BYGL Weekly News for April 16, 2018
The following articles were compiled during the last 7 days by members of the Extension, Nursery, Landscape, Turf (ENLT) team to benefit those who are managing a commercial nursery, garden center, or landscape business or someone who just wants to keep their yard looking good all summer. Access the BYGL website for additional information on other seasonal topics at: http://bygl.osu.edu
For more pictures and information, click on the article titles.
| Turf Tips |
| Managing Crabgrass in Turf
Date Published: April 9, 2018
With these rains the lawn is beginning to grow and the weeds are not far behind. Some of the earliest emerging broadleaf weeds have begun to emerge. The biggest problem with weeds in turfgrass is reduced aesthetic value, although some weeds can out compete turfgrass when management is reduced. Smooth and large crabgrass, yellow foxtail, and annual bluegrass are the most frequent annual grass weeds in turfgrass.
Smooth crabgrass emerges in the spring before large crabgrass. Smooth crabgrass emergence begins slowly when soil temperatures in the upper inch of soil reaches 54F for seven days and moisture is available. This 54F soil temperature occurs many times when the dogwood begin to flower and the forsythia flowers begin to fade. The current soil temperature for Columbus, Ohio is 41F which is 7.6F lower than the 5-year average! Visit this website to track soil temperature for your area: http://www.greencastonline.com/tools/soil-temperature . Based upon the current 10 day forecast, crabgrass preventer does not need to be applied until sometime after April 10th and likely much later. Waiting to apply crabgrass preventer until just before emergence will ensure control of smooth and large crabgrass later into the season. Peak crabgrass emergence is from mid-May to July 1st. Crabgrass preventer must be applied before plants emerge, otherwise it will not be effective. After applying the crabgrass preventer irrigate the lawn to get the herbicide incorporated into the soil. If crabgrass densities are high, a postemergence herbicide application may be required. If you have used preemergence crabgrass preventer for many years and have successfully controlled the crabgrass, it may be wise to stop applying the crabgrass preventer and scout to see whether any crabgrass will emerge. If it does emerge then apply a postemergence herbicide. Crabgrass can be controlled with some postemergence herbicides, but timing and rate are very important to effectively control crabgrass. Effective postemergence herbicides include Dimension, Methar 30, Acclaim Extra, MSMA Turf Herbicide, and Drive 75 DF, but some of these may be difficult to obtain. Acclaim Extra can injure certain bluegrass varieties. When applying postemergence herbicides be sure to obtain thorough coverage and do not mow for two days before and after the herbicide application.
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| Tigers on the Prowl
Date Published: April 14, 2018
I spotted one of my favorite insect predators darting about on forest trails yesterday: Six-Spotted Tiger Beetles (Cicindela sexguttata). Their common name is well justified as these tiny “tigers” hunt, kill, and eat other insects.
The shiny beetles are more emerald green in color than Emerald Ash Borer (Agrilus planipennis) (EAB) causing them to be commonly mistaken for the non-native borer. Indeed, these tiger beetles have excellent eyesight, quick speed, and they are agile flyers; traits that make it difficult for people to get a close look for accurate identification.
Six-Spotted Tiger Beetles have a curious affinity for hanging out on woodland trails; they can certainly liven up a walk in the woods. The beetles have elongated bodies with the thorax about half the width of the front wings and abdomen. They have long legs and their bulging black eyes (the better to see you with, my dear!) make them look like they’re wearing dark goggles.
As the common name implies, six-spotted green tiger beetles have white spots that are arranged along the trailing edge of the wing covers, three spots per side. The spots are small and sometimes obscured by light bouncing off their highly reflective shiny green bodies.
This ferocious predator sports powerful sickle-shaped mandibles that are used to grab and dispatch luckless arthropod prey; a trait that is shared with other tiger beetles (family Carabidae (Ground Beetles); subfamily Cicindelinae (Tiger Beetles)). A word of caution: these carnivores can also use their impressive mandibles to deliver a painful bite to the hand of the overly curious.
Even the larvae of this tiny tiger are predators. However, instead of actively hunting their prey, they conceal themselves in vertical burrows in the soil to await hapless victims. When a meat item such as insects or spiders walks past, the tiger larva springs forth like a jack-in-the-box to grab dinner with their powerful mandibles.
The bottom line is that six-spotted tiger beetles are highly effective and important predators throughout their life cycle. So, keep your eyes peeled for and hands away from these tiny tigers prowling our woodland trails … and don’t kill them since they are good guys!
For More Info: · University of Kentucky, Kentucky Critter Files http://www.uky.edu/Ag/CritterFiles/casefile/insects/beetles/tiger/tiger.htm
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| Browned Boxwoods
Date Published: April 13, 2018
Boxwoods with light brown to golden brown leaves are common this spring in Greater Cincinnati. Some of the leaf browning is due to winter injury with foliage at the tips of branches, particularly at the tops of plants or on the windward side of plants, most heavily affected.
Some was caused by salt damage either directly with “ice melt” or rock salt inadvertently thrown onto foliage, or indirectly with “salt spray” carried onto foliage from nearby roadways. Salt damage is sometimes, but not always, concentrated on wide side of the plant.
However, a close examination may also reveal the telltale blister-like leaf symptoms caused by the boxwood leafminer (Monarthropalpus flavus). Leafmines may be found throughout the plants although the highest concentration also occurs on foliage at branch tips.
Normally, the blister mines turn brown a bit later in the spring. However, I’m noticing this year that the blister mines are turning brown much earlier and there appears to be a connection to widespread winter injury. I’m not certain if winter injury is magnifying the leafmining damage, or vice versa.
Gently separating the upper and lower leaf surfaces (the leafminer had already done most of the work!) will reveal the bright yellow leafmining larvae (maggots) of this midge fly wiggling around in their blister mines. The larvae will soon complete their development and pupate. The pupae are also bright yellow at first, but turn orangish-yellow as this stage nears completion.
This non-native midge fly was accidentally introduced into North America from Europe in the early 1900s and is now common throughout Ohio, particularly in the southern and central parts of the state. Adults emerge at around the same time red horsechestnuts (Aesculus × carnea) and doublefile viburnums (Viburnum plicatum) are in full bloom (440 GDD). Except for their bright orange abdomens, the adults superficially resemble miniature mosquitoes.
Females use their needle-like ovipositors to insert eggs between the upper and lower leaf surfaces of boxwood leaves. Each leaf may contain multiple oviposition sites with several eggs per site. These sites will become individual leafmines producing the blister-like leaf symptoms.
Eggs hatch in early-summer and the resulting larvae spend the remainder of the season consume interior leaf tissue as they develop through the 1st and 2nd instar stages. Winter is spent as 3rd instar larvae inside the leafmines. The larvae resume feeding in the spring and develop through a 4th instar stage.
Much of the leaf damage occurs in early spring with the ravenous larvae rapidly expanding their leafmines. Multiple leafmines in individual leaves may coalesce causing the upper and lower leaf surfaces to delaminate over the entire leaf. Individual mines may turn reddish-green at this time of the year with heavily mined leaves turning from yellow to orangish-brown causing the leafmining damage to be mistaken for winter injury.
A close examination of the leafmines at this time of the year may also reveal small translucent “windows” created by the larvae in the lower leaf surface. The pupae will wiggle through these weak points to ease emergence of the fragile adults.
This pupal activity is responsible for one of the most unusual features of this midge fly: reports of hissing, crackling, or rustling sounds coming from heavily infested boxwoods. I’ve reported on this strange phenomenon in past BYGLs. So, reports from gardeners or landscapers that they’ve heard boxwoods going snap, crackle, and pop should be taken seriously as the odd sounds are an indicator of a heavy boxwood leafminer infestation.
Damaging boxwood leafminer infestations can be suppressed through applications of neonicotinoids such as imidacloprid (e.g. Merit, Xytect, Marathon, and generics) or dinotefuran (e.g. Safari, Transtect, Zylam). However, application timing has been modified in recent years to avoid negative impacts on pollinators.
Boxwood blooms attract a wide range of pollinators; blooming plants can literally buzz with their activity. Therefore, the insecticide applications must be delayed until AFTER boxwoods bloom. Some minor miner damage will occur, particularly with the imidacloprid that is taken-up more slowly compared to dinotefuran. However, this is a small price to pay for protecting pollinators.
You may find recommendations for topical applications of pyrethroid insecticides such as bifenthrin (e.g. Talstar) to target adult leafminer females before they lay eggs. However, adults typically emerge in Greater Cincinnati while boxwoods are in full bloom, so I no longer recommend this application.
Plant selection provides a more long term solution to the depredations of boxwood leafminer by removing insecticides from the management equation. A helpful research-based listing of the relative susceptibility of boxwoods to the leafminer was published in 2014 by the American Boxwood Society in their “The Boxwood Bulletin” [see More Information below].
For More Info: · American Boxwood Society, Boxwood Leafminer Evaluation http://www.boxwoodsociety.org/uploads/54_1_2014_Summer.pdf#page=9
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| Watch Your ASH!
Date Published: April 16, 2018
Many of the Green Ash trees, Fraxinus pennsylvanica are dying in Perry, Ohio – Lake County. Why? Green ash is popular as a shade tree in residential areas because of its good form and adaptability to a wide range of sites.
It is susceptible to Emerald Ash borer, an invasive species.
Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an exotic beetle that was discovered in southeastern Michigan near Detroit in the summer of 2002. The adult beetles nibble on ash foliage but cause little damage. 5449380 Debbie Miller, USDA Forest Service, Bugwood.org
The larvae (the immature stage) feed on the inner bark of ash trees, 5471796 Kenneth R. Law, USDA APHIS PPQ, Bugwood.org
disrupting the tree’s ability to transport water and nutrients. Emerald ash borer probably arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating in its native Asia. As of August 2017, it is now found in 31 states, and the Canadian provinces of Ontario and Quebec. Since its discovery, EAB has: · Killed hundreds of millions of ash trees in North America. · Caused regulatory agencies and the USDA to enforce quarantines and fines to prevent potentially infested ash trees, logs or hardwood firewood from moving out of areas where EAB occurs. · Cost municipalities, property owners, nursery operators, and forest products industries hundreds of millions of dollars. http://www.emeraldashborer.info/ Symptoms include defoliation, D-shaped exit holes in the bark, wood pecker damage (as they hunt for the larvae) and ‘blonding’, which is large portions of bark that fall off the tree reveal a patch of wood that looks ‘blond’ in color. A tree that shows severe infestation will die within the year. The danger is these trees soon become a fall hazard and need to be removed before injury or property damage occurs. It is recommended that you hire a tree removal service that is ISA certified and/or bonded.
Now that the Emerald Ash Borer has infested Lake County, Ohio, many Green Ash trees in the landscape and forest woodlots have died. But the real danger is right overhead.
With dead trees and wind combinded, it can be a costly and deadly combination. A tree that shows severe infestation will die within the year. The danger is these trees soon become a fall hazard and need to be removed before injury or property damage occurs.
Our understanding of how EAB can be managed successfully with insecticides has advanced since this bulletin was initially published in 2009. This version has been revised to address frequently asked questions and reflect the current state of understanding of insecticide options for controlling EAB and their effectiveness. It is important to note that research is an ongoing process. Scientists from universities, government agencies, and companies will continue to make discoveries and advance EAB management and ash conservation. http://www.emeraldashborer.info/documents/Multistate_EAB_Insecticide_Fact_Sheet.pdf
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| They’re Baaack!
Date Published: April 10, 2018
Last Friday, Larry Parker (Cincinnati Parks) sent to me the images below of Boxelder Bugs (Boisea trivittata, order Hemiptera) hanging out on a park building. ‘Tis the season.
These boxelder bugs didn’t fly to the building this spring; they were already there. This fall home invader overwintered somewhere in the building (walls, attic, etc.) and spring temperatures are beginning to roust them from their winter barracks. The bugs were clustered as they awaited outdoor temperatures that will support their flight; they were gone from the building as of yesterday.
The bugs Larry photographed had successfully made their way outside, but this is not always the case. Occasionally, they become confused by warm indoor temperatures and find their way into homes and other structures. They don’t bite or represent a threat to anyone or anything inside a structure, but they can be serious nuisance pest as they frantically crawl or fly around looking for a route to the great outdoors.
This is the first report I’ve received this spring of boxelder bugs emerging from their overwintering sites. However, with the predicted warm-up this week, I’m sure this is just the beginning.
We can also expect other fall home invaders to soon make their spring appearances. These include Western Conifer Seed Bugs (Leptoglossus occidentalis); Multicolored Asian Lady Beetles (Harmonia axyridis); and the notorious Brown Marmorated Stink Bugs (Halyomorpha halys).
Boxelder bugs range in size from 1/2″ – 3/4″ long. They are narrow-shaped, flat-backed, and dark gray or dark brownish-black. They have three highly visible orangish-red stripes running lengthwise on the pronotum, the area behind the head; “trivittata” is Latin for “three-striped”.
The bugs are seed-feeders and are so-named because of a strong association with Acer negundo; however, both the adults and nymphs will commonly use their piercing-sucking mouthparts to draw juices from the seeds of other trees in the Acer genus. They have also been observed feeding on alder, apple, buckeye, cactus, geranium, grape, honeysuckle, lilac, linden, oak, peach, plum, spirea, strawberry, and tulip. I’m aware of boxelder trees being cut down in an attempt to eliminate the bugs; however, their wide-ranging feeding activity illustrates why this management effort may fail.
The best offense against these and other fall home invaders buzzing or lumbering around inside homes and other structures is a strong defense. Large openings created by the loss of old caulking around window frames or door jams provide easy access into homes. Such openings should be sealed using a good quality flexible caulk.
Poorly attached home siding and rips in window screens also provide an open invitation. The same is true of worn-out exterior door sweeps including doors leading into attached garages; they may as well have an “enter here” sign hanging on them. Venture into the attic to look for unprotected vents, such as bathroom and kitchen vents, or unscreened attic vents. While in the attic, look for openings around soffits. Both lady beetles and stink bugs commonly crawl upwards when they land on outside walls; gaps created by loose-fitting soffits are gateways into home attics.
For More Info: · University of Minnesota Fact Sheet https://www.extension.umn.edu/garden/insects/find/boxelder-bugs/ |