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Weekly vegetable update 7/7/22

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

We are nearing peak summer, when CSA boxes and farmers markets really begin to diversify. After a week of high humidity, disease questions are starting to roll in. Precipitation patterns remain variable across the state; some farmers experienced 4-5 inches of rainfall in a single day this week, while others are experiencing very dry and even moderate drought conditions.

Crop updates

  • Tomatoes and peppers: Most tomatoes and peppers are still a couple of weeks from maturity, and we've received quite a few reports of blossom end rot in developing fruit. This is normal for the first flush; simply remove fruit with symptoms. We're also starting to get more reports of leaf spot diseases; make sure you're scouting and pruning regularly, and sending samples to the plant disease clinic for diagnosis. I saw my second case this year of damage from landscape fabric, this time in tomatoes (last time it was in peppers). The air underneath landscape fabric can be extremely hot, and as it moves in the wind, currents of hot air can harm plant stems. This is especially true for drought-stressed or otherwise stressed plants.
Tomato stem damaged from heat under landscape fabric. Photo: Natalie Hoidal

  • Garlic: A few people have asked questions about Aster Yellows this week. As garlic is beginning to mature, it's normal that we would be seeing some yellowing of tips, so don't assume that yellowing is due to aster yellows. As far as we know from the IPM team's scouting efforts, aster leafhopper has not yet been seen in MN this year. Continue irrigating your garlic to maintain consistent soil moisture until about 50% of the leaves have turned brown.

  • Peas: I've seen some reports on listserv groups about contamination of sugar snap peas with 5-10% snow peas. Apparently this is true across seed companies, and is something that many seed companies are actively working to prevent. I also saw a couple of diseased pea plants this week, which is not surprising given the humidity we're seeing across much of the state. 
  • Potatoes and beans: Potato leafhopper has officially arrived in Southwest Minnesota. Alfalfa growers are actively cutting alfalfa stands right now, so growers near alfalfa fields should begin scouting both potatoes and beans regularly for potato leafhoppers, which often migrate right after an alfalfa harvest. More about potato leafhoppers. 
PLH nymph
Potato leafhopper nymph (E.C. Burkness, UMN).
  • Carrots: Carrot germination has been spotty across the state, especially in areas with heavy rainfall events. 

  • Cole crops:  This week I saw the first black rot infested broccoli plant I've seen this year, and it was all the way up in Cotton Minnesota. Cole crop caterpillars are also quite active right now; review recommendations for caterpillar management and black rot management. Broccoli head quality is not uniform this year, and in many cases the high heat has caused heads to emerge more loosely than would be ideal. I'm also seeing sun scald in recently transplanted cucurbits; remember to give your cool season crops some extra TLC when hardening them off in the middle of the summer.
  • Fennel: I don't usually write about fennel, but I received a photo from a grower of a caterpillar, likely a cutworm, eating a fennel bulb. They said that while damage was sporadic, there were caterpillars eating multiple bulbs. Are any of you seeing this too? If so we'd love to hear about it!
Fennel-eating caterpillar. Photo: Anna Racer

  • Cucurbits: While I've seen some cucumber beetles here and there, the situation seems less dire than last year. That said, make sure to keep monitoring their populations. I've received multiple reports of spider mites in high tunnel cucumbers this week. These insects are small and usually stay on the undersides of leaves, meaning they often go unnoticed until they reach damaging levels. Scout the undersides of leaves in your high tunnels, and look for very small chlorotic spots on the leaves of your cucumber and tomato plants. For conventional growers, there are many effective miticides that can be used: see the midwest veg guide for a list. Organic growers can use insecticidal soaps and horticultural oils. Good coverage is necessary for these products to work, and they work best when used preventatively, before populations really begin to build. There are various predatory mite species that can be introduced to greenhouses as well, but these also work best when used preventatively.
Typical damage from two spotted spider mite. Photo: Whitney Cranshaw, Colorado State University,

Problems in the field / things to note this week

Mid season drought outlook

While this summer has been one of the hottest on record so far, we've had enough precipitation to keep most of us out of drought. From last week to this week, the area experiencing abnormally dry conditions expanded just slightly (only about 1%), and shifted west, and a small area in Dakota and Washington counties shifted from abnormally dry to moderate drought. July is projected to stay hot, so make sure your irrigation systems are ready to be put to the test if needed.

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, and you can submit questions and diagnostic help below. 

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