Yellow Star Thistle

Is there something good about yellow star thistle? Ask a beekeeper and the answer will be yes! I’ve driven around “star thistle country”, looking and sniffing the air for lush concentrations of the plant, my excitement growing proportionately with the height of the plant – 3 or 4’ high and I’ll stop and talk to the landowner, offering honey in trade for use of the location. Some of my fondest July beekeeping memories are seeing beautiful pristine, white, hexagonal combs of beeswax full of yellow-amber honey with a blooming field of star thistle in the background. Extracted, this honey has a wonderful taste and fresh clean fragrance (hint of lemon) making it one of California’s finest varietal honeys. Yellow star thistle flowers (Centaurea solstitialis) yield nectar and good protein-rich pollen over a long slow period during the hot summer days of June, July and August. These flowers provide the major source of summer honey in the Sacramento Valley. The pollen ensures that the bees will raise abundant brood, the young bees which keep the hive healthy during the fall and winter.

Honey bees (Apis mellifera) help pollinate many farm and garden crops including flowers, fruit and nuts, squash, melons and cucumbers and seed crops such as sunflowers, onions and alfalfa. Healthy hives with abundant bees work many flowering plants and weeds concurrently, including some extra-floral and honeydew secretions. In the process they gather the nectar and the protein/amino acid and mineral balance that they need for healthy reproduction. The individual foraging bees from these hives, however, concentrate on just one plant species at a time as they work, a fact which makes them especially effective as pollinators.

Unfortunately, all is not well with the honey bees and their brood these days. Two small parasites are creating havoc with beekeeping across the country. The tracheal mite (Acarapis woodi) firs entered the country in 1984 and the Varroa mite (Varroa jacobsoni) in 1987, even later (1990-91) in California. Reports of commercial and hobby beekeeping losses of 50-80% have been confirmed across the US – the largest in beekeeping history. In addition, in many states formerly abundant feral colonies have been decimated. The tracheal mite is microscopic and it infests the breathing tubes of trachea of the honey bee. If ignored, it becomes very serious and can lead to large losses during over-wintering and spring buildup. It is being managed by feeding the bees vegetable shortening and by vaporizing food grade menthol crystals in the hive. The Varroa mite is even more serious and if untreated, it kills nearly all hives within one, two or three years. This mite is visible to the naked eye, and it reproduces on the developing bee pupae in the sealed cell, resulting in a deformed and weakened bee, and in failing populations. Furthermore, mite-stressed hives are more susceptible to viral, bacterial and fungal diseases. Varroa mite is controlled currently with fluvalinate (Apistan ®) a synthetic pyrethroid. These products are applied once or twice a year during non-productive periods in the season. Research is underway to find alternative controls (essential oils, etc.) which can be alternated, and to develop mite-resistant or tolerant bee stock. The latter involves selecting strong productive colonies for hygienic and grooming behavior and for brood development time, and then breeding new queens from these stocks. It will take some years to assess the success of this important work.

Gardeners and farmers can help honey bees and feral honey bees by planting and by tolerating important pollen and nectar-producing plants that will help to provide season-long forage for bees and other pollinating insects. A few examples include trees such as linden species, willow (Salix spp.), eucalyptus species, black locust; legumes such as clovers, trefoil and vetch; shrubs like wild and cultivated berries, vitex, coffeeberry, toyon, salvia species, doveweed, poison oak, tarweed, blue curl, baccharis and rabbitbrush; and herbs such as oregano, lavender and rosemary. Equally important is creating and not disturbing habitat where other important pollinating insects nest. These include the many solitary and social bees, bumblebees and wasps which can be of great local importance in pollination Nesting sites include holes in the ground or in wood, or nests fabricated from mud, leaves or wax. Observing and identifying species and enhancing habitat or even raising some of these insects is possible.

Even though the control of yellow star thistle on productive farmland is an important task, knowing of the plants’ benefits in the inter-connected webs of farm ecology can help with our attitude toward a troublesome weed. Unused areas and corridors of yellow star thistle, like clover pastures, riparian habitats with sweet clover, willow and mustard, or nearby chaparral can provide important sources of honey and pollen which help keep honeybees and other pollinating insects alive and thriving.

Jim Nelson


Other insect pollinators:

Dr. Keith S. Delaplane
Associate Professor Dept. of Entymology
University of Georgia
Athens, Georgia 30602

American Bee Journal
51 S. 2nd. St.
Hamilton, IL 62341
(217)847-3324  fax (217) 847-3660

The Forgotten Pollinators
Dr. Stephen Buchmann & Dr. Gary Nabhan
Shearwater Books/Island Press, July 1996

Honey bees and mite problems:

American Bee Journal (see above)

Bee Culture
A.I. Root Co.
Medina, OH 44258

Jack Griffes
Honey Bee Improvement Program Coordinator and Cooperator
7056 Samaria Rd.
Ottawa Lake, MI 49267
(313) 856-8845

Diana Sammataro, PhD.
Ohio State University
OAROC/Dept. of Entymology
Extension Bee Lab
1680 Madison Ave.
Wooster, OH 44691
(330) 263-3912  fax (330) 262-2720

James E.Tew
State Apiculture Specialist
Ohio State University
Wooster, OH 44691

Don Jackson
RR 3, Box 81
Pequot Lakes, MN 56472

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