Bulletin #2385, Organic Materials Review Institute (OMRI)–Approved Inputs for Organic Wild Blueberry Production

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By Lily Calderwood, Ph.D., wild blueberry specialist and associate professor of horticulture, University of Maine Cooperative Extension; Seanna Annis, Ph.D., Extension professor and professor of mycology, University of Maine; Philip Fanning, Ph.D., assistant professor of agricultural entomology, University of Maine; and Leala Machesney, Extension and research professional, University of Maine Cooperative Extension

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Introduction

While many fertilizers and pesticides are available to conventional wild blueberry growers, few fertilizer and pesticide options are available to organic-certified Maine wild blueberry producers. In Maine, organic certification is administered by the Maine Organic Farmers and Gardeners Association (MOFGA), in accordance with National Organic Program (NOP) standards. Certified organic wild blueberry producers may apply only fertilizers and pesticides that comply with NOP regulations. This means that all organically certified wild blueberry farms can apply only products on the Organic Materials Review Institute (OMRI) list. This list is updated annually and growers should ensure a product is currently listed before each use. In addition, growers are legally required to read and fully comply with the organic product label before each use.

Weed Management and Fertilizers

Reducing the soil pH and burning are the two key management practices for organically managed wild blueberry fields. Lowering your soil pH using organically approved sulfur will create an acidic soil environment that your wild blueberry plants can live in but most grass and broadleaf weeds cannot. High-concentration vinegar is the only recommended and OMRI–approved burn down herbicide available to organic producers. Nutrients should be applied after weeds are under control to prevent fertilizing weed species.

90% Elemental Sulfur: pH Lowering

Apply sulfur based on the results of soil testing to reach a soil pH of 4.0–4.3.

Pelleted Chicken Manure: Nitrogen Source

Provides nitrogen for growth and plant health. Only apply pelleted chicken manure after weeds are under control.

Solubor (Boron): Boron Source

Use Solubor only if soil and leaf testing indicate a boron (Bn) deficiency. Solubor can improve fruit set, but do not over-apply, as plant toxicity can occur.

Wood Chip Mulch: Increased Organic Matter

Tractor spreading softwood chip mulch.
Image 1. Apply 1.0–1.5 inches of soft wood chip mulch for optimal soil moisture retention and weed suppression.

Wood chip mulch can prevent erosion in wild blueberry fields, improve soil water-holding capacity, and prevent the establishment of weed species stands. As mulch decomposes, it becomes soil organic matter.

High-Concentrate Vinegar

High-concentration non-food-grade vinegar can be sprayed as a burn down herbicide. It will not kill the plants but knocks them back, similar to the action of cutting weeds above the blueberry canopy. This type of vinegar can be found at box stores and ranges from 30% to 45% vinegar, which can burn your skin. Diluting high-concentration vinegar with water down to 20% will still burn down the tops of weeds.

Further Reading

Insect Pest Management

Flea beetle on leaf.
Image 2. Flea beetles are common pests found in Maine wild blueberry fields.

Organic insecticides often have shorter residuals compared to synthetic insecticides. Regular field scouting with sweep nets and traps is required to understand the pest pressure in your field(s) and determine the appropriate time to apply insecticides.

Entrust SC

Active ingredient: Spinosad
Target pests:

  • Spotted wing drosophila (Drosophila suzukii)
  • Strawberry root worm (Paria fragariae)
  • Spanworm larvae (Itame argillacearia)

Estero SC

Active ingredient: Spinosad
Target pests:

  • Spotted wing drosophila
  • Strawberry root worm
  • Spanworm larvae

GF 120 NF Naturalyte

Active ingredient: Spinosad
Target pest:

  • Blueberry maggot fly (Rhagoletis mendax)

Bacillus thuringiensis (Bt)

There are many OMRI–approved formulations of this active ingredient.

Target pest:

  • Spanworm larvae

BotaniGard ES

Active ingredient: Beauveria bassiana
Target pest:

  • Flea beetle (Altica sylvia)

AzaGuard

Active ingredient: azadirachtin
Target pest:

  • Spotted wing drosophila

Further Reading

Disease Control

Mummy berry blight infection in wild blueberry flowers.
Image 3. Mummy berry blight can infect wild blueberry flowers and blooms.

The best organic control for most wild blueberry diseases is burn-pruning. Burn-pruning decreases fungi in the leaf litter and thereby decreases spores to infect plants in the following season. More than 15 organically approved fungicides have been tested for mummy berry (Monilinia vaccinii-corymbosi) control in wild blueberry over the past 15 years. Only Serenade had some effectiveness.

Burn-Pruning

Burn-pruning of fields after harvest will decrease the number of overwintering mummy berries and other fungal structures. Spot-burning under a clone with a lot of mummy berries can locally decrease disease incidence.

Serenade

Active ingredient: Bacillus subtilis
Target diseases:

  • Mummy berry blight
  • Botrytis (Botrytis cinerea) blossom blight

Note: The level of disease control achieved with Serenade depends upon both potential disease pressure and weather.

Further Reading

Critical Reminders

Check with your Certifier

Always confirm a product’s status with MOFGA (or your specific certifier) before you spray. Labels change and a product that was OMRI listed last year may not be listed this year.

Protect Pollinators

Honey bee pollination of wild blueberry plants.
Image 4. Honey bees and bumble bees, as well as other native bee species, are important pollinators of wild blueberry plants.

Even organic products such as Entrust SC can be toxic to bees. Apply pesticides late in the evening when bees are not foraging and avoid application when blueberry and/or weeds are in bloom. For more information, refer to UMaine Extension Bulletin #2009, IPM Tactics to Reduce Pesticide Exposure to Honey and Native Bees.

References

Organic Materials Review Institute. (Jan. 2026). OMRI products list. Retrieved April 2, 2026, from https://www.omri.org/omri-lists/download

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2026

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