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Weekly Vegetable Update 7/30/2020

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

After weeks of intense heat, we finally had some respite. Most growers took full advantage of this week to catch up on harvesting, weeding, and other tasks. We have reached peak summer; tomatoes and peppers are producing in full, and melons are starting to come in. Compared to previous years, we are about two weeks ahead.

Crop report

  • Tomatoes and peppers: Production is ramping up, and most farmers are now harveting tomatoes and peppers regularly. The hot peppers we anticipated harvesting in mid to late August are fully mature already as far north as Long Prairie! We've received a lot of calls and emails about blossom end rot. 
  • Cole crops: I've been seeing much more normal looking broccoli this week. Flea beetles continue to be an issue for some farmers, as do our standard caterpillar insects. Disease pressure is substantially reduced this year compared to previous years. I did get some reports of heat stressed cauliflower, and saw boron deficiency symptoms. For an overview of boron deficiency and what you can do about it, check out our recent Great Lakes Vegetable Producers Network episode (linked below). 
  • Cucurbits: Many farmers harvested their first melons this week. We are in peak cucumber season, and zucchini and summer squash harvest is still underway. I'm seeing more reports than usual of diseases in cucumbers, particularly angular leaf spot and moisaic viruses. 
  • Asparagus: Continue to scout for diseases and asparagus beetles. This period where the ferns are nearly fully developed is the time when multiple foliar and spear diseases show up. 
  • Garlic harvest is complete, and most farmers are curing. We did get some reports of soft rots this year in both garlic and onions; check your storage areas regularly and remove any garlic or onions that seem diseased.  
  • Potatoes: Just north of the Twin Cities we are harvesting potatoes this week. There was such intense defoliation damage from potato beetle that we decided to harvest to prevent the potatoes from rotting in the ground. 
  • Beans and peas: green bean harvest is in full swing. For dry beans or beans that will not be harvested for a while, leafhopper damage remains high. Keep a close eye on fall pea plantings, this year has been pretty bad for pea diseases. 
Boron deficiency symptoms in cauliflower
Photo: NH

Problems in the field

Vertebrate pests

Over the last couple of weeks I've received numerous complaints of vertebrate pest damage ranging from crows eating cucumbers to racoons eating melons to deer eating beans and Brassicas. Last year we interviewed our vertebrate pest specialist John Loegering about the best options for managing these various critters. Check it out on What's Killing my Kale (episode 24, 2019).

Pepperless peppers

Peppers and pumpkins are very sensitive to nitrogen dynamics; we're seeing this play out mostly with peppers this week. Too much nitrogen before flowering can cause the plant to invest in leafy green production instead of flowers and fruit. They are especially sensitive in the couple of weeks prior to flowering. The plant is getting ready to enter its reproductive phase, but too much N can keep it in its vegetative phase. In this situation, you can expect to see reduced flowering.

If you're seeing a normal amount of flowers that are just drying up, it is more likely a pollination or heat issue. Pepper flowers can abort around 90 degrees F; bell peppers are much more sensitive than hot peppers.

Pepper field in Long Prairie
Hot peppers are ahead of schedule in our trials this year
Photo: NH

Insect and disease forecast


The humidity has dropped quite a bit since last week, but keep scouting for diseases. At this point in the summer, I've pretty much seen it all. I continue to see A LOT of viruses, especially in cucurbits. I'm finally starting to see more black rot in brassicas. Alternaria pathogens (early blight in tomatoes and potatoes, Alternaria leaf blight / spot in cucurbits and brassicas, Alternaria fruit blight in peppers). Scout regularly, send samples to the disease clinic for identification, and removed diseased tissue if possible (only when conditions are relatively dry and your hands / tools are clean). Most growers should be implementing preventative spray programs (including organic growers) on crops that consistently have disease issues. 


I heard far fewer insect complaints than normal this week. Our crops colleagues are seeing two spotted spider mite issues in soybean fields in West Central and South Central Minnesota. (More info about TSSM). While we haven't heard reports of spider mites from vegetable growers, they certainly do impact vegetable crops. They are typically problematic in high tunnels, but our warm dry summer
has facilitated their development outdoors. Scout your tomatoes, peppers, and cucurbits for mites, aphids, and other small, soft bodied insects that thrive in hot, dry conditions this week. All of these insects have rapid reproduction cycles and their populations can build rapidly.
Twospotted spider mites adults and eggs.
Photo: David Cappaert, Michigan State University,

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 cover crops; our most recent episode was about irrigation. 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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