On April 13, 122 of you joined us for the annual WSCGA and UW-Madison Division of Extension Spring Mini-Clinic. Intended to kick off the growing season with research updates and tactical information, as well as to give growers a forum to discuss urgent questions, we were glad to have participation from all counties and all aspects of the cranberry industry.

For those who weren’t able to virtually join us, a recap is offered here. If you would like to view the video, send a message to allison.jonjak@wisc.edu. Recordings are made and kept for grower access, so you can receive a personal link to watch the recording.

Jed Colquhoun-NR 151 on Nitrates and Groundwater

Jed Colquhoun is a member of the Technical Advisory Committee during the development of the DNR’s proposed revisions to NR 151.

NR 151 establishes a goal for performance standards focused on water quality, and is coupled with ATCP 50, which outlines technical methods for achieving the goal. The proposed revisions will establish a targeted nitrate standard.

The rule is currently being put into draft form, and will open for public comment in summer 2021. We will encourage all growers to get involved in discussions during this public comment period, and WSCGA will offer more details as they become available.

Christelle Guédot-Leafhoppers and Early Scouting

Many growers have been asking questions about Blunt Nosed Leafhoppers as we begin the 2021 growing season. It is important to sweep net pre-bloom, in May and June, to check your nymph pressure. Many species of leafhopper are found in Wisconsin, and Blunt Nosed are not the most common—but they are important for cranberry growers to monitor, as they are the only known species to vector the pathogen of false blossom disease.

Telling the difference between Blut Nosed Leafhoppers and other, more common, and non-disease-transmitting leafhoppers requires a microscope and lots of experience. Luckily Ocean Spray, Lady Bug IPM, Red Forest IPM, and UW-Madison Extension (via the Insect Diagnostic Lab, https://insectlab.russell.wisc.edu/samples/ ) are able to make these identifications. For control options, see Christelle’s article in this issue of the CCMJ.

Allison Jonjak-Phenocams

New research spearheaded by Jyostna Devi Mura’s lab for 2021 will give cranberry farmers precise foundational information that farmers from other crops have pioneered. Understanding the phenological progression of each popular variety, plus new varieties, through the growing season will help growers time nutrient applications and make more informed frost-protection decisions to exactly suit the varieties they grow.

Cameras, connected to affordable Raspberry Pi computers, will monitor upright status of many varieties throughout the 2021 season. Pilot systems were designed and trialed during part of 2020, so research can cover the full growing season for 2021. 

Amaya Atucha-Anoxic Stress

All plants need oxygen for the process of respiration, which involves using sugars produced through photosynthesis plus oxygen to produce energy. Most of this oxygen enters the plants thorough the stomata in leaves, but also through lenticels in stems, or through diffusion in roots. When cranberry plants are flooded, oxygen may enter the plant through diffusion if the concentration of oxygen in the flood water is higher than inside the plant. However, when plants are submerged for an extended period of time, they will continue to respire and use the sugars they have stored and, in the process, consume oxygen. The combination of low levels of oxygen in the flood water plus the consumption of reserve sugars will cause substantial stress to the plants.

There are three critical factors when it comes to oxygen availability during a flood: the amount of dissolved oxygen and temperature of the water during the flood, and the length of time the water is held. Muddy water or water with lots of algae will have less available oxygen than clear water, when used for a flood. The colder the water temperature is, there will be less consumption of oxygen by the plants. (Think of a trout stream—colder water means more oxygen, and thus more and healthier trout.) Finally, as water is held across several days, the cranberry plants use the existing oxygen, and without turbulence, there’s no way for new oxygen to be introduced. Keep floods short when temperaturers are high or when your source water is cloudy to avoid anoxic stress.

Shawn Steffan-Nematode Spring Update

Work on the two native nematodes, Oscheius onirici and Heterorhabditis georgiana, will continue in 2021. These microscopic predators have been shown to kill several important cranberry pests, such as cranberry fruit worm and sparganothis fruit worm, without harming natural predators like spiders.

Work for 2021 will include tests against additional pests, including timing and monitoring for flea beetle and for CFW larvae; scaled-up production to enable full bed applications; and safe application so that nematodes arrive at the bed’s soil ready to hunt prey.

A workshop will be hosted May 6, beginning at 1pm, by Shawn’s student Brandon Gominho. The workshop will be hosted at a marsh in Warrens. Please email allison.jonjak@wisc.edu or contact Pam Verhulst to RSVP so we can give location information and have enough supplies available.

Pam Verhulst-Observations from the Field and Looking Ahead

Unseasonably warm weather the week before the Mini-Clinic was followed by colder than usual overnight temps, causing many growers to wonder about frost protection. Pam led a series of grower polls, using photos from the day before the mini-clinic, showing different varieties at different stages of bud progression about frost protection the for week of April 12 across Wisconsin’s three growing regions.

The interactive polls generated lively discussion, and helped growers to understand what factors influence neighbors to protect or not protect, and, if protecting, whether to flood or irrigate.

Pam also discussed leafhoppers and early weeds, echoing Christelle Guédot’s comments about early scouting and relying on assistance for identifying leafhoppers to the species level.

Leslie Holland-Fungicide Resistance and Lab Work

Indar and Abound are frequently used, economic, and effective fungicides. However, since we have no other FRAC groups in common use, there is concern that repeated use could result in fungicide resistance over time. Leslie’s lab will perform tests using spiral plate technology in 2021 to establish baseline sensitivities of different fruit rot pathogens. This work will support our fundamental understanding of fungicide efficacy and sensitivity, and help identifiy fungicide resistant isolates. Along with trials focused on assessing effectiveness of new chemistries and new biological controls, Leslie will focus on finding new tools that will allow functional group rotations so that Indar and Abound don’t lose their efficacy.

Allison Jonjak-Field Trials for 2021

Following the retirement of Jack Perry, Allison will be conduction field trials to assist the specialists’ inquiries into the best products, timings, and management controls to product profitable cranberry crops. This year, three trials will be done in the pathology realm, three trials in the entomology realm, and three trials in the weed science realm.

Disease trials will include:

1. Candidate Fungicides for Fruit Rot at early bloom and late bloom.
   • 9 chemistries, Indar+Abound, control to broaden FRAC groups
2. Reduced Risk/Biologicals for Fruit Rot at early bloom and late bloom.
   • 4 products, Indar+Abound, control to explore biologicals & organics
3. Use Patterns for Fruit Rot at 20% bloom and 80% bloom, vs 1 at 50% bloom.
   • 3 chemistries, Indar+Abound, control to explore differences in control at different spray timings. Will be tested on newer varieties.

Insect trials will include:

1. Leaf Hopper trials pre-bloom (nymph) and post-bloom (adult).
   • 8 chemistries, control to ensure control against new-old pest
   • Observing: insects in sweeps at 7, 14, and 21 days after application
2. Flea Beetle Adult Trials
   • 8 chemistries, control to explore reg & non-reg chemistries
   • Observing: FB in sweeps at 3, 7, and 10 days after application
3. Degree Day Model targeting egg hatch of Sparg & Cran Fruit Worm.
   • Spray timing: Altacor at 10%, 25%, and 40% sparganothis hatch
   • Spray timing: Altacor at 10%, 25%, and 40% cranberry fruit worm hatch
   • Observing: insects in sweeps at 7, 14, and 21 days after application

Weed science trials will include:

1. Pre-Emerge Herbicides pre and post bloom.
   • 3 experimental herbicides to establish crop safety & spectrum of control and tank-mixed growth regulators to trick weeds into growing when herbicides are present
   • Observing: visual eval of weed control, crop injury, yield, and quality
2. Post-Emerge Herbicide
   • broadleaf active with grass/sedge/rush tank mix to refine rates and timings
   • Observing: visual eval of weed control, crop injury, yield, and quality
3. Plant Growth Regulators
   • commercially available but not reg. for cranberry, naturally occuring hormones to close canpoy faster after renovations
   • Observing: vine length; canopy cover (digital measurement)

Actionable Information

At the end of the mini-clininc, 18% of respondents reported learning 6 or more things, 93% learned 2 or more things, with all respondents learning at least 1 thing. 53% of respondees will use something they learned immediately, and 47% will use something they learned over the course of the growing season.

This article was posted in Cranberry and tagged 2021 Spring Mini-Clinic, Allison Jonjak, anoxic stress, Cranberries, cranberry, field trials, fungicide resistance, Fungicides, groundwater, Leafhoppers, Nematodes, nitrates, phenocams.