Emerald Ash Borer Treatment- Toxic To Bees?

Image Source: Wikipedia

The emerald ash borer, Agrilus planipennis a beetle native to China, Japan and Korea was introduced into North America in the Great Lakes area in the early 1990's and populations were identified in 2002. It is suspected that this beetle was introduced from ash shipping crates. Emerald ash borer beetle larva burrow through the outer bark of ash trees, Fraxinus spp. and into the living cambium tissue.

As the larvae feed on the cambium, they create 'S'-shaped galleries in the wood. The galleries created from a large infestation weaken the ash trees causing canopy thinning and eventually canopy die-back. A secondary symptom is numerous shoots forming around the base of the ash tree.

Current Map of Emerald Ash Borer Range
Source: emeraldashborer.info

As a homeowner living in Minnesota just outside the range of emerald ash borer, I started to research the treatments being offered by local tree care companies. I only have one ash tree on my property and do not plan to treat it but many of the suburban neighborhoods in the Twin Cities were heavily planted with ash trees in the late 1970's and early 1980's. I am reminded when driving through these neighborhoods that planting a diversity of native plant species in your landscape will help with weathering the impacts from invasive species and climate change.

"Systemic insecticides containing the active ingredients imidacloprid, dinotefuran or emamectin benzoate are commonly used to protect ash trees from EAB." (Potential Side Effects of EAB Insecticides) Imidacloprid belongs to the group of neonicotinoid insecticides which has been linked to Colony Collapse Disorder (CCD). Read a recent Xerces Society report here: Are Neonicotinoids Killing Bees? Today, a coalition of bee-keepers have filed a suit against the EPA for failing to suspend the use of neonicotinoid pesticides.

Imidacloprid, sold under the trade names Merit, Xytect, Optrol, ArmorTech, Enforce, Hawk-I, Turfthor, Malice, Premis, Criterion, Hunter, Submerge and Touchstone is typically applied as a soil drench or soil injection annually as a preventative treatment for emerald ash borer. For a homeowner with several ash trees, the cost can be very high. The city of Minneapolis now recommends replacing ash trees on residential properties rather than treating them due to the environmental risks from the treatments including, leaching into the surface or ground water, uptake by other plants visited by pollinators for nectar and pollen and non-target effects on woodpeckers feeding on EAB larvae.

Are your ash trees worth saving or should you be preparing for their replacement? Are the risks of using neonicotinoids too high? Purdue University offers a cost calculator for EAB treatment for homeowners here. Trees with structural defects, poorly sited, or with no historical or aesthetic value should not be treated. Read more guidelines here.

Perhaps our efforts should be focused on the conservation of ash tree species. Volunteers are needed for the collection of ash seeds to help preserve genetic variation and with a long-term goal of the reintroduction of ash trees into affected areas. Find out more information on how you can help collect ash tree seeds.

References:
The Effects of Neonicotinoids on Honey and Bumble Bees.Vera Krischik, Entomology, University of Minnesota.
Chemicals Implicated. BeyondPesticides.org
Blacquiere, T., Smagghe, G., Van Gestel, C. A., & Mommaerts, V. (2012). Neonicotinoids in bees: a review on concentrations, side-effects and risk assessment. Ecotoxicology, 1-20.
Emerald Ash Borer Info

Wild Geranium Pollinators & Floral Visitors

Like many spring-flowering native plants, wild geranium flowers have the ability to self-pollinate when no pollinators are present. However, the flower matures to ensure cross-pollination when insects are present, with the row of outer anthers developing on the first or second day after the flowers open, followed by the inner row on the second or third day. The stigma becomes receptive after the anthers have dehisced on the third or forth day.

Bees, flies and beetles visit the flower for nectar and pollen. Nectar is secreted from five glands located between the stamens and sepals. In a study by Bertin et al, bees visiting for nectar were responsible for depositing more pollen than pollen collecting bees. Larger bees such as bumble bees and mason bees are considered effective pollinators because pollen brushed onto the underside of their abdomen contacts the stigma. Smaller bees are able to circle around the base of the stamens feeding on nectar without coming into contact with pollen from the anthers above.

Wild geranium flowers are over one inch in width and extremely showy. Dark lines on the flowers act as nectar guides, showing pollinators the location of the nectaries at the base of the stamens.

Small Carpenter Bees, Ceratina spp.
Smaller bee species circle the base of the flower seeking out nectar without coming in contact with the anthers and stigmas above.

Cuckoo Bees, Nomada spp. 
Wild geranium is a nectar source for this cuckoo bee in early spring. Female Nomada bees lay their eggs in the nests of ground nesting native bees, especially mining bees (Andrena spp.). The cuckoo bee eggs hatch and the larvae kills the host bee larvae and consumes the provisions provided by the host. Nomada bees are reddish-brown to black with yellow or white markings.

Mason Bees Osmia spp. 
Mason bees visit wild geranium for both pollen and nectar. Females land on top of the anthers gathering them together with her legs. Pollen is brushed onto the pollen-collecting hairs on the underside of the abdomen. Wild geranium is an important source of pollen and nectar for mason bees, it flowers when females are provisioning their nests.

Sweat Bees Lasioglossum spp.
Sweat bees visit the flowers to feed on nectar.

Fruitworm Beetles Byturus unicolor 
Long, dense hairs cover the elytra of these beetles where pollen grains attach. Adults emerge from the soil in early spring, feed on host plants (raspberries, blackberries and avens), mate, then lay eggs. Larvae burrow into the flower buds and fruit of the host species and buds drop off or decay. Fruit becomes misshapen and ‘wormy’. Look for adult beetles feeding on the pollen of woodland natives in early spring such as Viriginia waterleaf and wild geranium.


References 
Bertin, R. I., & Sholes, O. D. (1993). Weather, pollination and the phenology of Geranium maculatum. American Midland Naturalist, 52-66. Retrieved from: http://www.jstor.org/stable/2426435

Willson, M. F., Miller, L. J., & Rathcke, B. J. (1979). Floral display in Phlox and Geranium: adaptive aspects. Evolution, 52-63. Retrieved from: http://www.jstor.org/stable/2407365