When I was in California it was common practice to spray Roundup down the open rows.

I am not that much of a fan of the idea, I water only under the trees and not much grows in the middle once summer comes.
If I spray off the winter weeds to save mowing I find the soil moisture that stays in the soils grows nasty summer weeds.

In time you end up with an orchard full of weeds that are resistant to roundup.
So then you would need to use Basta or some other herbicide

I live on the other side of the world but I think the same things would happen anywhere

Do you think application once or twice a season would hurt the trees?

Blackrag:

I have used Roundup around my fruit trees for years, and also 2,4-D on dicots. Roundup is the only solution I have found for deep-rooted perennial weeds like Bermuda grass, which would be impossible to dig up. Not only might deep digging disturb the tree roots, but the rhizomes of these grasses break up underground and come back quickly. I spray in about a 6-8 foot circle around the trees. I also mulch heavily about once a year, usually over the winter, but this does not stop weeds for long.

Before spraying, I try to ensure that any root suckers are clipped off at ground level to reduce any intake by the trees. I have never observed any tree damage from this use of Roundup, nor have I developed any resistant weeds.

Don Yellman, Great Falls, VA

Thanks for your response, Don & Mike.

Blackrag,

It's a very common practice in orchards in the Midwest to keep the area under trees free of weeds. Around here most commercial guys use a combination of gramoxone (Paraquat) and glyphosate (Round-up). I follow Don's approach, and use mulch, supplemented with glyphosate when things start to get out of hand.

Mike has a different, and interesting, approach to controlling tree vigor, and it appears to have worked for him in Australia. I don't think it would work here in the Midwest. Weeds and grass under the trees suck up too much moisture and nutrients, causing all kinds of problems.

You'll want to try to keep glyphosate off the bark of the trees, and certainly off the foliage. Young smooth bark is the most susceptible to absorbing glyphosate and translocating it to the roots. Gramoxone is not absorbed by the bark.

Good stuff. Thanks!

In Goodfruit a few months back one academic posted an article about research that indicated that after about mid-summer, there is very little benefit from active weed control. Here that would be by the second week of July.

This year I discontinued weed control after June in my nursery and orchard and even though the weeds are high, the trees look great. I stopped wacking weeds outside of the mulched circles of my orchard trees just so they could slurp up some of the surplus water- rain has been excessive.

It is standard practice in free-standing dry orchards (not irrigated) in the northeast to maintain herbicide treated strips about 10' wide with the trees in the center and with 10' sod middles. Usually such strips are allowed to grow new grass in the fall to hold on to soil over winter and add organic matter.

I keep a small circle under each of my nursery trees mulched over several layers of newspaper. My orchard trees get a much larger circle.

Be careful with stonefruit especially when young if you intend to use round-up- you might want to use a wick-stick (from AMLEONARD.COM). Any green tissue is likely to absorb the glysphosphate- suckers also.

I've read that before, that is, to stop weed control in order to help trees harden off and add organic matter. Middle of July might be a little early for here though. With our longer growing season, there can be a lot of hot dry weather ahead, in which case I think the trees would still benefit from weed control.

Blackrag,

You may be interested, that mature commercial orchards do get some glyphosate overspray on the bark of trees. The older (rough) bark won't translocate enough of the chemical to hurt the tree, IF it's sprayed early in the season. That's why they generally recommend an early to mid-summer cut off point for glyphosate applications. A few weeks ago the IL fruit newsletter mentioned they were past the cut-off point for gyphosate use under trees.

Glyphosate under young trees is a no no. Heard a story of a guy who sprayed a young peach orchard with glyphosate. Got enough of the chemical on the trunks that it wiped out the whole three year old planting.

Gramoxone you need pesticide license to buy. Its only chemical I buy skull&bones on jug. It run taste of some fruits has some limbitation on use in orchard floor mangement. Most orchard guides are for one crop Gramoxone use in all orchards before the first fruiting year fruiting year on its no no.

The point of the article- which was written for Washington State fruit growers who have quite a long season, is that most of the bang for the buck is the early control. Later weeds don't adversely affect size of fruit much, apparently, or the overall growth of trees.

I wonder about stone fruit though, when trees are very young and you are trying to size them up. They get a lot more of their growth later in the season than apples and pears. It's hard to believe that weed control wouldn't be important at least until late summer. I grow my nursery peaches using fabric so I'll not bother experimenting on that one.

Gator,

I wasn't suggesting Blackrag use gramoxone, just indicating what some commercial folks use. You're right, it's one of the very few orchard chemicals that has a poison signal word. It is highly poisonous, if taken orally. It leads to a slow painful death (about 30 days) with no known antidote. You are incorrect that it can't be used for fruiting orchards. I don't know what formulation you have, but Syngenta's formulation has a pre-harvest interval of 14 days for bearing peach orchards. It is also labeled for post-harvest use.

Commercial or otherwise I would not spray gramoxone with a hand sprayer of any kind. It's just too toxic. Bad enough doing fieldwork with an enclosed cab sprayer with the stuff.

Orchard I was at two weeks ago applies gramoxone with tanks on 4 wheelers and wands. It's the best way to keep it off the foliage of young trees. Although it won't translocate to the roots, it will kill any foliage it touches. It's labeled for spot spraying. The real risk of gramoxone is ingestion. Sygneta's formulation has an oral LD50 of only 283, whereas the dermal LD50 is >2000. Lorsban has very similar numbers (oral and dermal) and the only way to apply drenching trunk sprays for borer control is with tank and wand. Both products require a respirator, but that's not uncommon with ag chemicals.