Pam Bennett, Barb Bloetscher, Joe Boggs, Jim Chatfield, Erik Draper, Dave Dyke, Dave Goerig, Tim Malinich, Jane Martin, Hannah Mathers, Pam Sherratt, Amy Stone, and Curtis Young
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April 21, 2005
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This is the Third 2005 edition of the Buckeye Yard and Garden Line (BYGL).
BYGL is developed from a Tuesday morning conference call of Extension
agents, specialists and other contributors in Ohio.
BYGL is also made available on the Internet from the Ohio State University
Horticulture and Crop Science (HCS) in Virtual Perspective website
(http://bygl.osu.edu). Additional fact sheet information on any of
these articles may be found through the OSU fact sheet database (http://plantfacts.osu.edu).
BYGL is a service of OSU Extension and is aided by major support
from the Ohio Nursery and Landscape Association (ONLA), with additional
funding from the Ohio Chapter of the International Society of Arboriculture
(ISA) to the OSU Extension Nursery Landscape, and Turf Team (ENLTT).
Participants in the April 19, 2005 conference included: Barb Bloetscher (Entomology); Joe Boggs (Hamilton/Piketon); Jim Chatfield (Center at Wooster/Horticulture and Crop Science [HCS]); Erik Draper (Geauga); Dave Dyke (Hamilton); Hannah Mathers (HCS); Joe Rimelspach (Plant Pathology); Dave Shetlar (Entomology); Nancy Taylor (Director, C. Wayne Ellet Plant Pest Diagnostic Clinic); Curtis Young (Allen) and Randy Zondag (Lake)..
Additional factsheet information on any of these articles may be found
through the OSU Factsheet Database (http://plantfacts.ohio-state.edu/)
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WEATHER WATCH
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Here is the weather summaries from selected OARDC weather stations across the buckeye state. The information is a summary of data collected from April 1 - April 21.
| Weather Station |
Region of Ohio |
Ave. High Temp F | Ave. Low Temp F | Ave. Temp F | Normal Ave. Temp F | Total Precip " | Normal Precip " | | Perry |
NE |
63.6 |
39.8 |
N/A | N/A |
0.16" |
N/A | | Hoytville |
NW |
67.9 |
37.3 |
52.3 |
47.0 |
0.80" |
2.29" |
| Columbus |
Central |
70.5 |
43.4 |
57.1 |
49.4 |
1.41" |
2.66" |
| Miami |
SW |
71.8 |
44.8 |
58.4 |
49.2 |
0.63" |
2.44" |
| Jackson |
South |
73.1 |
40.0 |
56.8 |
50.5 |
1.66" |
2.70" |
For additional information, or to see the locations of all of the OARDC weather stations in Ohio, check out the website at http://www.oardc.ohio-state.edu/centernet/weather.htm
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HORT SHORTS
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PLANT PHENOLOGY
From the Northwest, Amy Stone reports the weather has been wonderful, but that they are in the need of some rain. Forsythia is still blooming, magnolias are looking great. First bloom was just observed on P.J.M Rhododendron and they are beginning to notice dandelions blooming and earthworm calls continue to be most popular this past week in the office.
It central Ohio, Spring appears to just steamroll along. Pam Bennett reported these plants in full bloom: Amelanchier canadensis, Pyrus calleryana, Chaenomeles speciosa, Acer platanoides, dandelions, both White and Green Ashes, Pulmonaria, and Virginia bluebells. Just opening - Cercis canadensis and Malus 'Sugar Tyme'.
In the Wooster area, forsythia, cutleaf toothwort, and some of the early cherries and saucer magnolias are in full bloom or just beginning to fade.
Finally, way up in the great white North of Geauga County, Erik Draper reports forsythia in full bloom and without any winter damage, saucer magnolias and star magnolias are full and glorious in bloom. Amelanchier canadensis, serviceberries are just beginning to explode into bloom, as are the early ornamental cherries and flowering plums.
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GDD (GROWING DEGREE DAYS)
GDD is a measure of the daily maximum and minimum temperature and directly relates to growth and development of plants and insects. The GDD of any zip code location in Ohio is estimated using the GDD of ten OARDC weather stations and available on the web at: http://www.oardc.ohio-state.edu/gdd/
The range of GDD accumulations in Ohio from north to south is 120 to 286. Following is a report of GDD for several locations around Ohio as of April 20, 2005: Painesville, 120; Cleveland, 123; Toledo, 158; Youngstown, 144; Lima, 148; Wooster, 182; Coshocton, 146; Columbus, 165; Springfield, 204; Dayton, 240; Cincinnati, 286; Ironton, 278; and Portsmouth, 278.
To put these GDD accumulations into perspective, the following is an abbreviated listing of plant and insect species with their respective phenological event and average GDD accumulations at which these events occur. Due to variations in weather, temperature, humidity, etc., these events may occur a few days earlier or later than predicted by the average GDD. By looking at a city, town, or village near you from the above list, or visiting the above web site, you can see what could be taking place in the landscape around you.
Norway maple, first bloom, 116; border forsythia, full bloom, 116; chanticleer callery pear, first bloom, 123; sargent cherry, first bloom, 127; larch casebearer, egg hatch, 128; saucer magnolia, first bloom, 133; bradford callery pear, first bloom, 142; European pine sawfly, egg hatch, 144; weeping Higan cherry, first bloom, 145; P.J.M. rhododendron, first bloom, 147; Chanticleer callery pear, full bloom, 149; Norway maple, full bloom, 149; inkberry leafminer, adult emergence, 150;sargent cherry, full bloom, 151; star magnolia, full bloom, 151; Allegheny serviceberry, first bloom, 153; Manchu cherry, full bloom, 155; Spring Snow crabapple, first bloom, 155; apple serviceberry, first bloom, 159; spruce spider mite, egg hatch, 162; Bradford callery pear, full bloom, 164; Allegheny serviceberry, full bloom, 169; saucer magnolia, full bloom, 174; PJM rhododendron, full bloom, 178; boxwood psyllid, egg hatch, 179; weeping Higan cherry, full bloom, 179; Koreanspice viburnum, first bloom, 185; regent serviceberry, first bloom, 186; Japanese flowering crabapple, first bloom, 189; eastern redbud, first bloom, 191; gypsy moth, egg hatch, 192; Koreanspice viburnum, full bloom, 205; azalea lace bug, egg hatch, 206; Spring Snow crabapple, full bloom, 209; common flowering quince, full bloom, 214; birch leafminer, adult emergence, 215; coral burst crabapple, first bloom, 217; elm leafminer, adult emergence, 219; common chokecherry, full bloom, 221; alder leafminer, adult emergence, 224; honeylocust plant bug, egg hatch, 230; common lilac, first bloom, 234; Ohio buckeye, first bloom, 245; common horse chestnut, first bloom, 251; hawthorn lace bug, adult emergence, 253; hawthorn leafminer, adult emergence, 260; flowering dogwood, first bloom, 263; red buckeye, first bloom, 265; blackhaw viburnum, first bloom, 269; imported willow leaf beetle, adult emergence, 274; and sargent crabapple, full bloom, 298.
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WOODY PLANT OF THE WEEK: CRABAPPLES
In this year's BYGL we are highlighting an outstanding landscape plant or two each week. The descriptions for these plants come directly from two new publications: "Landscape Plants for Ohio" and "Perennial Plants for Ohio", both published by the Ohio Nursery & Landscape Association (the Perennials book will not be out until May). The descriptions and photographs of these plants were provided for these new publications by the OSU Extension Nursery Landscape and Turf Team with great help from friends such as Bill Hendricks and Fred Hower.
This week's choice crabapples are already blooming in southern and central Ohio and will probably peak the first week of May in northern Ohio. There are over 1000 taxa of crabapples. Here are a few of the many outstanding choices for Ohio landscapes.
Crabapples (Malus spp. and cultivars)- Popular genus with numerous species, cultivars and hybrids of small flowering trees with wide range of flower, foliage, form and fruit features. From uprights to weepers, from white to coral pink flowers, from dark green to purple foliage, from cherry red to golden fruits, this is an ornamental tree for all seasons. Following are a few crabapple cultivars and species which illustrate their range.
* 'Adirondack'. One of the few outstanding crabapples with narrow upright tree form. Clean foliage, orange-red fruits, and showy white flowers. Excellent autumn foliage and fruit combination of reds and oranges. 15 foot.
* 'Excalibur'. Symmetrical globe-shaped tree form. Golden yellow fruits maturing to cider colors are ornamental in the fall months. Petite white flowers and fruits lining branches are outstanding features. 10 foot.
* 'Holiday Gold'. Rounded to open tree form. Golden yellow fruits with red blush attractive early fall to late winter. Consistent white blooms. 18 foot.
* 'Louisa'. Outstanding weeping form with graceful arching branches. Soft pink flowers. Fruits are a golden orange color. 12 foot. Other crabapples that are spreading-weepers but not as much true weepers include 'Anne E', 'Molten Lava', 'Mary Potter' and 'Candymint'.
* 'Prairifire'. Rounded to open tree form. Consistent stunning display of coral-pink flowers. Attractive glossy green foliage with a purple tinge. Purple fruits are ornamental from late June to early December and are paired with orange fall color of spur leaves. 18 foot.
* 'Red Jewel'. Upright oval tree habit with outstanding cherry red fruits that are highly ornamental little mini-apples all the way into early spring. Snow white flowers. 15 foot.
* M. sargentii. This species is a spreading dwarf type to 8-10 feet. Excellent petite white flowers and attractive scarlet fruits. Effective landscape use is to plant in groups of three.
* 'Sargentina'. Smaller yet variation on the Sargent crabapple, growing to 4-5 feet in height with dainty white flowers and attractive red fruits.
* 'Sugar Tyme'. Good rounded overall form, but the flower and fruits are the main attractions. Sugary white mass of blooms consistent from year to year followed by showy apple red fruits that are ornamental well into the winter months.
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POISON-HEMLOCK RISING
Joe Boggs reported that poison-hemlock (Conium maculatum) rosettes are currently rising in southern Ohio, and its feathery, dark green, fern-like foliage is becoming obvious. Over the past several years, this highly toxic, non-native, biennial plant has become a frequent topic of calls to Extension offices. Whether this is because the plant has become more common in Ohio, or just more commonly recognized, is open to debate. Regardless, this plant deserves respect. After all, it is generally believed that it was poison-hemlock, a native of Europe, that was responsible for the philosopher Socrates' untimely death...and possible famous last words: "I drank what?"
Both poison-hemlock and the similar looking native perennial SPOTTED WATERHEMLOCK (Cicuta maculata) are among the most toxic plants in North America. All parts of the plants are toxic, especially the young leaves, stems, and seed. The toxicity of poison-hemlock centers on toxic alkaloids, including coniine and gamma-coniceine, which cause respiratory failure and death when ingested by humans and other animals.
Poison-hemlock is a biennial member of the carrot family (Apiaceae (= Umbelliferae)), and it thrives along borders of fields, along roadsides, ditch banks, and in meadows. It has also become a landscape challenge, particularly in new housing developments built on fallow farm land. The plants may grow to a monstrous size, towering up to 8-10' tall, and it produces white umbel-like flowers which are typical of this family. In fact, poison-hemlock's flowers, dark glossy-green, fern-like, triangular leaves, and general growth habit may cause it to be mistaken for other weeds in the same family including QUEEN ANNE'S LACE, or wild carrot (Daucus carota).
Queen Anne's lace is not toxic and not a serious problem beyond its general status as a weed. This biennial plant has dark-green, hairy stems that are deeply ribbed vertically, and the leaf margins are hairy. Waterhemlock and poison-hemlock have light-green to bluish-green, hairless stems, that are smooth to only slightly ridged vertically. Their leaves lack hairs along the margins. Leaves of waterhemlock are 2-3 times pinnately compound while leaves of poison-hemlock are 3-4 times pinnately compound. Leaflets of both are much larger and more sharp-pointed than the twice-pinnately compound, lobed leaves of Queen Anne's lace. While both waterhemlock and poison-hemlock have purplish spots on the stems, waterhemlock's spots tend to become more elongated into streaks. Waterhemlock has a cluster of fleshy taproots at the base (it is a perennial weed), a feature that is not shared with poison-hemlock or Queen Anne's lace.
Waterhemlock and poison-hemlock can be controlled using selective post-emergence herbicide mixtures containing 2,4-D, 2,4-DP and MCPP, or 2,4-D, dicamba, and MCPP (e.g. Trimec). These weeds can also be killed using a non-selective post-emergence herbicide such as glyphosate (e.g. Roundup) where conditions pose a minimal risk to preferred plants. Applications of herbicides made now will control both the first season rosette stage of poison-hemlock and the second season flowering stage, before seeds are produced.
 
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BUG BYTES
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SAWFLY LEAFMINERS FLY
Based on plant phenology as well as GDD, the adults of four leafmining sawflies should be flying, or soon flying in southwest Ohio. Three of the sawflies are in the genus Fenusa. These include: ELM LEAFMINER (F. ulmi); EUROPEAN ALDER LEAFMINER (F. dohrnii); and BIRCH LEAFMINER (F. pusilla). The fourth sawfly is the HAWTHORN LEAFMINER (Profenusa canadensis). Larvae of these sawflies mine the leaf parenchyma; producing large, blister-like, reddish-brown "blotch" mines. These mines usually extend from the leaf margin toward the midvein. The hawthorn and elm leafminers have one generation per year and the alder and birch leafminers have three generations.
For most insect pests, the occurrence of multiple generations usually means upwardly spiraling populations and ever increasing damage as the season progresses. However, for birch leafminer, the opposite is true. Larvae can only mine new leaves. So, most damage occurs in early spring when the first generation larvae mine the new, expanding leaves. After they finish feeding for the season, around 80% of the first generation larvae drop to the ground and remain as pre-pupae until next spring. Control efforts should target the first generation since the second and third generations do little damage, unless the tree is re-foliating after leaves were stripped by some other problem.
Imidacloprid (e.g. Merit; Bayer Advanced Tree & Shrub Insect Killer Concentrate) has proven effective in controlling these sawfly leafminers when applied as a soil drench over the root zone in October or November. It is too late for soil applications made this spring to prevent all damage since it takes around 30 days for the insecticide to move into the plant in concentrations sufficient to provide control. However, a soil drench application made now will kill larvae in their developing mines. Foliar applications of pyrethroid insecticides may also provide some control, although all leafmining activity will not be suppressed where adults have already started laying eggs.
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BUMBLING BEETLES GO BUMP IN THE NIGHT
The familiar "bzzzzzzz...thud!" sound made by MAY/JUNE BEETLES bouncing off walls, doors, and windows as they fly around porch lights at night is now being heard in southern Ohio. There are five species of beetles in the genus Phyllophaga in Ohio that share the general common name of May or June Beetles. The 1/2" to 1" long adults are slightly oblong, and reddish-brown to black in color. Their obnoxious evening behavior often causes them to be dismissed as nuisance pests. In most cases, this is true. Although adults of most of these species feed at night on flowers, or tree and shrub foliage, they seldom cause significant damage.
However, large numbers of these beetles occasionally produce noticeable leaf damage, and their nocturnal life-style makes them a deceptive defoliator. In 2000, conspicuous defoliation of oaks and maples caused by these beetles was reported in central Ohio and in some areas of Kentucky. In a few cases, the damage literally occurred overnight. The defoliation involved the removal of all of the leaf tissue with the exception of the main veins. Since the beetles are night feeders, casual observers were left in the dark trying to explain the damage. Although damage may appear severe, the beetles only fly for a few weeks, leaving plenty of time for defoliated trees to produce new leaves.
Larvae of these beetles are white grubs, with feeding habits similar to masked chafer and Japanese beetle grubs, but they prefer pasture grasses. Hence, damage to trees most often occurs near pastures. Likewise, significant grub populations are seldom found beneath older lawns, but are sometimes observed where new homes occupy ground which was recently in pasture. Larvae require anywhere from 1- 5 years to complete their development, depending upon the species.
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IT FIGURES... CHIGGERS
With warmer temperatures comes the urge to walk through the fields and thickets, sit on the freshly mowed lawn, and scratch fervently at the newly hatched chigger nymphs which latched onto your skin. These tiny (0.6- 0.25mm) reddish 6- legged larvae can cause considerable redness, itching, and swelling within 2- 6 hours after finding the host, which may ultimately result in red welts or wheals if scratched excessively. The incessant itching may continue for 2 weeks, and although the mite may be dislodged by the scratching, secondary infections often occur.
Contrary to common belief, chiggers do not tunnel under the skin, instead they stay on the surface of the skin, or crawl to the base of a hair follicle to feed. They are usually found around the ankles, knees, waist, or armpits. Once settled, the larva injects the skin with digestive fluids using its piercing, sucking mouthparts (capitulum), then ingests the "cell slurry soup". After a few days, the larva drops off and enters the nymphochrysallis stage. Once it has emerged as a nymph, it will no longer be parasitic. Both the nymphs and adults feed on springtail eggs and other small insect parts, and no longer feed on mammals.
To avoid being the victim of chiggers, avoid walking through brushy areas or wear long white pants with the socks pulled over the pant legs. Insect repellents such as DEET can help to ward off chiggers. Keep the area around homes and offices mowed to reduce the number that are dropped near the building by animals, and check yourself immediately after walking in "wild" areas. It takes several hours for the chiggers to settle, so the tiny red mites may be seen running on your skin. Washing the bites with warm soapy water and covering them will help to reduce infection. Calamine lotion and similar products will help to reduce itching. In certain cases, lawns can be sprayed by a pest control professional, although it is usually not necessary.
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CARPENTER BEES BUZZING
Those bumblebee look-alikes have resumed their terrifying habits of buzzing around wood, people, and pets, as if planning to elicit a barrage of stings. In truth though, these bees are all males and thus, have no stinger. The strafing activity is the males strategy to chase off its competitors and to determine if the strafee is a candidate for mating.
The females drill perfect holes 3/8 - 1/2" in diameter along exposed horizontal strips of cedar, pine and fir wood. Once in the wood, the females turn 90 degrees and tunnel the length of the board for 6 - 10", then pack pollen with eggs into these tunnels. The newly developed adults emerge and exit the tunnels in the fall.
To manage the bees, protect the wood with an oil based or polyurethane paint, or replace with another species of wood, such as Douglasfir, which isn't as attractive to them.
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EMERALD GREEN TIGERS?
As springtime temperatures warm, numerous individuals are venturing out into landscapes and woodlots to commune with nature armed with a heightened awareness to look for signs and symptoms of exotic insects, especially the EMERALD ASH BORER (EAB). The threat of discovering an infestation of EAB and the consequences that follow such a discovery, have the adrenaline following in the would-be discoverers. As a result, panic can set in when a EAB look-a-like is observed in the landscape or wood lot.
Curtis Young reported encountering one of these look-a-likes in a wood lot in Allen County, not too far from some of the known EAB infestations. While walking a nature trail through a metro park complete with numerous ash trees, a streak of emerald green caught his attention. Following the green streak until it came to rest, Curtis was able to identify the insect as the SIX-SPOTTED TIGER BEETLE, Cicindela sexguttata.
Six-spotted tiger beetles are about 1/2 inch long. They have brilliant metallic green bodies, legs and antennae. The front wings, called elytra, each have three to five white spots or six to ten spots in total.
Six-spotted tiger beetles can be found in open woods, and along paths and streams. Their movements are very wasp-like as they flit from spot to spot inches above the ground. They are relatively fast moving and also flick their wings like sphecid wasps (e.g. mud daubers). Tiger beetles, both larvae and adults, are predators that eat ants, spiders, and other small prey they can grab. They can be seen from April through August approximately the same time span that adult EAB will be out and active. Thus, the moral of this story is ID before you call 1-888-OHIO-EAB.
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A TWISTED TALE: HONEYLOCUST TORTURE BEGINS
Joe Boggs reported observing HONEYLOCUST PLANT BUG (Diaphnocoris chlorionis) nymphs scurrying amongst the expanding foliage of their namesake in southwest Ohio. Feeding by these lime-green sucking insects can cause the new foliage to become twisted, stunted, and occasionally discolored. Their feeding injury may mimic symptoms produced by growth regulator herbicides.
Examine expanding leaflets carefully since the nymphs are very mobile and they scramble away from probing fingers. The beating-tray pest disclosure method used for spruce spider mites also works well for honeylocust plant bug nymphs.
Damage produced by the nymphs will remain visible throughout the season. It has been generally recommended that a control application be considered if more than 5 nymphs are found per leaf. However, insecticide applications targeting this insect have been implicated as a contributor to the development of damaging population levels of honeylocust spider mite. Insecticides may kill beneficial mites which would otherwise keep the spider mites under control. Monitor trees closely and weigh heavily the need for making insecticide applications. Refer to OSU Extension Bulletin 504, "Insect and Mite Control on Woody Ornamentals and Herbaceous Perennials," for a list of control materials. If an insecticide application is necessary, it may need to be repeated, so check foliage 7 to 10 days after treatment.
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MORE BUGS BADGER
Landscape and nursery managers in central and southern Ohio should be monitoring their plants for LACE BUGS. Lace bugs are grouped in the Hemipteran family, Tingidae. Their common name comes from the lacy-like venation of the broad, flat, whitish-colored forewings that cover most of the insects body. As with all Hemipterans, lace bugs feed with sucking mouthparts.
Most lace bugs feed on the underside of leaves, but symptoms appear on the upper leaf surface. Damage symptoms first appear as small yellow spots, or stippling. The spots may coalesce causing leaves to become bronze colored, which superficially resembles spider mite feeding damage. However, lace bugs produce brown to black tar spots of excrement that is readily apparent on the undersides of the leaves.
Species of lace bugs that feed on broadleaf evergreens spend the winter as eggs on the underside of leaves. These eggs have already started to hatch in central and southern Ohio. A few examples of this form of lace bug include: andromeda lace bug (Stephanitis takeyai); azalea lace bug (S. pyriodes); and rhododendron lace bug (S. rhododendri).
Lace bugs that feed on deciduous trees and shrubs overwinter as adults in the bark crevices of their hosts. These bugs move to newly expanding foliage in the spring. Some notable species in this group include: oak lace bug (Corythuca arcuata); sycamore lace bug (C. ciliata); hawthorn lace bug (C. cydoniae); and walnut lace bug (C. juglandis). Joe Boggs reported that hawthorn lace bug adults are being found on the foliage of their namesake in southern Ohio.
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LOOKING FOR MR. CRANE FLY
Looking for the EUROPEAN CRANE FLY, Tipula palodusa, that is! Ohio has many native species of crane fly. These insect species are not only common but are easily recognizable as adults. Crane flies are two-winged insects (i.e. true flies) that are often mistaken for giant mosquitoes. Despite their somewhat scary appearance, they dont bite, suck blood, or carry diseases. The adults are not only harmless, but they are an important food source for birds and other animals. The larvae, called leatherjackets, of many crane flies are aquatic and their presence is an indicator of good water quality. They can be an important food for fish. Other crane flies are terrestrial decomposers and help break down decaying organic matter. Some of these decomposer species can be found in moist to wet turfgrass areas where they eat plant material found in the soil/thatch zone. However, a few species feed directly on roots of tree seedlings, young plants, and grass roots and blades. If large populations of these species are present, they may cause considerable damage. This damage has been observed in rangelands, pastures, seedling crops, and turfgrass areas including home lawns.
Two exotic species of crane fly, the European Crane Fly and the MARSH CRANE FLY, T. oleraceae have been introduced and have become established in the northwestern U.S., British Columbia and the Maritime Provinces of Canada, and more recently discovered in Ancaster, Niagara Falls, Hamilton mountain, Scarborough, Uxbridge, Oshawa/Whitby, Brampton, Markham, Kitchener/Waterloo, Guelph, Windsor, Cambridge and St. Catharines. Many of these locations are not far from Ohio.
Both species are native to central and southern Europe, it is not certain, how or when, either species was first introduced or became established in North America. A likely source of introduction for these species would be movement with soil media. These crane flys larvae are terrestrial root feeders and are serious turf and seedling nursery pests. They also have the potential to affect cereal and other crops, as they do in Europe. Neither species have been found in Ohio.
Have you seen this pest? Curtis Young has conducted surveys in 2002, 2003 and 2004 searching for these new exotic crane flies in Ohio. Leatherjackets were found in turfgrass on sod farms, golf courses, parks, grassy fields and home lawns, but none were found to be the exotic species of interest. Curtis will be conducting this survey again in April, May and June of 2005. It is hoped that private homeowners and the lawn care industry may be a source of information for locating these pests. Thus, if you know of an area that has experienced leatherjacket activity, please let Curtis know so the site can be included in the survey. These crane flies cause excessive damage and could become a serious pest in Ohio lawns. You can contact Curtis at the following e-mail address: youngce@postoffice.ag.ohio-state.edu, or call (419)222-9946.
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DISEASE DIGEST
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ENVIRONMENT AND PLANT DISEASE
Moisture is a key environmental ingredient in many plant diseases. Understanding how this moisture plays a part in real-world disease development and its associated subtleties are important. For example, lets take a look at fireblight of Callery pear and apple scab on crabapple.
In last week's BYGL we mentioned that two primary ingredients for development of severe fireblight on Callery pear were both wetness and warm weather in the mid 60s and higher during bloom. When such conditions occur, blossom infections by the fireblight bacterium are favored. Fireblight bacteria (Erwinia amylovora) overwinter in cankered areas on stems and then are splashed or spread by bees and other insects to blossoms, with subsequent movement into shoot tissue. Although other tissue, including leaves and shoots, can also be directly infected, the disease is typically most severe in a given season if early blossom infections are favored by environmental conditions. Considering the weather during Callery pear bloom in southern and central Ohio this year then, warm but relatively dry for blooms that are now fading, it seems likely that this will not be a major fireblight year for Callery pear. The verdict is still out for more northerly areas of Ohio with bloom still peaking.
This brings up the question of apple scab on crabapple. Does this recent dry weather mean apple scab will be relatively less severe than usual this year? After all, infections by the apple scab fungus (Venturia inaequalis) also are favored by wet conditions. Alas, this story has not yet unfolded, and each disease tells its own story.
The apple scab fungus overwinters in fallen scabby leaves and crabapple fruit mummies that remain on the trees. During its overwintering, the fungus undergoes sexual reproduction with several mating types of the fungus coming together. These sexual spores provide the inoculum of the fungus (the form of the fungus that causes infection) that initially infects the leaves and fruits of crabapples each spring. These sexual spores developing in last year's infected plant tissue are called the primary inoculum of the apple scab fungus. From these infections, throughout the season, new spores develop. These spores are not the products of sexual reproduction of the fungus, and are called secondary inoculum, and form in apple scab lesions that develop in the new season. One of the reasons that prevention of primary infection with fungicides in the spring are the most important is that since secondary inoculum develops in the lesions caused by primary inoculum, prevention of the primary infections from overwintering inoculum does double duty.
So, does the recent dry weather mean we are out of the woods relative to severe apple scab in 2005? No, unfortunately unlike fireblight of Callery pear, in which blossom infections are so critical to how bad each year's disease severity will be, primary infections of crabapples from overwintering inoculum can still occur for a number of weeks yet. So how bad apple scab will be this year depends upon how wet it will be for some time to come.
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GENETICS AND PLANT DISEASE
So, with apple scab preventive fungicide controls still may be an important part of disease control, given the likelihood that periods of wet weather are likely to arrive this spring. However, there is another form of preventive disease control that in the long run goes much deeper than fungicides. That is prevention of disease through use of genetically resistant crabapples. An excellent example is with apple scab-resistant crabapples. In our research here at Ohio State University we have identified a number of crabapples with outstanding resistance to apple scab disease. A good place to start is with the list of crabapples in this week's PLANT OF THE WEEK feature ('Adirondack', 'Excalibur', 'Holiday Gold', 'Louisa', 'Prairifire', 'Red Jewel', Malus sargentii, 'Sargentina', Sugar Tyme'.) All of these crabapples have outstanding to good resistance to apple scab disease. If you are interested in learning more about evaluations of other crabapples for apple scab incidence, check out the recent article on crabapples in the OSU Ornamental Circular. Contact Jim Chatfield at chatfield.1@osu.edu if you want a copy of the article.
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TURF TIPS
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ROLLING LAWNS IN SPRING
As lawnowners begin their spring lawn care activities, many individuals are encountering soft and often lumpy lawn surfaces. Two distinctly different phenomena are responsible for the unevenness.
First, the soft nature of lawns may be due to heaving. The late winter and early spring freezing and thawing cycles create this condition. Through these freeze/thaw cycles, the sod can be partially separated from the underlying soil surface. This condition is usually most severe on heavy clay and/or poorly drained sites. A second cause of uneven surfaces is due to the late fall/early spring activity of earthworms. These earthworms deposit castings (soil like material brought to the surface of the lawn from earthworm tunneling underground) in mounds near the openings of their burrows. The castings can reach heights of one to two inches and are especially noticeable on heavy clay soils. As these mounds dry, noticeable unevenness results. Other factors that may cause uneven turf include moles, tire tracks, and foot traffic.
One way to try and remedy these conditions is to roll the lawn. Rolling is best performed in the early spring after the freezing and thawing cycles are over. Ideally, the soil should be moist but not saturated. A variety of rollers are available from rental services or for purchase from most lawn products retailers. With most models, water is added to the drum to develop weight. The proper weight is where the soil surface is smoothed yet the soil is not heavily compacted. It is recommended to fill the drum approximately one-third full of water, then make a pass. If the desired degree of smoothness is achieved, continue rolling. If a spongy and/or uneven surface remains, add more water, then make an additional pass. Repeat these steps until the desired results are achieved. The process is relatively simple but it may be challenging to get the desired results. The degree of unevenness, soil conditions, and the equipment used are some factors that will influence the results.
Rolling should NOT be performed in an attempt to level lawns which were not properly graded prior to the establishment or are naturally uneven. Excessive rolling or rolling with too much weight can lead to compacted soils resulting in poor root development and a general reduction in turfgrass quality. If core aerification is also planned for this spring, core aerification should be performed AFTER the rolling activity.
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BROWN SPOTS IN LAWNS
At this time of year there are various reasons for why brown spots may be in lawns. Often in the spring there are many unusual patterns and colors of grass in lawns. Recovery from winter and variable weather conditions are often involved in these situations. The following are some cases encountered around the state:
*Snow Mold - There are still samples coming in from northern Ohio. Check the base of plant for new leaves. In most cases the affected areas will recover.
*Warm Season Grasses - there have been questions and samples of nimblewill (Muhlenbergia schreberi) and Zoysiagrass (Zoysia sp.) These grasses are alive but require consistent warm temperatures (daily 80 degree F temperatures) to grow new leaves. At this time these grasses are brown but not dead.
*Drought Stress - It seems odd for spring but there are areas that are dry. If lawns are on poor quality or compacted soil, or have a weak and shallow root systems, these will be the first to go brown from moisture stress. Check the soil, if dry water or wait for rain.
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INDUSTRY INSIGHT
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WET SPRING 2004 AND DRY 2005 = WEED PROBLEMS
We had a very wet spring last year and may preemergent herbicide applications were simply leached away or could not be put on because of wet conditions. As a result many weeds went to seed and have added significantly to the seed bank in the soil. Hannah Mathers, therefore, predicts 2005 will be a bad year for weed infestations in nurseries and landscapes. Another circumstance that is adding to the creation of 2005 as a bad weed year is the dry spring we are experiencing in many parts of the state. The dry conditions are effecting postemergent application and preemergent application effectiveness.
Herbicides are applied either to the foliage of growing weeds (postemergence) or to the soil to prevent germination (preemergence). Postemergent foliar herbicides are either contact or systemic chemicals. Contact herbicides are generally most effective against annuals. Complete coverage is essential in weed control with contact herbicides. An example of a contact herbicide is Gramoxone. Systemic herbicides include the phenoxy herbicides (ex. 2,4-D) and dicamba, plicoram, amitrole and glyphosate. Systemic herbicides are translocated throughout the plant to their sites of physiological action. Translocated herbicides are effective against all types of weeds; however, they have their greatest advantage when used to control established perennials. Complete coverage is not required with translocated materials; however, uniform applications are critical. Postemergents are generally best when applied to young plants and may take several days to work.
Poor results can occur with postemergent applications if the weed is under stress at the time of application. Our dry spring has meant many weeds are under drought stress. The ability of the postemergent to be effective, particularly on perennial weeds, has thus been weakened. If rainfall occurs within 6 hours or if heavy rainfall occurs within two hours systemic postemergents will also be non-effective.
This is also the time of year to be getting your preemergent herbicides out if you havent already. Preemergent herbicides (e.g. Surflan, Pendulum, etc..) are applied either to the soil or growing medium surface and are usually absorbed by root systems, or by emerging shoot tips as they make their way through the soil surface during seed germination. Most must be dissolved in the soil/medium to work.
Generally, one-half inch of irrigation or rainfall after application of a preemergent is required to activate the chemical barrier. If premergents are not watered in many will not work. Again, because of dry conditions, preemergent applications are not being watered in or soil activated and will be non-effective. Preemergents must be applied to weed free surfaces and because our weed pressure was so high in 2004 many weeds are already up including all the winter annuals (some are going to seed), some summer annuals like marestail and many perennials. It will be very important to stay ahead of your weed problems in 2005. Now is the time to control your weeds timing is everything in weed control if you let them get out of hand you will be playing catch up "for years" to come.
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COMING ATTRACTIONS
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ORNAMENTALS RESEARCH DAYS
Come learn more about ornamentals research at Ohio State University. Details later, but start by getting these dates on your calendars:
* June 29, 2005: Ornamentals Research Program Tour at the Ohio Agricultural Research and Development Center (OARDC) at Wooster. Sponsored by the OSU Extension Nursery Landscape and Turf Team (ENLTT), OARDC, and the OSU Extension Center @ Wooster (contact: Jim Chatfield).
* July 1, 2005: Ornamentals Research Program Tour of the OSU Centers at Piketon. Sponsored by the ENLTT and the OSU Extension Center @ Piketon (contact: Joe Boggs).
* September 22, 2005: Ornamentals Research Tour at the OSU Main Campus in Columbus. Sponsored by OSU College of Food Agricultural and Environmental Science, the OSU Department of Horticulture and Crop Science, and the Ohio Nursery Landscape Association (contact: Hannah Mathers).
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SALSA (SECREST ACADEMY FOR LANDSCAPE SCIENCES AND ARTS)
This "churning urn of burning funk" of a horticultural program starts this summer at OSU's Secrest Arboretum at the Ohio Agricultural Research and Development Center in Wooster. It is for individuals with professional or personal interest in an intensive, hands-on landscape learning experience and is a program of Ohio State University's Secrest Arboretum and the Ohio State University Extension Center at Wooster. Faculty for session I of SALSA are Jim Chatfield, Ken Cochran, Joe Cochran, and Erik Draper.
SALSA I will focus on the following topics: Making Plant Names Work For You, Discovering How Plants Grow, Selecting Plants for Landscape Solutions and Minimizing Maintenance, Diagnosing Plant Problems, Putting Plants in their Place, and Producing Plants: From Propagation to Pricing. SALSA I will involve 3 full-day sessions on July 18, August 15, and September 19 and is part of a five-part, 15 session/15 month overall Academy.
SALSA is a learning experience, advancing your knowledge of the arts and sciences of landscape horticulture, through linked interactive hands-on programs. SALSA is not a series of isolated single-topic programs, nor it a full-fledged 2- or 4- year degree program. SALSA occupies the landscape between these two ... rooted in dedication, blooming with creativity. Class size is limited. The cost of SALSA I is $300 for the full three days of programming. This fee includes considerable reference material and class curriculum notebooks, diagnostic aids such as hand lens, lunches and refreshments. For more information contact Joe Cochran at Secrest Arboretum (330-263-3886; cochran.58@osu.edu).
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PLANT HEALTH CARE/WOODLAND AND WILDLIFE WORKSHOP TO BE HELD IN TOLEDO
In celebration of Arbor Day in northwest Ohio, a workshop will be held on Saturday, April 30 in Ottawa Park (across from Toledo Hospital) from 12:00 - 4:00 pm. The event is free and open to the public and will highlight demonstrations and educational sessions for kids and adults. Information on the emerald ash borer, a portable sawmill demonstration, tree pruning and planting, and a chainsaw carver are just a few highlights. The program is sponsored by OSU Extension and the local Soil and Water Conservation Districts. To register, or for additional information, please contact the OSU Extension at TBG office by calling 419-578-6783, or emailing Amy Stone at: stonea@ag.osu.edu.
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BYGLOSOPHY
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"In the spring, at the end of the day, you should smell like dirt".
- Margaret Atwood
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