Weekly vegetable update

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

Now that the growing season has started, I'll be posting weekly vegetable updates with a crop report, problems or interesting things we're seeing in fields, a pest forecast, and educational opportunities. Since we are not able to travel to farms due to COVID-19, we have a little less insight this year than we typically would. 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): hoida016@umn.edu
Fruit questions go to Annie: kloddann@umn.edu
Food safety questions go to Annalisa: hultb006@umn.edu

Crop report

After a few years of nonstop spring rain, we've had a lovely spring with plenty of dry days for bed and field prep. With a few dry days in the forecast and weather that will be a bit too cold for transplanting, consider getting out and establishing some stale seed beds, or getting your raised beds ready for transplanting. 

• Garlic - It's time for a final N application if you have not done so already. Applications should be made when plants are between 4 and 6 inches tall. Typically you want to do your spring fertilizer applications before the first week of May but things are a bit delayed this year since it's been cold. That said, don't hold off too much longer or you could delay bulb set. More info on garlic management. 
• Cole crops are going in. Some experienced frost damage this week, but will likely recover. Keep an eye out for cabbage maggot for the next couple of weeks. 
• Potatoes are being planted. Some growers started last week, others are planting now.
• Asparagus is coming up in Southern and Central MN.
• Peas are establishing, and most early season direct seeded crops are emerging in Southern to Central MN. 

Image: Natalie Hoidal. Ideally fertilize your garlic before this point!

With the cold weather forecasted for this weekend and early next week, consider holding off on transplanting for a few days until this cold spell passes (even cool season transplants).

Problems in the field

Most crops are off to a healthy start with few problems to report!

Mysterious frost damage

Image: Meg Cowden

We've seen some very odd damage in Cole crops across the region, including nearby states. The youngest leaves are essentially peeling away on the lower leaf surface; the epidermis separates from the rest of the leaf, the parenchyma (cells in the inside of the leaf) separate from each other, and the upper leaf surface becomes distorted. We've shared these photos with experts around the region, and while it does not look like standard frost damage, the best guess is that this is a result of cold weather, and potentially ice crystal formation in the leaves. Have you seen this type of damage on your farm? If so, we're curious to hear about it to get a better sense of how widespread this damage was. 

Greenhouse issues

I've received multiple photos of transplants over the last couple of weeks that indicate over-watering. While some of the photos came from beginning growers who are just getting the hang of things, some came from experienced growers as well. One of the most common causes is that a grower will try a new potting mix, or in some cases they'll use the same product, but the texture seems different from bag to bag.

Grower submitted photo

During cold weather, your plants will not be actively growing much, and will thus not take up much water. If you stick to a scheduled watering regime in your greenhouse (or wherever you start your seeds), you're likely to end up over or under watering. Rather than sticking to a preordained schedule, keep an eye on the weather and your plants, and water accordingly.  Some telltale signs of over watering are: green algae-like growth, brownish or soaked perlite, and soils that are visibly wet.

Every once in a while I get a very mysterious photo from a grower. This week's photo showed peppers coming up without any cotyledons. After some investigating, we figured out that mice were the most likely culprit, and that they were chewing off the cotyledons and leaves as soon as they emerged. Greenhouses are warm, protected places for mice, so keep an eye out and consider setting some traps!

Pest forecast

Cabbage maggot should be emerging across the lower half of the state this week, as will seedcorn maggot. Both of these insects are attracted to fields with rotting organic matter. If you've just disked / chopped a cover crop and have decomposing matter in your fields, take extra care. They tend to be worse in very wet and cold years. This year has not been wet, but it's been cool, so germination and seedling growth may be delayed, thus making plants more susceptible to these insects than they would be in a warmer year. 

Cabbage maggot: consider holding off on planting cole crops (if you haven't started already) until the first generation of maggots has laid their eggs. Using row cover for a couple of weeks will also help to prevent egg laying. 

Seedcorn maggot: this insect has a wide host range, but will lay its eggs at the base of cole crops as well as snap beans, kidney beans, sweet corn, and cucurbits. Waiting to plant is one option, as is row cover. 

Both insects are attracted to yellow. By placing yellow pails filled with water in your fields, you can keep an eye on populations. The degree day models tell us when emergence is occurring, but population levels will vary, so scouting on your farm can help inform your management decisions. 

More info on cabbage maggot and seedcorn maggot.

Educational opportunities

What's Killing my Kale podcast: we're uploading new episodes every couple of weeks! This week's series is about measuring soil biological activity, and nutrient management in wet soils. 

Great Lakes Vegetable Producers Network: join us during your lunch break on Wednesdays for a 30 minute discussion about vegetables. Next week's topic (May 13th, 11:30am) will be about bed prep and transplant holding.