The forest pansy (Cercis canadensis "Forest Pansy") is a small eastern redbud variety that brightens up outdoor landscapes in U.S. Department of Agriculture plant hardiness zones 5 through 9. Featuring showy clusters of purplish-pink blooms and heart-shaped, purplish-green leaves, this North American native makes an attractive flowering ornamental tree for small yards and woodland gardens. Like other redbud tree varieties, the "Forest Pansy" is somewhat susceptible to several pest insects and plant diseases. (all ref 1)
The forest pansy redbud attracts various foliage-feeding caterpillars, but the redhumped caterpillars (Schizura concinna) often cause the most unsightly damage. Mature caterpillars range between 1 and 1 1/2 inches in length and have red heads and yellow bodies with enlarged, bright red, front abdominal segments. The adult female moths lay groups of white to creamy white eggs beneath the leaves. Newly hatched larvae feed together and skeletonize the undersides of leaves, while older caterpillars consume the remaining leaf tissue. These voracious feeders frequently defoliate entire branches on large redbud trees and can completely defoliate small trees. Fortunately, healthy redbuds typically recover and suffer no long-term damage.
Redbud trees occasionally attract armored scale insects, including the oleander scale (Aspidiotus nerii) and the greedy scale (Hemiberlesia rapax). These tiny pests typically don't get any larger than 1/8 inch in diameter and have unusual, plate-like coverings. Scales frequently look less like insects and more like bumpy, unsightly masses on bark or leaves. That's because these pests settle into a feeding spot soon after hatching and never move again. Scales feed by inserting their slender mouthparts into plant tissue and sucking out the fluids. Feeding injury can cause leaves to yellow, wilt, curl and prematurely drop. Scale-infested bark might crack and ooze a gummy liquid.
Experts at the University of California Statewide Integrated Pest Management Program don't recommend using insecticides to tread redhumped caterpillars because most gardeners simply spray too late for the chemicals to work. Prune out and destroy any foliage hosting redhumped caterpillars or small scale populations. Large scale populations can often be managed with a 2 percent horticultural oil spray if you time the application to coincide with egg hatching. Once the scales settle into their feeding spots, they excrete a hard substance that covers their bodies and protects them from chemicals.
Forest pansy redbud trees sometimes attract canker pathogens, particularly those that cause Cytospora canker (Cytospora spp.). This fungal disease primarily occurs on trees suffering from environmental stress caused by winter injury, drought, sunscald or pruning wounds. The pathogens grow into the inner wood tissue, causing sunken, yellow, black or brownish-orange cankers to form on infected bark. Cankered branches often bear wilted, brown or yellow foliage. Cankers sometimes girdle and kill branches and even entire redbud trees.
Verticillium wilt sometimes attacks and kills forest pansy redbuds. The soilborne fungal pathogens (Verticillium spp.) invade the tree's roots and quickly spread throughout the entire vascular system. The fungal growth interferes with the transfer of water and nutrients, which results in fading, browning or yellowing leaves that defoliate early. Verticillium wilt infections often attack one side of the tree first and then spread until the entire tree becomes infected and dies.
No chemical control exists to treat canker or verticillium wilt as of May 2013, so prevent fungal pathogens from attacking by keeping your tree healthy and vigorous. The forest pansy tolerates various soil conditions but requires a planting location with good drainage that receives full sun to partial shade. This redbud prefers consistently moist soils and needs to be watered whenever the surrounding soil feels dry to the touch. During each irrigation session, give your tree about 10 gallons of water for each inch of the trunk's diameter. Prune out diseased branches and foliage as soon as you notice them, making sure that you cut down into healthy wood tissue.
- Cal Poly Urban Forest Ecosystems Institute: Purple Leaf Eastern Redbud
- University of California Statewide Integrated Pest Management Program: Redhumped Caterpillar
- University of California Statewide Integrated Pest Management Program: Scales
- Colorado State University Extension: Caring for Trees in a Dry Climate
- University of California Statewide Integrated Pest Management Program: Canker Diseases
- University of Florida IFAS Extension: Cercis Canadensis "Forest Pansy"
- University of California Statewide Integrated Pest Management Program: Verticillium Wilt
- Ryan McVay/Lifesize/Getty Images