Weekly vegetable update 7/20/22

Author: Natalie Hoidal, UMN Extension educator, local foods and vegetable crops 

The main story this week is the heat. Keeping yourself and workers safe can be challenging during intense heatwaves, and plants are struggling to keep up. We also experienced the first wildfire smoke related air quality effects this season, and forecasters are predicting that we may see more air pollution in the coming weeks.

Problems in the field / things to note this week

Expect limited fruit set in tomatoes, peppers, zucchini, cucumbers

Hot weather, especially when it remains hot at night, is bad news for many vegetables. The heat causes a variety of problems including flower and pollen deformation, changes to the ratio of male to female flowers in cucurbits, and poor pollination due to decreased pollinator activity. High heat can also interfere with fruit maturation. Due to the current heat wave, expect more fruit and flower abortion, and delays in ripening. You can read more about these issues in this article from last year. 

 

A pumpkin fruit that was unable to mature due to poor pollination. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org.

Deadline for frontline worker pay 7/22

This Friday at 5pm is the deadline for applying for MN frontline worker pay. To be eligible, you must meet the following criteria:

• Must have been employed at least 120 hours in Minnesota in one or more frontline sectors between March 15, 2020, and June 30, 2021 (this includes agriculture!)
• For the hours worked during this time period the applicant –was not able to telework due to the nature of the individual's work and worked in close proximity to people outside of the individual's household;
• Must meet the income requirements for at least one year between Dec. 31, 2019, and Jan. 1, 2022–workers with direct COVID-19 patient care responsibilities must have had an adjusted gross income of less than $350,000 for married taxpayers filing jointly, or less than $175,000 for other filers and for workers in occupations without direct COVID-19 patient care responsibilities, the adjusted gross income limit is $185,000 for married taxpayers filing jointly, or $85,000 for other filers; and must not have received an unemployment insurance benefit payment for more than 20 weeks on a cumulative basis for weeks between March 15, 2020, and June 26, 2021.

To apply, visit: https://frontlinepay.mn.gov/submit

Compost woes

I visited two urban farms in the last week that were growing vegetables on pure compost. It wasn't working very well in either case. Germination was really poor, even for weeds, and transplants were stressed. We decided to test the compost and found that in both cases, the electrical conductivity was above 4. This is one of the potential issues with growing in compost, and with deep compost mulch systems. Compost can be high in salts, and when this is the case, it can inhibit germination. 

This does not mean growers shouldn't use compost! There are a few best practices that can help you avoid issues: 

• Don't grow in 100% compost - make sure it's mixed in with soil
• Test your compost when using large volumes and make sure the salt levels are reasonable. Over time the salts will leach with rain water, but this can take a year or more.
  

Not much growing in these compost beds, even weeds. Photo: Natalie Hoidal

Crop updates

• Tomatoes and peppers: Peppers are coming in more reliably this week, while tomatoes seem to be slower. Tomatoes tend to resist ripening when conditions are really hot, so don't be too worried if you feel like your tomatoes have been green longer than they should be. You may notice a dip in production of new fruit associated with the heat wave this week.
  

• Garlic: We are getting close to garlic harvest! Most of the garlic I've seen is still a couple of weeks away. The ideal time to harvest is when 50% of the leaves have turned yellow.
  

• Peas: I've seen powdery mildew really take off this week in peas. If your peas are slowing down production considerably, consider just removing plants, especially if fall peas are important to your farm. 
  

• Cole crops:  This is the time when we really start to see varietal differences in broccoli and cabbage. In our June 1 planted broccoli trial in Waseca, we are harvesting consistent and large heads from some varieties, while others have not even begun to form their heads. Some are tolerating the heat well, while others are not at all. Our two earliest varieties so far have been Monty and Castle Dome - the Monty heads have been quite nice, whereas the Castle Dome heads are showing signs of heat stress. We're seeing the standard caterpillar feeding on cole crops at this point, and a little bit of black rot and Alternaria. So far I have not seen any major disease issues, which makes sense given the heat and lack of moisture.  

"Castle dome" broccoli. Leaves growing through the head is a sign of heat stress. Photo: Natalie Hoidal

• Asparagus: At this point in the season, farmers are busy and asparagus often gets ignored. However, this is also the time when asparagus diseases start to emerge, and they can have impacts next year. Take some time every couple of weeks to scout your asparagus field and check for disease pressure. See the Growing Asparagus in Minnesota guide for an overview of the top 5 asparagus diseases in MN and their management.

• Carrots: Spring planted outdoor carrots are now reliably ready to harvest in most parts of the state. 
  

• Cucurbits: Winter squash and pumpkins are flowering, and in a few cases, beginning to set fruit. This is around the time we typically see squash bugs ramp up, so continue to actively scout your cucurbits for squash bugs, cucumber beetles, and squash vine borer. Field cucumber harvest is ramping up, providing a welcome replacement for growers who are having trouble with spider mites in their tunnels.
  

• Sweet corn: The first sweet corn of the season is making its debut at farmers markets around the state. I've heard some growers say that maturity has been slow and spotty this year, most likely correlated to uneven rainfall. I've seen some northern corn rootworms, which are typically not thought of as a major pest in sweet corn as long as you are rotating. European corn borer counts are still quite low across the state, but the degree day models suggest that adult moths will be flying across the Southern half of the state this week. With limited corn tasseling, ECB sometimes lay their eggs in peppers.
  

Northern corn rootworm on a corn plant. Photo: Natalie Hoidal

Connect with the fruit & vegetable team

If you're seeing interesting things in your fields, need help identifying problems, or just want to share photos, we'd love to hear from you! Growers can reach out directly to me any time at hoida016@umn.edu, and you can submit questions and diagnostic help below.