Nov 1, 2013 ... Mistletoe. The Good, the Bad, the Birds. Lindy Brigham ... From: Botany under the
Mistletoe: Twisters, spitters, and other flowery thoughts for ...
Mistletoe The Good, the Bad, the Birds Lindy Brigham
Neal Kittelson
PAG EPAC November 1st, 2013
Parasitic Flowering Plants • Plants that live on other plants and draw nutrients and/or water from them • May or may not be green (capable of synthesizing own food) • Examples • Rafflesia • Dodder • Striga • Mistletoe • Dwarf • True From: Essential Plant Pathology, Gail Schuman and Cleora J. D’Arcy, APS Press, 2006
Oddities
Tristerix aphyllus
Phoradendron scabberimum
From: Botany under the Mistletoe: Twisters, spitters, and other flowery thoughts for romantic moments By Susan Milius - Science News - Week of Dec. 23 & 30, 2000; Vol. 158, No. 26 & 27
True vs Dwarf Mistletoe
Leaves, stems, and berries of mistletoe (Phoradendron serotinum).
A female (fruiting) dwarf mistletoe (Arceuthobium campylopodum) parasitizing a shore pine in British Columbia, Canada .
From: Essential Plant Pathology, Gail Schuman and Cleora J. D’Arcy, APS Press, 2006
Local True Mistletoes • • • • •
Phoradendron juniperum (all juniper) Phoradendron coryae (oaks) Phoradendron capitellatum (alligator juniper) Phoradenron densum (Cyprus) Phoradendron pauciflorum (white fir)
Christmas mistletoe (Phoradendron macrophyllum) infests cottonwood, ash, black locust, hackberry, maple, pecan, walnut, sycamore and willow (not oak).
Desert mistletoe (Phoradendron californicum infests typical Sonoran Desert leguminous trees and shrubs. This is the mistletoe that we see growing in mesquite, palo verde, ironwood, and acacia.
Desert Mistletoe - Phoradendron californicum
Desert mistletoe, mesquite mistletoe •
•
• •
The main host plants are Acacia, Olneya, Par kinsonia, and Prosopis species, which are desert trees and shrubs in the Pea Family (Fabaceae). The plants are dioecious with tiny, inconspicuous, yellowish flowers. Producing luscious red berries. Insects are the main pollinators
Life cycle
In Arizona, the stem-parasitic mistletoes produce fruits which begin to ripen in November. Ripe fruit remains on the plant until April and are often the only succulent fruits available in this part of the Sonoran Desert during winter.
Seed dispersal – the Birds P. californicum has special requirements for germination and establishment of sites. Seeds must be eaten and deposited by a bird on a live branch of an appropriate host. Desert mistletoe berries are most frequently eaten by a specialist frugivorous (fruit eating) bird, the Phainopepla, which also possesses a modified digestive system that allows the unprotected seed to bypass the grinding surfaces of the gizzard. Berries are also eaten by generalists like the Gila woodpecker (Melanerpes hypopolius) and the mockingbird (Mimus polyglottus) Phainopepla nitans
The Bad - Disease outcomes • Mistletoes must have a living host plant on which to grow. Although true mistletoes are flowering plants and contain chlorophyll, they have no true roots and must obtain some carbohydrates as well as all their water and mineral nutrients from their hosts. • Infections cause reduced host vigor because mistletoes compete with their hosts for nutrients and water.
But it’s not all bad • True mistletoes reduce the growth of infected hosts, but it usually takes many years to kill a mature tree of shrub (Mary Olsen – UA Plant Pathologist – AZ1308) • In 40 years of observing mesquite trees in Pima County with infections, few were seen to succumb to the infection. (Steve Smith – UA Ecologist, personal communication) • An evolved parasite does not kill its host. Mistletoe and the trees it infests have been co-evolving for thousands of years
The Good – mistletoe’s contribution to biodiversity • Keystone species – disproportionately large effects on its environment relative to its abundance
• Nests for birds and mammals • • • •
80% of phainopepla nests in or under clumps 50% of Albert’s towee 18% of cactus wren Some birds of prey use sprigs for their nests
• Food for birds and mammals
• Pollen and nectar for bees and other insects • Dominant in the winter diet of 11 bird species • Fruit and leaves eaten by pronghorn antelope and mule deer • Up to 65% of the winter diet of white-tailed deer
• Reproduction
• The Great Purple Hairstreak (Atlides halesus) uses mistletoe as a larval host
In conclusion • The mistletoes on legumes in the Sonoran Desert cause modest stress on those plants due to the competition for water and nutrients • The infestations rarely kill the trees • Mistletoe serve many functions in the ecology of the region • The berries are often the only fruits available in winter for frugivorous birds such as the phainopepla • “Control of mistletoe can be difficult. Some horticulturists do not feel that mistletoe harms their hosts that much, so advise that we should not worry about it in our trees.” – Sonoran Tree Service - http://sonorantreesvc.com/03/mistletoe/
