional news and environmental data throughout Massachusetts.

During the months of May and June this newsletter will be updated weekly. The next update will be available on July 10, 2008.

SCOUTING INFORMATION BY REGION

REGIONAL NOTES -

Cape Cod Region (Barnstable) – General Conditions: Nice summer weather has occurred over most of the past week, with the humidity rising on Sunday, June 22.  Pop-up afternoon thunderstorms provided some much needed rain on Monday, June 23. Early summer perennials are coming into bloom.  Kousa dogwood is especially lovely at this time.  Pests/Problems:  Crawlers of cottony taxus scale are active on holly and Taxus.  Slugs and snails are feasting on hosta.  Cicadas are still in full flight in those areas where they are present.  Sphinx moth caterpillars are present.  Oriental beetle adults are just beginning to show up.  Japanese beetles cannot be far behind.  Plant bug feeding was identified on herbaceous plant material.  Spittle bugs are quite evident on perennials.  Lacebugs are active on pieris, sycamore, and azalea.  Mosquito populations are quite active; green head flies are active in coastal areas.  Black spot is developing on susceptible roses.

Southeast Region (Hanson) – General Conditions: No report available this week.

East Region (Boston) – General Conditions: Summer-like with scattered thunderstorms and blustery winds.

Metro West (Waltham) – General Conditions: No conditions report available. See Environmental Data and Phenology below.

Metro West (Hopkinton) – General Conditions: We’ve had frequent thunderstorms and tropical air prevailing in the area.   Pests/Problems:  Have seen the first signs of apple scab on susceptible plants.

Central Region (Boylston) – General Conditions: No conditions report available. See Environmental Data and Phenology below.

Pioneer Valley Region (Amherst) - General Conditions: Water is standing in some fields after the northern portion of the Pioneer Valley received over two inches of rain on Monday and Tuesday morning this week.  Lawns and landscapes continue to be lush as the seasons advance this year.  Daylilies, primroses, and columbines mingle their colors with summer annuals in gardens while northern catalpa as well as oakleaf and smooth hydrangea are a tree and scrubs in full bloom.  Pests/Problems:  The orange-yellow spots of cedar-apple rust and the gray-green blotches of apple scab are visible on susceptible crabapple leaves.  In addition, an assortment of mushrooms is erupting in lawns. 

Berkshire Region (Great Barrington) - General Conditions: Frequent thunderstorms have kept soil moisture high.  However, many of the storms have been severe, some with large hail stones, and have caused localized damage to landscapes and gardens.  Most of the trees damaged by storms showed signs of internal decay, branch dieback, and conks emerging from the trunks.  Many of these could have been classified as hazard trees.  Municipalities and private property owners need to be more vigilant with respect to the health of trees that are located near structures, highways, and walkways.  Pests/Problems: No new pest problems observed this past week.

ENVIRONMENTAL DATA -

The following growing-degree-day (GDD) and precipitation data was collected for a one-week period, June 18, 2008 through June 24, 2008.  Soil temperature and phenological indicators were observed on June 24, 2008.  Accumulated GDDs represent the heating units above a 50° F baseline temperature collected via our instruments from the beginning of the current 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.

PHENOLOGY -

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

Indicator Plants - Stages of Flowering (begin, b/full, full, f/end, end)
PLANT NAME (Botanic/Common)	CAPE	SOUTH EAST	EAST	METRO W.		CENT.	P.V.	BERK.
				Waltham	Hopkinton
Oxydendron arboreum (Sourwood)	*	*	*	begin	*	*	*	*
Lythrum salicaria (Loosestrife)	*	*	*	*	begin	*	*	*
Stewartia pseudocamillia (Japanese Stewartia)	begin	*	begin	*	begin	begin	begin	*
Rhus typhina (Staghorn Sumac)	*	*	begin	b/full	begin	b/full	full	begin
Tilia cordata (Littleleaf Linden)	*	*	b/full	b/full	begin	full	full	*
Hydrangea arborescens (Smooth Hydrangea)	begin	*	b/full	*	begin	*	full	full
Cotinus coggygria (Common Smokebush)	b/full	*	b/full	full	begin	full	full	*
Ligustrum spp. (Privet)	b/full	*	full	*	begin	*	full	full
Sambucus canadensis (American Elderberry)	full	*	*	full	full	full	full	b/full
Itea virginica (Virginia Sweetspire)	full	*	*	*	*	full	*	b/full
Cornus kousa (Kousa Dogwood)	full	*	full	f/end	full	full	end	full
Cornus sericea (Red Osier Dogwood)	*	*	full	*	begin	f/end	*	full
Philadelphus spp. (Mock Orange)	full	*	full	end	full	end	*	full
Syringa reticulata (Japanese Tree Lilac)	f/end	*	full	end	end	f/end	f/end	full
Rosa multiflora (Multiflora Rose)	f/end	*	full	full	full	full	f/end	f/end
Kalmia latifolia (Mountain Laurel)	f/end	*	f/end	end	end	f/end	end	full
* = no activity to report/information not available

CAPE COD REGION - Roberta Clark, Horticulturist for Barnstable County, Barnstable.

SOUTHEAST REGION - Deborah Swanson, Horticulturist for UMass Extension in Plymouth County, Hanson.

EAST REGION - James R. Allen, Horticulturist and Greenhouse Manager for UMass Biology Department, Boston.

METRO WEST REGION – Mark Sawyer, Horticulturist, Weston Nurseries, Hopkinton.

METRO WEST REGION – James Martin, Consulting Arborist, reporting from the UMass Extension Center, Waltham.

CENTRAL REGION - Joann Vieira, Superintendent of Horticulture, Tower Hill Botanic Garden, Boylston.

PIONEER VALLEY - Dan Gillman, Plant Pathologist, UMass Extension Plant Diagnostic Lab, UMass, Amherst.

BERKSHIRES - Ron Kujawski, Specialist, UMass Extension Landscape, Nursery & Urban Forestry Program, Amherst.

WOODY ORNAMENTALS

INSECTS -

Lepidopteran Caterpillars:

• Gypsy Moth - No reports of large numbers of this pest in MA have been received, yet.  It is assumed that numbers are low and that this pest will be of little concern this year.  This caterpillar is now about two inches in length.  Pupation
  
  
• Fall Webworm - The snow-white adult moths of this webworm have been found attracted to porch lights at night in much of the state now.  Mostly, they go unnoticed.  Larvae will not appear until July, and their large silken webs on the terminals of branches will not be seen until late July or August. 
  

Hymenoptera Sawfly (Caterpillar) Larvae:

• Dogwood Sawflies − When we encounter dogwood sawfly in MA on gray as well as redosier dogwood it is usually Macremphytus tarsatus.  The larvae of this particular species start to appear approximately mid July, and their activity can extend into the autumn months.  As the larva ages, they begin producing a white wax over their bodies.  This, along with their tendency to sit on the foliage in a curled body shape, gives them the appearance of a bird dropping.  It is suspected this is a defensive posture that they have evolved to avoid predation; no known parasites or predators have been detected for this species.  One report from Plymouth County was received early this month about sawfly caterpillars on dogwood.  It was too early in the season for it to be M. tarsatus.  However, there is another dogwood sawfly (M. varianus) that appears to be little known, but it does occur earlier in the growing season than M. tarsatus.  It can share the same host plants.  It is suspected that this is what was found.  Both species consume all but the main veins of the host foliage.  If necessary, treat either species with a product that contains spinosad.  Very young larvae can be treated with an insecticidal soap spray. 
  
  
• Imported Pine Sawfly - This sawfly is more commonly found in the eastern parts of MA than it is in the central and western parts.  It will become active by late June or early July.  It shares many of the same host plants as the European pine sawfly, including mugo pine.  Monitor for the yellow blocky egg patches within needles.  Remove and destroy needles with eggs.  Once the larvae emerge, treat with an insecticidal soap or a product that contains spinosad.
  
  
• Birch Sawfly − The caterpillars of this pest are active and feed by wrapping their bodies around the margins of foliage of birches as they consume all but the main veins of the leaves.  Although not abundantly common in the state, it does appear somewhere here every year and is capable of causing serious defoliation if not treated.  Spinosad products or one of the registered pyrethroids work well.  Also, insecticidal soap works well when the larvae are still quite small.   
  

Beetles:

• Japanese Beetle adults will begin to appear by the end of next week.  At first, the numbers will be low but as more and more emerge from the soil each day, this will change quickly.  Make note of those plants that may require protection. 
  
  
• Asiatic Garden Beetle remains active and is becoming more common, along with its feeding damage.  This small, robust and oval-shaped scarab beetle is only active at night.  It feeds on a wide variety of deciduous landscape plants as well as many different garden plants.  Monitor at night with a flashlight between the hours of 9 PM and midnight.  This pest can cause much ragged foliage to favored plants.
  
  
• Lily Leaf Beetle - Adults, larvae, and eggs can all be found now.  As the larvae feed by skeletonizing the foliage, they begin to cover their bodies with their own excrement.  Entire plants can be consumed to the soil if this pest is not treated.  Some adult beetles are still actively mating and laying eggs.  NEEM works well for the larvae, once they appear, but needs to be reapplied every 10-14 days.  Spinosad products also work very well for the larvae.  Adult lily leaf beetle is best controlled with a pyrethroid insecticide.
  
  
• Viburnum Leaf Beetle  - Numerous  reports concerning new finds of this serious invasive pest have been received from throughout Berkshire County.  The first find in Franklin County (Conway, MA) was recorded just last week.  Also, we received a possible find in Bristol County.  We are waiting for the adults to appear to confirm its presence there; right now it is damaged plant material.  Inspect all viburnum plants brought into the region from areas that already have this pest.  The larvae have dropped to the soil and are undergoing pupation right now.  Adult beetles will emerge within the next 2–3 weeks.  Spinosad products work well for the larvae but not the adults, which require something like a pyrethroid insecticide. Report any new finds in MA to Bob Childs rchilds@psis.umass.edu or 413-545-1053.  Treat the same as for lily leaf beetle. For current information about this pest, visit the Cornell web site at http://www.hort.cornell.edu/vlb
  
  
• Imported Willow Leaf Beetle remains active.  The adult beetle is rather small, rounded, and metallic green/blue in color.  The adult beetles will chew holes into the foliage, but it is the small black-colored larvae that create most of the injury.  Larvae will line up together on the foliage and scrape the upper layers.  This action causes the still-intact leaf to eventually die and turn brown.  This pest has multiple generations per year, and its damage can become severe by August when virtually all of the foliage on a willow will appear bronze in color, as if fire-swept.  All willows are susceptible.  Treating the adult beetle requires a pyrethroid insecticide while a product that contains spinosad works well for the larvae. 

Piercing-Sucking Pests:

• The Red-Banded Leafhopper (a.k.a. Sharpshooter Leafhopper) will be arriving in MA any day now from more southern states.  This pale green leafhopper with two chevron-shaped stripes on its back is attracted to rhododendrons that continue to produce new foliage through July and August.  The egg-laying in the new leaf tissue causes the leaves to become stunted and distorted.  It is purely an aesthetic pest, but it can be an important pest, especially in the nursery.  Visually monitor for this insect by gently shaking foliage to dislodge the leafhoppers, which will fly up and then land again nearby.  When found in large numbers this pest should be treated.
  
  
• Maple Leafhopper − This is another leafhopper that migrates into the state every year and is mostly attracted to maples in the landscape and nursery.  Their piercing sucking feeding can create such extensive injury that foliage will appear to have been damaged by bleach; very chlorotic yet finely stippled foliage.  Monitor visually by shaking branches.  Treat if found in large numbers.
  
  
• Lacebugs remain very active.  These serious pests always feed from the underside of the foliage, but they create the fine, yellow stippling feeding injury on the upper surface of the leaves.  Look at the bottom leaf surface of such affected leaves for the telltale signs of the brown fecal spots and the lacebugs themselves.  Inspect common host plants for this pest for last year’s damage.  Common hosts are:  Japanese andromeda, evergreen azaleas, rhododendron, cotoneaster, and hawthorn.  Systemic imidacloprid appears to be quite effective for managing this pest.  Also, horticultural oil sprays or insecticidal soap sprays that are targeted to the foliage underside is also effective for the small nymphs.  Susceptible plants growing in sunny areas will experience more damage given that heat greatly encourages lacebug populations. 
  
  
• Miscellaneous Aphid species are appearing now and building in numbers.  Monitor for honeydew and sooty mold.  Treat if necessary.  Systemic imidacloprid, or insecticidal soap sprays, or horticultural oil sprays are all effective treatments.  Maples, catalpa, tuliptree, lindens, and many others are common hosts.
  
  
• Taxus Mealybug remains active.  Move the foliage of taxus back and inspect the inner branches and smaller stems for white, cottony masses.  This insect produces honeydew, which leads to the  unsightly buildup of sooty molds.  Also, large populations can cause stunting and chlorosis of the foliage.  Treat with a systemic imidacloprid product or spray the inner branches and stems with either a horticultural oil spray or one of
  
  
• Spider Mites - Inspect spruce, hemlock, fir, and others for the signs of feeding damage by these tiny but very prolific and potentially damaging pests.  Inspect very closely for the active mites, which will require a good hand lens or microscope.  If found, treat with an oil spray or with one of the new mite growth regulators.  Monitor for the actual mites by shaking a branch over a white piece of paper and then inspecting with a hand lens for the mobile mites.
  
  
• Hemlock Woolly Adelgid - The second generation is becoming active.  Much feeding is occurring now.  This pest will go dormant in another 3-4 weeks, but it can still be managed even in that stage.  A horticultural oil spray at the summer rate (be careful of tender new foliage now emerging), systemic imidacloprid, or systemic dinotefuran (Safari™) are all effective against this very serious pest. Note: Safari™ is a State Restricted Use pesticide in Massachusetts.  (See Elongate Hemlock Scale, which appears next.)
  
  
• Elongate Hemlock Scale (aka Fiorinia Scale) − Inspect hemlocks closely for this pest.  If the plant appears weakened or sickly and has hemlock woolly adelgid, which is very obvious, take the extra time to closely inspect the undersides of the needles for this scale.  Fiorinia scale is very small, brown and mostly oval in shape.  Many of these may be present per needle (on the underside only).  In some cases, it will be the primary reason that a hemlock looks to be in ill-health.  Imidicloprid, which works pretty well systemically for hemlock woolly adelgid, does not have much of an impact on this scale.  Horticultural oil sprays, which also work well on hemlock woolly adelgid, tends to provide minimal control for this scale.  Safari™ (dinotefuran), a relatively new neonicotinoid, does show good promise for fiorinia scale and works well when utilized as a systemic.  However, in Massachusetts, it has a “State Restricted Use” labeling due to groundwater concerns.  Fiorinia scale is difficult to control.  Unlike most armored scales in the Northeast, it produces crawlers throughout much of the growing season.  If found, treat it aggressively.  Fiorinia scale is a very serious pest of hemlock and can occur on conifers other than hemlock.  
  
  
• Cryptomeria Scale was found on Cape Cod last fall as well as in Rhode Island (not far from the MA border).  This was the first time that this scale has been found in MA.  Two finds were on Christmas trees—both firs—in the nursery (plantation).  This scale attacks various conifers and has the potential to be a serious pest.  Inspect needles for yellowing (stippling) and the presence of the scale on the needle undersides.  Treat with a horticultural oil if found. 
  
  
• Cottony Camellia Scale (aka Cottony Taxus Scale) remains active.  Inspect the foliage of taxus and certain hollies for white, oval and waxy scale coverings.  If found, inspect foliage further for the tiny yellow nymphs which have overwintered on the twigs and have now migrated to the foliage.  This pest has been actively feeding already this spring.  If this pest was active last year, then look for the buildup of sooty molds as well.  Larger population numbers can contribute to poor plant growth and unsightly sooty mold.  Systemic imidacloprid or dintotefuran (Safari™) should be effective.  Oil sprays also are effective but be careful with their use on hollies, which may be sensitive to oils. 
  

Leaf Miners:

• Arborvitae Leafminer − There are two species of what is commonly called “Arborvitae Leafminer” in Massachusetts.  The more common species remains within the foliage as a larva until early to mid June whereupon it pupates (within the foliage) and the tiny off-white moths then appear around mid to late June.  The adult moths are not attracted to yellow sticky cards, so to monitor for their presence, gently shake foliage to dislodge the moths.  Treat with a pyrethroid insecticide when the adults are found to prevent reinfestation.  The other species, which is more common in coastal areas of MA, emerges early in the season and spins a small silken cocoon that slightly resembles a fuzzy grain of rice.  In large numbers, there may be countless numbers of these cocoons visible on the foliage.  Again, wait for the adults to emerge and treat the same as the other species.  Eggs of both species are deposited on the foliage and not within the foliage.  A well-timed horticultural oil spray may be effective for managing these eggs, but timing is essential.  Most eggs (both species) will be on the undersides of the foliage.
  
  
• Native Holly Leafminer − This pest of American holly has been in the foliage as a larva since last June.  It creates a serpentine (winding) mine initially.  It then settles in one part of the leaf and makes a large blotch mine.  Several mines may be present per leaf when it occurs in large numbers.  Pupation will begin soon, and the adult flies start to emerge around mid June.  Monitor for the adult flies with yellow sticky cards and treat with a pyrethroid insecticide when present to prevent re-infestation.
  

Wood Attackers:

• Bronze Birch Borer − The adults of this pest are beginning to emerge now and will continue to emerge and be active into September.  This pest kills trees, but it can only survive in previously weakened trees.  Keep trees healthy to avoid attack.  Drought stressed trees (so far, not a problem this season) are candidates for attack as are old trees or those growing in compacted soils.  Treatments become a challenge once infestation occurs.  Some arborists do not like to prune birches from June into September to avoid releasing plant volatiles that may attract beetles.  However, if the tree is healthy, then there should be little concern for colonization by this insect.

• Dogwood Borer − This clear-winged moth will be active and seeking wounded dogwood trees from now until late August.  The females deposit eggs near bark crevices, such as branch collars, and around wounds.  The wood-boring caterpillar of this species tunnels into the cambium and later into the older wood.  Signs of an infestation now will be sap exudation on the trunk and scaffold branches.  Avoid wounding dogwood trunks with mowers and line trimmers.  Pheromone traps are available to monitor for the adult moths.  This caterpillar pushes out the sawdust as it tunnels thus leaving its tunnels open, unlike most wood borers.  Nematode products sprayed on the trunk are extremely effective for new infestations. 

Other Stuff:

• Periodical Cicada − Peak emergence has passed.  Thousands upon thousands of cicadas have emerged and are now mating and laying eggs within the stems of deciduous trees, especially oaks.  Smaller trees may need to be netted.

• White-Spotted Pine Sawyer (WSPS) is now active as an adult.  This adult beetle is commonly confused with Asian Longhorned Beetle (ALHB), which has never been found in MA.  WSPS is native and is only attracted to very weak or freshly dead pines.  It is not considered to be a pest.

A Few Comparisons/Differences Between ALHB and WSPS:

• ALHB has a very shiny black body, like that of patent leather; the pine sawyer is more of a dark mottled grey.
• ALHB has crisp white spots; pine sawyer has more diffuse white spots.
• ALHB has a blue-ish cast to the color of its tarsi (feet); pine sawyer does not.
• Both have antennal segments that alternate between white and black

Reported by Robert Childs, Entomologist, UMass Extension Landscape, Nursery and Urban Forestry Program, Amherst

DISEASES -

Mushrooms in lawns often develop from thatch, buried logs, dead roots, stumps, or even construction debris.  They have many different sizes, colors, shapes, and habits of growth and develop fruiting structures or mushrooms in lawns after prolonged wet weather.  The fungi that produce these mushrooms are beneficial because they decompose organic matter in the soil, making nutrients available to other plants.  These mushrooms usually are harmless to grasses, but some people consider them unsightly or want to get rid of them because young children play in the area.  Neither spray applications nor drenches of fungicides are effective in controlling these mushrooms.  Simple way to remove mushrooms is to mow the lawn while collecting the clippings or by raking them up.  Elimination of excess thatch and aerating the soil to improve water penetration also helps in some cases.  In addition, the mushrooms gradually disappear without interventions if the weather becomes drier.

Horsechestnut (Guignardia) leaf blotch is visible as scattered, irregular-shaped orange-brown blotches on infected leaves.  They are primarily affecting lower, inside leaves.  However, as the summer progresses the impact of the disease may be more noticeable, but chemical intervention at this time for this season is of little benefit.  Keep in mind that horsechestnuts infected year after year continue to grow vigorously in spite of Guignardia leaf blotch.  However, if appearance is important, begin fungicide applications as buds break open; and if wet conditions persist, reapply 1-2 additional treatments at labeled intervals.

Powdery mildew fungi are visible as a dusty, gray to white areas on red horsechestnut (Aesculus x carnea), dogwood, sycamore, phlox, and roses.  Once established on plants, powdery mildews grow superficially on both upper and lower leaf surfaces as well as green shoots and flower buds.  They are obligate parasites and derive sustenance only from living host plants.  They do this using minute, tube-like structures (haustoria) that penetrate the epidermal cells and draw out material they need to survive.  Later this summer spherical, black fruiting structures are visible with a hand lens on the underside of leaves in the dusty, gray mycelia.  Generally, the damage caused by powdery mildew is of minor consequence to healthy plants and does not warrant chemical control if unsightliness is not a critical concern.  If considering chemical control there are a number of unconventional applied materials labeled to protect susceptible plants.  They include summer horticultural oil, commercial baking soda preparations (sodium bicarbonate and potassium bicarbonate), anti‑transpirants, as well as a number of conventional fungicides.  Chemical spray programs are most effective when begun just as symptoms of powdery mildew begin to show.  Once powdery mildew is extensive on the plant, there is little benefit from chemical control that season.  Applications need to coat both surfaces of all susceptible plant parts to prevent infection.  Spray on a regular schedule, and repeat more often during warm, humid weather.

Reported by Dan Gillman, Plant Pathologist, UMass Extension Plant Diagnostic Lab, Amherst

LANDSCAPE TURF

INSECTS -

Armyworms − We have had an unconfirmed report of an armyworm (Pseudoletia unipuncta) infestation attacking a low maintenance turf area in the metropolitan Boston area.  The report is "unconfirmed," since I have not personally seen samples of the caterpillars, but is pretty likely to be accurate.  I was able to send digital photos of armyworms to the turf manager, and he confirmed that his specimens looked just like my pictures.
 
In their medium and larger stages, the caterpillars are very dark (described as black or navy) on the top, with a straw-colored stripe along the side of the body.  The head capsule has two shades of brown (dark and light) with a kind of "honey-comb" pattern.  And the fleshy legs on the abdomen usually have a dark stripe near where the leg attaches to the body.

Some of you will remember the remarkable infestations that appeared during June 2001 in some parts of southern New England.  In that case we believe the armyworms were blown in (while in the moth stage) from New Jersey and other regions south of New England during a large coastal storm early in June.  Many turf managers that year reported caterpillar infestations of "biblical proportions"—the caterpillars emerged in incredibly high densities and marched, like an army, across turf areas and pavement, leaving death and destruction in their wake.

We have not yet heard of other reports of armyworms, so I don't know whether this latest report will turn out to be an isolated instance or whether we may see large areas affected like in 2001.  If the activity turns out to be more widespread, I offer the following suggestions:

• If the caterpillars are already nearly full sized (they typically reach 1.25 inch in length during their last instar), there are no chemical or biological control strategies that will provide significant levels of control.  In that case, about the only thing you can do is minimize stress on the turf.  Raise the mowing height a bit (to try and increase the photosynthetic surface), which may help the turf a little. And if possible, water the area as needed, again to help the turf through the stress period.

• If you notice the caterpillars early enough that they are still small (less than half an inch), you should achieve reasonable levels of control – at least knock the population back to a dull roar.  You can use a pyrethroid or carbaryl (Sevin™).  In addition, a product containing spinosad (often sold as Conserve™) provides good control of many caterpillars; and while I don't have any data either way, it might also be effective against armyworms.

Sod webworms − I have had an unconfirmed report of sod webworms activity in central Massachusetts (Sterling area).  The turf manager reported that webworm moths were flying in the area, and that some turf appeared to be showing damage from caterpillars.  While that report is unconfirmed, I went home that evening and noticed that large numbers of webworm moths were flying in my own lawn, so I fully expect that the "diagnosis" was accurate.

In most cases we do not see damage from sod webworms in New England, but it does occasionally happen.  There are several species of webworms, each of which produces caterpillars that feed in the turf and can leave straw-like patches of dead grass.  Several of the webworm species spend the winter in New England in a late caterpillar stage, feed briefly in the spring, and then pupate and emerge as moths.  These are the moths that flit aimlessly, just above the turf, dropping eggs as they go.

Again we normally do not see damage from these insects, but there can be exceptions.  If you have reason to believe that the damage your turf incurred a couple weeks ago was caused by webworm caterpillars and you see webworm moths flying now, consider applying a pyrethroid in the area about a week or two after peak moth flight.  That gives the moths time to produce and lay eggs and the eggs to hatch into tiny caterpillars. Water very lightly, just enough to knock the material off the blades and into the thatch.

Reported by Pat Vittum, Extension Entomologist, UMass Department of Plant, Soil and Insect Sciences, Amherst.

This message is produced by the UMASS Extension, Landscape, Nursery and Urban Forestry Program. The copy is prepared by Anna Greene from data and reports provided by the staff and faculty of the UMass Landscape, Nursery and Urban Forestry Program and the UMASS Extension Turf Program as well as cooperating horticulturists and Green Industry professionals. The text is adapted for access via the Internet by Jason Lanier.

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