Pam Bennett, Barb Bloetscher, Joe Boggs, Jim Chatfield, Erik Draper, Dave Dyke, Gary Gao, Dave Goerig, Dan Herms, Tim Malinich, Jane Martin, Pam Sherratt, Amy Stone, and Curtis Young.
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August 19, 2004
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This is the twentieth 2004 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 August 17, 2004 conference included: Pam Bennett (Clark); Barb Bloetscher (C. Wayne Ellett Plant and Pest Diagnostic Clinic); Joe Boggs (Hamilton/South East Region); Dave Dyke (Hamilton); Dan Herms (OARDC, Entomology); Tim Malinich (Cuyahoga); Pam Sherratt (HCS); Amy Stone (Lucas); Nancy Taylor (CWEPPD 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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Cooler than average temperatures have blanketed much of the state of Ohio. In Columbus, Jane Martin reported that the area is 5.9F degrees below average for the month of August. Other central Ohio weather highlights include: the rainfall total for August was 0.35", which is minus 1.56" when compared to the monthly average; and the year-to-date precipitation total was 32.41", which is 6.97" on the plus side when compared to the average.
Although temperatures are cooler, lack of moisture is also being felt in the Greater Cincinnati area. Joe Boggs reported that this area is experiencing an extended dry period of 13 straight days with no measurable rainfall, although (hopefully!) is in the forecast. Weather highlights from the south include: in August, 1.43" of rain has been recorded, which is minus 0.72" when compared to the average; and 30.62" of precipitation has fallen in 2004 thus far, which is plus 2.06" when compared to the average.
Finally from the great north, Amy Stone reported that storms did pass through over the weekend leaving varying amounts of rain, and in some instances hail. Although the rain was a welcomed sight, the area continues to fall behind the year-to-date average by more than 3.5", and is looking for more.
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HORT SHORTS
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TREES IN ROUGH SHAPE
Pam Bennett noted that trees are looking pretty straggly at this time. Insects and diseases have rendered some trees naked, while others are losing leaves daily and showing some signs of fall color. In some areas of Ohio, diseases such as walnut and ash anthracnose have led to severe leaf loss in many of these trees. Insects such as locust leafminer on black locust and mimosa webworm on honeylocust have left these trees pretty ragged, in many areas of the state. The good news is that since these are deciduous trees, for the most part, there is always next year.
Several BYGLers also made the observation that many trees were already showing fall colors. Short days and cooler temperatures led to fall coloration. However, Dan Herms noted that certain trees may always show early fall color, and we just haven't made note of it. For instance, a silver maple on his property always starts to turn this time of the year. He challenged BYGLers (and anyone else who would like to participate) to make note of a few specific trees that are showing fall color at this time. Watch them again next year and see if they are indeed turning color around this time. Of course, trees that are turning early due to stress may or may not turn next year. Pick a few different trees around your area to track and let your local BYGLer know.
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TAKE THE ZOO TOUR
Now is the time to gather your family and spend a day visiting the display/annual trial gardens at the Cincinnati Zoo and Botanical Garden. The 150 varieties featured in beautiful garden settings are some of the best and latest from PanAmerican Seed, Ball Seed, and Proven Winners. See how they have fared through the summer ... and get some great ideas on their uses in the landscape. These trials are a joint effort of the Cincinnati Zoo and Botanical Garden, the Cincinnati Flower Growers Association, and The Ohio State University Extension, Hamilton County.
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BUG BYTES
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BILLOWING MIDGES CLOUD ISSUES
Just as presidential candidates vie for approval at this time of year, gnat-like flies garner attention by gathering in clouds around landscape plants, athletic fields, streams, and ponds. These are swarms or mating swarms of NON-BITING MIDGES (Chironomus spp.). The swarms can easily be seen from a distance when the sun is low in the sky. At this time of day, the swarms may appear to be pillars of smoke that mysteriously arise from the ground. Although beneficial as aquatic larvae, which consuming algae, plankton, and decaying organic debris, the emerging swarms alarm some people who assume they are mosquitoes, biting gnats, or ubernatorial groupies. Instead, midges are often harmless and merely looking for love.
Non-biting midges are mosquito-like insects ranging in length from 1/8" to 1/2". Adults are humpbacked, multicolored (many are tan to brown and gray), and males have large, feathery antennae. Of course they lack the piercing/sucking mouth parts of true mosquitoes. Midge adults are short lived and converge at dusk to mate. Normally, the males gather to await, with great anticipation, the arrival of females. After mating occurs, the females drop egg masses into water edges, or on plant material in the water. Both males and females die (happily?) shortly after mating. Larvae eat and develop for 4 weeks under water, then pupate near the surface of the water and emerge 48 hours later.
The midge swarms are strictly a curiosity to see, or at most a moderate nuisance ... especially to walkers, joggers, and bikers who accidentally pass through the swarm. Swarms close to roads can foul windshields with numerous little, sticky splats. Because non-biting midges are of little pest significance, there are few practical control options other than eliminating breeding sites. Of course, this control option could carry significant implications regarding negative environmental impacts, which is hardly justified for a non-biting, nuisance insect.
Since midges fly from surrounding areas and usually swarm for a short period of time at dusk, fogging or spraying is not practical. In addition, they are a valuable source of food for bats birds, fish, frogs, and other aquatic creatures. Instead of trying to control the elusive midges, it is best to prohibit them from swarming around people and slipping into buildings. Wear light-colored clothes for outdoor activities and refrain from wearing scented products. Replace outdoor white lights around homes with yellow lights and make sure window screens and other passageways are sealed tightly. Close shutters or curtains at night so that they are not attracted to windows.
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ASIAN AMBROSIA BEETLES PRODUCE A SAWDUST PELLET SHOWER
Randy Zondag reported receiving a shower of sawdust pellets while standing under a tree in northeast Ohio. The pellets were produced by the Asian ambrosia beetle (Xylosandrus crassiusculus ), which is an introduced non-native pest in Ohio. Normally, the pellets showering Randy would stick together, causing trees to become festooned with tan colored toothpick-like spines of boring dust protruding from small holes in the bark. This insect was first found in the U.S. in 1974, infesting peach trees in Charleston, South Carolina. It was first found in Ohio in 2002, infesting magnolia nursery stock.
In Ohio, this beetle has been found most often on magnolias, but elsewhere in the U.S., it has been found infesting ornamental and fruit cherries, peach, plum, Japanese maple, golden rain tree, dogwood, sweet gum, oaks, elms, and azalea. Unlike other ambrosia beetles that attack stressed plants, this beetle attacks healthy plants, as well as stressed plants. They also show a distinct preference for small caliper trees.
The tiny (approximately 2mm long), dark brown beetles excavate into the xylem and introduce a symbiotic ambrosia fungus into the tree. The fungus serves as food for the larvae. It also grows throughout the xylem, and eventually disrupts vascular flow. Branches or the entire tree may eventually die from the fungus and the beetle damage. The fungus is easy to culture after the beetles have entered the plant, and initiated fungal infection. Cut infested stems in half lengthways, and place them in a plastic bag with moist paper toweling. The fungus will appear within 24 hours as a white, soft, hair-like growth covering the cut surface. Unlike fungi associated with other ambrosia beetles, the fungus carried by the Asian version does not stain wood blue.
The adults and larvae bore into twigs, branches, or small-caliper trunks and make a tiny entrance and exit hole. Frass is exuded as they bore and often clings together to produce the toothpick-like spines. However, wind and rain may knock the protruding frass off infested trees onto unsuspecting Extensioneers, or to the ground producing an accumulation of frass at the base of the tree. Controls include applying insecticide treatments (permethrin or cyfluthrin for homeowners; Astro for commercial growers) to trunks and branches at 4-week intervals throughout the growing season.
The Asian ambrosia beetle tends not to be a landscape problem. It is more of a nursery pest problem, where there are high populations of young trees in close quarters. Growers do need to be aware of this pest, and scout for it.
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CRAWLING THE WEB IN SEARCH OF A BEETLE
Curtis Young reported encountering a beetle he had not seen before while on a diagnostic walk for Master Gardeners in Hancock County. The beetle was discovered devouring the foliage of over half of a 20' long by 8' wide stand of sumac in an ornamental planting. Multiple plants were completely defoliated with obvious branch die back. Numerous beetles were present on the remaining foliage and were easily collected. While looking at the beetles in the palm of his hand, they began to jump like flea beetles. Digital pictures were taken of the unknown beetle and were shared with other entomologists who also were unfamiliar with the insect. The beetle was also not identified in any of the standard field guides and reference books, thus a search of the internet was conducted.
To conduct the search, both Joe Boggs and Curtis used a couple of potential common names, the sumac leaf beetle, and the sumac flea beetle. Their searches produced a limited number of potential web references for either of these common names. Fortunately, a couple of the sites included images of beetles that could be compared to the beetle in question. The images appeared to be a match. One of the sites that made reference to the sumac flea beetle was a Colorado State University Fact Sheet by Whitney Cranshaw of Colorado State University Extension. The digital images were forwarded to Whitney for confirmation. Whitney concurred with our identification that the beetle was the sumac flea beetle, Blepharida rhois.
Additional searches using the genus species name produced only a few additional hits. Most were species lists of insects held in museums or of insects collected in biodiversity surveys. Only a little basic biology of the insect was found. Whitney reported that the beetle apparently feeds exclusively on sumac, however there is reference of the beetle on current which may be in error.
The sumac flea beetle has a body shape is very similar to the Colorado potato beetle (CPB); however, the beetle is only about 1/4-1/3 the size of the CPB. It is one of the largest flea beetles in the US. The head and thorax of the beetle is a shiny caramel brown color, some of the females have a caramel olive green color. The rest of the body is a dark chestnut brown color. The elytra (front wings) also are chestnut brown overlaid by varying amounts of white. It looks like the elytra were sprayed with artificial snow used to frost windows. The hind legs of the beetle have the enlarged femurs typical of flea beetles.
Little basic sumac flea beetle biology information was found on the internet, however the beetles were currently mating and laying eggs. The eggs were discovered on the main trunks, branches and stems of the sumac plant. Initially, the egg masses were overlooked because they look like piles of fecal material. Samples were collected and examined more closely. The female lays a random pile of eggs, and then defecates on the pile. This is a behavior practiced by several insects to disguise the eggs to conceal them from predators and parasites. The sumac flea beetle may overwinter in the egg stage.
If anyone else has observed this beetle feeding on sumac, please let us know. We would like to know how wide-spread the sumac flea beetle may be in Ohio. Send your observations to young.2@osu.edu.
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HIBISCUS SAWFLY
Barb Bloetscher reported that her old nemesis, hibiscus sawfly (Automacerca decepta), has returned to plunder perennial hibiscus, buttonbush, and rose-of-Sharon plants until the leaves are browned and ragged. These sneaky greenish-striped sawfly larvae hide on the lower side of leaves undetected ... until suddenly the area around the scraped-off lower leaf tissue turns brown. At this point, the sawflies have nearly finished their nasty work, and more often than not, have snuck away to pupate. Growers with this perennial problem should note the date of their appearance and be ready next year at this time to treat with an insecticidal soap, or other insecticides if necessary.
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DISEASE DIGEST
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CHEWING ON TUBAKIA
This is typically the time of year when some landscape managers begin to see spots ... on oak leaves. The numerous small spots on the oak foliage are often due solely or in part to a fungus, Tubakia dryina (formerly Actinopelte dryina). This fungal disease is most frequently observed on members of the red oak group (which includes pin oak). In most seasons, the disease is very limited in occurrence, but during years of high rainfall, conditions are favorable for multiple infections and affected trees may end the season with heavily freckled foliage, foliage with larger tan-brown spots, or heavily blighted foliage. This disease tends to become apparent in late summer, in August or September. Although the fungus is present every year, the severity of the problem on the red oak group this year is due, in part, to frequent rainfall events in some parts of the state, which have created conditions highly favorable for infection and disease development.
Since this disease is primarily considered a cosmetic problem which only affects the foliage, treatment is usually not warranted since it shows up in late summer when trees are beginning to stop growing for the year. As with most foliar diseases, once symptoms are visible, treatment would be ineffective. Fungicides would need to be applied before symptoms are visible.
Research on this disease is scanty. Infections appear to occur in mid-late summer. If fungicide treatments are to be made, they should begin in mid-summer and continue through early September. As stated above, the disease is insignificant when we have a typical Ohio summer with the onset of dry weather in June or July and continuing through August. If the outlook is for frequent rainfall through July and August, or if trees are in a situation where they are continually exposed to leaf wetness, as would occur with overhead irrigation, preventive fungicide treatment before the onset of symptoms may be considered. Under other circumstances, treatment would not be warranted.
There is no research on effectiveness of fungicides toward this leaf disease. Any fungicide treatments would be on a trial basis only. If the weather outlook suggests Tubakia will be a problem, one might consider the fungicides labeled on oaks for other leaf diseases, as outlined in OSU Extension FactSheet HYG-3048, titled "Anthracnose Leaf Blight of Shade Trees" (http://ohioline.osu.edu/hyg-fact/3000/3048.html).
Note: As stated above, research is scanty. But, field observations indicate that the disease is commonly observed on pin oak that are chlorotic as a result of iron deficiency. Even in a dry year, the leaf disease does appear on chlorotic pin oak. If a pin oak is suffering from iron deficiency, the deficiency problem should be addressed. Refer to OSU Extension FactSheet HYG-1009, titled "Iron Chlorosis" (http://ohioline.osu.edu/hyg-fact/1000/1009.html).
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FOLIAR NEMATODE ON HOSTA
Nancy Taylor reported that a foliar nematode is causing problems in landscapes and nurseries. She identified the nematode as being in the genus Aphelenchoides, with the specific epithet probably being fragariae. These microscopic roundworms feed on foliage and stems, causing angular lesions, or striping, delimited by the leaf veins. Healthy tissue next to necrotic areas can indicate a potential nematode problem. These pests feed internally, so once they enter the leaf control is difficult. Additionally, available nematicides are not labeled for landscape use.
Since the nematodes spread by contact between wet foliage, their spread can be limited by increasing space between plants ... the legless microscopic roundworms are apparently poor jumpers! Similarly, do not unintentionally spread the pest by carrying them from plant to plant on tools, hands, or other vehicles of nema-commutes. Destroy infested leaves or entire plants and control leaf wetness through proper watering and the use of drip irrigation. Thorough fall cleanup is also recommended, and is a good idea even if foliar nematode is not a problem. Nematodes are also killed by heat, so heat-treating crowns is a labor intensive option.
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BOTRYOSPHAERIA CANKER ON OAK
Infections of the fungus, Botryosphaeria quercuum, is a problem popping up on oak in Ohio. This fungus infects twigs and stems, causing wilting and dieback of fully expanded leaves. The damage manifests itself like the flagging that results from cicada egg laying activity: dead, or dying branch tips. However, the problem is not from egg laying damage to the twigs, but from cankers forming on the twigs below the dead leaves.
The cankers are dark brown, or black. They may eventually crack where they meet healthy tissues. Callus ridges may also form around large older cankers. Internally, infected stems will have brown areas running through the sapwood. Cankers may progress down branches, but it is uncommon for infections to kill an entire tree. Currently, the most effective method for controlling this disease is to prune out infected branches once trees become dormant.
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TURF TIPS
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TIME TO THINK TURF RENOVATION OR RESEEDING
If your lawn looks bad, now is the perfect time to begin lawn renovation, or for making plans to over-seed your lawn. Dr. Bill Pound, formerly an OSU Extension State Turf Specialist once said that "a bad fall seeding is better than a good spring seeding."
Where does one begin when considering lawn renovation? First, take a close look at the existing turf and determine how much desirable grass remains. If the turfgrass is brown, take a close look at the crowns to determine whether or not the brown grass is still viable. Also look for signs of new shoots. If the majority of the turf is pretty good, an early fall fertilization may be sufficient.
If there are voids in a Kentucky bluegrass turf that are around 4" to 6" in diameter, allow these areas to fill in this fall. If the areas are larger, you may need to reseed. If the lawn is a non-rhizome type grass, such as tall fescue or perennial ryegrass, you should spot seed. Do not spot seed with a another species of grass. If the lawn is tall fescue, spot seed with tall fescue.
If you have perennial grassy weeds, such as nimblewill or tall fescue in a Kentucky bluegrass lawn, you need to treat those areas with a non-selective, post-emergent, non-residual herbicide (e.g. glyphosate) and reseed. Keep in mind that the grassy weeds need to be green and growing in order to absorb the herbicide and that this can hopefully be done now in order to provide ample time to kill the grassy weeds and reseed.
If you have 50% or more of broadleaf weeds such as plantains, clover, and dandelion, you should consider total renovation, which means everything is killed with a non-selective, post-emergent, non-residual herbicide. Two applications of the herbicide, made 10-14 days apart, are recommended to assure complete kill of the lawn weeds. If the lawn is currently drought stressed, apply water to make the weeds healthy ... so you can kill them!
If the lawn is 70% turfgrass and 30% weeds, a good fertilization program should be sufficient, when followed in the spring with broadleaf weed control. However, plans should be made to core aerate and over-seed in September to thicken the lawn.
One good way to renovate an existing lawn is to use a slice seeder or slit seeder. First, mow the existing lawn short, about one inch tall. A slice seeder cuts slices or grooves in the soil to a depth of 1/4" to 1/2" and drops grass seeds into grooves at the same time. The seed selected should be the same type as your existing lawn. After slice seeding or overseeding, apply a turfgrass starter fertilizer. A starter fertilizer should be high in phosphorus, such as 18-24-6. It is also a good idea to apply lawn fertilizers three weeks later and one more time around late October or early November.
Regardless of the method you select for seeding your lawn, keep in mind that newly seeded lawns need water, water, and more water, until the grass seedlings appear. Grass seed must be kept moist throughout the germination period to support viable germination. This may require daily watering for a significant number of days, depending upon environmental conditions such as high temperatures and no rainfall. For example, the seed of some cultivars of Kentucky bluegrass takes around 20 days to germinate!
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INDUSTRY INSIGHT
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CONTROL OF BLACK VINE WEEVIL LARVAE
Dan Herms reported the results of an insecticide efficacy trial he conducted targeting first instar black vine weevil (Otiorhynchus sulcatus) larvae infesting yews growing under landscape-like conditions. His research showed imidacloprid (Merit) was highly effective when applied in mid-August as a soil drench, or as granules applied to the soil and watered in. Dan stressed both applications require that mulch be pulled away, and the insecticides applied directly to the mineral soil.
The adult stage has been the primary target for insecticide applications in landscapes since larvacidal applications have largely yielded inconsistent results. Adults are active for an extended period during the growing season, so multiple applications are required. However, Dan targeted a "bottleneck" in the life cycle of the weevil: in mid-August, a high percentage of the population is in the first instar larval stage. The trial results provide a welcome option for managing black vine weevil in landscapes.
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PRODUCT GAINS MERIT FOR SCALE CONTROL
Dan Herms also reported the exciting results of his study in which imidacloprid (Merit) was used at different times in the season to control MAGNOLIA SCALE Neolecanium cornuparvum. Surprisingly, this systemic insecticide can be applied in spring, summer, or fall and still impel deterioration of the colony! The importance of these results is that crawlers emerge periodically from mid summer through fall, requiring multiple, consistent sprays of conventional insecticides, oils and soaps to intercept each brood of nymphs. However, imidacloprid will enable one application to control the crawlers and adults for that season! Tests are now underway to study its efficacy on other insects.
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COMING ATTRACTIONS
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WOSU GREEN SCENE
Join host Tom Wiebell this Friday night for AM 820 AM, WOSU's Green Scene gardening and landscape Q&A call-in show. Regular Deb Knapke, Columbus State's "Garden Sage," will be joined by the inimitable Curtis Young. This dynamic-duo will offer matchless advice in solving gardening problems. Be sure to stump them with your horticultural and entomological conundrums and puzzlers from 6:30 to 8:00 p.m., by calling 614-292-8513.
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BYGLOSOPHY
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"Doubt is not a pleasant condition, but certainty is an absurd one."
- Voltaire
"The nature of science is such that every case is perpetually open to appeal on procedural grounds or in light of new evidence. This chronic uncertainty is what irritates many of the observers of science - and it is precisely what excites the practitioners."
- Jeffrey Lockwood, in "Locust"
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