Fruit and Vegetable News

Authors: Annie Klodd and Natalie Hoidal, Extension Educators for Fruit and Vegetable Production

In the last week, Annie visited berry farms in Quebec that are growing raspberries, strawberries, and blueberries under protected culture like high tunnels and exclusion netting. Natalie visited multiple farms around the metro area. 
What we did not see: Late blight!  We had a false alarm this week - someone sent us a photo that looked eerily like late blight, but the UMN Plant Disease Clinic confirmed that it was not late blight. Phew! We checked in with our potato growing colleagues who run the NDSU / UMN Potato Late Blight spore trapping network, and as of last week, no late blight spores or DNA have been identified in filters, and no reports have been made. 
Tomato problems: the common culprits, Ramsey County
Septoria, bacterial spot, early blight, blossom end rot - these are all common problems at this point in the summer. In this case, we found all four (three diseases + blossom end rot…

Bill Hutchison, Eric Burkness & Suzanne Wold-Burkness
Minnesota Extension IPM Program, Dept. of Entomology, UMN, St. Paul campus

This past week, our trapping network detected the first significant increase in corn earworm (CEW), Helicoverpa zea, moth flights at for two locations: Blue Earth (MN/IA border), and Owatonna. 
In previous years, Blue Earth is often the first location to experience the first increase in moth flights, and this year’s catch is right on schedule for early August. Moth flight numbers averaged over 12 per night at Blue Earth (as of 8/13), and over 5 per night at Owatonna.  Our action threshold to initiate sprays for CEW in sweet corn is when trap catches average more than 5 moths per trap per night for 2 consecutive nights, and sweet corn is between 15 to 50% silk (for the first spray).  
Subsequent sprays should be based on continued moth flight activity with sprays applied approximately every 5-7 days prior to harvest (see below). As noted previously, CEW i…

Authors: Bill Hutchison, Eric Burkness, Chulwoo Kim, Brianna Pomonis, Anh Tran, Dominique Ebbenga & Suzanne Wold-Burkness
MN Extension IPM Program, Dept. of Entomology, University of Minnesota, St. Paul campus

Spotted-wing Drosophila (SWD) trap catches continue to remain very high in all on-farm and research locations monitored. Traps in our network are effective at catching both male and female flies (Fig. 1).   Growers should remain diligent in alternating insecticides as much as possible (e.g., Delegate or Entrust [organic-certified], Mustang Maxx, and Malathion), and follow the pre-harvest and re-entry intervals, noted on the label for each insecticide. The most significant increase was Hastings this week, where wine grapes are now at véraison, with approx. 60% green berries. We will have more information next week regarding SWD management strategies for wine grapes. SWD numbers usually increase in wine grapes from late-August to mid-September, through harvest.

Authors: Bill Hutchison, Eric Burkness, Anh Tran, Dominique Ebbenga & Suzanne Wold-Burkness
MN Extension IPM Program, Dept. of Entomology, University of Minnesota, St. Paul campus

Spotted-wing Drosophila (SWD) trap catches continue to remain very high in all on-farm and research locations monitored, especially the past 2 weeks. Traps in our network are effective at catching both male and female flies (Fig. 1).  See Table 1 below for details. Growers should remain diligent in alternating insecticide products as much as possible (e.g. Delegate or Entrust (organic-certified) and Mustang Maxx, and malathion if needed), and follow the pre-harvest intervals noted on the label for each product.


An additional reason for the concern with high SWD numbers in traps is not only for the SWD catch within berry crops, but also the concern with the SWD “reservoir” confirmed again this summer in nearby forested areas or “tree lines” that often occur near berry fields.

Our previous sampling has show…

Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production

Several apple growers have reported increased incidence of "silver leaf" on their trees this season. One question asked around this topic is whether the cold winter could have contributed to silver leaf. Before answering that question, let's talk a bit about what silver leaf is and how it spreads:

Silver leaf is a fungal disease of apple trees and many other deciduous trees that makes the leaves appear "silver" or gray. This is caused by a fungus called Chondrostereum purpureum. In addition to infecting leaves, it also forms conks (fruiting structures) on the trunks and branches of trees.
How Silver Leaf Spreads During wet conditions in the spring and fall, the conks release spores that can then infect wounds on the trees, like pruning cuts, splits from winter injury, or broken branches from heavy snow.

The fungus then resides in the xylem of the branches, and a toxin from the fungus moves…

We're adding a new column to the newsletter called "Sightings from the field". Since our team does regular farm visits, we see a lot of diseases, insects, and nutrient issues, but also a lot of cool and exciting things! By sharing what we're seeing on farms around the state, we hope that you'll appreciate an inside look at what other farmers are dealing with, and the creative approaches they're taking.

This week: July 29th. Natalie and Annie were up on the iron range visiting farms, so many of our photos this week come from the far north.

Chimera, Aitkin County


This one had us stumped at first. The grower had a row of peppers in the field, and about half of them were showing this streaking pattern on both the leaves and the fruit. We considered herbicide drift (not likely given the situation), a nutrient deficiency, or maybe even "burn" from an over application of fertilizer.

It turns out the streaking was caused by chimera, a genetic mutation that c…