Resistant Pests and Weeds

Agricultural weeds and honey bee pests regularly develop resistance to chemical treatments, especially when the chemicals are used repeatedly. Six authors present diverse views on the increasing problem facing American industrial agriculture as the list of weeds resistant to the most commonly used herbicide increases. Log onto today’s New York Times opinion piece at http://roomfordebate.blogs.nytimes.com/2010/05/06/invasion-of-the-superweeds/ to read these authors’ thoughts on the causes of ten species of weeds evolving a resistance to Glyphosate. They also offer a range of possible solutions to correcting the problem by changing agricultural practices. Glyphosate, known by the name Roundup and other names, is used extensively with genetically modified crops that have been designed to be tolerant of the effect of the herbicide. While weeds evolve a resistance to Roundup in the fields, honey bee pests evolve a resistance to chemicals in the small environment of the bee hive. Beekeepers have seen American foulbrood, a bacterial disease, become resistant to antibiotics. Parasitic Varroa mites rapidly evolved to become resistant to each of the chemical miticides used in the bee hive. Corn, soybean, and cotton farmers are finding it necessary to use different herbicides and mechanical cultivation techniques to control Roundup-resistant weeds. Many beekeepers are moving away from the use of antibiotics and miticides in an effort to keep bees healthy without building strains of resistant pathogens and pests.

Today’s picture shows Palmer pigweed, one of the six species of Roundup-resistant weeds found in Arkansas. The plant, taller than a person’s head, stands outside a hundred-year-old barn at Peace Bee Farm. I regularly see Palmer pigweed standing above crops in nearby fields. Roundup is a most useful herbicide used by beekeepers to control foliage around bee hive stands. As a test, I sprayed the pigweed by the old barn with Roundup. The tall weed was easily killed by a single spraying at the labeled concentration; it was not resistant. Row-crop farmers and bee farmers should continuously evaluate their Integrated Pest Management approaches.

--Richard

Elderberry and Pigweed

The elderberry is a tall, common shrub of roadsides and forest margins. Throughout July, the plants were crowned with broad clusters of small, white, fragrant flowers. Now the flowers, pollinated by honey bees and other insect pollinators, are giving way to prolific bunches of berries. In the photo, the elder berry shows white flowers as well as green and dark purple berries. The ripe berries will darken and turn black in color. Elderberry is one of the flowering plants that go a long way toward supporting wildlife. The plant is browsed by deer. The berries are eaten by rabbits, fox, and squirrels. At least 25 species of birds including indigo bunting, bluebird, catbird, mockingbird, brown thrasher, phoebe, robin, dove, quail, turkey, and woodpeckers regularly eat the fruit of the elder berry plant. The elderberries are used to make pies, preserves, and wine.

The Memphis Commercial Appeal reported yesterday that hundreds of thousands of acres of soybean and cotton fields in the Mid-South have been infested by an herbicide-resistant strain of a common weed, Palmer pigweed. The pigweed is thriving in the presence of the most commonly used chemical herbicide, glyphosate, which is commonly sold under the trade name Roundup. Soybeans, cotton, and other plants have been genetically engineered to withstand glyphosate, allowing the weed killer to be sprayed directly on the crops. The herbicide-resistant pigweed can’t be controlled by glyphosate, so farmers are being required to return to labor-intensive hand chopping of the weed. We find in agriculture that chemical resistance commonly occurs. That has been the case with beekeeping, as strains of miticide-resistant mites replaced the first mites to enter this country. The beekeepers are having to adjust their mite control tactics; now the row-crop farmers will have to do the same.
--Richard