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Weekly vegetable update 8/6/2020

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

Most farmers had another lovely week weather-wise - not too hot, and gentle rains across the state. Everything is ahead of schedule, which has made for a couple of chaotic weeks of harvesting while trying to keep up with other farm tasks.

Crop report

  • Cucurbits: Cantaloupe production is ramping up, with many growers reaching peak harvest season. Watermelons are close behind. I've heard reports from a few different growers about vertebrate issues in melons this year, from raccoons to crows. Now is a good time to remove cucumber and zucchini / summer squash plants that are winding down, as they can be disease sources for other cucurbits.
  • Tomatoes and peppers: Tomatoes and peppers are reaching peak summer production. I'm seeing a lot more blossom end rot issues this week - make sure you're irrigating and maintaining soil moisture. We're also reaching the time when the flowers being produced now might not make it to full maturity before the first frost. In the week or two to come, consider pruning out flowers to allow plants to invest more energy in ripening their existing fruit.
  • Cole crops: This has been a generally good week for cole crops - we've had a few nice, not too hot weeks for good head development. Flea beetles are (mostly) under control, and while we're seeing some diseases, few are very advanced at this point. Keep practicing good preventative disease management and managing for the three cole crop caterpillars.
  • 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. 
  • Onion harvest is ongoing. Soft rots do well in hot weather, so take extra precautions this year during harvest to avoid bruises and scrapes, which allow soft rots to enter the bulbs. Take some extra time with your storage onions to sort out anything that is bruised or scraped.
  • Potatoes: harvest times vary considerably - some farmers have already harvested their potatoes, and others won't harvest for another month or so. See the onion advice above - I'm seeing more and more soft rot issues lately, so it's worth investing the time to remove potential sources of disease from any potatoes you plan to store.
  • 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. 
Habanero harvest in Long Prairie, NH

Problems in the field

Aging cucurbit plantings

 With all of the activity of the last couple of weeks, it's been hard to stay on top of everything. As early plantings of cucumbers and summer squash / zucchini wind down, they become very susceptible to various diseases. Get these plants out of the field as soon as possible, as they serve as a source of spores, bacteria, etc. in your field, which can impact other cucurbit plantings, as well as future plantings.
Old plantings of cucumbers are more likely tosuffer from various diseases, NH

Moisture problems

I have seen more blossom end rot this year than probably ever before. While this problem is not entirely due to inconsistent moisture, moisture is a big part of the equation. If you have not done so already, really consider investing in a soil moisture monitoring system - these can range from very fancy systems costing thousands of dollars, to pretty simple systems with $30-40 sensors, and $150-250 handheld devices that connect to the sensors. Most of the farms I've visited are chronically under-watering. at this point in the season, you should be watering for a couple of hours every 2 days or so for optimal fruit set. Though, this of course depends on your soil and the weather.


I'm starting to see more bacterial diseases this week, including black rot (cole crops), and bacterial spot and speck (tomatoes). I've also started to get reports of Phytophthora pathogens in various crops. Ben Phillips, a veggie colleague at Michigan State, recently compared Phytophthora to diabetes - once you have it, you pretty much have it for the long-haul, and it takes regular concerted management to keep it under control. Start by investing in a few key preventative steps, such as power washing your tractor wheels and boots as you move from field to field.

Make sure you're identifying diseases as you see them; send samples to the plant disease clinic for verification.


Picnic bugs: I was surprised this week to see a major infestation of picnic bugs in a tomatillo field. In many cases, they were entering the fruit through cracks related to moisture, but in some it actually looked like they were creating holes in otherwise healthy looking fruit. I consulted with some UMN entomologists, and their guess was that another pest like corn earworm was doing the initial damage, and then the picnic bugs moved in and irritated the initial culprit enough that it moved out. While I doubt many of you are having picnic bug issues this week, I thought I'd share it as an example of the fact that things are not always as they seem, so it's good to do some investigating before developing a treatment plan.

Picnic bug inside a tomatillo, NH

Mites, and aphids: I'm seeing a lot of aphids and mites this week. These insects, especially mites, are often impossible to see unless you're looking closely. You may start to notice tiny white specks on plant leaves (spider mites), or leaf elongation, wrinkliness, and leaf bronzing (broad mites). In general, these sap sucking insects will cause stunting. Make sure you're scouting regularly and checking the undersides of leaves for mite and aphid presence. See the Midwest Vegetable Production Guide for product recommendations; various OMRI approved products can also be used for mites, but most are contact products, so use a higher spray pressure for good coverage.

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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