Webworm & Vascular Wilt in Mimosa Trees

Mimosa trees are considered invasive in some states.

Mimosa (Albizia julibrissin), or silktrees, are not native to the United States and, in fact, are considered an invasive species in some states. The trees grow easily from seeds falling from the tree or scattered by the wind and are a common sight in California as well as the South, Northeast and Southwest.

Features

Mimosa trees have dark green, fern-like foliage and wispy flowers with white centers. The tree's crown forms a spreading, irregular vase shape that is susceptible to wind damage. Varieties include Rosea and Rubra, which have pink flowers, and Alba, which has white flowers. Mimosas are highly susceptible to vascular wilt disease, commonly called Mimosa wilt. Only three varieties are wilt resistant: Charlotte, Union and Tyron. The tree is hardy in U.S. Department of Agriculture plant hardiness zones 6B through 9B. Mimosa is easy to grow from seeds or root cuttings and tolerates poor soil. The tree is drought tolerant and can be grown in either acid or alkaline soils.

Vascular Wilt

According to the U.S. Forest Service, mimosa wilt devastates trees from Maryland to Florida and westward into Texas. A fungus, mimosa wilt may appear as small areas of spore-bearing tissue on dead twigs. The fungus causes discoloration and wilting foliage, which usually results in the death of the tree within six weeks. The best way to avoid mimosa wilt is to plant only wilt-resistant mimosa varieties. Using a balanced fertilizer such as 10-10-10 may reduce the symptoms of wilt but will not cure infected trees. Water the trees frequently, prune and burn dead wood.

Webworms

The mimosa webworm (Homadaula anisocentra) may have been imported into the United States in the first half of the 20th century and has made itself at home, feasting on mimosas as well as other tree species. The worms build silky nests around groups of leaves and feast on the tender foliage. The larvae overwinter in the soil. Mature larva are gray to brown with five white stripes running the length of the worm. Several chemicals may be used to control mimosa webworms. Look for products that contain permethrin, pyrethrins, acephate, carbaryl or Bacillus thuringiensis and follow package directions. Treat the tree as soon as the first-generation larvae hatch in mid- to late June. A second generation may hatch in August. Pull off any caterpillars you see and destroy them.

Uses

Mimosas can grow 20 to 40 feet tall but can be pruned to a smaller size suitable for patio plantings or containers. Allowed to grow unchecked, the canopy's broad, open spread of up to 35 feet on multiple, smooth-barked trunks make mimosas an interesting specimen plant.

References

• The University of Texas at Austin: Ask Mr. Smarty Plants: Where do Mimosas Grow?
• Missouri Botanical Garden: Albizia Julibrissin
• U.S. Forest Service: Mimosa Wilt
• Missouri Botanical Garden: Caterpillars - Leaf Tiers, Rollers, Bagworms and Web Formers
• New Mexico State University: Mimosa Vascular Wilt; Natalie Goldberg, R. Gary Smith; 1999
• Penn State: Woody Ornamental Insect, Mite, and Disease Management; 2008

Resources

• Duke University: Silktree Mimosa (Albizia Julibrissin); C.W. Cook; rev. 2008
• University of Florida IFAS Extension: Albizia Julibrissin; Edward F. Gilmans; rev. 2007
• The United States National Arboretum: USDA Plant Hardiness Zones