Beekeepers don't like their "girls" foraging in California buckeye (Aesculus californica)
It's poisonous to bees.
"The signs of poisoning can be as severe as dying adult bees and brood, only dying brood, brood that barely makes it and emerges misshapen, brood that emerges undersized, and probably bees that don't live normal lifespans, but we haven't proven that," says Extension apiculturist emeritus Eric Mussen, who, although retired, continues to maintain an office in Briggs Hall, UC Davis campus.
Is it the pollen or the nectar that's poisonous?
Possibly it's only the pollen that contains the toxin, "but some pollen always ends up in the nectar and honey," Mussen says.
"It is all a matter of dilution. When many different plants are producing pollen and nectar at the same time as the buckeye, sometimes the bees escape undamaged. However, beekeepers have long known that on dry years the buckeye is the best producer of both pollen and nectar, so the bees go for it.
What to do? Bees can fly some five miles from the hive to collect nectar and pollen. It isn't always possible for beekeepers to move their bees out of areas with buckeye, "especially on dry years--we've had more than enough of those," Mussen says.
"Otherwise, they feed the bees with substitute, pollen traps might help a bit but most beekeepers don't have them, they feed sugar syrup, and if they can do it, they take the buckeye-pollen combs out. If the combs are left in, the buckeye pollen gets stored. It gets covered up when fresh pollens start coming in, and things seem to straighten out."
"Then long comes another pollen and nectar dearth and the bees dig into the stores. It is not uncommon to have the bees 'buckeyed' twice in one year," Mussen says.
"California buckeye was discovered in the early 1800s in California and described by Edouard Spach in 1834 (Little 1979, Hickman 1993)," writes Frank Callahan of Central Point, Ore. writing for the Native Plant Society of Oregon.
"All parts of California buckeye are toxic to humans and livestock," Callahan points out. "Poisoning is from glycosidal compounds that are present in all plant parts. Humans have been poisoned by honey made from the flowers (USDA Forest Service 1974). The flowers are toxic to European honeybees (Apis mellifera); however, native pollinators relish the collection of nectar without side effects. The adult pale swallowtail butterfly (Papilio eurymedon) appears particularly fond of this plant."
Yes, we've seen butterflies nectaring on the buckeye. Never seen a buckeye butterfly (Junonia coenia) nectaring on a California buckeye, though!
It won't bloom until summer, but already many eyes are on the California buckeye.
The tree's blossoms are poisonous to honey bees. Bees are attracted to them and forage on them, but the end result of the food provisions to the colony can be deformed larval development.
We've seen bee hives within a quarter of a mile of California buckeyes (Aesculus californica). And we've seen honey bees, native bees and other pollinators foraging on the blossoms.
At the recent UC Davis Pollinator Gardening Workshop hosted by the California Center for Urban Horticulture, Extension apiculturist Eric Mussen talked about the poisonous plants. (See PowerPoint presentations.) That led to one workshop participant wondering if the flowers of the California buckeye are poisonous to native bees. (Honey bees are not native; the European colonists brought them to the Jamestown colony, Virginia, in 1622).
Responded Mussen: "My guess: either the native bees that have been in the areas around California buckeye for a long, long time are not poisoned by the pollen or they have been selected (by death of the other genetic types) to avoid the pollen, that eons of natural selection have adapted them to coexist with California buckeye while using their resources."
Native pollinator specialist Robbin Thorp, emeritus professor of entomology at UC Davis, shared: "We know California buckeye nectar and/or pollen is toxic to honey bees from years of experience with managed hives. Toxicity to native bees and other flower visitors is not so easily determined and to my knowledge has not been investigated. The fact that populations of native bees and butterflies visit California buckeye flowers and continue to persist in areas where the tree is a dominant part of the plant community tends to confirm what Extension apiculturist Eric Mussen says about them. Some good research projects here. So we still do not know if it is the nectar, pollen, or both that may be toxic to honey bees, much less to native flower visitors."
According to gardeningguides.com, the seeds in their raw state are poisonous to humans, but native Americans learned to get around that and use them for food. They pounded the seeds into flour and then cooked the mixture. "This tree had multiple cultural uses among California Indian tribes," the website says. "Many indigenous groups utilized buckeye seeds for food, often when other plant food sources were scarce. These tribes included the Costanoan, Salinan, Kitanemuk, Serrano, Wappo, Sierra Miwok, Coast Miwok, Chumash, Kawaiisu, Northern Maidu among others. The Pomo ate the seeds even when other important food plants were plentiful. The seeds are poisonous to humans in the raw state. Thus, the nuts were cracked open with a rock, the shells removed, the seeds pounded into flour, and their toxic saponins removed in a lengthy leaching process. The meal was subsequently cooked and eaten. There are many different methods for processing and cooking buckeye seeds for food, depending upon the tribe. The seeds have medicinal properties and were cut into pieces, mixed with water, and made into suppositories for hemorrhoids by the Costanoan and Kawaiisu. The Pomo cut bark from the base of the tree and made a poultice, which was laid on a snakebite. Young buckeye shoots were sometimes used as spindles or twirling sticks in fire-making kits of the Sierra Miwok, Northern Maidu, Wappo, Yahi and other tribes. Many tribes mashed buckeye nuts and poured the contents into quiet pools to stupefy or kill fish."
And, no wildlife will eat buckeye seeds except squirrels, such as the California ground squirrel (Citellus beecheyi).
Meanwhile, the poisonous blossoms continue to beckon the honey bees--and their colonies keep producing deformed bees.
A miss is as good as a mile...or a smile.
The Buckeye (Junonia coenia) is a striking butterfly patterned with eyespots and white bars. We saw one today nectaring on sedum, but with chunks of a wing missing. Perhaps a bird or a praying mantis tried to grab it. It narrowly escaped predation.
A lucky day.
It's quite a common butterfly, as common as it is recognizable.
The Buckeye "is found in southern Manitoba, Ontario, Quebec and Nova Scotia and all parts of the United States, except the Northwest," according to Wikpedia. It's also found throughout Central America and Colombia.
"The Buckeye breeds on plants containing bitter iridoid glycosides, including plantains (Plantago, especially P. lanceolata), various Scrophulariaceae (especially Fluellin, Kickxia), and Lippia (Lippia or Phyla nodiflora)," says butterfly expert Art Shapiro, UC Davis distinguished professor of evolution and ecology, on his website. "The spiny, black-and-white caterpillar has a bright orange head. Its behavior suggests its diet makes it virtually immune to vertebrate predation, but the pupa and adult are quite edible."
Well, this is one adult that got away.
The California Gold Rush (1848-1855) has nothing on honey bees.
Sometimes foraging honey bees are covered with their own kind of gold--pollen--or protein for their colonies.
We saw this honey bee dusted with gold from head to thorax to abdomen as she gathered pollen from blanket flowers (Gaillardia). Her flight plan seemed uncertain, as her load was heavy and her visibility, poor. She struggled to take off, but take off she did.
Speaking of the Gold Rush and honey bees, entomologists always associate the arrival of honey bees in California with the California Gold Rush. That's because honey bees were introduced to California in 1853, right in the middle of the Gold Rush.
Back then, the hills were covered with wildflowers where bees gathered nectar (carbohydrates) and pollen (protein). Today, however, scientists are worried about bee malnutrition.
"Honey bee colonies need a mix of pollens every day to meet their nutritional needs," says Extension apiculturist Eric Mussen of the UC Davis Department of Entomology and Nematology. "In fact, they should have a one-acre equivalent of blossoms available to them daily to meet their demands. They can fly up to four miles from the hive--a 50-square mile area--to gather that food and water (and propolis, plant resin)."
A worried beekeeper recently asked him about the declining bee population and wondered why his own colonies were dwindling. In addition to malnutrition, Mussen listed a few other possibilities:
Varroa mites – "They suck the blood from developing pupae and adult bees, shortening their lifespans. They vector virus diseases, the easiest to see being deformed wing virus. If you have adult bees around the colony with curly, undeveloped wings, then you have too many mites. If you see mites on the bees when you look in the hive, that is too many mites."
Nosema ceranae and other diseases – "You need a microscope to see the spores of a Nosema infection. Go to Randy Oliver’s webpage, Scientificbeekeeping.com, and look at the information on Nosema ceranae and spore counting."
Contact with toxic chemicals – "Since your bees can fly up to four miles away to forage, that also is the distance within which they can get into trouble with bee-toxic chemicals. It is not likely that the organic farm is a source. However, if there are other farms around, or if your neighbors (golf courses, shopping centers, parks, playgrounds, etc.) are having problems with sucking or chewing insects, they may have used one of the neonicotinoids on their shrubs or trees. Turf and ornamental dosages are considerably higher than those used in commercial agriculture. So, the amounts of toxins in nectar and pollens can be toxic to honey bees and other pollinators."
Mussen also acknowledged that California buckeye blossoms are toxic to bees. "This was a fairly dry spring," he said. "Not too many weeds and wildflowers were around when the California buckeye came into bloom. Buckeye pollen is toxic to developing bee brood and to adult bees, if it gets to be their primary food source in the colony."
The problem could also be due to other issues as well, Mussen said. "Maybe the queens did not mate with enough drones, or the queens got too hot or too cold during their journeys to your hives, etc."
"As beekeepers, it is up to you to stick your nose in the hive, look at everything and try to determine what may be going wrong. If you are feeling way too new at this to have any idea of what is going on, then contact your local bee club--there is one in practically half of the California counties--and find someone to help access your problems."
And the pollen, that precious protein? "When beekeepers examine their hives, they should see a good supply of pollen with many colors," Mussen says.
They're definitely attracted to it.
Honey bees forage furiously on the California buckeye (Aesculus californica).
It's not a good bee plant, though. It's poisonous.
Of California's main bee-poisonous plants--buckeye, death camas (Zigadenus veneosus) corn lily (Veratrum californicam) and locoweed (Astragalus spp.)--the most hazardous to bees because of its wide distribution is the buckeye tree.
Its distribution includes the UC Davis campus. If you walk behind Hoagland Hall, you'll see a thriving buckeye.
And bees and other insects foraging on the blossoms.
"Symptoms of buckeye poisoning usually appear about a week after bees begin working the blossoms," according to the Cooperative Extension booklet, Beekeeping in California, published in 1987 by the UC Division of Agriculture and Natural Resources. "Many young larvae die, giving the brood pattern an irregular appearance. The queen's egg-laying rate decreases or stops, or she may lay only drone eggs; after a few weeks, an increasing number of eggs fail to hatch or a majority of young larvae die before they are three days old."
The booklet, co-authored by six bee experts--five from UC Davis--points out that "Some adults emerge with crippled wings or malformed legs and bodies."
"Foraging bees feeding on buckeye blossoms may have dark, shiny bodies and paralysislike symptoms. Affected colonies may be seriously weakened or may die."
UC Davis Extension apiculturist Eric Mussen edited the publication. Other co-authors were UC Davis entomology professors/apiculturists Norman Gary and Robbin Thorp (both now emeriti); apiculturist Harry H. Laidlaw Jr., UC Davis professor of entomology (deceased); and apiarist Lee Watkins (deceased). Also lending his expertise: Len Foote of the California Department of Food and Agriculture.
If the name Harry H. Laidlaw Jr. sounds familiar, that's because the bee facility on Bee Biology Road, about a mile west of the central campus, carries his name.