Natalie Hoidal & Marissa Schuh
More severe weather affected some farms over the last week, though the steady warmth of this week is sending solanaceous and vine crops leapfrogging ahead. We got the 30-day forecast for July from NOAA this week, calling for above average temperature and average amounts of precipitation.
How do you want to manage your virus infected crop? It's a decision you can make based on the severity of the infection, the value of the crop, and the risk of spread. Our two options are remove the plant to get rid of a source of future infection, or leave the crop and see what happens. We can’t spray anything or cure infected plants in any way.
In beans, there are over 20 viruses that can be found in beans. If we were seeing symptoms like the picture above sporadically throughout a planting, we could choose to remove infected plants or just leave it be. To make this decision, we could check and see if the plants were still flowering normally and making normal looking pods. We might think how much longer we are going to be harvesting this crop of beans. The grower whose farm we took this picture at late last week chose to do nothing, and plants are growing and producing well.
Early July is a great time to do some foliar testing on your farm to refine your fertility plan for the rest of the season. For most crops, this should be done when plants are entering the reproductive phase (flowering and starting to fruit). Foliar testing can be especially valuable for high value crops in high tunnels. Read more about how to take a foliar test and how to interpret results here: https://extension.umn.edu/growing-guides/foliar-nutrient-tests
Green beans are being harvested.
Potatoes are flowering. July is the most important time for water in potatoes, as tubers are sizing up. Even moisture will result in larger, evenly sized potatoes. Irrigation can also help promote overall soil biology, which can help other microorganisms outcompete the bacteria that causes potato scab.
More vine crops are starting to flower and fruit.
Early sweet corn plantings are starting to . Some growers using season extension methods may have corn by the weekend. As successions start to have green silks, there is risk for damage from corn earworm. If you’ve had worms in your corn in the past, this is likely the culprit. Weather models suggest we may have had some early season pressure from this pest, though it might not be felt if the field corn in your area is also silking.
More severe weather affected some farms over the last week, though the steady warmth of this week is sending solanaceous and vine crops leapfrogging ahead. We got the 30-day forecast for July from NOAA this week, calling for above average temperature and average amounts of precipitation.
Surprising pest of the season? Plant viruses
Every crop we grow has at least a few (and for some crops many) viruses that can infect them. We typically see more of these during dry, hot weather, as the insects that move viruses around are small, heat-loving pests. Why are we seeing so much of this this year? Hard to say. Data from aphid trapping efforts indicate that we've had good weather for moving aphids around. We’ve seen virus symptoms in tomatoes and vine crops, which we see some level of every year, and some crops where we see them less often, like garlic and beans.How do you want to manage your virus infected crop? It's a decision you can make based on the severity of the infection, the value of the crop, and the risk of spread. Our two options are remove the plant to get rid of a source of future infection, or leave the crop and see what happens. We can’t spray anything or cure infected plants in any way.
Perfect, light green circles in bean are a virus symptom. Photo: Marissa Schuh, UMN Extension.
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The mosaic of yellow speckles in this garlic plant could be one of a couple of viruses. Photo: Marissa Schuh, UMN Extension.
Garlic is a very different crop. Viruses can be moved around by insects, but we can take it into our next crop if we save infected cloves. Many garlic growers make good money selling seed, if that is your main market, remove infected plants to protect the rest of your crop.
Check in Fertility
Early July is a great time to do some foliar testing on your farm to refine your fertility plan for the rest of the season. For most crops, this should be done when plants are entering the reproductive phase (flowering and starting to fruit). Foliar testing can be especially valuable for high value crops in high tunnels. Read more about how to take a foliar test and how to interpret results here: https://extension.umn.edu/growing-guides/foliar-nutrient-tests.jpg)
Garlic is a very different crop. Viruses can be moved around by insects, but we can take it into our next crop if we save infected cloves. Many garlic growers make good money selling seed, if that is your main market, remove infected plants to protect the rest of your crop.
Crop Updates
Cole crops overall did well in our cool, wet June. Imported cabbageworm, diamondback moth, and flea beetles are the main pests active right now. Remember, Bt (strain kurstaski) products like Dipel are affordable, easy to use, and super effective at managing caterpillars. A simple threshold to use for treatment is 10% of plants with a caterpillar for leafy cole crops. For heading cole crops, start treatment at 20% if the head has started to form.Green beans are being harvested.
Potatoes are flowering. July is the most important time for water in potatoes, as tubers are sizing up. Even moisture will result in larger, evenly sized potatoes. Irrigation can also help promote overall soil biology, which can help other microorganisms outcompete the bacteria that causes potato scab.
More vine crops are starting to flower and fruit.
Early sweet corn plantings are starting to . Some growers using season extension methods may have corn by the weekend. As successions start to have green silks, there is risk for damage from corn earworm. If you’ve had worms in your corn in the past, this is likely the culprit. Weather models suggest we may have had some early season pressure from this pest, though it might not be felt if the field corn in your area is also silking.
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