Weekly Vegetable Update 8/4/2021

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

After a week of heavy wildfire smoke, the air is finally clearing. While more of the state has entered "extreme drought" conditions, rain is on the horizon for most of us in the coming week. We're starting to get more consistent yields of summer favorites like sweet corn and tomatoes, and pepper harvest is right around the corner. Many farmers are struggling to keep up with weeds, especially with the limited amount of time folks were able to safely spend outdoors last week.

Crop updates 

• Tomatoes: Tomatoes are coming into peak production, and most farms are starting to have enough tomatoes to sell more regularly. We always get a few questions this time of year about funky looking tomatoes, so I wanted to share some of the common physiological issues in tomatoes this week: 
  • Catfacing: Catfacing is a term used when the blossom end of a tomato is scarred, and particularly when that scar becomes elongated. This can sometimes result in oddly shaped fruit. A variety of interacting factors lead to tomatoes with these symptoms, including too much nitrogen, over-pruning, and low nighttime temperatures (which we shouldn't have to worry about this year).
    
  • Cracking: Tomatoes can crack when they grow too quickly, or when they are exposed to large fluctuations in temperature or soil moisture. Cracks can be vertical slits down the side of the plant, or round circular cracks. We often see insects feeding on cracked tomatoes, and sometimes growers assume that the cracks were caused by the insects, but they are almost always a secondary symptom.
    
  • Internal white tissue: This is a common issue in larger slicer tomatoes, and is primarily a response to heat stress. Consistent moisture helps, and some varieties are more susceptible than others.

    

    Catfacing. Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

• Potatoes: The first potatoes are looking and tasting good. They continue to be a bit scabby, but this is to be expected during hot, dry weather. Start to slow down irrigation 4-6 weeks before you plan to harvest.
  
• Cucurbits: This week farmers are harvesting cucumbers and zuchhini galore, and melons are slowly beginning to ripen. This is a good time to check in on your winter squash and pumpkins, especially for powdery mildew and insects like squash vine borer and squash bug.
  
• Garlic and onions: Garlic harvest is mostly finished, and onion harvest continues. Onions are ready to harvest when about half of the onion tops are dry and falling over. Now that we actually have some rain in the forecast, be mindful of soil moisture. Field curing (where you loosen the soil with an undercutter or manually with a spading fork, then let the onions hang out in the soil for a few days) works well when the weather is warm and dry. If you need to harvest onions before a rainfall, bring them indoors to cure. Most onions at this point are for fresh markets, but if you plan to store your onions, read about proper curing and storage here. 
  
• Beans - There seems to be a general abundance of green beans this week, with many June plantings producing all at once. Dry beans starting to develop beans inside their pods, and are looking good across the state with no major issues. 

 

Dry beans forming in their pods. Image: Natalie Hoidal

• Peppers: Peppers are looking good and slowly starting to ripen. Green peppers like shishitos are ready for the market at many farms, and it will likely be a week or so before we start to see significant quantities of red peppers. Just like with tomatoes, the first round of peppers are the most susceptible to blossom end rot, so try to focus a little extra time on keeping soil moisture consistent in peppers this week.
  
• Cole crops: There are no major brassica updates this week. The usual insect suspects are around. There may be some final fall successions going in the field this week, but for the most part planting is wrapping up. We are still not seeing much, if any disease pressure this year.
  
• Sweet corn: We continue to see a bit of poor tip fill and zippering, but most of the sweet corn I've seen looks great without pollination issues. Corn earworm trap counts have been low for the past few weeks, below the threshold of 5 moths / trap / night.
  

Vegetable weather report

There is finally some rain in the forecast for most of Minnesota! Scattered showers are projected today and Thursday, but these should bring very minimal rain. The larger rain storm is expected to come over the weekend, leaving the eastern part of the state with anywhere from 0.75 - 1.25 inches total. The northwestern part of the state, where drought is most severe, is projected to receive less than half an inch over the next 7 days. Temperatures should remain moderate with highs in the 80s, and nighttime lows in the 60s, but we can expect slightly warmer weather (highs around 90) after the storm system passes through early next week.

7 day precipitation forecast, weather.gov

Problems in the field and things to anticipate this week

Talking to your customers about funky vegetables

Based on your feedback, Marissa developed one more fact sheet you can hand out at your farmers market stand or in your CSA to inform your customers about wormy corn. We made similar fact sheets explaining cosmetic issues in potatoes and cucurbits last week.

 

Flavorless melons

I've heard from a few farmers that their melons don't taste great this year, and noticed the same thing with my own melons. Melon flavor is impacted by a few important factors: 

• Water: Overwatering can dilute the flavor of melons. I've seen photos of overwatering symptoms in a wide range of crops this summer - it seems that in our anxiety to keep things irrigated, many of us may be overwatering out of an abundance of caution. This seems to be especially true in high tunnels. The flavor impact of overwatering is most pronounced in the weeks leading up to harvest, so make sure you are slowing down irrigation prior to harvest. 
• Harvesting too early: Make sure your melons have reached their full maturity at the time of harvest. There are a few ways to do this: keep track of the days to maturity on the seed label for a ballpark estimate. If you gently tug on the vine, the fruit should come off easily and cleanly. If you're needing to tug on the fruit, it's not ready. Color is another indicator, but this varies by variety. Typically watermelons will develop a yellow soil spot when they are mature, and cantaloupe melons will lose all of their green coloring. While some melons continue to ripen off the vine, others do not. This is not actually a yes or no situation, but rather a spectrum of continued ripening postharvest. Generally, watermelons do not exhibit significant ripening after harvest, whereas usually cantaloupe do. Honeydew melons fall somewhere in between, with differences between varieties, but generally fairly long shelf life with limited postharvest ripening.
• Diseases: Pathogens like Anthracnose, Alternaria, Gummy Stem Blight, etc. can impact melon flavor. Any time you have significant leaf area loss, the plant loses its ability to photosynthesize and develop sugars. Similarly, plants growing in a very weedy field where they have to compete for nutrients, or plants growth with insufficient nutrients will struggle to produce the sugars necessary for good tasting fruit. 

 

Gently pull on the stem where it meets the fruit. If it doesn't come off easily, it's not ready yet. The green stripes on this melon are another sign that it's not ready to harvest. Image: Natalie Hoidal

Educational opportunities

The Vegetable Beet: join us during your lunch break on Wednesdays for a 30 minute discussion about vegetables. Next week's topic will be about pumpkins.

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 requests for diagnostic help here.