Aminopyralid poisoning of garden plants

Hi Permies, I am starting this thread in cider press so people can discuss topics related to herbicide contamination on organic amendments, symptoms of injuries in garden plants and how to fix it when the garden soil is contaminated.

Here is an article that is well written and there are more information online from university extension units as well.
https://theprepared.com/blog/aminopyralid-contamination-is-a-growing-gardening-problem/

Gardeners are getting more and more aware of contaminated organic amendments originated from pasture such as: straw, hay, manure and compost. They usually are able to see the plants developing signs quickly. Recently I saw an upsetting trend of herbicide contamination in branded bagged garden soils as well. Since they are premixed and the level of contamination is much lower, the symptoms of injuries can be obscure but still cause crop reduction.

I am going to show the cases of my tomatoes and peppers in the hope of helping other gardeners. If acting early, the plants can be saved without wasting time and money fighting the sick plants.

This summer I took a cutting of a tomato plant, rooted in water and planted into a pot filled with purchased potting soil and placed in shade. Two weeks later I realized something was wrong with the cutting: new growths showed typical symptoms of filigree leaves seen in aminopyralid poisoning.

I took quick action and wash all the soil away and replanted the tomato in clean medium. I removed the sick elongated part of main shoot and let the suckers grow out. As you can see in the picture below, leaves in the suckers showed cupping in the lower 4-5 leaves then gradually got back to normal. The plant is setting fruits and the new growths are healthy now.

It prompted me to think how many gardeners thought their tomatoes were not producing well because of water/heat/nutrition issues but actually the contaminated potting soil for transplants was the culprit. Sometimes the roots outgrow into good soil quickly and the plants recover quickly. It's also possible the tomatoes remain stunted for a long time and the gardeners lose time and money trying to bring them back to life.

So beware of anything products from outside even they are from some well known companies.

The sick tomato was a blessing in disguise because I also grew a bell pepper plant in the same potting soil. The symptoms that plant exhibited solved a mystery I couldn't figure out for more than a year.

The sick bell pepper had excess flower buds and stunted vegetative growth, and fruits were smaller and flat with little seeds. I had several plants like that but never suspected herbicide poisoning. They included: plant in ground with horse manure mixed in ( seller claimed It had been aged for four years), a healthy plant brought indoor for overwintering but gradually declined, potting soil was added to fill the pot,  and a couple seedling transplants. I tried giving them extra nitrogen or calcium but it didn't work.

In a healthy bell pepper plant, it grows about a dozen leaves followed by the first flower on the apical meristem. Two side buds develope symmetrically and each grows another flower bud and two side shoots. Now the plant has four branches and only branches out occasionally after that.Some hot pepper plants tend to branch more frequently but they also have small fruits.
However, in the sick plant, such regulation is impaired and the number of flower buds increases exponentially at the expense of vegetative growth. The leaves get smaller and stems shorter over time.

Since aminopyralid is a auxin like substance and interferes with many aspects of plant development, it is not surprising that the affected plant has so much chronic problems.

I also failed to grow eggplants this year because flea beetles attacked them like crazy. Now I doubt the pest issue was the consequence rather than the cause and the plants were contaminated with herbicide too. I will try again next year.

I don't think the herbicide carry over is brand or product specific. It's getting so widespread that individual bag of soil/potting mix needs to be tested to be sure. Giving all the hassles I am going to just make my own seeding potting mix from now on.

A pepper plant is basically a small tree and it follows the da Vinci's rule: the branch cross-sectional area below a given branching node is equal to the sum of the cross-sectional areas of daughter branches above the node.

In a normal plant, there are about four branches with diameters 1/2 of the main trunk. Side shoots mainly grow small cluster of leaves and the flower buds tend to abort. In the herbicide affected pepper, at each node, it's branching symmetrically, leading to the branch diameter to be half of /√2 or 0.7 of the previous branch. Quickly the size reduces so much it is unable to support leaf growth both structurally and functionally.

I tried washing and trimming the roots of affected pepper plants to see if they would recover. Unfortunately, both the younger transplant and the 2nd year old one still have abnormal growth after a month. So unlike tomato, herbicide injury seems to be unsalvageable.

Currently beans and peas are used for herbicide contamination assay. I don't know if they are sensitive enough for crops like peppers and maybe eggplants.

photos of injured plants and fruits vs normal ones: