I bought Brunnings Path Weed Killer as I have done for many years and never had a problem. This time a bright white residue stained the pavers and is extremely hard to remove. I contacted Brunnings by email but they insist that they have not changed the formula of the weed killer.
Hi @corryadri, welcome to the community.
Was it the premixed spray bottle or the concentrate?
It was the ready to use spray bottle.
Hi Corry, If you are looking for an alternative can I suggest boiling water instead? Works a treat, lasts as long as the chemical sprays, and cheaper with no staining. I got this tip from a golf greenkeeper and haven’t used chemicals since. If you’re trying to remove the white stain, I’m sorry I haven’t got any suggestions for that. Sam
If the product has not changed, is it possible the root cause lies elsewhere. The white stain may be due to the herbicide or it may be coincidental.
Paving can be sealed using a spray or brush on product that resists water. Is it possible the pavers were so treated, and the treatment has now failed? Alternately is there a soil condition the salts from the ammonium thiocyanate in the weed spray have reacted with?
There may be other possibilities. I’d not suggest boiling water is an equally effective solution. It is however much safer, especially for the environment. I’m not familiar with the ingredients in the Path Weeder product. At least one can persist in the soil for many months and readily translocates. It would be advisable to positively identify the cause of the white residue before attempting to clean using any chemicals.
The active ingredients of the premixed spray is…
- 1,3,5-Triazine-2,4-diamine, 6-chloro-N,N’-diethyl- (3.7 %)
- 1H-1,2,4-Triazol-3-amine (2.1 %)
- Thiocyanic acid, ammonium salts 1.8 %
The remainder of the mix are Ingredients determined to be Non-Hazardous, but unspecified. It is likely it will be mainly water with possibility of a surfactant and chemical stabilisers. The surfactant are compounds which break surface tensions of liquids to ensure better spread on/cintact with plant leaves and stabilisers to prevent breakdown of the active ingredients during storage.
Does the bottle have a date of manufacture or use by date? The spray bottle may be one which has been stored for some time.
If the mix hasn’t changed its recipe, it is likely that the white residue are compounds which may result from the breakdown of the mix from long term storage. These may be salts which are less soluble in water making them harder to remove from pavers/surfaces when the spray dries leaving the salt residue behind. Try using household surfactants like dishwashing liquid/clothes washing detergents mixed in water to see if these will dissolve the residue, allowing it to be washed away. It might need a broom or good hosing to assist with removal. Only do this after a few days to allow the spray to work on the plants. Also ensure any wash water from cleaning doesn’t enter a drain/gutter.
I ran out of time this morning, but following on from my earlier post…
There are possibly two other sources of the white residue.
The first being the spray has reacted with something on the pavers. This could be for example other chemicals used (say to clean the pavers) or from sources such a pool water or soil water. As it appears that this is the first time the residue has appeared, this potential source is less likely unless something has changed with the pavers recently.
The last is what is called efflorescence. If you live in an area which has experienced a lot of rainfall recently (like much of the east coast of Australia), then it is possible that the ground beneath the pavers has become saturated, causing salts from the ground (or within the pavers) to rise to the surface. These salts can appear on the surface of the paver or around the cracks when the pavers dry. When you wet the pavers, the white residue may appear to disappear, but will reappear after they dry out again. Dealing with efflorescence on pavers can be challenging as it may reappear each time the ground becomes saturated again, and washing with water may make the efflorescence worse.
Efflorescence won’t be influenced by the weed spray, but the underlying soil conditions.