Is Trifluralin (Preen) Safe on Grapes and Strawberries

Two of the fruits I grow which I struggle the most with during the season when it comes to weeds are grapes and strawberries. Grapes are super sensitive to glyphosate and straberries by nature are hard to keep weeded and I haven’t yet found an affordable post emergent spray which is safe to use on strawberries.

With all that being said, is it safe to use Trifluralin(Preen) on strawberries and grapes (both safe to eat as well as not harmful to the plants)? I read the container and saw that this is an off label use but various vegetables are approved for use of the product.

Treflan(Preen) is not labeled for either crop, Prowl h2o is labeled for vineyards but couldn’t find any label for strawberry. Treflan is a 6 wk long preemerge and then you would apply it again. Must be incorporated to work well. The best info you can get might be in the midwest spray guide from Purdue U.

1 Like

Most things have a usage “label” because that particular usage was financially worth getting the EPA registration. I would not be afraid to put it on strawberries, for example, AFTER the crop was all harvested for the season.

(But I wouldn’t tell any nosy do-gooder neighbors what I had done. )

I had some ProwlH20 leftover from 2019 hemp production(I sprayed ‘middles’ between mulched beds), sprayed strawberry bed early last spring, just after tillage & bed-making, but before planting the plants. May not have been an approved usage, but it worked.

1 Like

BlueBerry, thanks for the insight. Any reason why you would wait for after the strawberries to be done fruiting rather than applying it before summer weeds emerge / before the strawberries fruit? The Trifluralin (Preen) is in granual form.

In fact treflan is labeled for strawberries.Spring application only.
Not advocating anything here ,the use Of herbicides .
But I do sometimes read the labels on line .
Wish other people who use them did . !

1 Like

And prowl is labeled too…


1 Like

The problem with Treflan, is that it’s highly toxic to some aquatic life , which I place a higher value on than having no weeds in my strawberries

Same reason I don’t eat lunch after handling Preen without washing my hands… :slight_smile:

1 Like

Caution on Prowl. Don’t eat any part of strawberries for 1yr after application, probably similar warnings for Treflan. That’s why @BlueBerry is saying not to use before harvest. Remember your berries are laying on the same ground you just treated.


So, I’ve been able to do some more research, in part through the help I’ve got on here and it looks like:

  1. Treflan, which has the active ingredient Trifluralin, has a 60 day PHI in vineyards so the Preen version of Trifluralin in granual form is likely safe.
    Weed Management in Small Fruit Crops | Oklahoma State University

  2. According to the University of Maryland publication Fruit Weed Control, Trifluralin is not translocated in plants. Does this mean that it is not absorbed the plants? Aka trifluralin Preen granules sprinkled on the ground before fruit forms are not absorbed by the fruit?

If the Malithion, Guthion, or other pesticides that are sprayed on apples had a active life of 60 days and more before degrading…and you can see spray residue on the peel even if the apple didn’t absorb any of the pesticide…you wouldn’t hesitate to go ahead and eat the apple without washing it or rubbing it thoroughly…?

But you can do whatever you like. Personally I would not put Trifluralin on something that lies there on the ground to keep weeds from sprouting (and the strawberries are lying on that same ground for weeks before they ripen and you eat them). Of course, if you feel good about having lunch after handling preen without washing, then put it all over the strawberry row a few days before harvest. (It won’t kill any existing weeds, but will keep more from coming.)

I do sympathize that weeds are the biggest impediment to a successful growing of strawberries. Been there, done that. Including getting the hoe or even pulling weeds several times a year from down on the ground.

1 Like

Chikn, I agree completely.

Yet, they put highly poisonous chlorine and flouride in our drinking water and proclaim it ‘safe’.

So, a little bit of this stuff on a strawberry or two isn’t the end of the world…

but if it’s strong enough to keep weeds from sprouting for somewhere between 60 and 360 days…just how much would be ‘safe’?

On one berry, probably no biggie.

But I wouldn’t want to purchase strawberries from a farmer’s market if I knew they had had
PREEN applied within the past few weeks prior to harvest!

My final (personal opinion) conclusions on using Trifluralin (Preen) on Grapes and strawberries in my garden:

  1. Sounds safe for use on grapes as the commercial version of Trifluralin, Treflan, had a 60 PHI on grapes and is labeled for use in vineyards.

  2. Treflan is labeled for use on strawberry beds prepared in the spring, it does not translocate, and the Preen version of Trifluralin is labeled for use on Cucumbers and Carrots, both of which have contact with the ground where the Preen version of Trifluralin would have been applied. So overall, it sounds safe for use in my garden strawberries.