Skip to main content

Weekly vegetable update 7/2/2020

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

The weather went from hot and dry to humid this week. After some intense rainfall and flooding of fields, we're facing at least 10 days or so of high humidity. Stay extra vigilant about disease monitoring. This is also a very busy time of year - remember to take breaks and drink plenty of water!
  • Tomatoes and peppers are setting fruit, both in the field and high tunnel! Some of you are already harvesting tomatoes this week. Tomato disease season seems to have begun - keep scouting regularly. For fungal pathogens, pruning out diseased tissue when conditions are dry (and regularly sanitizing your clippers) can help to prevent disease spread, as can preventative fungicide applications. 
  • Cole crops are being harvested, and second successions are being planted. Diamondback moths are still present, and we're seeing more and more imported cabbage worm. After three terrible years of black rot and Alternaria, disease pressure is limited this year (hooray!). 
  • Cucurbits: are vining and flowering. Cucumbers are setting fruit. I'm seeing various diseases in cucumbers this year, and fewer in melons. The next couple of weeks will be key for pollination and flower development. 
  • Asparagus has reached the fern stage for most growers at this point. Invest some time in weed management this week as the fern canopies start to fill in. 
  • Garlic is in the bulb forming stage. Some of you are thinking of harvesting in the next week or two. For large plantings, start spot checking semi-regularly to see how far along your garlic is. 
  • Potatoes are flowering. Colorado Potato Beetles are VERY active this year, as are leafhoppers. For organic growers, we've passed the point where most insecticides will be effective. 

Problems in the field

Too much water; soaked plants

Water soaked spots in lettuce. Photo: Fresh Earth Farms
This Monday I received photos from two different growers showing water soaked lesions on lettuce. It almost looked like bruising from hail damage, but there was no hail. We hypothesized two causes: either there was just so much water that the leaves became saturated (the pore space between cells filled up with water), or there was actually some cell wall breakage that caused bruising. In both
cases, the majority of spots cleared up over the next couple of days, but a few remained. If you have remaining spots from water damage, it is likely that you had some cell walls burst, in which case shelf life will likely be reduced. Communicate with your customers that they should eat the water damaged crops quickly to prevent spoilage.

Soft rot and flowering issues in cucurbits

Summer squash and zucchini tend to develop female flowers before they develop male flowers, and so early in the season we often see some parthenocarpic fruit (non-fertilized fruit produced by female flowers). These zucchini and squash tend to stay quite small and often have a funny curved shape. This is fine for growers with CSAs and farmers markets who want to get early veggies to their customers, and whose customers tend to be more forgiving than wholesale markets. Harvest these fruit early; since they remain small, we often leave them on the vine too long thinking they'll grow, and they become susceptible to soft rots.  

Physiological issues

Blossom end rot in summer squash
Gerald Holmes,
We are seeing pretty major swings in precipitation and temperature. It was hot and dry for a few weeks, followed by intense precipitation and flooding. We're now seeing some more hot days without rain, with storms in the forecast next week. Variable conditions like this can lead to all sort of physiological issues related water-transported nutrients. These include things like blossom end rot,
boron deficiency symptoms, and hollow heart. Make sure you're actively monitoring soil moisture and trying to maintain fairly stable moisture conditions using irrigation.

Insect and disease forecast


This week has been extremely humid, and we can expect more humidity in the forecast. 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).

Whitney Cranshaw, Colorado State University,
We're starting to see Aster Yellows symptoms in ornamental plants, and we've seen evidence of aster leafhoppers in fields. The University of Wisconsin's commercial vegetable grower manual has an excellent guide to aster yellows thresholds on page 16, based on susceptibility of your carrot variety. Keep in mind that you may also see potato leafhoppers in carrot fields; potato leafhoppers do not transmit aster yellows. Aster leafhoppers are a dark olive green color, whereas potato leafhoppers are a light, neon green. 


Not a lot of new information here. We continue to see high populations of cucumber beetles, potato beetles, potato leafhoppers, cabbage caterpillars, fourlined plant bugs, some tarnished plant bugs, and aphids. See reports from the last couple of weeks for more information on these insects.

We've seen a few squash bugs in fields, but not at damaging levels.

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 biostimulants. You can also visit the network page for recordings of all previous episodes, and listen along to the mp3 recordings while you work. Previous topics include:

  • Getting elemental with Boron
  • Avoiding the powdery mildew blues
  • Predicting pest pressure
  • Do's and Don'ts for submitting samples and reading results
  • Hoophouse nutrient mangaement
  • Pumpkin planting for halloween markets
  • The white thread: early season weed management
  • Seedbed prep + healthy transplants: freeze addition
  • Weathering the COVID-19 content storm

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. 

Print Friendly and PDF