Japanese Knotweed - how to kill?

dryan · 23-06-2017 12:23pm #1

http://www.breakingnews.ie/ireland/residents-fear-for-homes-over-japanese-knotweed-infestation-794801.html

Started of with a small infestation 2 years ago in a beech hedge at the road entrance to the home place.
Was out trimming the hedge earlier in the week and i see thats its spreading at an alarming rate along the hedge on the site boundary.

Also starting to notice it in the farm boundary fences as well.

Is there any product out there that will kill it?

pedigree 6 · 23-06-2017 12:47pm

Grazon 90 will kill it.

yosemitesam1 · 23-06-2017 1:32pm

Roundup will kill it too, but don't go near it yet. Wait until mid to late August to treat it and get the best kill, if you go before the plant starts sending food back down to the roots for winter you won't get full translocation of whatever you spray and it'll be back

kay 9 · 23-06-2017 1:39pm

Takes 7 years to kill it off completely they've said here in Galway. People have been told not to cut or spray.
Apparently the stem needs to be injected but that seems like a prick of a job.

my3cents · 23-06-2017 1:48pm

Nothing will kill it in one spray if its well established. Consider getting rid of it a long term project.

I'd spray asap with whatever you have now, grazon 90 or anything glyphosate based and again when it regrows at the end of the season.

Then next year follow up with a dose in May and another in early September until its gone.

In subsequent years keep an eye on the area and spray any regrowth.

Even if it seems to have died out avoid disturbing the soil in the area as damaging the roots can stimulate it back into growth.

The September spray before the leaves die off is the most effective because the plant takes any available nutrients and the herbicide back down into the roots over winter. However a spray early in the season can keep the height of the plants down so you can get at them all in September. If near a drainage ditch or water then glyphosate with a clearance for aquatic use is the only choice.

DO NOT trim the back the JK in the hedge as it roots from the material you cut off and may be why its spreading at an alarming rate.

Markcheese · 23-06-2017 1:48pm

I've sprayed a bit on the boundary ditch... Then burnt it in spring and gave another couple of sprays of roundup through the year... Think i got most of it now...

Kristopherus · 23-06-2017 1:52pm

my3cents wrote: »

DO NOT trim the back the JK in the hedge as it roots from the material you cut off and may be why its spreading at an alarming rate.

Is that why we're seeing a myriad of small signs on roadsides now saying "Japanese Knotweed. Do not cut"

my3cents · 23-06-2017 2:00pm

Kristopherus wrote: »

Is that why we're seeing a myriad of small signs on roadsides now saying "Japanese Knotweed. Do not cut"

Thats it. The coco's used to flail mow it in the hedges and are responsible for spreading a good bit of it themselves.

Worse still the heavy tread on the tractor tyres can plant the cuttings when they run over them on the verge giving them even more chance to survive and grow.

In other areas like ours by the side of rivers and near the sea it washes down stream growing in the banks where it ends up and even gets washed up on the beach and grows but in that case its the roots that are the agent that propagates it.

dryan · 23-06-2017 3:32pm

Any spray out there that will kill the JK but wont kill my beech hedging?

my3cents · 23-06-2017 4:44pm

dryan wrote: »

Any spray out there that will kill the JK but wont kill my beech hedging?

No, but you can inject the JK stems with glyphosate.

You can buy a tool to inject the stems, cheapest one is about €100 or you can do a DIY method with a large syringe and large gauge needle. The trick is to make a hole in the correct part of the stem first with a small piece of wire or a cocktail stick otherwise making the hole with a std needle just results in the needle blocking up.

You can look up the application rates and where exactly to inject the stems online.

_Brian · 23-06-2017 4:54pm

kay 9 wrote: »

Takes 7 years to kill it off completely they've said here in Galway. People have been told not to cut or spray.
Apparently the stem needs to be injected but that seems like a prick of a job.

It only needs injection if it's growing on a river bank and can't be sprayed.

I've read that August/ September is the best time to spray, and spraying with roundup is fine. Repeated sprays will be required.

Came across a huge stand at work this week, maybe 1/3 of an acre and 12 ft tall.

Base price · 23-06-2017 9:24pm

When I was doing my spraying course (hand held) there were a couple of lads who did contract work for the County Council. They were using a product called Synero for japanese knotweed. They said that it has been trailed n NL and GB over the last 5 years with good success. They said that knotweed has rhizomes (as opposed to a root system) which can be as deep as 15 foot under ground. As yosemitesam said timing is crucial when spraying/injecting, apparently Autumn is the best time so that the pesticide can be carried with the sap to the rhizomes.
http://uk.dowagro.com/products/synero/

pedigree 6 · 23-06-2017 9:43pm

Nom, Nom, Nom and Nom......... And Nom.:D

Edit: Chà Ching!

my3cents · 23-06-2017 10:20pm

Base price wrote: »

When I was doing my spraying course (hand held) there were a couple of lads who did contract work for the County Council. They were using a product called Synero for japanese knotweed. They said that it has been trailed n NL and GB over the last 5 years with good success. They said that knotweed has rhizomes (as opposed to a root system) which can be as deep as 15 foot under ground. As yosemitesam said timing is crucial when spraying/injecting, apparently Autumn is the best time so that the pesticide can be carried with the sap to the rhizomes.
http://uk.dowagro.com/products/synero/

But the problem is that synero is for non-crop area only which means you can't use it on a hedge row without killing the hedge.

For the control of a wide range of deep-rooted PERENNIAL and HERBACEOUS WEEDS on NON-CROP LAND such as motorway and railway embankments, roadsides, grassland of no agricultural interest, and industrial areas (but excluding airfields).

Base price · 24-06-2017 1:30am

my3cents wrote: »

But the problem is that synero is for non-crop area only which means you can't use it on a hedge row without killing the hedge.

I think it refers to its use for food crops.
I'm sure that there are other's on here that have come across it.

patsy_mccabe · 24-06-2017 6:20pm

Is this it?

SmartinMartin · 24-06-2017 6:33pm

Yes. A lot of info here;
http://invasivespeciesireland.com/toolkit/invasive-plant-management/terrestrial-plants/japanese-knotweed/

50HX · 24-06-2017 7:55pm

patsy_mccabe wrote: »

Is this it?

that's it rotten stuff

they had to dig a huge site in london when they came across it building the Olympic village

as in a previous post there is a window in early sept to spray it

have it here with 5 years and spraying is just about keeping it under control never mind kill - know another lad who has it longer and sprayed with various stuff

the forestry companies use to use a product that is ment to do the job but i think it's now band

i have been told to use I-CADE

ment a guy on a course one day and he was telling me he was nearing the end of completing a stone wall around the farmland boundary that his grandfather started back in the early 1900's and came out one morning to find a section of it after giving way coz of the JK

patsy_mccabe · 24-06-2017 8:09pm

Feck it anyway. Only last week cutting a privet hedge on the farm/yard boundary and a relative said to me that it was Japanese Knotweed. Never knew I had it.

50HX · 24-06-2017 8:13pm

patsy_mccabe wrote: »

Feck it anyway. Only last week cutting a hedge on the farm and a relative said to me that it was Japanese Knotweed. Never knew I had it.

it'll be up again just watch out for it other spots as when it's cut it has a tendancy to sprout elsewhere

think toots can be connected underground up to 5 meters

they recommend no cutting burning or digging

all we've left is to spray em....cursed bucking stuff

what did you cut the hedge with??

GhostyMcGhost · 24-06-2017 8:20pm

dryan wrote: »

http://www.breakingnews.ie/ireland/residents-fear-for-homes-over-japanese-knotweed-infestation-794801.html

Started of with a small infestation 2 years ago in a beech hedge at the road entrance to the home place.
Was out trimming the hedge earlier in the week and i see thats its spreading at an alarming rate along the hedge on the site boundary.

Also starting to notice it in the farm boundary fences as well.

Is there any product out there that will kill it?

The article is annoying. No money to fix the problem? They'll pay more in the long run going to court and having to end up repairing up to 3 homes

It's not the knotweed that needs eradicating...

patsy_mccabe · 24-06-2017 9:56pm

50HX wrote: »

what did you cut the hedge with??

No I didn't cut any of the Japanese knotweed. Relative warned me not to.

dodod · 24-06-2017 11:42pm

+1 for icade found it very good

cosbawn · 28-05-2018 7:49pm

There is a substantial crop of JK on neighbouring property. Small country lane divides us. Some small shoots are right at the edge of the road. I’m sick at the thoughts of it coming in. So much so that I’m gonna spray it in the autumn. But In the mean time would it be worth my while spraying those young smaller shoots to stop them getting too tall. No water course nearby no animals grazing

TomOnBoard · 28-05-2018 7:54pm

cosbawn wrote: »

There is a substantial crop of JK on neighbouring property. Small country lane divides us. Some small shoots are right at the edge of the road. I’m sick at the thoughts of it coming in. So much so that I’m gonna spray it in the autumn. But In the mean time would it be worth my while spraying those young smaller shoots to stop them getting too tall. No water course nearby no animals grazing

Call the local County Council first. If they're no help then a dose of Roundup won't hurt. But do NOT cut, strum or anything like that.

my3cents · 28-05-2018 7:57pm

cosbawn wrote: »

There is a substantial crop of JK on neighbouring property. Small country lane divides us. Some small shoots are right at the edge of the road. I’m sick at the thoughts of it coming in. So much so that I’m gonna spray it in the autumn. But In the mean time would it be worth my while spraying those young smaller shoots to stop them getting too tall. No water course nearby no animals grazing

Yep thats standard practice. One dose end of May to keep them from getting too big then another end of August beginning of September or later depending where you are.

cosbawn · 28-05-2018 10:07pm

TomOnBoard wrote: »

Call the local County Council first. If they're no help then a dose of Roundup won't hurt. But do NOT cut, strum or anything like that.

There are numerous notices about put up by the council to stop hedge cutting. That seems to be the height of it ! Maybe they gonna spray in the autumn. No I won’t cut or anything like that. Give a good spray tomorrow. Thanks

28-05-2018 10:40pm

My under standing is roundup will kill it if if sprayed on leaves but takes several years longer with more applications. Injecting helps kill plant quicker but harder to do. Timing important as previously mentioned

orm0nd · 29-05-2018 6:09am

Roundup Bioactive or Garlon Pro

Spray early August and repeat mid September doing any missed sprouts and re growth

Spraying in May. While it might look good originally is actually doing more harm than good long-term cos the chemical is not getting far enough into the root system

Clearance takes 3 to 7 years

It spreads on soil do not cut on road sides is for fear of even tidy amounts of clay being transported with the flail hedge cutters

It can remain dormant for decades and suddenly burst into life if soil is disturbed

Not spread by seeds or stems if soil free

yosemitesam1 · 29-05-2018 8:29am

cosbawn wrote: »

There are numerous notices about put up by the council to stop hedge cutting. That seems to be the height of it ! Maybe they gonna spray in the autumn. No I won’t cut or anything like that. Give a good spray tomorrow. Thanks

Spraying this early will cause some of the root system to go dormant and it will reappear over a long period

blue5000 · 29-05-2018 9:06am

My advice is wait until a warm, sunny day in mid-august to spray the whole plant with roundup+a sticker. If you miss any of it spray it again about 2-3 weeks later. I had some in a hedge and killed it this way.

orm0nd · 29-05-2018 9:49am

I have some pics stored somewhere on cloud (but can't find them now) of a massive "crop" we are trying to eliminate

it was over 4 mtrs high and approx 40 mtrs X 30 mtrs in size we are working our way inwards about 3 to 4 mtrs each year

most important points

Timing: of application and as many leaves as possible getting thorough wetting

Chemical: (Roundup BIOACTIVE or Garlon Pro,)

mixing: 200 ml chemical to 10 ltrs water, ( no more no less)

weather conditions at time of spraying

Markcheese · 29-05-2018 10:37am

If you can get some red and white warning tape put a boundary around the stuff on the roadside and also a sign with roundup do not cut...and spray mid to end summer....
Not a whole pile else you can do... As its not your land...

forgottenhills · 29-05-2018 11:15am

cosbawn wrote: »

There is a substantial crop of JK on neighbouring property. Small country lane divides us. Some small shoots are right at the edge of the road. I’m sick at the thoughts of it coming in. So much so that I’m gonna spray it in the autumn. But In the mean time would it be worth my while spraying those young smaller shoots to stop them getting too tall. No water course nearby no animals grazing

If the JK on our neighbours property is close to their house then you could let them know that their property value will be severely reduced by the presence of JK and that if it gets close to their house it will undermine the house's foundations. That might get their attention.

As far as I know you now have to declare that your property is JK free when selling a property in the UK.

cosbawn · 29-05-2018 3:18pm

Thanks so much for all the advice everyone. There is no house on neighbouring property and the land is totally unkempt. Is that the word to use? It’s just wild. You couldn’t walk into the fields without at least a pair jeans you’d be ripped to pieces from briars. I’ve never seen anything like it I never see anyone around. But if I do I’ll mention it. I don’t mind doing it. It’s in my own best interest. I’ll wait till August and then do a second spray few weeks later. Fingers crossed in the mean time ðŸ€žðŸ€ž

patsy_mccabe · 29-05-2018 5:09pm

patsy_mccabe wrote: »

Is this it?

Just checked the knotweed I sprayed last year and all dead as a door nail. Then 20 feet or so away spotted a new Bush. Jeez, could be an ongoing battle.

professore · 29-05-2018 5:18pm

It might finally push the govt to tax the hell out of land left sitting idle.

my3cents · 29-05-2018 5:22pm

patsy_mccabe wrote: »

Just checked the knotweed I sprayed last year and all dead as a door nail. Then 20 feet or so away spotted a new Bush. Jeez, could be an ongoing battle.

What I think happens and I've seen the same thing happen time and time again is that you can get a good kill on the main plant but the root system is so extensive that the furthest most bits of root from the main plant are still alive.

The following year these roots now disconnected from the dead main plant produce buds of their own and you get new plants.

It may be a battle but the new plants shouldn't have anything like as much strength as the original established plants so are easier to kill.

TomOnBoard · 29-05-2018 5:25pm

professore wrote: »

It might finally push the govt to tax the hell out of land left sitting idle.

A bit harsh, unless its building land that's being hoarded as such. A smallholding of briars and rushes may well be someones retirement home or simply his expression of nature at its most beautiful.

That said, any land containing unmanaged noxious weeds are subject to legal oversight and possible action. This used to be fairly rigorously policed in times past in respect of ragwort. Perhaps JK should be similarly managed, if its not already.

my3cents · 29-05-2018 5:32pm

cosbawn wrote: »

Thanks so much for all the advice everyone. There is no house on neighbouring property and the land is totally unkempt. Is that the word to use? It’s just wild. You couldn’t walk into the fields without at least a pair jeans you’d be ripped to pieces from briars. I’ve never seen anything like it I never see anyone around. But if I do I’ll mention it. I don’t mind doing it. It’s in my own best interest. I’ll wait till August and then do a second spray few weeks later. Fingers crossed in the mean time &#55356;&#56350;&#55356;&#56350;

If you can get into it now then there is no reason not to spray it.

You are a little late as the point of an early spray in May is to reduce the height of the weed so its easy to get the important dose of glyphosate on it in September. Its no point waiting till August or September and then having a crop so large you can't get anywhere near it with a spay lance.

If you have the time in late August then two sprays with two weeks gap increase the kill rate.

cosbawn · 30-05-2018 12:59am

my3cents wrote: »

If you can get into it now then there is no reason not to spray it.

You are a little late as the point of an early spray in May is to reduce the height of the weed so its easy to get the important dose of glyphosate on it in September. Its no point waiting till August or September and then having a crop so large you can't get anywhere near it with a spay lance.

If you have the time in late August then two sprays with two weeks gap increase the kill rate.

Yes it’s already fairly high. But I had planned to use a high step ladder from the road side at least to try and reach in. I know that I may not be able to get right into the middle of it this year as ground is very rough lots of large rocks & no point getting injured. It will be a work in progress. I have Grazon Pro which replaced Grazon 90. I’ll let ye know how I get on hopefully it won’t be too windy

Bass Reeves · 30-05-2018 1:19am

Monsanto have bought out Roundup capsules/bullets for killing the roots of trees. You drill a hole and plant them in the trunk of the tree. These are slow and long acting. Would these be any use in the fight against knotweed

orm0nd · 30-05-2018 5:59am

Bass Reeves wrote: »

Monsanto have bought out Roundup capsules/bullets for killing the roots of trees. You drill a hole and plant them in the trunk of the tree. These are slow and long acting. Would these be any use in the fight against knotweed

No

cosbawn · 30-05-2018 7:41am

Well it’s done. But no where near as good as I’d hoped. I couldn’t get near the JK in places due to the briars. So I sprayed them and will continue to do so over the summer and try and kill them off. SBK be ok for this?
“Brushwood Weed Killer - Directions for Use
Woody weeds: Apply from May to October”
How often should I use do ye think?

I’ll hold on to Grazon for “good use”. Not to cheap that stuff.
Well all beginners are weak and sure if it was easy we’d have no need for Boards !!

my3cents · 30-05-2018 9:00am

cosbawn wrote: »

Well it’s done. But no where near as good as I’d hoped. I couldn’t get near the JK in places due to the briars. So I sprayed them and will continue to do so over the summer and try and kill them off. SBK be ok for this?
“Brushwood Weed Killer - Directions for Use
Woody weeds: Apply from May to October”
How often should I use do ye think?

I’ll hold on to Grazon for “good use”. Not to cheap that stuff.
Well all beginners are weak and sure if it was easy we’d have no need for Boards !!

Roundup or other glyphosate based weed killer will do a fairly good job on briars and tbh because it cheaper than many of hormone weedkillers (like SBK and Grazon) on uncropped land its the obvious choice.

The problem is that you will end up with just bare soil when you use glyphosate, the hormone weedkillers leave the grass.

orm0nd · 30-05-2018 9:37am

professore wrote: »

It might finally push the govt to tax the hell out of land left sitting idle.

my3cents wrote: »

Nothing will kill it in one spray if its well established. Consider getting rid of it a long term project.

I'd spray asap with whatever you have now, grazon 90 or anything glyphosate based and again when it regrows at the end of the season.

Then next year follow up with a dose in May and another in early September until its gone.

In subsequent years keep an eye on the area and spray any regrowth.

Even if it seems to have died out avoid disturbing the soil in the area as damaging the roots can stimulate it back into growth.

The September spray before the leaves die off is the most effective because the plant takes any available nutrients and the herbicide back down into the roots over winter. However a spray early in the season can keep the height of the plants down so you can get at them all in September. If near a drainage ditch or water then glyphosate with a clearance for aquatic use is the only choice.

DO NOT trim the back the JK in the hedge as it roots from the material you cut off and may be why its spreading at an alarming rate.

my3cents wrote: »

Yep thats standard practice. One dose end of May to keep them from getting too big then another end of August beginning of September or later depending where you are.

my3cents wrote: »

What I think happens and I've seen the same thing happen time and time again is that you can get a good kill on the main plant but the root system is so extensive that the furthest most bits of root from the main plant are still alive.

The following year these roots now disconnected from the dead main plant produce buds of their own and you get new plants.

It may be a battle but the new plants shouldn't have anything like as much strength as the original established plants so are easier to kill.

your problem is that you are using the incorrect approach

you are spraying far too early in the season and even worse giving out wrong advise on here to get more people in the same situation as yourself

this not a personal attack on you, I value your posts on other forums but you are out of your league here please do not continue to post misleading information

for any body in the north tipp area or passing through , Dow & Arrabawn co-op held an excellent information morning in Garrykennedy last year, there is a large growth at the rear of Larkin's pub,

it was late in the year & I don't know if it was sprayed or not but would be interesting to see the results

also a big mistake a lot of the cc's are making is not checking inside the roadside hedges

my3cents · 30-05-2018 11:41am

orm0nd wrote: »

your problem is that you are using the incorrect approach

you are spraying far too early in the season and even worse giving out wrong advise on here to get more people in the same situation as yourself

this not a personal attack on you, I value your posts on other forums but you are out of your league here please do not continue to post misleading information

for any body in the north tipp area or passing through , Dow & Arrabawn co-op held an excellent information morning in Garrykennedy last year, there is a large growth at the rear of Larkin's pub,

it was late in the year & I don't know if it was sprayed or not but would be interesting to see the results

also a big mistake a lot of the cc's are making is not checking inside the roadside hedges

Ok so a professional gardener who has been dealing with Japanese Knotweed for the last 35 years is out of their depth and someone who goes to an information morning is an expert?

How many sites with Knotweed have you treated and how many have you eradicated it from?

I will state again spraying early in the year mid May being ideal so we are getting too late for that is good practice because it reduces the height of the crop when it comes to the main spray timing at the end of the growing season.

You are advising people to fail in their task by allowing the weed to get too big. How do you advise spraying a weed that is 3m high and so dense that you can't even fight your way into without a machete?

my3cents · 30-05-2018 11:58am

So here is Monsanto's recommendation where specialist spray equipment isn't available - Hmmm I wonder what they make?

https://www.alci.ie/fs/doc/Round%20Up%20-%20Japanese%20Knotweed%2014-05-10.pdf

2) TWO FOLIAR SPRAYS AT 1 METRE STEM HEIGHT
Spray the plants at 1-1.5m tall, in late May, with a rate of 5.0 l/ha and repeat on any regrowth
later in the season once they reach 1.5m again. This technique can be used where
stands are particularly thick, as part of an integrated control programme or where long lances
are not available.

I modify that slightly and leave the second spray until the end of the season rather than just spraying the regrowth as it occurs. I have no argument that the later spray is the most effective because I have seen the results myself loads of times.

blue5000 · 30-05-2018 3:55pm

Let's all take a step back folks, and calm down a bit.

In a severe infestation it may take several years to eradicate it. If possible wait till August when the plant translocates the herbicide down to the roots.

Monsanto advice;

Treatment in early season is usually less effective because the plant is naturally pushing
nutrients strongly upwards to the developing canes. This can lead to a good initial top kill
of leaves but less transport to the rhizomes. Regrowth after early season treatment can
often be ‘epinastic’ ie stunted and distorted and because it is not actively growing it is
more difficult to kill.

Full leaflet here.

https://www.alci.ie/fs/doc/Round%20Up%20-%20Japanese%20Knotweed%2014-05-10.pdf

Mousewar · 04-06-2018 8:19pm

So looks we have this in our estate here in Dublin. It's about 8ft tall already in a garden across from me and is now running along the wall on the common green area where it is about 5ft. There's a few other patches on it here and there as you go along.
I have two questions.
First, is there anything in particular I can do to ensure it doesn't come onto my property? My garden is about 7 or 8 metres from it.
Second, we have informed the council who say they'll be out. This would be dun laoghaire rathdown. Does anyone have experience with the council treating this? Basically I'm wondering can I trust them to do it properly or should I be thinking of taking matters into my own hands?

TomOnBoard · 04-06-2018 8:23pm

Leave it to the Council IMO

Japanese Knotweed - how to kill?

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