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Register to join our Ask a Pro LIVE interactive eventon Thursday , April 10 at 1:30 EDT : Dr. Shawn Askew will be taking your questions about all thing weed eradication and control and offer his solution for your unique weed issues !
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Meet the Expert: Shawn Askew, PhD Turfgrass Weed Specialist, Virginia Tech
Shawn Askew is a prof of turfgrass weed skill at Virginia Tech ’s School of Plant and Environmental Sciences , where he has precede research and outreach for over 24 years . As Virginia ’s extension specialist for turfgrass smoke science , he spearheads statewide weed control program for cosmetic turf and industrial botany , while wield the Phytochemistry and Radioisotopes Laboratory . Dr. Askew offers expert guidance on identifying , preventing , and controlling lawn Mary Jane using sustainable methods . With over 24 years of research , he can talk about pragmatic weed management techniques , forward-looking approaches like thermal and liquified N applications , and turf health maintenance . He has authored over 100 peer - reviewed papers and delivered more than 2,000 presentations on turf grass direction . A respected leader in turfgrass weed skill , he offers practical solutions for sustainable locoweed control .
To learn more about Shawn , check out his work on Virginia Tech’sYouTubeandX ( Twitter)pages .
When do you put down pre-emergent? The instructions are confusing, so I end up putting down post-emergent instead. I’ve had to replant my St. Augustine grass because it was killed off in the places I sprayed.—Cty Chx. Tx via Facebook
Shawn ’s advice : In a subtropic clime , where St. Augustine is typically grown , many weeds are considered “ annual ” and they just do n’t quit . That does not mean that pre - herbicides wo n’t aid , but they may not get all of the sess . Remember , they only ferment on smoke that have not yet sprouted . For summer gage like finger grass and goosegrass , it ’s best to apply pre - herbicide ( such as prodiamine or dithiopyr , which are safe for St. Augustine forage ) before soil temperatures jump above 55 degree . This will typically be between January 1 and mid - February . If you are going after winter weeds , apply pre - emerging granules around September 1 as soil temperature neglect below 70 degrees . As with any mealy weed killer , H2O within a workweek of software if no rain happen . This will safely handle some , but not all , of your grassy weeds in a St. Augustine lawn . When you employ post - herbicides , make out that St. Augustine is one of the most sore grasses . Broadleaf products like2 , 4 - Dand green goddess product like atrazine can thrash St. Augustine , especially during spicy conditions ( above 85 degrees ) or in spring when the Gunter Grass is greening . Pre - emergent products are always safer . recall , use in bounce before soil temperatures are consistently above 55 degrees and in fall before soil temporary worker are consistently below 70 degrees . judge to apply post - emergent products as “ spot treatment ” only , specially when the air temperature is above 85 degree .
How often should I weed my yard?—Cassie U. via Instagram
Shawn ’s advice : Ah , the pet prof response : it bet ! look on what ? 1 ) What eccentric of lawn grass do you have and what weeds are the problem ? Most weeds become problematic in late wintertime or late summertime . If you are hand - weeding , your window of opportunity to act as is leading up to these time , which is when weeds mature . clock time your hand - weeding when the soil is dampish so the weeds will be easier to airlift . If you have repeated widow’s weeds ( wiregrass in tall fescue ) , you will need to weed those patches every 2 to 3 weeks for the time of year to prevent a modest problem from getting big . 2 ) How dense is your lawn ? A thick lawn kills weed for you . The best way to improve lawn density is to better the filth . Happy sward with good land may want weed less than once per year , adopt you are doing what you need to keep the lawn glad ( fertilizing , irrigation , right mowing ) . patch of weeds are indicators that there is a job in the lawn . Compacted soil , tree shade , and poor filth pH or mineral depicted object are some lesson of problems that can go to spot of skunk . By identifying and correct these underlie problem , the lawn green goddess will start out working for you , and you ’ll expend less time weeding . Be sure to add turf seed whenever you off weeds to fill the break that permit the weeds to punch through the greensward canopy .
How do you prevent crab grass? Are clover lawns a good idea? What are the best mulches that won’t attract termites?—@_amberger_helper via Instagram
Shawn ’s advice : Crabgrass is well prevented by having a sizeable lawn turf , but that ’s not enough in some environments . In Virginia , where I live , the clime is where the warm humid areas to the South transition to the coolheaded humid country to the North . This makes smoke control challenging . Regardless , weed pressure is lowest in a healthy lawn . inquiry shows that crabgrass can be abbreviate by 99 per centum just by having a healthy lawn . To hedge your stake against mood and pathetic soil , apply a pre - emergent weedkiller . These are employ before soil temperatures systematically exceed 55 degrees . you may also come after other indicator : use the mathematical product before dogwood buds turn white , before Narcissus pseudonarcissus blooms are 100 per centum wilted , and before forsythia cast 50 percent of its blooms . These indicators may variegate regionally , so be certain to tick local information .
As for trefoil lawns being a ripe idea or not , it depends on what you want from your lawn . If you ’re using your lawn to play games with your ducky and kids , clover lawns may not be the good option in that exceptional country — lawn Grass will be more resilient . Plus , some clovers create blooms that appeal pollinators like bee . This is dandy for the bee , but may be less ideal for space for your kids or pets . The point is that the use of a particular part of your lawn is your main consideration . We can feed in bees and play badminton , just not in the same place . A benefit of a trefoil lawn is that the trefoil will feed the dope with nitrogen . A downside , even for microclovers that do n’t make as many flowers , is that the uniformity of the lawn will not match that of pure turfgrass .
Unfortunately , I ’m a turfgrass weed specialist and do n’t love much about the fundamental interaction of mulch and termites . Note from the editor : Check out this clause for more information aboutwhether or not mulch attracts termites .
How do you kill a weed that is low-growing with little nodules throughout the length of the vine, with small leaves with a white flower? It’s very invasive and drowns out the grass. I live in South Mississippi.—Teresa via the newsletter
Shawn ’s advice : I have intercourse enigma and “ locoweed ” riddles even more . In contemplating your description , I come up up with two potential green goddess .
1 ) Florida betony will traverse the lawn with creeping roots that have chains of tubers that look like nodules . It is often called “ rattlesnake smoke ” as these chains of rootage nodule are shaped like the snake ’s rattles . They are white and often look like orotund grub , but are clearly impound to the beginning . The plant also has small heart - shaped leaves and snowy blooms . Use2,4 - Danddicambain former spring and repeat the treatment every 3 to 4 week ; be cautious at greenup with sensitive dope like centipede grass or St. Augustine grass . touch regale only . Useisoxaben ( Gallery ) pre - emergentin recent summer to keep new weeds from emerging in the fall .
2 ) Chamberbitter or long - stalk phyllanthus are plants that have chemical compound leaf that consist of diminutive leaflets line up in rows ( like mimosa ) . These leave have a course of circular seed capsule along the bottom of the midrib that appear like nodules . The locoweed can cover large arena of the lawn quick as they grow up to 1000 seeds per plant . The blossom are diminutive and lily-white to green , and are often look out on . bridge player pull before come shatter ( before mid - May ) . Spray over the top with2,4 - Danddicambain former spring ( March to April ) . Applyatrazine pre - emergentbetween November and January to prevent new weed emergence next bounce .
How do I get rid of the viney grass that grows in my yard choking all my new grass?—Deborah via the newsletter
Shawn ’s advice:“The viney grass ” in this slip must be the curse of all cool - season lawn : wiregrass or bermudagrass . This is one of the most troublesome problem in my orbit of Virginia due to our modulation - zona mood . Both warm and nerveless - time of year grasses grow in Virginia , and the bermudagrass ( wiregrass ) often invades the tall fescue or Kentucky bluegrass . Hand extract is difficult but not unwarranted . The locoweed gain both rhizomes ( subway stems ) and stolons ( above - ground stems ) and creep up all over the place . Just pulling the runner does not toss off all of the works , but personally , I take capital pleasure in knowing that it took the wiregrass a week to get that 12 - column inch stem that I snatched up in just two seconds . On a sidereal day when soil wet is eminent , take the time to root for , pull , pull . Be sure to discard the stems carefully to avoid overrun other area . I pile up and bulge them to be sure they do n’t blow out to fresh surface area and sprout .
The first tone in any wiregrass ascendancy broadcast is to raise the mowing height of the lawn to at least 4 inches . Wiregrass is always favored over tall fescue grass when the mop tiptop is down in the mouth .
weed killer can be used in marvellous Festuca elatior or Kentucky Bluegrass Country lawn . Fenoxaprop ( Acclaim Extra)and triclopyr ( Hi - Yield , Turflon ) can be fuse at 3 and 4 teaspoons per gallon of water system , respectively . Add 2 teaspoonful nonionic surface-active agent or dish washing liquid per gallon of water as a spreader . This answer can be applied once or double in early summertime and three times in fall . The fall treatments down wiregrass well , the early summer treatments retard the summer expansion . recur the intervention at 3 to 4 week intervals . If you intend to do all five discussion in one class , deoxidise the former summer treatments to 2 teaspoons of Acclaim Extra so that you could use the full 3 - teaspoonful charge per unit for the 3 handling in the fall and not exceed EPA bound . Do n’t utilize this assortment on Kentucky bluegrass less than 3 months old , and be very conservative on young Kentucky bluegrass . It ’s better for magniloquent fescue lawn . Do n’t use this mixture with broadleaf herbicides , or the Acclaim will not put to work well . As a side note , Acclaim Extra can also be used to control wiregrass , crabgrass , goosegrass , foxtails , and most other grass in your ornamental bed or garden . It only wound Mary Jane . Most other plants will not even know you have sprayed . hold in the label for a full lean of ornamental plant for which Acclaim Extra is good . Do n’t use the Turflon near any ornamentals , but it can be used anywhere in your lawn grass to kill broadleaf plants .
An alternate organic approach is to “ shade it out . ” localize a while of plywood over each patch of wiregrass and consider it down with a brick . will in place for 2 month ( July and August ) , then remove the plyboard and seed raw tall fescue in September . This only works if you compensate the intact patch . Hand green goddess , especially mid - summer , but do n’t hand grass correctly before an herbicide treatment .
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