- Author: Brad Hanson
Published on: May 8, 2011
I went on a farm call last week (early May) in response to a suspected herbicide injury issue in a recently replanted almond orchard. The grower had applied a tankmix of glyphosate and Goal as a preplant burndown treatment a week or so before planting. In some areas of the field, the first leaves were badly stunted and yellowed and the grower and PCA wondered if was caused by the preplant treatment.
Although the symptoms are pretty classic for glyphosate exposure (stunted leaves, shortened internodes or "witches brooming", and chlorosis of the newest growth), this injury didn't make sense with the herbicide application in this field. There was not an obvious pattern of injury spatially across the field; however, the symptoms were only in one variety (nonpariel and the two pollinators were on the same rootstock).
I'm fairly certain that the symptoms are from glyphosate exposure but is not from the preplant application. Glyphosate is tied up pretty strongly to soil (especially to organic matter and clay particles) and this orchard has a fairly heavy soil for the area. Instead, what I suspect happened is that the affected trees probably were exposed to glyphosate drift the previous fall (in the nursery in this case, since they were replants). The herbicide was taken in by the green bark and/or foliage but may not have shown symptoms if it was late enough in the fall. The glyphosate, which is fairly stable in plants, was stored in the tree until spring and the symptoms became obvious as new growth resumed this spring.
A couple of interesting points about glyphoste:
1. it is tied fairly tightly to soil - significant exposure via root uptake is very rare.
2. it is pretty stable in plant tissue. In soil it is broken down primarily by microbial action but this would be slow or nonexistent in dormant (and cold stored) plants.
3. the greatest concentration of the target enzyme for glyphosate (EPSPS) is in new tissues where the most synthesis of new cells is occuring. This area is also where the greatest use of stored carbon and new photosynthates are being used.
4. glyphosate moves in the phloem of plants (just like photosynthates) and will be found at the highest concentration in the meristematic regions (like shoot tips and new buds). That's why you usually see glyphosate damage in the youngest tissue first.
Will this injury kill these trees? Probably not - but it will significantly delay their early growth. Tom Lanini and I did a small project last year where we appled glyphosate to young trees in the fall. When they leafed out in the spring they look just like this. At lower rates, the trees mostly recovered by late spring but at higher rates they were still stunted in late summer. A year later, the growth looks normal (but the growth of the worst trees is behind).
A local lab is running samples to confirm that this is indeed from glyphosate. If it is glyphosate and not some other problem, I suspect that the grower will replant the affected trees because these were new transplants and it is still early in the spring. If it was later in the year (too late to replant successfully), he might wait and see how they recovered because they would be delayed in growth.
Take care,
Brad
Tags: herbicide chemistry (45), orchards and vineyards (101)
Comments: 13
Brad
I have caused the same type of injury on my own roses. Just like on the almond trees in the post, roses with glyphosate injury will usually express the symptoms as yellow chlorotic leaves, stunted leaves, and shortened internodes giving a "witches broom" appearance. Glyphosate and other amino acid inhibiting herbicides have the fastest and greatest activity in the areas of the most new growth like the shoot tips or new buds.
Roses and similar plants can be very sensitive to herbicides like glyphosate because of their thin bark. Exposure via drift or even a few droplets on leaves, canes, or other above-ground tissues can result in pretty obvious symptoms. If the damage is not too severe, your roses will probably recover just fine although they may look pretty tough for a month or so. Good luck.
I've never seen the symptoms you've described that could be attributed to glyphosate. That's not generally the symptomology that would be expected from that mode of action. Although I'm certainly not an expert in pomology, this overgrowth sounds more like something related to rootstock-scion compatibility.
Good luck,
Brad
We had a Tomato field that was treated with glyhosate 5 days before planting. Only the the furrows where treated and the beds where cover with plastic mulch. Tansplant tomatos where plant and the plant showed signs of yellowing and burning. Samples were send ( entire plants plant roots and all, cleaned) We got back GLP 0.038 ppm and AMPA 0.015. I havn't been able to find out if this is a high level . I don't know if the cost of replaning is needed.
Thank You, Alan
We had a Tomato field that was treated with glyhosate 5 days before planting. Only the the furrows where treated and the beds where cover with plastic mulch. Tansplant tomatos where plant and the plant showed signs of yellowing and burning. Samples were send ( entire plants plant roots and all, cleaned) We got back GLP 0.038 ppm and AMPA 0.015. I havn't been able to find out if this is a high level . I don't know if the cost of replaning is needed.
Thank You, Alan
It can be hard, sometimes, to make a decision based solely on sample test results as these numbers can vary a lot (for example, due to plant size). Colleagues of mine in the SE USA have had some problems equating AMPA values to yield loss. If you got glyphosate on the plastic, and didn't rinse it off prior to transplanting, injury could occur. What rate of glyphosate did you apply, and were any other products applied either under the tarp or in the furrows? How many days out are you from your initial injury symptoms? How does the new plant growth look? Glyphosate is translocated to new tissues so you will want to observe the appearance and growth of young leaves at least 10-14 days after initial symptom development. If you want, you can e-mail me pictures of your original injury and pictures of the newer tissues at lynn.weed.science@gmail.com.
Lynn offered some good thoughts on your symptoms and I agree. The yellowing "could" be from glyphosate but the burning is not typical from that class of herbicide. Especially if only the furrows were sprayed, I'd probably investigate other causes (fertilizer?, water quality?). I don't have a lot of experience in tomato, but the level of glyphosate and AMPA that you shared is pretty low (not far above the limit of detection in many labs) and my initial thought is that it's probably incidental if glyphosate is used in the field or adjacent areas. For your frame of reference, the almond tree in the photo in this post had about 10 times higher tissue levels of glyphosate and I've seen only very slight symptoms on almond with 5 times higher levels than your sample.
Good luck.
Brad
I wonder if you can tell me about the same kind of injuries in a recent plant almond orchard but not due to glyphosate but due to pendimetaline and oxifluorfen action. I have analyzed my plants and they have 0,079 mg/kg of oxyfluorfen and 0,029 mg/kg of pendimetalin. I made the application before planting. Did I take a bad decission by applying these herbicides?
If I understand your question correctly, you are asking if these same kind of symptoms could come from oxyfluorfen or pendimethalin in young almonds.
I would say, no, those two herbicides act in a very different way than glyphosate and would not cause similar symptoms.
I wouldn't necessarily recommend using those herbicides prior to planting almonds because of the chance of moving treated soil into the planting holes. Neither of them is very mobile in soil (or in plants for that matter) but if you put treated soil down in the root zone they could be affected until the roots grow through the treated soil. Risk and outcome depends on the amount of herbicide moved into the root zone.
Good luck
Brad
Thank you very much for your answer. I have found that the company which applies the phytosanitary products for us, made an herbicide application along March, (post-plantation) during a windy day (very bad business) so now we are talking with a our lawyers.
We lost the 70% of our orchard. The herbicide was detected on the upper side of the seedling. Our agronomist says that the only explanation for that is an herbicide application during a windy day, as we have found in the files.
Thank you very much again.
Andrés