APIS Volume 2, Number 3, March, 1984
In this issue
- Poisonous Plants in Florida
POISONOUS PLANTS IN FLORIDA
It may come as a shock to some, but all nectar-producing plants are not beneficial to honey bees. Two plants in particular, both found in Florida, are considered deleterious to colonies. This should not be surprising, considering that some plants are cultivated so that their toxins can be used as insecticides (e.g. pyrethrin). Fortunately, poisonous plants are in the minority and usually nectar flow or pollen production is not prolific enough to damage colonies. However, at certain times and when conditions are optimal, they may pose a threat to honey bees.Carolina jessamine (Gelsemium sempervirens), sometimes called yellow jessamine, is a woody vine which may grow to a height of forty feet and have a diamteter of an inch or more. The plant is well described in Lillian Arnold's classic work, Some Honey Plants of Florida, Bulletin 548, Agricultural Experiment Stations, September, 1954, which is now out of print. "Sometimes it is seen as a low upright shrub, 2 feet or less tall, with slender stems. Its habit may be solitary or colonial...twigs are numerous, slender, crooked, usually intertwined, reddish-brown, smooth and shining." The leaves are evergreen, opposite, thin, smooth, dark green and shining above, much paler beneath, 1 to 3 1/2 inches long, with long-pointed tips and wavy margins. The flowers are yellow, funnel-shaped, 1 1/2 to 2 inches long, with 5 rounded lobes...strongly fragrant. The fruits are oblong, flat, dry, brown, about 3/4 inches long.
This plant occurs in hammocks and swamps from eastern Virginia to as far south as Highlands County, Florida just north of Lake Okeechobee. It may be found as far west as Texas. In Florida, Carolina Jessamine blooms in January and February, and the nectar is reported to be poisonous to bees, but little scientific data exists on the subject. Brood death has been described during the bloom in Texas, but other reports indicated more losses to young nurse bees. The plant's toxicity to bees comes as little surprise because large doses of extracts to other animals are known to be fatal.
I have heard no reports of bee poisoning due to Carolina jessamine, however, that's not true for a plant known variously at summer ti ti (Cyrilla racemiflora), American cyrilla or southern leatherwood. The common name here is unfortunate, because it may cause confusion with the other ti ti (Cliftonia monophylla) or buckwheat tree, which is considered an excellent honey plant. However, the latter is called spring ti ti and flowers in February and March in contrast to summer ti ti, which flowers in May and June.
Summer ti ti, according to Ms. Arnold, may grow to 25 or 30 feet with trunks as large as 1- to 14 inches. Usually, however, it's found growing as a shrub. The crowns are broad, often one-sided, and the twigs are slender and smooth. The leaves are late-falling, shiny above, duller beneath, 2 to 4 inches long, with narrow bases and entire, wavy margins. The flowers are small, white and arranged in spikes 4 to 6 inches long. The plant is found in common with the spring ti ti (buckwheat tree). Both have ranges similar to Carolina jessamine, and in Florida, are generally found in the north and west in swampy areas.
The nectar and/or pollen of the summer ti ti is responsible for a condition sometimes seen in beehives called "purple brood." The brood turns a deep purple and dies; larvae, pupae and newly emerged bees are all affected. The condition appears to vary from year to year, depending on prevailing conditions. Perhaps the worst outbreak occurred in the 1932, when half the colonies in many apiaries of north Florida (Madison, Taylor and Jefferson counties) succumbed. This was reported in a 1933 study by C.E. Burnside and R.E. Foster, "Plant poisoning of brood of bees; tracing down the cause of heavy loss of colonies in Western Florida," Gleanings in Bee Culture 61:470-473.
The small amount of research done so far on causes of "purple brood" appears to implicate the nectar. According to C.E. Burnside and G.H. Vansell in 1936, as reported in Honey Bee Pests, Predators, and Diseases, R.A. Morse, Editor, Cornell University Press, 1978, the "disease" was not transmitted by combs, brood or stored pollen in experiments, but instead by combs of honey transferred to healthy colonies. Feeding a colony extracted honey also killed brood. Neither the nectar nor resultant honey appears to be harmful to humans.
Given that both Carolina jessamine and summer ti ti are implicated as being deleterious to bee colonies, what can the beekeeper do? There appears to be no better advice than that of Ms. Arnold, who labelled the plants in her publication as "undesirable," and said the best course of action was to avoid them as much as possible. Experienced beekeepers do this routinely in areas where bee losses have occurred by moving their colonies out of locations where large tracts of these plants exist. In order to determine if either of these plants might be a problem in your specific area, the best piece of advice is to attend a local beekeepers meeting and/or find an "old timer" who's been around a few years and ask. Sincerely,
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (352) 392-1801, Ext. 143 FAX: (352)-392-0190
http://www.ifas.ufl.edu/~entweb/apis/apis.htm
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
©1984 M.T. Sanford "All Rights Reserved
