Like many gardeners, I’ve seen plenty of tomato problems in my garden over the years. Early blight, late blight, blossom end rot and insect damage have cropped up from time to time, but these twisted leaves had me stumped.
I looked for images of similar problems online and checked my Tomato MD app, but I couldn’t find anything else that looked like that deformed growth.
In a great gardening coincidence while I was finishing my Colorado Master Gardener continuing education requirements, I clicked on a Small Acreage Management (SAM) webinar, and the mystery was solved.
These SAM webinars are posted on YouTube, so any gardener can watch them for free. The one that helped me diagnose my tomato plant problem is called “Herbicide Carryover and Fall Garden Care” led by Darrin Parmenter of CSU Extension in La Plata County, dated Sept. 4, 2013.
Herbicide carryover can happen when gardeners use herbicide-treated hay, straw or grass clippings as mulch or compost in their gardens. Herbicide carryover can also occur if gardeners apply manure from livestock that ate treated pasture or crops. Tomatoes and members of the tomato family are especially susceptible to herbicide carryover.
I’ve used well-aged horse manure in my garden for years and there’s never been a problem until this season. It turns out that herbicide carryover from horse manure is the top pathway because herbicides can pass through horses so quickly.
As soon as I understood the problem, I started a remediation program to improve soil microbial activity in the two containers with the affected tomato plants. I’ve cultivated the soil to increase oxygen, added a different kind of organic matter to increase beneficial soil organisms and used a home-made organic mulch. I’m also keeping the soil evenly moist and using a liquid fertilizer once a week.
According to Darrin in the webinar, the tomato plants may recover if there’s enough vegetative growth. I’m certainly going to be more thoughtful with how I amend my garden soil in the future.
By Jodi Torpey
A Colorado Master Gardener