Reminder: TREE FRUIT TWILIGHT MEETINGS
Thursday and Friday, May 8 and 9, 4:00-6:00 pm

Join the Vermont Tree Fruit Growers Association and UVM Extension on May 8 at Yates Family Orchard, 1074 Davis Road, Hinesburg, VT or May 9 at Wellwood Orchard at 529 Wellwood Orchards Road, Springfield, VT. Topics discussed include tree fruit management practices, value added products, marketing, pest and disease updates, pollinators, and funding opportunities and challenges. The events are free and geared to commercial growers and people that work with them, and offer one VT pesticide recertification training credit for categories 1A, 1, 2, 3, 4, 5, and 6. Registration is not required, but helpful for any unexpected announcements regarding the meetings. To let us know if you plan to attend, contact Laura Johnson at laura.o.johnson or 802-656-4827.

We are in full scab management season with ascospore maturity creeping up, and significant, extended wetting that can discharge a lot of spores. Hours required for infection to occur are relatively low with the temperatures in the 50s and 60s that we are seeing this week. Fungicide coverage should be maintained during this wet week, and a material with kick-back activity (FRAC codes 3, 7, 9, 11- be sure to rotate among these!) applied should you have any question on coverage of protectant fungicides. Use of these materials should help with management of other diseases, including powdery mildew and cedar apple rust, as well.

For the time being, I’m fairly confident that we can consider fire blight a non-issue heading into bloom. That can change quickly should things warm up, and trees are susceptible to blossom blight any time blooms are open. The number to watch for in the NEWA fire blight model is the value in the “Infection Potential EIP value” column (data shown for UVM Horticulture Research and Education Center in South Burlington, VT):

That number refers to the Epiphytic Infection Potential, a relative value that predicts the size of the population of the Erwinia amylovera bacteria that causes fire blight infection. When that number reaches 100 the population is considered large enough to cause disease infection. That number is affected by accumulated heat units, so cool conditions cause it to decrease, whereas hot weather can rapidly cause bacteria to multiply rapidly, The other conditions that are included in the model include wetting events, temperature during bloom, and presence of open blossoms. The EIP values predicted for the next five days are just too low for fire blight to be of concern. This carries across all parts of the state, although southern Vermont orchards are seeing or expecting warmer temperatures that check the “average 60°F during bloom” box which makes the relative risk higher (i.e., yellow flagged). But keep an eye on that EIP number – if it’s well under 100, you’re likely in good shape.

Insect management should be on your mind, though. Many growers know that I am generally not in favor of insecticide sprays at pink unless scouting indicates a need because of the residues that would be present for pollinators to be exposed to at bloom, but this is a great time to be monitoring pest populations to be prepared to manage them when the time comes. I checked white sticky traps hung on 4/24 for European apple sawfly and found none, same for codling moth traps hung last week. For those who are following along, we use this monitoring summary to plan our trapping. In addition to codling mothy and obliquebanded leafroller listed there, we are also trapping for Oriental fruit mothy and dogwood borer, both traps can go up now. For the latter pest, my M.S. student Eli Wilson wrote a summary on them a couple of years ago:

Here is what you need to know about the dogwood borer (DWB):

Identification:

The adult form of the dogwood borer is a small, clearwing moth that is shown in the image below. They have approximately a 1-inch wingspan and have a black and yellow color pattern making them resemble wasp. They have mostly clear wings with circular windows at the tips. The larvae of the dogwood borer (DWB) are about ½ inch long and can range from white to light pink with a large brown head.

This is the time of year that the adult dogwood borers begin laying their eggs in the crevices of tree bark, so it is important to be monitoring for their presence in your orchard.

Damage:

The dogwood borer larvae are the ones that cause the damage, feeding on the phloem and cambium layers of the tree. Signs of an infestation may first appear as a pile brownish red frass on the outside of an entry hole in the tree trunk. While a few borers will not cause significant damage a population can build over the years and lead to reduce tree vigor and even girdling. An image of the larval form of the dogwood borer (DWB) is also shown below.

Trapping:

You will be using two orange TRÉCÉ PHEROCON VI DELTA TRAPs to monitor the dogwood borer in conjunction with lures labeled “DWB”. The lures should be replaced every 4 weeks and you can replace the stick liners every week if you choose. If you do not replace the liners each week, be sure to remove all the trapped dogwood borers after recording that week’s catch total. The orange Delta Traps should be hung within the tree canopy at approximately 4-feet off the ground as shown in this instructional video: Hanging Delta Traps

I hope this information is helpful, if you have any questions, comments, or concerns please feel free to reach out!

Happy trapping!

Best,

Eli Wilson

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

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PAT credit listed 2025-spring-tree-fruit-twilight-meeting.pdf