This was a tough week for vegetables and for farmers - we heard reports from all around the state about significant hail damage, and we saw multiple fields underwater today. The weekend was brutally hot, followed by intense rainfall, so it’s been hard to keep up with weeding, trellising, and other farm tasks. The week ahead looks drier and warmer, hopefully bringing respite and a chance to catch up!
Hail damage, flooding, and other crop losses - what to do now?
If you have fields that have been significantly damaged by hail, flooding, insects, or something else, what are your back-up options at this point in the season? We’re doing a whole webinar about this next Tuesday July 1 at noon - click here to register. If you can’t make it, here are some things to consider:- Midsummer into mid/late July is a great time to plant beets, carrots, green beans, broccoli, and other crops with a ~50-60 day lifecycle.
- Consider looking into wholesale options for fall. The Minnesota Department of Agriculture recently published a list of recipients of 2025 Farm to School and Early Care grants. Check out the list, see if there’s a school or early care center near you, and reach out to see if they are still looking for fall veggies.
- The varieties you plant now should not be the same varieties you planted this spring. Look for descriptors like “for fall harvest”, and disease resistance (we often see more plant disease issues in the fall). Some seed companies like Johnnys have handy guides that help you identify varieties best suited for early vs. later planting (here’s an example for broccoli).
- Use our crop planning tools to figure out estimated yields and how much seed you need to meet your yield goals.
Time to consider shade cloth in the tunnel
Shade cloth is probably the last thing on your mind during cold, rainy weather. But, if you have a high tunnel, late June to early July is the time to start thinking about shade cloth. Using 30% shade cloth (50% is too much) can actually improve your marketable yields of tomatoes and peppers by reducing sunburn and stress, and it makes it infinitely easier to work in the high tunnel as the summer gets hotter. Shade cloth for a high tunnel ranges from around $250 for a smaller (~50 ft) tunnel to $550 for a larger (~100 ft) tunnel, and can be used for many years if it’s stored well. Most farmers put it over the top of the plastic, using clips to secure it to the base of the tunnel. We occasionally see farmers that use it inside the tunnel, hanging it from the purlins. It really depends on the basic construction of your high tunnel and whether or not it will get in the way of your trellising system.
Biocontrol in high tunnels
We're starting to see the common soft-bodied insect pests we typically see in high tunnels at pretty much every farm we visit. These include spider mites in cucumbers, aphids and thrips in peppers, and thrips in basil. Generally these pests are present at low levels, but they can take off very quickly during hot weather. Now is a really good time to consider biocontrol options for your high tunnel. Introducing beneficial insects generally works best when pest insect populations are low. They help to keep populations low and help to delay or avoid the use of pesticides. Biocontrol does not usually work well as a rescue treatment when insect pests are already out of hand. Generally we recommend reaching out directly to a company that specializes in biocontrol and having them recommend specific species that will help manage the problems you're seeing in your tunnel. Two companies with reps in Minnesota are:
- Koppert Biocontrol. Heidi Doering is the Midwest IPM rep: hdoering@koppert.com
- Beneficial Insectary is associated with Biobest, and based in Michigan: https://insectary.com/
Crop Updates
Asparagus season has wrapped. Immediately after a final, thorough pick is a key window for weed control, read “Weed Management Options for Asparagus” for more information.
Basil plants are unhappy with all the cooler, cloudy weather. We saw some high tunnel basil with extensive thrips damage this week. While looking a plants from a distance, they looked yellow with distorted leaves, on the underside leaves was the telltale “silvering” left behind by thrips. Areas they’ve fed often take on a silvery white appearance. If you have a hand lens/good eyes, you might see the black specks of their poop, and the tiny, yellow thrips themselves.
Thrips damage on a basil leaf. Photo: Natalie Hoidal
Peas are being harvested. Early successions and high tunnel peas are slowing down.
Pepper growth both in high tunnels and outdoors is slow – peppers like consistent heat, which we haven’t really had. In both peppers and tomatoes, keep an eye out for viruses, especially as your prune and trellis. Both crops can be afflicted by many species of viruses, but the most common ones are moved around by insects and produce perfect circles on the surface of the leaf. Infected plants do not get better as the virus is systemic, and infected plants should be removed so the virus can’t hitch a ride with an insect or your pruner into another plant. As you prune, sanitize your pruners after every couple of plants (and after every single plant if there are disease symptoms) to avoid transmitting diseases from plant to plant.
Viral spot on a tomato. Photo: Natalie Hoidal
Tomatoes in high tunnels are setting fruit, tomatoes outside are getting staked. Remember plant disease as you do these tasks – minimize plant damage, sanitize pruners often, and do these tasks at time when conditions are dry. We’ve seen a lot of tomatoes that need a good pruning - it’s been hard to keep up with all of the humidity and after the high heat last weekend. As a reminder, at each “node” on a tomato plant there is a leaf and a new shoot. The leaf is always on the bottom, and the new shoot is always on top. We want to prune out the shoots to help the plant focus on growing leaves and setting fruit. If we allow too many shoots, our plants become tree-like and hard to manage. You can remove both leaves and shoots up to the first cluster of fruit - this helps to provide good air flow around the base of the plants, and prevents pathogens from splashing up onto the lower leaves.
Node of a tomato plant with the "sucker" (a new stem) on top, and a leaf on the bottom. Photo: Natalie Hoidal
We saw quite a bit of blossom end rot on tomatoes this week. It is very normal / common to see blossom end rot on the first flush of tomatoes, especially in high tunnels. This weather hasn’t helped: tomatoes need very consistent growth conditions to set healthy fruit. We’ve had cold weather followed by very hot weather, followed by cold and wet weather. This means growth is speeding up then slowing down, and as plants are just getting going and trying to grow vegetatively and set their first fruit / flowers at the same time, there’s a lot of cell division happening. It can be hard for your plants to transport calcium (a notoriously clunky nutrient) efficiently under these conditions, and so the calcium just can’t make it to the developing fruit in time. If you’re seeing some blossom end rot, discard the fruit immediately so the plant can focus its energy elsewhere. Keep an eye on varieties that are particularly bad and consider avoiding them next year, and try to keep your soil moisture as consistent as possible.
Blossom end rot on an early tomato fruit. Photo: Natalie Hoidal
Finally, we are starting to see some of the common early season tomato diseases like early blight. For fungal pathogens like early blight, focus on pruning out symptomatic leaves, pruning to allow great air flow in the lower canopy, and keeping your pruners cleaned and sanitized.
Early blight. Photo: Natalie Hoidal
For vine crops, the recent warm weather has pushed them along. As some crops are setting their first round of female flowers, remember that it is normal for bees to have not quite found the first set of female flowers and for these fruit to never develop after the flower drops. Pollination typically picks up after this first round of female flowers.
On the pest side, we are in the window where Squash Vine Borer adults are flying and laying eggs in most of south and central Minnesota. The adults look like wasps, they fly in the day, have clear wings, and are orange and furry. For large plantings, the damage from these guys is often manageable, but in small plantings, squash vine borers can be very destructive. What can we do? It is hard to manage these guys effectively.
- Eggs are laid on the base of the plant. These are small, but if you can find them, you can remove them.
- In very small plantings, some growers surgically remove the larvae. This can work, but can also kill the plant and make it more vulnerable to disease.
- If using pesticide, timing needs to be very targeted. The window when we can hit squash vine borer with labelled insecticide is when the caterpillar hatches out of the egg but before it is fully bored into the stem. Once they are in the stem, they are protected from pesticides. Target applications at the crown of the plant.
- The Midwest Vegetable Production Guide lays out conventional options. For organic options, the organic products that have shown efficacy in trials is Bt strain aizawai (most common trade name is Agree), Entrust, and Azera.
- I’ve gotten questions in the past about some novel insecticide application methods like injection. These uses are not on the label of most pesticides, meaning this is an illegal use.
- Whether using organic or conventional insecticides, remember to protect pollinators by making your applications later in the day when flowers are closed.
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