May 20, 2005

In this issue

Landscape and nursery

§ How late can homeowners drench or inject to control EAB?

§ Trees reverting to form

§ Choosing an arborist

§ Phenology report

§ Plants that can host Asian soybean rust

§ Shade tree pruning demo and true firs tour offered

Turfgrass

§ Turfgrass insect update

§ Seedheads in lawns

Other news

§ Weather news

How late can homeowners drench or inject to control EAB?

Dave Smitley, Entomology

We have been asked, “How late can homeowners use the imidacloprid drench or ACECAP trunk injections for emerald ash borer?” The homeowner guide for controlling EAB says to use an imidacloprid soil drench in April or May, or ACECAP trunk injections in early May. In heavily infested areas, homeowners should use both of these products together the first year or two.

April to early May is the optimum time for treatment. However, you can still use both of these products through June. We have not done the research to determine when it is too late, but it is likely that they will still work well when used in June, because most of the EAB larvae are actively feeding in July, August and September.

Trees reverting to form

Bert Cregg
Horticulture and Forestry

Among the “What’s wrong with my tree?” calls I get, some of the most interesting deal with a phenomenon called reversion. When a conifer or hardwood tree with an unusual ornamental characteristic begins to send out shoots with normal foliage or growth for the species, the new growth is said to have reverted.

How does a reversion take place? Remember that many ornamental cultivars begin when an alert plantsman or plantswoman notices a tree or part of a tree with a unique growth characteristic (unusual leaf color, weeping growth habit). These atypical plants or shoots arise through genetic mutation. Buds or cuttings from the plants are then grafted onto standard trees and, if they remain true to form and have horticultural merit, they ultimately make their way into the nursery trade. Just as the original genetic mutation occurred to produce the unique character, occasionally a reverse mutation occurs and portions of the plant ‘revert’ back the species’ normal growth. Some of the more common examples of reversions occur in dwarf spruces (Photo 1) and variegated plants such as Harlequin maple (Photos 2 and 3). In the case of dwarf spruces, homeowners will often report “a tree growing out of my tree.”

What to do with a reversion

When a reversion occurs, it’s time to follow the advice of the wise TV sage, Barney Fife, and “Nip it, nip it in the bud!” Examine the tree and determine where the reversion originated and prune off the reverted shoots. Often reverted shoots grow more vigorously then the rest of the tree. If left un-pruned, reversions will dominate the tree and the homeowner who paid extra for a dwarf Alberta spruce or variegated maple is eventually left with a plain old white spruce or Norway maple.

Choosing an arborist

Bert Cregg
Horticulture and Forestry

Spring is a time when many homeowners will need the services of a professional arborist or tree service company. Between emerald ash borer, Dutch elm disease, and the usual round of spring storms, arborists will be in demand to treat, prune, and remove trees. One question we commonly receive from homeowners is how to choose an arborist.

Just a click away

Both the National Arbor Day Foundation and the International Society of Arboriculture web sites have resources that can help in selecting an arborist.

The Arbor Day Foundation presents eight guidelines for selecting an arborist. In the interest of space I won’t list them all here, but the keys are to make sure the arborist is insured and has professional training.

http://www.arborday.org/media/stormrecovery/3_watchforscams.cfm

The International Society of Arboriculture provides professional training and certifies arborists. Arborists certified by ISA must pass knowledge tests and receive continued professional training to maintain their certification. Most arborists that are ISA certified will note this is their yellow pages ad. Also, the ISA website has a search feature that enables you to find arborists in your area simply by entering your zip code.

http://www.isa-arbor.com/findArborist/findarborist.aspx

Homeowners occasionally experience “sticker shock” when they receive a tree for service bid. Remember, as with most things in life, you get what you pay for. High quality tree work requires training, skill, experience, and proper equipment. Reputable arborists must also cover the costs of bonding and insurance. If you get multiple bids for tree repair or removal, look at the bid in terms of the overall package (site clean up, wood removal) rather than just cost.

Phenology report

Diane Brown-Rytlewski
Nursery & Landscape ICM Integrator

On campus

The large, jelly-like orange spore masses of cedar-apple rust are evident on juniper hosts now. Cedar quince rust is still active too, infecting hawthorn, crabapple and other trees and shrubs in the rose family. With the cool, wet weather we experienced this past week, you might also start to see symptoms of anthracnose soon on some of the susceptible hosts. A check of sycamores on campus showed some freeze injury on the developing leaves, but not the characteristic browning along the veins that is symptomatic of anthracnose.

As of May 17 growing degree day accumulations (GDD) were at 273 base 50. The normal for this date is 268 GDD base 50. Last year’s GDD accumulation for this date was 422, about two weeks ahead of normal. The cool weather has prolonged bloom of some trees and shrubs on campus. Blackhaw viburnum, red stemmed dogwood, yellow stemmed dogwood, Vanhoutte spirea and ‘Tinkerbelle’ lilac are at first bloom. Maries viburnum, and red buckeye are at early bloom. Most redbuds and lilacs are still at full bloom, as are yellow buckeye, common horsechestnut and viburnum ‘Mohican’. Sargent and Japanese flowering crabapple are at late bloom or finished blooming. Herbaceous perennials in bloom in the perennial garden include: Siberian iris ‘Charming Darlene’, Allium aflatunense, and Camassia ‘Blue Danube’. Spring ephemerals in bloom include trillium, alumroot, goldenseal, merrybells, and jack-in-the pulpit.

The soft green tips of new growth are evident on most spruce and fir trees now. The appearance of new growth on fir signals the period to begin scouting for balsam twig aphids. Pine bark aphids have laid cottony masses of eggs on white pine twigs just below the base of candles. The pale whitish spots that appear where elm leafminer have laid their eggs in leaves are visible on foliage now. Adelgids on European larch are becoming more evident, as they produce their fluffy, white wax. Boxwood psyllids are still feeding on young leaves of boxwood; the psyllids have formed wing pads and will be maturing soon. Boxwood leafminers have pupated within the leaves, and the adult flies should be developing soon. Large numbers of black bean aphid, Aphis fabae, are showing up on Euonymus alatus. Foliage curls in response to feeding, and there is abundant honeydew. The aphids are coal-black in color with legs that shade from black at the tips to pale yellow in the center. Their overwintering hosts are euonymus and viburnum. Later in the year, they switch hosts to feed on vegetables such as beets, beans, cucumbers and lettuce. See accompanying photos.

Elsewhere in the state

Report from Berrien County: Frost and freeze injury have been reported on several ornamentals. Horsechestnut, snowball viburnum and cranberry viburnum are a first bloom; spirea is at early bloom. Black cherry and Russian olive are at full bloom, lilac is at late bloom, and crabapples are done blooming. In Muskegon County, Lilac, honeysuckle, European mountainash and hawthorn are in full bloom. Freeze injury is showing up on maples. In Monroe County, Frost and freeze injury have been reported. Chokeberry and Alleghany viburnum (V. x rhytidophilloides ‘Alleghany’)are at full bloom. Columbine leafminers are creating mines in foliage. In Washtenaw County, common lilac, European mountain ash, ‘Prairiefire’ crabapple and hawthorn are in full bloom. Korean lilac is beginning bloom. Cedar apple and cedar-quince rusts are visible on junipers. Up north in Grand Traverse County, Lilac, and apple trees are blooming; tart cherry trees haven’t started blooming yet. Some spruce trees are just breaking bud. Rhabdocline needlecast and rhizosphaera needlecast have been reported on Douglas-fir.

Other states

The Plant Health Care Report from the Morton Arboretum in Lisle, Illinois dated May 13 listed black cherry, red buckeye, red chokeberry, redosier dogwood and Vanhoutte spirea in early bloom. Blackhaw viburnum, common lilac and Ohio buckeye are at full bloom. Insects they have seen include honeylocust plant bug nymphs, leafhoppers on elm, ash and maple, and larch adelgids. Gypsy moth larvae have hatched. Their degree day total as of May 10^th was 256 GDD base 50. The full report is at http://www.mortonarboretumphc.org/

The Buckeye Yard and Garden Line (Ohio State University Extension) will have a new report on May 19. It can be accessed at: http://bygl.osu.edu/.

Species		Date	GDD
		5/17/ 2005	273
Magnolia 'Ann'		E
Cercis canadensis	redbud	C-D
Viburnum carlesii	Koreanspice viburnum	E
Prunus serrulata	Japanese flowering cherry	E
Syringa vulgaris	common lilac	C -D
V. juddii	Judd viburnum	E
V. burkwoodii	Burkwood viburnum	D-E
Malus floribunda	Japanese flowering crabapple	D-E
Malus sargentii	Sargent crabapple	D-E
V. lantana ‘Mohican’	Viburnum 'Mohican'	C-D
V. prunifolium	Blackhaw viburnum	A
V. maresii	Doublefile viburnum	B
camperdown elm	leafminers	Laying eggs
Spruce	spidermites	feeding
European larch	adelgids- Adelges laricis	2nd instar
Mugho pine	Euro. Pine sawfly	Early instars feeding
White pine	Pine bark adelgid	Eggs laid on twigs
Aesculus pavia	red buckeye	B
Aesculus flava	yellow buckeye	C
Aesculus hippocastanum	horsechestnut	C
Burningbush	Black bean aphid	Feeding on foliage
Boxwood	Boxwood psylllids	Nymphs feeding
Boxwood	Boxwood leafminer	Pupal stage
Cornus sericea	Redosier dogwood	A
Syringa ‘Tinkerbelle’	‘Tinkerbelle’ lilac	A
Key- A- 5% or less flowers open “first bloom” B- >5% to <95% “early bloom” C- 95% or more flowers open –“full bloom” D- flowers dropping- “late bloom” E- done blooming

Plants that can host Asian soybean rust

Steve Gower
Diagnostic Services

In addition to soybeans, there are a number of forage legumes, beans, weeds and ornamental plants in Michigan that could potentially serve as hosts of Asian soybean rust (Phakopsora pachyrhizi). Worldwide, there are more than 30 species of legumes reported to be hosts of soybean rust in nature and more than 60 species when considering successful inoculation under greenhouse conditions. Many of these host plants are not found in Michigan. For this reason, a list was compiled of plants in Michigan that could be infected with soybean rust (Table 1).

Kudzu (Pueraria lobata) is a weedy legume that infests roadsides, fencerows, abandoned fields and non-crop areas throughout the southeastern United States. It has been described as the “vine that ate the south” because of its aggressive, climbing and trailing habit. Kudzu is a susceptible host of Phakopsora pachyrhizi. Due to the prevalence and location of kudzu, it is believed that this weed will serve as a continual source of soybean rust inoculum for southern soybean growers. The good thing – kudzu is not believed to exist in Michigan.

There are occasions when only a plant genus is listed in Table 1. In these cases, there is not sufficient information on the potential host range of soybean rust in the United States. Keep in mind that other potential soybean rust hosts could be species in the same genera as those listed in Table 1.

It is our goal to make this host list as complete as possible. If you are aware of other “legumes” or “beans” grown in Michigan fields or greenhouses, please contact Steve Gower at 517-432-9693 or sgower@msu.edu

Table 1. List of host plants of Asian soybean rust found in Michigan¹

Scientific name	Common name
Coronilla varia	Crownvetch
Crotalaria spp.	Rattlebox
Desmodium spp.	Ticktrefoil
Glycine max	Soybean
Kummerowia stipulacea	Korean clover
Lespedeza bicolor	Shrubby lespedeza
Lespedeza spp.	Lespedeza
Lupinus spp.	Lupine
Melilotus officinalis	Yellow sweetclover
Melilotus spp.	Sweetclover
Phaseolus lunatus	Bean (lima, butter)
Phaseolus vulgaris	Bean, dry-shelled (black, cranberry, kidney, navy, great northern, pinto, small red)
Phaseolus vulgaris	Bean, edible-podded (green, string, snap, wax)
Phaseolus spp.	Bean
Pisum sativum	Garden pea
Senna spp.	Senna
Trifolium incarnatum	Crimson clover
Trifolium repens	White clover
Trifolium spp.	Clover
Vicia spp.	Vetch
Vigna unguiculata	Black-eyed pea
Vigna spp.	Cowpea

1. List compiled from various references, including:

§ Soybean Rust Action Plan, Michigan Department of Agriculture.

§ USDA Office of Pest Management Policy, November 26, 2004.

§ Known and suspected Indiana hosts of Phakopsora pachyrhizi, compiled by Greg Shaner and Ian Thompson, Purdue University.

§ USDA, NRCS. 2004. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

§ Michigan Flora, Part II: Dicots.1985.University of Michigan Herbarium.

Shade tree pruning demo and true firs tour offered

Tom Dudek
District Extension Horticulture Educator

Shade tree nursery pruning demonstration - Wednesday June 1, 1:30- 4:00 PM

Pruning shade trees grown in the nursery requires some skills and training to develop the proper form for the tree as it grows in the nursery. Shade tree nursery growers can obtain the latest pruning techniques – whips, lightly branched liners and older liners – by attending this program.

Drs. Bert Cregg and Tom Fernandez from MSU’s Department of Horticulture will be discussing and demonstrating pruning techniques for shade tree nursery growers on Wednesday June 1 from 1:30 to 4:00 PM at the Twin Lakes Nursery’s Tree Farm located just east of the intersection of 52^nd Street and Snow Avenue southwest of Lowell, Michigan.

If you are planning to attend please make a reservation by contacting Thomas A. Dudek, District Extension Horticulture Educator, MSU Extension, Ottawa County at 616-846-8250 before May 31. Please bring your own pruning shears.

True firs: New conifers For Michigan landscapes tour and discussion -- Wednesday June 1, 10:00 -11:30 AM

Michigan’s nursery growers raise over 10,000 acres of evergreen conifers for landscape purposes. Unfortunately a number of these include Austrian pine and Colorado blue spruce which have some serious disease and insect problems. True firs (Abies sp.) have some great landscape appeal. Starting in 2001, Dr. Bert Cregg, MSU Department of Horticulture, developed a planting of 23 different Abies cultivars at the Clarksville Horticulture Research station. The purpose is to evaluate them for adaptability to Michigan’s diverse soils and landscape sites.

On Wednesday June 1 from 10:00 to 11:30 AM Dr. Cregg and I will be hosting a tour of the plantings at the Clarksville site. Data on drought to tolerance, cold tolerance, pH tolerance and pest problems will be discussed.

If you are a nursery professional who is looking for some new plant possibilities, please join us that morning. Please contact Thomas Dudek before May 31 at 616-846-8250 if your planning to attend.

The Clarksville Horticulture Research Station is located at 9302 Portland Road, Clarksville, Michigan. It is 15 miles east of Grand Rapids. Exit highway I-96 at the Clarksville exit… Nash Road ( EXIT #59) go south to Portland Road ( 1/2 mile). Turn west and go 1 mile to the research station. We will meet in the parking lot by the office.

Turfgrass insect update

Dave Smitley
Entomology

Grubs feeding period almost over in home lawns

The European chafer and Japanese beetle grubs are almost done feeding this spring and will soon pupate and turn into beetles. In Lansing, you can expect to see the first European chafer beetles in late June and the first Japanese beetles in early July. Because the grubs are nearly done feeding, I don't recommend any insecticide applications at this time. The next treatment window is July, when you can apply Merit, Mach 2, or Arena (Bayer Season Long Grub Control or GrubEx) to lawns with a history of grub problems. A July application of one of those products will prevent grubs next fall and the following spring.

European chafer found in Alpena and Traverse City

Just this week European chafer grubs were found in patches of dead turf in home lawns near Alpena and Traverse City. This is one part of the state (the northern Lower Peninsula) where grubs are still actively feeding, and will continue to feed for another two weeks. This is a big range expansion for European chafer. Previously, it had only been found south of Clare, except for one rest area on I-75 north of Grayling.

Golf courses should consider treating fairways, tees and greens for grubs in late May

Although July is the optimum time to use Merit or Arena for grubs, treating in late May gives superintendents some additional bang for their buck. Merit in late May will also control Ataenius and Aphodius, and give some suppression of ants and cutworms. Arena should work in a similar way. But don't try to use these products in late May for European chafer in the rough, because they won't work very well. Wait until July to treat for grub problems in the rough.

June beetles have started flying in Lansing

I was standing on my front porch talking to a neighbor last night about 8:00 PM when I heard a thud, like a stone hitting the storm door. I looked down to see a dark brown June beetle on the welcome mat, wiggling his legs, trying to get back on his feet. These large clumsy beetles tend to scare people with their spiny legs that tend to scratch skin when they cling, but the truth is they are completely harmless to people. However, a big emergence of June beetles could mean more grubs the next two years. There is no need to do anything about it now, but plan on some additional scouting next fall and the following fall in areas with a big June beetle emergence.

Seedheads in lawns

Kevin Frank
Crop and Soil Science

They’re starting to pop-up in lawns all over the state – not dandelions, those have been popping for weeks now – turfgrass seedheads are popping. It’s an annual right of spring for turfgrass, seedhead production. Kentucky bluegrass, perennial ryegrass, and of course Poa annua (otherwise known as annual bluegrass, po, poer, po anna etc.) are all currently sprouting seedheads. The seedheads not only detract from the appearance of the turf but the seed stalks are tough to mow. If you were derelict in sharpening your mower blade this spring, now might be the time to sharpen it up because mowing the seed stalks is a tough task. However, even with a sharp blade, you still may see a sheen or whitish look to the turf after mowing due to the seed stalks. I’ve heard of some recommendations that suggest you should lower your mowing height to get rid of the seedheads but I don’t subscribe to that theory and strongly advise you to keep your mowing height high. Poa annua seedheads are often a problem on golf course putting greens and some of those greens are mowed at heights of 1/8 inch. So, do you really think by lowering the height from 3 to 2 inches you’re going to eliminate all of the seedheads in your lawn? There are growth regulators that help reduce seedhead production in turf, but they are currently not available for the homeowner market. The best advice is to keep on top of your mowing schedule and make sure the blades are sharp.

Some things to watch for over the next couple of weeks as the seedheads hit peak. The turf may start to look stemy and lose density. This is natural, it will come back strong once this period of seedhead production ceases. Basically right now the plant is putting a lot of energy into popping those seedheads. Once it’s done the turf should be back to its old self.

Weather news

Jeff Andresen
Agricultural Meteorology
Geography

Upper air flow across the Upper Midwest is expected to gradually shift from the ridging pattern currently in place to a troughing pattern by early next week. These conditons will be accompanied by a temporary moderation of temperatures to normal levels. On the surface, an area of high pressure over the northern Great Lakes region Friday morning (May 20) will maintain fair and dry conditions statewide Friday through Saturday evening. A cool front will approach from the northwest late Saturday, bringing a good chance for showers and a few thunderstorms to the state beginning overnight Saturday in northern sections of the state and continuing Sunday in the south. Rainfall totals will likely reach 0.25-0.50" in most areas of the state, with up to an inch in some areas. Temperatures will approach normal levels the next few days, with highs ranging from the upper 60's to low 70's Friday and Saturday, falling back into the 60's on Sunday. Low temperatures will range from near 40 in the north to the low 50's south through Sunday.

Slightly cooler temperatures are likely for at least the first half of next week with the chance for scattered, mainly afternoon and evening showers each day. In the medium range time frame, latest forecast guidance calls for a return of upper air troughing across the eastern U.S. with a broad ridging pattern across the western U.S. The NOAA Climate Prediction Center 6-10 Day and 8-14 Day Outlooks (for May 25-29 and May 27 through June 2) call for temperatures to fall back to below normal levels, with near normal precipitation totals. Climatological normals for the third week in May include ranges of high temperatures from the low 60's north to the low 70's south and lows from the low 40's north to the upper 40's south. Normal weekly precipitation totals range from about 0.65 inch across northern and eastern sections of the state to about 0.75 inch in far southern sections of Lower Michigan and in western sections of the Upper Peninsula.