Weekly vegetable update 6/22/22

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

Following some extremely hot weather, the week ahead will provide some respite. As many crops reach their "critical periods" for development, consistent irrigation will become critical. Take some time this week to take stock of your irrigation plan to make sure your soil moisture is not fluctuating too dramatically.

Crop updates

• Tomatoes: The very first tomatoes are ripening in high tunnels, and field grown tomatoes are flowering and beginning to set green fruit. A lot of people are seeing blossom end rot. Even if you have watered consistently and supplied plenty of nutrients, it's common for the first few fruit to have it. This is especially true in very hot weather, as the heat results in rapid cell division, leading the fruit to grow faster than the plant can get calcium to the new cells. If you're seeing more blossom end rot than usual, don't panic! Just remove the fruit with symptoms so the plant can put its energy into new, healthy fruit.

• Garlic: Scape removal continues this week, which means we are about 3-4 weeks out from garlic harvest. As I mentioned last week, it's worth taking the time to do this carefully and by hand vs. trying to mechanize scape removal, as leaf damage at this stage can result in bulb yield decline. In these next few weeks, your garlic will size up considerably, and even moisture is important for good bulb development. Keep irrigating until at least 50% of the leaves have turned brown. 
  

• Potatoes: Many potato fields are flowering this week. This means that tuber bulking has begun, and we've entered the critical period for consistent irrigation. Maintaining consistent moisture will help you to avoid scab and hollow heart, two common problems for Minnesota potato growers. 

Potatoes in full bloom at a community garden in St. Paul. Photo: Natalie Hoidal

• Carrots: Probably due to the erratic rainfall, carrot germination has been spotty. Some farms haven't had an issue, and some have had near total losses. It's still not too late to plant a short season carrot for fall harvest if your previous successions have not germinated well.
  

• Cole crops:  Early broccoli and cabbage plants are starting to produce small heads. Continue to monitor regularly for the three cabbage caterpillars.

Lifecycles of common Brassica pests. See the full-size page here.

 

• Cucurbits: I'm starting to see (small) cucumbers and zucchinis in CSA boxes and farmers market stands. Cucumber beetle pressure seems surprisingly low, but it's possible that I'm just not hearing about it since this is a common insect pest that people typically have to deal with every year. We did see a squash vine borer adult flying at the arboretum in Chaska, so begin to keep an eye out for adult moth flights.  
  

Problems in the field / things to do this week

Irrigation check

As irrigation season begins, take some time to make sure your irrigation system is in proper working order. Our colleagues at Michigan state wrote this article last week with a list of things to check on. Their irrigation systems may be a bit bigger than what most Minnesota growers use, but many of the things on the list are still relevant.

Deformed pepper plants

Most of the pepper plants I've seen this summer have looked a little funky. This can happen for a variety of reasons, and sometimes it's difficult to dinstinguish symptoms from one another. There are three main things that can cause peppers to look like the plant in the photo below (basically, curled and deformed leaves).

 

Peppers with mottled leaves. Photos: Natalie Hoidal

 

1. Herbicide drift

 

It's been a hot and windy couple of weeks, following very wet weather that made it hard for farmers to apply their herbicides on time in the spring. This means that field crop growers may be spraying herbicides later than they typically would, and conditions are ripe for drift and volatilization. Usually if you're experiencing drift, you will see similar symptoms across the farm, with various crop families impacted.

 

2. Thrips, mites, and aphid feeding

 

These small insects are often difficult to see because of their size, and because they often spend time on the lower sides of leaves, or in plant crevices. They have straw-like mouthparts, allowing them to feed on plants without causing obvious large holes (like insects with chewing mouthparts would). Instead, their feeding can cause leaf deformations, and a general chlorotic appearance (yellowing leaves). Scout carefully for these insects if your pepper plants look deformed, as they may not be immediately obvious. These insects are very common in tunnels. Sometimes we see heavy feeding damage on transplants early in the season, and even if insect pressure decreases in the field, the foliage can remain deformed. These insects can also transmit viruses, so it's important to scout for them often.

 

3. Variety

Some peppers are honestly just odd looking. In our pepper trials over the years, we've found that habanero peppers and other very hot peppers like ghost peppers tend to have a more mottled appearance overall with curlier leaves.

Curiosity insect: Hackberry emperor

I don't know whether others are experiencing this right now, but I can't go outside without being swarmed by butterflies. My plants are covered in them, and they are especially attracted to animal feces. It turns out that they (at least the butterflies I'm seeing in Dakota County) are Hackberry emperors. If you have more than 1 hackberry tree near your farm and you live in Central or Southeast Minnesota, chances are you've seen them too. Since they eat animal poop, farms with livestock or dogs may be more likely to have higher populations. These insects lay their eggs on hackberry trees and are not considered a pest of any vegetable crops.

 

Hackberry skippers congregating on dog poop. 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.