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Weekly Minnesota Vegetable Report 5/21

Author: Natalie Hoidal, UMN Extension Educator, Local Foods and Vegetable Production

If you're seeing interesting things in your fields, insects and diseases, or just want to share photos, we'd love to hear from you! As always, don't hesitate to reach out with questions and pictures. We're still here for technical assistance over the phone, via text, or via email.

Vegetable questions go to me (Natalie):
Fruit questions go to Annie:
Food safety questions go to Annalisa:

Crop report

Following some much needed rain last weekend, some of you are still waiting for your fields to dry out. We're seeing some more rain in the forecast for this weekend, but after that we can anticipate a mostly dry, warm, and sunny week ahead. While it's been a bit cold this year, the drier than average conditions have been great for transplanting and early season cultivation. 
  • Asparagus may have been slow to regrow following the cold front, but it should be coming in now for most growers. If you're planting asparagus for the first time, check out Annie's article about best practices for planting. 
  • Potatoes are coming up! Others are just planting potatoes now. No signs of potato beetles or leafhoppers yet, but keep an eye out in the coming weeks. 
  • Cucumbers are being planted this week. Check out our latest What's Killing my Kale episode for a discussion about setting cucurbits up for success, and some insight about the flowering and fruiting issues we saw across the state last year. 
  • Tomatoes and peppers are going in to the field this week. We will be planting hot peppers late next week for a pepper variety trial - stay tuned for photos and video updates!
  • Cole crops are at various development stages depending on succession planting. Keep an eye out over the next few weeks for flea beetles and cabbage maggots, and consider row cover on your younger, more susceptible plantings. 
  • High tunnel tomatoes are at all different stages. Some farmers in Southern MN who planted early into heated tunnels are already seeing fruit set, others are just transplanting now.
Tranplanting warm season crops has begun! Listen to our most recent podcast about setting cucurbits up for success. Photo: Natalie Hoidal

Problems in the field

Most crops are off to a healthy start with few problems to report.

Heavy rainfall

Many of you experienced 5+ inches of rain over the course of a day or so last weekend. Heavy rainfall and flooding can results in nitrogen leaching; this is not as big of a deal for slow release fertilizers bound up in organic matter (like manure or compost). Listen to our recent WKMK episode for a more in-depth discussion of nutrient management in the context of wet weather. The more likely result of too much water is simply that growers are now having to wait to plant. 

Too much Nitrogen

Too much nitrogen right as a plant is starting to flower can push plants to produce vegetative growth, rather than invest in flowers and fruit production. We saw this in a high tunnel this week, where a grower saw some nutrient deficiency symptoms, and significantly increased their fertilization rate as their tomatoes were flowering and setting fruit. While this stage of plant growth is not yet upon us for field-grown vegetables, it's a good thing to keep in mind as the season progresses. Cucurbits are especially sensitive to N applications after they start to vine. Make sure you're applying enough N now to avoid deficiency later. If you're doing a split application or continuously applying nutrients through drip line, make sure to do so based on soil tests, and maintain consistent rates. 

Mole and vole damage

We've heard a few reports of tunneling vertebrates - moles, voles, gophers, etc. Stay tuned for resources in a follow up newsletter. In the meantime, here's a helpful resource from Missouri about managing moles. 


Early spring is likely the most critical period of the season for weed management. Listen to the recording from this week's Great Lakes Vegetable Producer's Network for a great discussion of early season weed management methods and tips.

Pest forecast


You may be tired of hearing about cabbage maggot and seedcorn maggot by now, but we are at peak emergence for both insects this week. With plant growth delayed by cold weather, take extra care to scout and protect your crops if necessary. Both insects are attracted to yellow. By placing yellow pails filled with water in your fields, you can keep an eye on populations. The degree day models tell us when emergence is occurring, but population levels will vary, so scouting on your farm can help inform your management decisions. More info on cabbage maggot and seedcorn maggot.


Last week we reported that cutworms have been flying in to Minnesota, particularly in the Western part of the state. Based on degree day modeling, the IPM program estimates that they've already started feeding, and they will likely start cutting soon (in the next week or so). This is mostly a problem for field crop farmers, but cutworms are generalist feeders, and we sometimes see them on crops like cucumbers. They are rarely stand limiting.

Seed borne diseases

As you're transplanting, take stock of any plants that look stunted, and plants with brown, yellow, or shriveled roots. Discard these plants, as they are likely to be diseased. We've already heard reports from growers of Alternaria leaf spot in Brassicas, and a likely case of angular leaf spot (to be confirmed) in cucumbers.

Ps - if you have not heard the good news, we've been conditionally approved for a Specialty Crop Block Grant for the 2021-2022 seasons to investigate tolerant cultivars to black rot and Alternaria leaf spot in broccoli! 

Educational opportunities

What's Killing my Kale podcast: we're uploading new episodes every couple of weeks! This week's series is about setting up your cucurbit plantings for success. 

Great Lakes Vegetable Producers Network: join us during your lunch break on Wednesdays for a 30 minute discussion about vegetables. Next week's topic (May 20th, 11:30am) will be about pumpkin planting. 

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