Diseases of pecan (
Mistletoe
Mistletoes are dioecious parasitic plants that depend on their host plant for water and nutrients. Pecan is susceptible to Phoradendron tomentosum, a species of the true mistletoes (broadleaf mistletoes). Trees are often heavily infected and large clumps of green mistletoe are easy to see in the canopy during winter months (photo 1). Phoradendron tomentosum infects many species of hardwood trees, but does not infect oak and is not the same species of mistletoe found in leguminous trees and shrubs such as palo verde and Acacia.
Leafy mistletoe seeds are disseminated by birds. After eating the fruits, the birds deposit seeds on twigs and limbs of host plants. The mistletoe grows into the host tissue as well as producing the green leafy growth that is visible.
Pecan trees will live for many years with mistletoe infections. Control measures are usually not practiced unless it is practical to remove the new growth as it emerges. Removing the visible part of the mistletoe will not kill it, and it will grow back. Wrapping infection sites with black plastic is not recommended since it does not kill the mistletoe growing internally in the host and may constrict growth or provide entry sites for other pests.
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February 5, 2008