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Weekly Vegetable Update 6/11/2020

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

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):
Fruit questions go to Annie:
Food safety questions go to Annalisa:

Crop report

So, the weather predictions from last week were totally off. This week has been soggy and wet, and many of you have not been able to get in to the fields. Here's to hoping the next 7 days or so of dry weather in the forecast are accurate! The first succession of most crops are now in the field.
Garlic is starting to produce scapes. Photo: NH
Melons are beginning to vine out. Photo: NH
  • Asparagus harvest continues but is past peak especially for recently planted fields. Hot weather may have impacted the tip quality for some growers. 
  • Garlic scapes are emerging! Make sure to harvest them for larger bulbs. If you have direct markets like a CSA or farmers' market, scapes are a great addition. I once knew a farmer who dried her scapes and sold them as a powder for added value - just an idea!
  • Pea season is here!
  • Potatoes have mostly emerged. Potato beetles are out and about laying eggs. This is the time to start thinking about spraying. 
  • Cucurbits: the main concern for cucurbits right now is cucumber beetle. In zucchini and summer squash we're starting to see flowers and even some fruit; don't expect the first fruit to be large, as they tend to be unfertilized. Consider removing them to allow your plants to put more energy into flowering and later fruit. Melons are starting to vine out. If you're using split fertilizer applications, initiation of vining is the time for your second application. 
  • Tomatoes and peppers are now in the field for most of the state. For the most part, they have grown out of nutrient deficiencies caused by cold weather. Start scouting now for foliar diseases. 
  • Cole crops are at various development stages depending on succession planting; all successions are facing major insect pressure this week. 
  • Dry beans are mostly planted at this point. Potato leafhoppers love beans, so keep an eye out, especially during this time of alfalfa harvest (more info below). 
  • Lettuce and leafy greens harvest remains in full swing

Problems in the field

Herbicide drift

This is a major window for corn and soybean farmers to make herbicide applications. We've heard from our colleagues that many farmers were not able to use pre emergent herbicides this year due to conditions not being quite right, so we may be seeing more than average post emergent herbicide applications. Growers have another 10 days in Minnesota to apply dicamba, so anticipate applications in your area.

If you haven't done so already, talk to your neighbors now! Make sure they know you are growing vegetables, and let them know that they need to take special precautions to avoid drift if they're spraying near your fields. Also consider calling your local co-ops to let them know you're there. There's a lot of turnover in co-ops, so even if they knew about you last year, it's a good idea to call and remind them to take extra care near your fields. Also, consider signing up for DriftWatch  If you suspect you've experienced drift on your farm, contact MDA immediately.

High tunnel insects

As the season progresses, high tunnel insects become more problematic. High tunnels favor small, soft bodied insects like aphids and whiteflies. Now is a great time to introduce biological control organisms to keep populations low. If you're spraying insecticidal soaps or horticultural oils, take care to avoid spraying during hot, dry conditions, as these products can burn plant leaves under these conditions. Additionally, for the same reason, make sure your plants are fully hardened off and adjusted to their new environment (if you've recently transplanted) before spraying these products.

Insect and disease forecast

Diseases: the weather has been humid with high nighttime temperatures. Make sure you're scouting regularly to identify diseases as early as possible

Potato leafhoppers are showing up in potatoes and beans. Potato leafhoppers tend to feed on alfalfa when they first arrive in Minnesota, and once the alfalfa fields are cut, they migrate into other crops. Alfalfa harvest has mostly finished, and we're starting to see leafhoppers in vegetables. Scout carefully. These insects are tiny and hard to see, and their damage is difficult to detect at first. More info on leafhoppers.

Cucumber beetles are out and feeding on young plants. Scout cucumber beetles regularly: they can transfer bacterial wilt when your plants are young. From Veg EdgeThe action threshold for first true-leaf plants is when SCB populations exceed 2 or more beetles/plant on 25% of the plants, or 1 beetle per plant on most plants.Once plants are at the 2nd or 3rd true-leaf stage, monitoring efforts should shift from monitoring beetles to checking the defoliation level.

So many Brassica insects this week!
Photo: NH
Potato beetles are emerging and starting to lay eggs. Now is the time to spray if you're going to. Btt products can be relatively effective for prevention, but not to knock down populations. If you're organic, consider applying spinosad, pyrethrins, or a mix of pyrethrins and neem (e.g. Azera) if you reach 5% defoliation; most of these will require a follow up application about 5 days later. Keep in mind that we are starting to see spinosad (Entrust) resistance in potato beetles. Beetles in areas where farmers commonly spray pyrethroid insecticides for soybean aphid may also have some pyrethrin resistance.

Cole crop insects are out in full force. Diamondback moth Moth larvae are feeding and in some locations are already pupating. We've heard reports of Imported Cabbage Worm adults as far north as Clay County (Fargo / Moorhead). Cabbage maggot larvae have hatched and are doing damage, and flea beetles continue to be a major problem.
  • In the early season before cupping has begun, the threshold for spraying Diamondback Moths is 50% of plants infested with at least 5 larvae. Most fields are no where near this point.
  • See our previous post about flea beetle management. 

Educational opportunities

Great Lakes Vegetable Producers Networkjoin us during your lunch break on Wednesdays for a 30 minute discussion about vegetables. All previous episodes can be downloaded as podcasts. 

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