Advice needed - any chemists or horticulturalists here??

[doug darter]

I have a large expanse of gravel drive to the front and side of my house, which I need to clear of winter weeds at the beginning of each spring.

Usually I use 'Pathclear' - Glyphosate 20%, Oxadiazon 20% and Diflufenican. This is supposed to kill growing weeds with one application, and stop further germination of new plants for six months. It does neither with any efficiency, and I find that I need to use it every couple of weeks. I use the full recommended dose in a 10l sprayer.

After taking advice from a friend, who swears by it, I have decided to use 'Roundup 3000' which is 100% Glyphosate. I have just bought a litre bottle, and it cost £48!! :shock: :shock:

I have read the instructions, which seem a little contradictory. It appears that this is a systemic herbicide, which kills by stopping the weeds photosynthesising, by coating the leaves with a film. Any run off from the leaves is supposed to be neutralised instantly on contact with soil.

OK, so far so good, this is quite easy to understand.

The instructions say that the dilution rate is 15ml/litre for watering cans, and 75ml/litre for sprays. My question is this: Are the manufacturers deliberately telling you to increase the dosage, because spraying means that you will use a lot less of their product, and consequently not have to buy replacement solution more frequently??

As I see it, 15 ml/litre in a can, and 15ml/litre in a sprayer is exactly the same concentration. If you give the leaves a good soaking with either implement, exactly the same amount of solution stays on the leaves, and the remainder runs off, and is neutralised, and is therefore not important in terms of the amount/concentration used. After all, a soaking is a soaking, whether a can or sprayer is utilised.

Am I right, or am I just being thick, and have missed something.

I suppose I could use Paraquat, but I'm always concerned that it will poison wildlife :shock: .

[rfrazier]

Perhaps the expectation is that with a watering can the application will be targeted and heavy, while with a spray application it will be general and lighter, and you need a certain coverage for it to be effective. They must reckon that a light cover of a 75ml solution is about the same as a heavy cover of a 15ml solution. (One bullet approach vs multiple shotgun pellet approach).

Best wishes,
Bob

PS But, of course, if the volume actually hitting the plants is the same in both cases, it doesn't make any difference. ;)
RLF

[doug darter]

Hi Bob,

Thanks for replying. I have given this a great deal of thought, and actually tried both methods this morning, in my greenhouse (a controlled environment). Using the Spray on a coarse setting is actually far more accurate, and much easier to direct. A one second spray over a tray 8"x10" containing a sheet of blotting paper saturated the blotting paper completely. A one second spray from a watering can with a standard perforated rose failed to saturate the sheet completely, but did saturate the bench!! The blotting paper that was sprayed took 8 minutes longer to dry than the sheet that was watered conventionally.

This leads me to believe that spraying is not only more efficient in terms of amount of solution used, but that more of the liquid stays on the subject, and there is less runoff.

??

[sundial]

Doug, Have you considered using a propane torch to eradicate the weeds?

http://www.softwindz.com/torch/torch.html

Cheers

dunk

[doug darter]

Hi Dunk,

I have one, and very useful they are too, especially for the tenacious little blighters like Horsetail fern. They are expensive to use over a large area though, and the effect is only temporary - the weed normally re-grows because the roots aren't destroyed. Thanks anyway :D

[rfrazier]

Hi Bob,

Thanks for replying. I have given this a great deal of thought, and actually tried both methods this morning, in my greenhouse (a controlled environment). Using the Spray on a coarse setting is actually far more accurate, and much easier to direct. A one second spray over a tray 8"x10" containing a sheet of blotting paper saturated the blotting paper completely. A one second spray from a watering can with a standard perforated rose failed to saturate the sheet completely, but did saturate the bench!! The blotting paper that was sprayed took 8 minutes longer to dry than the sheet that was watered conventionally.

This leads me to believe that spraying is not only more efficient in terms of amount of solution used, but that more of the liquid stays on the subject, and there is less runoff.

??

That's fine for a small test area. Just make sure you spray like that when it comes to the large driveway. Either (1) the method of delivery changes the nature of the material*, (2) they are simply trying to sell more, or (3) their experience of different amounts being effectively delivered by the different methods. Although I bet they would be happy to sell more, given what they've said, I suspect (3). If just (2), then they would have been better off saying to use the heavier concentration for the watercan method as well.

*By being vapourized.

Best wishes,
Bob

[swanbourne]

It helps if you can get a hood to fit over the end of the spraying lance and direct the spray better.

Eddie

[cb40]

I always found that sodium chlorate was the cheapest and most effective weedkiller for this purpose. The only thing is it kills everything and can persist for years. Oh yes - its also a strong oxidiser so its best applied in solution.

Cheers cb40

[Glamdring]

Usually I use 'Pathclear' - Glyphosate 20%, Oxadiazon 20% and Diflufenican. This is supposed to kill growing weeds with one application, and stop further germination of new plants for six months. It does neither with any efficiency, and I find that I need to use it every couple of weeks. I use the full recommended dose in a 10l sprayer.

Try it, then rinse out the bucket/sprayer with clean water a dozen times, then fill with clean water and spray clean your greenhouse plants. They'll all die. I know. :?

[doug darter]

Usually I use 'Pathclear' - Glyphosate 20%, Oxadiazon 20% and Diflufenican. This is supposed to kill growing weeds with one application, and stop further germination of new plants for six months. It does neither with any efficiency, and I find that I need to use it every couple of weeks. I use the full recommended dose in a 10l sprayer.

Try it, then rinse out the bucket/sprayer with clean water a dozen times, then fill with clean water and spray clean your greenhouse plants. They'll all die. I know. :?

:shock: :shock:

I must be doing something wrong then :?

[ernestrome]

Or maybe it's just that his greenhouse plants have no resistance to weedkiller, whereas weeds do?

[doug darter]

Or maybe it's just that his greenhouse plants have no resistance to weedkiller, whereas weeds do?

There may be something in this.

I grow the most wonderful weeds, real exhibition beasties, but often I have difficulty in getting annuals to look as good. :evil:

[Glamdring]

It was a greenhouse full of tomatoes my parents had left to be watered whilst they were away on holiday. The first watering left the leaves brown and - RIP tomatoes. :? :wink:

[doug darter]

It was a greenhouse full of tomatoes my parents had left to be watered whilst they were away on holiday. The first watering left the leaves brown and - RIP tomatoes. :? :wink:

Good thing too! I hate tomatoes :evil:

[Glamdring]

Oddly, so do I. You're only the second other person I know who'd admit to such.
This had no bearing on the watering, though. ;)

[doug darter]

Oddly, so do I. You're only the second other person I know who'd admit to such.
This had no bearing on the watering, though. ;)

You say that now.............. :twisted:

[sundial]

Oddly, so do I. You're only the second other person I know who'd admit to such.
This had no bearing on the watering, though. ;)

But apart from the taste ... would you agree that tomatoes "on the vine" have a wonderful fragrance?

Cheers

dunk

[Glamdring]

I suppose; I like plants and greenhouses.