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Weekly vegetable update 8/20/2020

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

After a truly devastating week for many farms (hail), this week was relatively calm with moderate temperatures and minimal rainfall. Most summer crops have reached peak production, and fall crops are coming along nicely.

Crop report

  • Cucurbits: Watermelons are ripe across most of the state. Acorn squash is close behind; many farmers in Southern Minnesota will be ready to harvest next week. Most cucurbits seem to be relatively disease-free this year (except for the mosaic viruses that showed up earlier this year), though powdery mildew continues to be a problem for growers not using resistant / tolerant varieties. I haven't received many reports of cucumber beetles being a problem at this point in the season. Continue to keep an eye on squash bugs. 
  • Tomatoes and peppers: Tomatoes and peppers are reaching peak production. Chiles are heating up (after harvesting for a few hours I could actually feel the capsaicin on my hands). Blossom end rot issues tend to slow down at this point in the season after the first flush of fruit, though it's still around here and there. Remove all flowers at this point for optimal production. 
  • Cole crops: Based on the very high late season flea beetle populations, I'm working with some UMN entomologists to try to figure out what's going on. If you are seeing a lot of flea beetles, please consider sending a sample! You can reach out to me for details. Physiological issues like brown bead and hollow stem seem to be less problematic than they were a couple of weeks ago, likely due to the cooler weather we've had. Cabbage caterpillars continue to cause problems. Bt is the go-to for cabbage caterpillars, though if you're seeing mostly caterpillars you may have more luck with spinosad at this point in the season.
  • Onion: Onions are laying down, and harvest is ongoing. The onions I've seen lately have been healthier than those harvested earlier in the summer (less soft rot), and thrip populations seem to be down. That said, continue to look for damaged bulbs as you harvest and pack, and remove anything that looks bruised or scraped. 
  • Potatoes: Same update as last week: While most potatoes are looking pretty good this year, I have received a slow trickle of questions about soft rot and scab. Potatoes with soft rot should be discarded immediately. Potatoes with scab are technically edible if peeled, but take extra care if you choose to store these potatoes, as they are more susceptible to secondary rots.
  • Beans: Beans continue to have some insect issues including leafhoppers, spidermites, and now Northern corn rootworm (see below). However, in most cases none of these insects have reached economic thresholds.
  • Garlic: Now is a great time to buy seed if you've not done so already. See last week's post for guidance. 
  • Sweet corn: Corn earworm populations are up this week in Southern Minnesota. Our entomology team expects that we will continue to see elevated populations for the next 4-5 weeks. More info here.
Onions laying down, ready for harvest, NH
Cabbage caterpillar damage, NH

Problems in the field

Impacts of hail 

After taking stock of last week's hail storm, many growers are realizing just how bad the damage was, with farms reporting over $100,000 of damage. This is truly one of the worst things that a farmer can experience, and it happened at the worst time possible. 

The first thing I want to share about hail is that the USDA is soliciting feedback about crop insurance options from farmers that sell into local markets. They are exploring the possibility of a new crop insurance program, and the need for this could not be more clear. While no one knows exactly what will come of these sessions, it's a good opportunity to make sure that policymakers hear from you all as they develop this new program. The Minnesota listening session for producers will be August 24th at 12pm. Here is the Zoom call information: 

Zoom information:
Passcode: local Meeting ID: 873 7287 2344

Telephone participants: +1 312 626 6799
Meeting ID: 873 7287 2344 Passcode: 746512 
The second thing I want to share is a list of mental health resources from MDA: Farming is hard enough in a good year, and this year has included so many additional stressors. With so many layered stressors (and exhaustion at this point in the season), we can only navigate so many new crises. MDA and Extension have a variety of resources and support available for free to farmers. See the link above for more details.

Residue management

In disease-heavy crops like Brassicas, make sure you're removing residues as soon as you harvest. In the field pictured below, the grower harvested cabbage about a week ago, but the plants were still in the field showing a lot of black rot symptoms. This time of year is so busy and it's easy to put field clean up at the bottom of your to-do list. However, especially where diseases are present, either removing residue or chopping it and tilling it under will help to reduce disease pressure next year. 

Cabbage plants after harvest with black rot, NH


Most Minnesota vegetable farms have successfully kept COVID-19 off of the farm this year. However, as schools start to open and our economy continues to open up, we should remain vigilant about prevention. I really encourage farm managers to start thinking about cohorting if you're not doing it already. There are many tasks on a farm that can't be done with 6' of distance, but you can still divide your crew into teams. That way if one person gets sick, they'll be less likely to spread it to the whole crew.
Creating cohorts can reduce transmission between crew members. Image NH.

Corn rootworm defoliation

The final thing I'll share this week is a sub-par image of Northern corn rootworm feeding on beans. If I had taken a better picture, you'd see that the beans were experiencing high defoliation pressure (~50% leaf area loss) on the upper 1/4 of the plant, but the bottom 3/4 or so looked fine. Sometimes defoliation can look more severe than it really is at first glance, as was definitely the case in these beans. 

Technical Assistance

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:

Educational opportunities: things to listen to in the field

Great Lakes Vegetable Producers Networkjoin us during your lunch break on Wednesdays for a 30 minute discussion about vegetables. All previous episodes can be downloaded as podcasts, and are available on Apple Podcasts. Next week's episode will be about Phytophthora, and last week's episode was about chile peppers. You can also visit the network page for recordings of all previous episodes, and listen along to the mp3 recordings while you work.

Also remember that What's Killing my Kale is ongoing, with recent episodes about flowering and fruit set in cucurbits, apple crop load management, measuring soil health, nutrient management in wet soils, Spotted Wing Drosophila updates, and climate change adaptation. These episodes are also available through the Apple Podcasts app, or can be downloaded directly online.

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