Weekly Vegetable Update 8/25/22

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

My colleague David said something this week along the lines of "at this point in the season, the cake is already baked". This is definitely true to some extent; the finish line is getting closer, and at this point most of what we're seeing in the field is a direct result of weather and management decisions that have already happened. But, we're still seeing some interesting things in the field, and there are still some important management decisions to make for fall crops as well as practices to implement now that can make your life easier next spring.

Problems in the field / things to note this week

Plant legume cover crops asap

While there is still plenty of time to plant cold hardy winter cereal cover crops, the windows for reliable establishment of many cover crops are closing in. Especially if you're hoping to plant a legume cover crop this fall, review the Midwest Cover Crop Council's decision tool to see the reliable establishment window for your county.

Take time to gather your notes from the season

Have you ever made a list of mental notes during the growing season and promptly forgot it by

the time February rolls around? I have done this more times than I’d like to admit. Before the

season is over, take a walk through your fields with a notebook and write down a list of all of the

insect pests that caused you trouble this year, any diseases you noticed, varieties that seemed

to perform better than others, and notes about things like mulches, row spacing, etc. So many of

the issues that we deal with on farms are best addressed preventatively with things like resistant

varieties and preventative pest management plans. By taking the time now to note exactly what

you’re dealing with, you can develop better management plans for next year.

 

Beyond your own notes, consider asking your crew to weigh in. I worked at a farm for a couple

of years with a giant map of the farm on the wall covered in plexiglass. Crew members were

asked to write notes on the board about things they noticed in the field, and each week we met

for 15 minutes to review what we noticed that week. The manager took photos of the board

each Friday and committed these photos to a notes folder, which he reviewed each winter.

Different people noticed really different things, and our collective brainstorming and discussions

each week led to quite a few management improvements on the farm. Even if you’re not doing

this regularly, a brainstorming session at the end of the season may provide valuable insights.

 

Finally, make sure you’re correctly diagnosing problems. Disease problems and nutrient

deficiencies can be very hard to distinguish using just your eyes and online tools. For significant

issues, consider sending samples to your local diagnostic clinic, or submitting tissue samples to

your local soil testing lab for foliar nutrient analysis. This will allow you to ensure that you are

selecting the right resistant varieties, or the right inputs for next year.

Crop updates

• Peppers and tomatoes: This week I've been working through a tricky technical assistance issue in peppers. A grower in Western MN is seeing internal fruit rot in 100% of his serrano peppers, but the plants and fruit look perfect on the outside. We know it's not seedborne because some other farmers are growing the same plants (same seed source, grown in the same greenhouse). Typically these internal rot diseases enter through the flowers or when the fruit are very young, and stay dormant until the fruit starts to ripen. This is especially likely when the flowers are wet for an extended period of time. Read more about these internal rots here. Tomatoes: I continue to get a lot of photos of cracked tomatoes. In most cases, people aren't watering enough between rainfall events. 

Internal fruit rot in serrano peppers. Grower submitted photo.

• Cucurbits: At least in the fields I've seen, this has been a pretty good year for powdery mildew. Typically we see much more widespread powdery mildew by this point in August. Many peoples' pumpkins are ripening and turning color already. As long as you have good foliar coverage, this isn't a huge problem. If you are losing significant foliage due to powdery mildew and other things, start to think about harvesting your pumpkins early and curing them in the shade to prevent sunburn. 
  

• Garlic: Last year I noticed pock-marked garlic at quite a few farms around the state. Many of the growers I visited said things like "oh this is just what garlic looks like sometimes". It turns out these pock marks are (in most cases) caused by microscopic garlic mites. While it's safe to eat garlic with mites, they can decrease the shelf life, and decrease yields. Take some time to go through your planting stock to make sure it is mite free. If not, there are some simple treatments you can do, like soaking the cloves in 2% mineral oil for 24 hours to kill them. Read more about bulb mites here.
  

Photo Source: Lindsey du Toit, Washington State University

• Cole crops: We did our second round of inoculations in our black rot trial this week. The June 1st planted trial had all kinds of issues, including pretty heavy disease pressure from both black rot and Alternaria (which in terms of our goals for the trial is great, but less great for growers who need a good crop).  Bolting Brassicas can be a really great resource for pollinators in your field. If disease pressure is low, consider allowing your bolted crops to flower for a bit. However, if disease pressure is high, it's worth removing residues immediately to prevent disease spread to younger crops. 

 Bumble bees and soldier beetles enjoying broccoli flowers. Video: Natalie Hoidal

• Sweet corn: Corn earworm trap counts remained high in Blue Earth last week, and started to increase in Rosemount. I saw some very odd corn in Waseca too. There are only a few Bt sweet corn varieties available. One common variety with good flavor is called Remedy, but one downside of this variety is that it can create some odd / ugly ears, and husk development can be less than ideal. Charlie Rohwer in Waseca reported that processing sweet corn yields are coming in very high in Southern Minnesota (~8.5 tons / acre in their research station trials, and other reports of good commercial yield).
  

Sweet corn with improper husk development. Photos: 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.