Weekly Vegetable Update June 25, 2026

The run of pleasant weather we’ve had for the last two weeks is ending, as the next week brings hotter temperatures and increased chances for storms. NOAA is saying that next Monday could be the first day of truly dangerous heat this year in Minnesota, with high daytime temperatures, high humidity, and high overnight temperatures. Take care of yourself and your workers with breaks, shade, and lots of water.

Heat reminders

Working in hot conditions can be dangerous, both for your immediate and long term health. Keep in mind the following as we transition into a hot week ahead.

Liquids & food:

When you’re working in hot weather, avoid caffeine, and try to drink about a litre of water every hour. By the time you feel thirsty… you are already dehydrated! Electrolyte drinks and powders help to replace the salt you loose as you sweat. While a lot of people just don’t feel hungry when they are hot, eating regular meals is critical.

Taking breaks

When temperatures are around 90 degrees F or higher, you should be resting more than you are working. Check out our chart of rest / work times for different types of work at different temperatures. If you don’t have an air conditioned place to cool down, try to access water and shade. Multiple farmers who have completed our climate cohorts have implemented kiddy-pool stations on their farms: they fill kid pools with water under a shade tree and take regular breaks there, then use the pool water to water the tree at the end of the day (your trees are also hot and thirsty!).

Does early herbicide drift affect fruit?

We have a weekly check in with vegetable educators from across the country, and drift has been the main topic of conversation for weeks - vegetable farmers in every state seem to be getting hit hard this year. Our colleague Stephen Meyers, a weed scientist at Purdue, shared photos from last year when tomatoes at his farm were drifted on by an auxin (likely 2,4-D or dicamba) herbicide shortly after transplanting, before flowering. Early symptoms looked like standard auxin injury, with leaf cupping and epinasty (downward curling of leaves). The first fruit produced by these plants were oval shaped: they looked like Roma tomatoes despite being slicers, and throughout the season the fruit became more round / normal looking. Are these tomatoes safe to eat? Unfortunately it's impossible to say just from looking at them. Only a lab test can determine which residues are present, and at what levels. 

Early drift symptoms, photo: Stephen Meyer

Early fruit compared to later fruit, photo: Stephen Meyer

What to do after hail?

Over the last week, different pockets of the state have seen severe weather with hail, and the next week will bring a continued threat of severe weather. What to do after hail damage?

• Wait until things dry out, then assess damage level.
• Give plants protection from plant disease that can flare up in wounded plants, something broad spectrum like copper is a good bet.
• If there are damaged tomatoes, summer squash, and other unmarketable products, remove them from the plants so the plant can focus on new, marketable fruit.
• Give plants a bit of N about a week after the damage occurs, this will help power new shoot growth and fruit development

For a good (well, it is well-researched and written, but kind of grim) crop-by-crop rundown of what we know about how hail damage impacts the yield, plant health, and product quality of different vegetables, Purdue has a good write up in their article “Hail Damage.”

Electric farm equipment

The Minnesota Department of Agriculture has an electric farm equipment grant grant due in early August. While you’re doing field work this summer, start brainstorming what kinds of equipment could help your operation and consider applying. As diesel prices rise, an electric cultivating tractor (either two wheel or a full scale tractor) could be a great addition to build resilience on your farm. Funds can also cover things like electric well pumps for irrigation (there have been some pretty cool solar powered well projects on MN produce farms in the past couple of years), electric mowers, a utility terrain vehicle, or even postharvest equipment like a forklift for the packshed. This grant can also be used to cover charging infrastructure like solar panels and upgrading outlets and fuses if these things are needed to charge your new equipment.

Crop Updates

Cole crops: Caterpillar pressure continues, with zebra caterpillars popping up on more farms. See last week’s vegetable update for a write up if you are seeing clusters of bright yellow caterpillars, or just holey kale or cabbage more generally.

Vine crops: Last tillage passes before vine out are occurring on some farms, and cucumbers in high tunnels are growing rapidly. We are starting to get reports of diseases both in the field and in high tunnels.

We got multiple reports of angular leaf spot in field grown winter squash. If you have winter squash or pumpkins that are looking kind of ratty, take a closer look. Angular leaf spot is aptly named, it is a bacterial disease that causes very blocky spots, bounded by the veins in the leaf. The underside of these spots have almost as shiny, glassy appearance (the result of bacterial goo forming and then drying). This disease can be seedborne, and moves as plants touch, on tools, and hands. There are some management options available (check the Midwest Vegetable Production Guide), but hopefully as crops vine out, new growth will be further out from these heavily infected leaves. Remember, anything you spray for plant disease is more preventative, and will slow down infection on new leaves, not cure the plant.

Angular leaf spot causes blocky leaf spots in cucumber and other vine crops. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

As for insect pests, cucumber beetles are out. Whether they are worth managing depends on the crop. For winter squash, summer squash, watermelon, and pumpkins, once the crop has four or more leaves, treat if you are seeing more than five beetles per plant, or greater than 25% leaf defoliation. For cucumbers, cantaloupes, and muskmelons that are vulnerable to bacterial wilt, consider treating if you are seeing an average of one beetle pre plant, especially if you have a history of bacterial wilt on your farm. Squash vine borer is also flying and laying eggs.

Tomatoes: In the high tunnel and in fields, alternaria has shown up. There is a type of alternaria for most vegetables (such as in brassicas, or, as it is known in tomatoes, early blight). While these are each different pathogens, the symptoms look very similar - brown spots with concentric rings and encircled by yellow halos. If in the high tunnel you could prune these leaves off as you deal with the crop. At the end of the season, make sure to remove and destroy crop residues, and rotate for at least 2 years. The New England Vegetable Production Guide recommends copper for organic management within the season, which may also help slow down anthracnose, the more common leaf spot disease we see in high tunnel cucumbers.

Alternaria in melon. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

Garlic: growers across the country are seeing high incidence of viruses in their garlic this year. There are many different viruses in garlic, which have different vectors, but most are spread by small insects like aphids. If you’re seeing bright yellow lines or splotches through your garlic leaves, it is most likely a virus. Garlic bulbs with viruses are usually still edible, but they will be quite a bit smaller than healthy bulbs, and you should not save the seed.