Bee-friendly plants and pest management strategies – Part 1

What does “bee-friendly” mean and how can ornamental plant growers produce plants that are safe for pollinators?

Honey bee on flower. Photo credit: Orangeaurochs, Flickr.com

Honey bee on flower. Photo credit: Orangeaurochs, Flickr.com

During the last two years, several new research studies and a major review paper indicate that bumble bees and other native bees can be affected by very low levels of neonicotinoid insecticide in pollen and nectar (less than 20 ppb). Honey bees appear to be more tolerant because of the large colony size and multiple food sources, but they can be affected too. Several environmental groups have been actively campaigning for more careful use of neonicotinoid insecticides or banning their use entirely. In June 2014, President Barack Obama issued a memorandum instituting a new Pollinator Task Force. Other national associations and organizations have also established new initiatives and programming on pollinator health. For example, the American Floral Endowment has established the new “Horticultural Industry Bee and Pollinator Stewardship Initiative” and AmericanHort recently released a call to action for the ornamental horticulture industry in the video, “Protecting Bees and Pollinators: What Horticulture Needs to Know.” The burgeoning number of new stories can leave anyone’s head spinning. What does “bee-friendly” really mean and how can an ornamental plant grower grow plants that are safe for pollinators?

In order to answer that question, Michigan State University Extension needs to address the meaning of “bee-friendly.” Plants that are bee-friendly provide pollen and nectar to pollinators – in other words, they are a good food source. However, bee-friendly can also refer to pest management practices used to grow plants with no harmful insecticide residue on the flowers or in the pollen and nectar.

Bee-friendly plant species

There are numerous plants that are attractive to pollinators or could be considered bee-friendly. Table 1 shows some examples of plants that were found to be the most attractive to pollinators in a 2014 study performed by researchers at the University of Sussex, UK. The listed plant species were the most attractive to a variety of pollinators in two years of observation. The pollinator types observed on the plants included bumble bees and other native bees, 16 different species of butterflies, moths, beetles, flies and yellow jackets. Most perennials that produce lots of flowers over a long bloom period are very good for pollinators.

Table 1. Plants found to be extremely attractive to pollinators in a study published in 2014.

Genus

Common name

Organum

Oregano

Agastache

Anise hyssop

Lavandula × intermedia

Lavender

Nepeta

Catmint

Echium

Viper’s bugloss

Salvia

Salvia

Borago

Borage

Dahlia

‘Bishop of Oxford’ Dahlia

Adapted and summarized from Garbuzov and Ratnieks (2014)

Table 2 lists several native Michigan plants that attract bees and other beneficial insects. More information about native Michigan plants can be found in MSU Extension Bulletin E2973, “Attracting Beneficial Insects with Native Flowering Plants,” and the MSU Native Plants and Ecosystem Services website.

Table 2. Native flowering plants that attract beneficial insects, listed as either good, better or best for attracting bees and beneficials.

Common name

Scientific name

Bees

Natural enemies

Golden Alexanders

Zizia aurea

Better

Best

Penstemon/hairy beardtongue

Penstemon hirsutus

Better

Better

Late figwort

Scrophularia marilandica

Better

Better

Swamp milkweed

Asclepias incarnate

Better

Better

Culver’s root

Veronicastrum virginicum

Best

Better

Yellow coneflower

Ratibida pinnata

Better

Best

Nodding wild onion

Allium cernuum

Better

Good

Meadowsweet

Spiraea alba

Better

Best

Yellow giant hyssop

Agastache nepetoides

Best

Better

Horsemint/spotted beebalm

Monarda punctata

Better

Best

Missouri ironweed

Vernonia missurica

Better

Better

Cup plant

Silphium perfoliatum

Best

Best

Pale Indian plantain

Cacalia atriplicifolia

Better

Better

Boneset

Eupatorium perfoliatum

Better

Best

Blue lobelia

Lobelia siphilitica

Best

Best

Pale-leaved sunflower

Helianthus strumosus

Best

Best

Riddell’s goldenrod

Solidago riddellii

Best

Best

New England aster

Aster novae-angliae

Better

Best

Smooth aster

Aster laevis

Better

Better

Adapted from “Attracting Beneficial Insects with Native Flowering Plants” by Anna Fiedler, Julianna Tuell, Rufus Isaacs and Doug Landis. MSU Extension Bulletin E2973.

Bee-friendly pest management practices

Choosing which pest management practices are best is still under debate among entomologists. There has not been enough research on insecticide residuals in ornamental plant pollen to develop reliable guidelines to protect pollinators. As a baseline, growers can use the following guidelines this season in order to produce plants that are safe for pollinators:

  • Don’t spray flowering plants with any insecticide, unless it is one of our listed alternatives in Table 3, during the last three weeks before shipping plants to your customer.
  • Avoid soil drenches with neonicotinoids and other systemic insecticides as much as possible. If systemic insecticides need to be used in hanging baskets, do not exceed the labeled rate and do not drench them any later than five weeks before shipping.
  • Growers should not use a systemic soil drench on linden trees or other trees and shrubs that are highly attractive to bees.

Table 3. Pest control products that can be used in the last two to three weeks before plant shipment.

Products

Target pest insect

Horticultural oil products (Ultra Pure, Suffoil, etc.) at 0.5% (1/2 gal per 100 gal)

Spider mites, whitefly, aphids, and thrips larvae

Insecticidal soap (M-Pede) at 1.0 % (1 gal/100 gal)

Spider mites, whitefly, aphids, and thrips larvae

Botanigard or Mycotrol (Beauveria bassiana, a fungal pathogen)

Whitefly, aphids, and thrips

No-fly (fungal pathogen)

Spider mites, whitefly, aphids, and thrips larvae

Neem products (Ornazin, Amazin Plus, Agroneem Plus)

Whitefly, aphids thrips

Spinosad (Conserve)

Thrips

Xxpire

Thrips and whitefly

Rycar

Whiteflies, aphids, thrips and mealybugs

Because of the ambiguity of the term bee-friendly, other phrases might be more indicative of what we are truly trying to portray to our consumers: that ornamental plants are being grown in a way that will not be harmful to bees and other pollinators in the yard and garden. Researchers are now conducting experiments that will give us more information for developing “best management strategies to protect pollinators.” Part 2 of this article will cover the consumer’s perceptions of bee-friendly and address why there might still be reasons to use it for marketing purposes.

Note: Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.

See Part 2 of this series: Why should you consider marketing your plants as bee-friendly? – Part 2

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