Marissa Schuh
A hot weekend shifted into a week of wildfire smoke over much of the state. Some areas got some soaking earlier this week, and there is some more rain in a forecast, a relief as much of greater Minnesota is abnormally dry or in D1 drought. Some beautiful early season produce is being harvested and heading to markets and CSA boxes.
The impact of the smoke will also vary depending on how close or far you are from the source , we may see different things in parts of Northern Minnesota where there were local fires, compared to the metro and southern part of the state, where smoke was blowing in from Canada.
If you want to go deeper about what we do and don’t know about wildfire smoke and plants, check out Managing wildfire smoke: impacts to crops and workers.
Herbicide drift can be hard to diagnose, and only lab diagnosis can confirm. These diagnoses are expensive and need to be done in certain ways in very specific time frames after the drift event has occurred.
The Minnesota Department of Agriculture will perform investigations and do lab testing, you can learn more about that process on their website. This process is the main way to get the testing done to confirm herbicide drift.
What does herbicide drift look like? It depends on what the herbicide is.
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The other herbicide we get occasional drift questions about is glyphosate. Glyphosate works by interrupting a protein pathway in the plant, so new growth will be off-color from the base of the leaf. Its primary use is in field crops, though there are formulations for home landscapes.
Another thing to do, especially if you run into a rainy day, is to list your farm on the DriftWatch registry so applicators know your farm and susceptible crops are out there.
A hot weekend shifted into a week of wildfire smoke over much of the state. Some areas got some soaking earlier this week, and there is some more rain in a forecast, a relief as much of greater Minnesota is abnormally dry or in D1 drought. Some beautiful early season produce is being harvested and heading to markets and CSA boxes.
Wildfire smoke and plant health
The effects of wildfire smoke on plants is poorly understood, and what we do understand is that it is complex. For example, while the smoke does block some sunlight, it also creates diffuse light, which can more easily penetrate the plant canopy than direct sunlight. If the smoke is high in ozone, this can damage plants, causing a variety of white and yellowing speckling on a wide range of vegetable crops.The impact of the smoke will also vary depending on how close or far you are from the source , we may see different things in parts of Northern Minnesota where there were local fires, compared to the metro and southern part of the state, where smoke was blowing in from Canada.
If you want to go deeper about what we do and don’t know about wildfire smoke and plants, check out Managing wildfire smoke: impacts to crops and workers.
Ozone damage on a young tomato plant. Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org
What can I plant/re-plant?
We’ve talked to some growers who planted some of their cold sensitive crops when we had high temps in mid-May. These plantings have been damaged by the cool nights we’ve had since then. For some crops, there might still be time to replant some varieties, especially vine crops. You can work backwards from your area’s frost free date to figure out what to replant. For example, for my office in Farmington, there is a 50% chance that the first frost will have happened on/by October 2. There are 120 days from June 4 to then, so a lot of vine crops, like zucchini, summer squash, and even some winter squash varieties would still be fine to plant. Obviously this will vary depending on where you are in the state, for example the 50% chance of frost date in Two Harbors is September 11. This gives you 99 days, which will rule out some winter squash varieties.Herbicide drift
We are in a window of time where we often get questions about herbicide drift. Dicamba had three formulations for use over the top of soybeans had their registrations vacated. These formulations were behind a lot of the news coverage around drift in the last decade.Herbicide drift can be hard to diagnose, and only lab diagnosis can confirm. These diagnoses are expensive and need to be done in certain ways in very specific time frames after the drift event has occurred.
The Minnesota Department of Agriculture will perform investigations and do lab testing, you can learn more about that process on their website. This process is the main way to get the testing done to confirm herbicide drift.
What does herbicide drift look like? It depends on what the herbicide is.
2,4-D is a type of product that has application scenarios in both field crop and lawn settings. It is an auxin herbicide, meaning they impact plant hormones and the way a plant grows. Susceptible plants that have been exposed to these types of herbicides often have twisted and distorted leaves and stems, as well as stunted growth.
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A pepper plant with 2, 4-D herbicide injury. Note stunted, cupped leaves, wiggly veins, and curving stems. Photo: David B. Langston, University of Georgia, Bugwood.org
Glyphosate injury on potato. Note the yellowing at the base of the new growth. Photo: Jed Colquhoun, University of Wisconsin, Bugwood.org
Glyphosate injury causes yellowing from the base of the leaf of the new growth on melons. Photo: Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org
When trying to figure out if what you are seeing is potentially drift or something else, look at neighboring vegetation, such as trees or weeds. They can display the same types of cupping, twisting, yellowing, and distortion that vegetable crops do..jpg)
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Sumacs are a common tree in Minnesota, this one is displaying symptoms of dicamba drift. Photo: William Jacobi, Colorado State University, Bugwood.org.
Another thing to do, especially if you run into a rainy day, is to list your farm on the DriftWatch registry so applicators know your farm and susceptible crops are out there.
Crop updates
Asparagus harvest is winding down. When you start seeing spears that are pencil size or smaller, it is time to stop picking.
Final harvest is a key time for weed control in asparagus. For conventional growers, the final pick is a key time to use herbicides. Synthetic auxin herbicides can be applied in the day-of or day-after final harvest (this helps limit damage to spears or fern). Another option for emerged weeds is glyphosate — to use this, remove all spears so that the patch is totally picked. You can mix glyphosate and a synthetic auxin. This is a helpful combo if you have tricky perennial weeds in your space. For more information on herbicides, see the Midwest Vegetable Production Guide.
For organic growers, after the final, clean pick is a good time for shallow cultivation between rows. This will work best on small, recently emerged annual weeds and won’t do much to control perennials like Canada thistle. Other organic options include flaming and, of course, hand weeding.
Cole crops are anywhere from just planted to ready for harvest. Insects make themselves known this time of year. If you’re running into flea beetles, learn more about them at this post. If you’re seeing caterpillars, you can get to know them and their management more at Caterpillars on cole crops.
For potato growers, weather models are suggesting that adult overwintering Colorado potato beetles are laying eggs and the first generation of larvae are emerging in the southern half of the state. Remember to use different modes of action when managing this one – this is an insect that can evolve resistance to pesticides very quickly.
Final harvest is a key time for weed control in asparagus. For conventional growers, the final pick is a key time to use herbicides. Synthetic auxin herbicides can be applied in the day-of or day-after final harvest (this helps limit damage to spears or fern). Another option for emerged weeds is glyphosate — to use this, remove all spears so that the patch is totally picked. You can mix glyphosate and a synthetic auxin. This is a helpful combo if you have tricky perennial weeds in your space. For more information on herbicides, see the Midwest Vegetable Production Guide.
For organic growers, after the final, clean pick is a good time for shallow cultivation between rows. This will work best on small, recently emerged annual weeds and won’t do much to control perennials like Canada thistle. Other organic options include flaming and, of course, hand weeding.
Cole crops are anywhere from just planted to ready for harvest. Insects make themselves known this time of year. If you’re running into flea beetles, learn more about them at this post. If you’re seeing caterpillars, you can get to know them and their management more at Caterpillars on cole crops.
For potato growers, weather models are suggesting that adult overwintering Colorado potato beetles are laying eggs and the first generation of larvae are emerging in the southern half of the state. Remember to use different modes of action when managing this one – this is an insect that can evolve resistance to pesticides very quickly.
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