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Weekly vegetable update 8/26/2020

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

Crop report

At this point in the season, a lot of crops are winding down. I'm going to stop giving updates about every crop, and instead only mention those that I have something interesting to say about.
  • Cucurbits: Farmers have started to harvest some of the smaller winter squashes such as acorn and some hubbards. Watermelon harvest is ongoing. I spoke a bit too soon about melons and pumpkins / winter squash being relatively disease free this year. I saw a particularly bad case of Anthracnose in cantaloupe this week, as well as more virus symptoms in watermelons. At this point in the season it is still worth treating powdery mildew, as it's important to have good canopy cover in late August to protect ripening fruit from sunburn. Some growers may be seeing heat stress symptoms (wilt, slightly yellowing leaves). 
  • Tomatoes and peppers: Tomatoes and pepper production are quite variable around the state. Some farms are slowing down field production due to diseases or simply because the plants are slowing down. Others are just ramping up, particularly with pepper harvests. I am seeing a lot of splitting, which is related to water management - often too much water at once, especially following dry periods.
  • Cole crops: While we've seen less disease pressure than normal this year, I'm starting to get a lot more reports of Alternaria leaf spot and Black Rot in fall successions of Brassicas. With the heat this week, I also expect to see some brown bead in the week or two to come.
  • Sweet corn: Corn earworm continues to be a problem. More info here. If you have late successions of sweet corn that you don't plan to harvest for a few weeks, keep a close eye on disease management. 

Problems in the field

Opportunistic insects and fruit splitting

 I received a higher volume of calls and emails about "new" insects this week than probably ever. By new, I mean insects that I have never seen before in vegetables. In almost all cases, the insects were not the ones causing the damage, they were simply taking advantage of an existing problem. For example, one farmer was seeing Bumble Flower Beetles on an okra plant that was experiencing fruit decay. I also received some more reports of picnic beetles. In most cases, the initial problem was related to fruit splitting. I will do some deeper dives this winter on the blog about irrigation management, but for now I will just reinforce the importance of consistent moisture, especially when temperatures are fluctuating so much. Check out our recent Great Lakes Vegetable Producer's Network episode (links below) about irrigation for more information. 

Bumble Flower Beetle, Photo: Judy Gallagher, Flickr

Black rot and Alternaria

These two diseases have almost come to define fall Brassica production in MN. After a relatively low-disease pressure year, I'm starting to see a lot more of both. I ended up having enough to say about management that I wrote a whole separate article, which you can find here. 

Some basic takeaways are: 

  • Fungicide options for organic growers are unreliable and can even reduce yields

  • Sanitation is key - especially consider how you're moving through fields each day and try to avoid moving from diseased fields into clean fields

  • Especially for Alternaria, it's really worth considering straw mulch.  

Phytophthora capsici?? 

In today's weekly Great Lakes Vegetable Producer's Network webinar (you can also listen as a podcast), we discussed Phytophthora capsici with Chris Smart from Cornell. It was a great discussion, and I realized that I don't know as much as I should about the distribution of this pathogen in Minnesota. I know of two farms that deal with it - one in Dakota County and another in Benton County. This leads me to suspect that others deal with it too and just haven't reported it. This is a serious pathogen that requires intensive management, and I would talk more about it if I knew that more growers were dealing with it. Have you dealt with P. cap on your farm? 


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 finishing pumpkins, and last week's episode was about Phytophthora capcisi. 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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