Crape myrtles (Lagerstroemia indica) are essentially trouble-free small-scale trees. The most common problems include powdery mildew, Cercospora leafage spot, aphids, Japanese beetles, and sooty mold. More information on successfully growing crape myrtles is available in HGIC 1008, Crape Myrtle, and HGIC 1009, Crape Myrtle Pruning.

Diseases

Powdery mildew coating the flower buds of crape myrtle.

Powdery mildew typically coats the flower buds (above) and foliage of crape myrtle.
James Blake, ©2007 HGIC, Clemson Extension

Powdery Mildew: Powdery mildew is one of the most mutual problems of crape myrtle, and it is caused by the fungus Erysiphe lagerstroemiae. Patches of white to grayish powdery growth occur on the surfaces of leaves, flowers, and new shoots. Heavily infected flowers may fail to open. Infected parts of the plant become distorted and stunted. The disease is most serious in shady, clammy locations, especially where plants are crowded and air circulation is poor. Evolution of the fungus is favored by loftier humidity at night and dry, balmy daytime conditions, every bit often occur during the spring and fall.

Prevention & Handling: The most constructive control measures include locating plants in full dominicus, removing sprouts from the base of the constitute, and planting resistant varieties. Susceptible varieties of crape myrtle should exist avoided. Removing diseased twigs and branches may exist possible if merely a few shoots are infected. Remove sprouts (suckers) at the base of the plant equally they occur since they are very susceptible to powdery mildew. Once these sprouts go infected, the fungus easily spreads to the upper portions of the plant.

Plant Resistant Varieties: The extent of resistance to powdery mildew for a detail variety may vary from location to location and may depend on item conditions occurring in the surroundings.

  • The Lagerstroemia indica x fauriei hybrids developed at the U. South. National Arboretum in Washington, D. C. are resistant to powdery mildew.
  • Varieties with very good resistance to powdery mildew and fairly proficient tolerance to Cercospora foliage spot include: 'Apalachee,' 'Basham'southward Party Pinkish,' 'Caddo,' 'Dodd #2', 'Fantasy,' 'Glendora White,' 'Hopi,' 'Lipan,' 'Miami,' 'Osage,' 'Pecos,' 'Regal Red,' 'Sarah's Favorite,' 'Sioux,' 'Tonto,' 'Tuscarora,' 'Tuskegee,' 'Velma's Royal Delight', and 'Wichita.' 'Apalachee' and 'Fantasy' are totally resistant to powdery mildew.
  • 'Catawba,' 'Cherokee,' 'Seminole', and 'Yuma' have some resistance to powdery mildew.

Varieties to Avert: 'Gray's Ruby,' 'Orbin's Adkins, ' 'Carolina Beauty,' 'Wonderful White,' 'Raspberry Sundae', and 'Potomac.'

If the disease is severe enough to warrant chemical command, select a fungicide containing ane of the following: myclobutanil, propiconazole, thiophanate-methyl, or copper-based fungicides (meet Table 1 for specific products). Multiple applications may be required. Apply all chemicals co-ordinate to the directions indicated on the label.

Cercospora Leafage Spot: Leaf spots caused by Cercospora lythracearum may announced on crape myrtles and are caused past the fungus Cercospora species. This disease typically occurs during periods of warm, moist conditions. Yellow spots (⅛ to ¼ inch diameter) appear on the upper leaf surface with white-grey sporulation of the fungus on the lower leaf surface. The illness can issue in well-nigh complete defoliation of the institute in belatedly summer and fall in susceptible cultivars.

Prevention & Treatment: Select resistant varieties for new plantings. The varieties 'Fantasy,' 'Tonto,' 'Tuscarora,' 'Tuskegee,' and 'Velma's Royal Delight' take exhibited resistance to Cercospora leaf spot in field trials. The corporeality of resistance may vary from location to location and may depend on detail ecology conditions. Provide good air circulation and avoid overcrowding plants. If the affliction is severe enough to warrant using chemicals for control, thiophanate-methyl or myclobutanil as used for powdery mildew volition control Cercospora leaf spot (see Table 1 for specific products). Utilise all chemicals according to directions on the label.

Insects & Other Pests

Very few insects are pests of crape myrtle. In South Carolina, the most common insect pest is the crape myrtle aphid (Sarucallis kahawaluokalani), institute on the leaves and twigs of crape myrtle. Crape myrtle aphids feed only on crape myrtle copse.

Japanese beetle (Popillia japonica) is also a pest and feeds on both leaves and flowers. In addition to crape myrtle, it will feed on about three hundred different plant species.

A heavy infestation of aphids on the underside of a leaf.

A heavy infestation of aphids on the underside of a leafage.
Image from John Herbert, University of Florida

Crape Myrtle Aphids: Crape myrtle aphids are stake yellowish-green in color with blackness spots on the abdomen. They vary in length from 1/16 to ⅛ inch long. They overwinter (survive the winter) as eggs, which hatch in the spring. During the growing season, females give birth to alive young. Since it takes near 10 days to accomplish maturity, several generations are produced each growing season. At the stop of the growing season, females produce eggs that overwinter.

Aphids feed by inserting their mouthparts into tender new leaves from which they suck plant sap. Plant sap has a loftier sugar content. When they feed, the aphids excrete large amounts of sugary liquid called honeydew. With a big aphid population, the honeydew tin can completely coat leaves. The honeydew serves equally food for the sooty mold fungi (Capnodium species), also as various insects, including ants, wasps, and flies.

As the aphid feeds, it injects saliva into the leaf. The saliva causes yellow spots to develop on the foliage. Their feeding on young leaves oftentimes causes foliage distortion. Buds, branch tips, and flowers can besides exist affected by feeding.

Control: The following crape myrtle hybrids (Lagerstroemia indica ten fauriei) have moderate resistance to aphids: 'Muskogee,' 'Natchez,' 'Tuscarora,' 'Acoma,' 'Tuskegee,' 'Hopi,' 'Pecos,' 'Zuni,' 'Biloxi,' 'Miami,' 'Wichita,' 'Apalache,' 'Comanche,' 'Lipan,' 'Osage,' 'Sioux,' 'Yuma,' 'Caddo,' 'Tonto,' 'Choctaw,' and 'Fantasy.' Consider using these in new plantings.

Several predators feed on the crape myrtle aphid. These include ladybird beetles (ladybugs) and their larvae (young forms), green lacewings and their larvae, hover wing maggots, parasitic wasps, and entomophagous (insect feeding) fungi. As much as possible, these natural predators should be allowed to reduce aphid populations. In addition, many aphids can be removed from plants past spraying with a stiff stream of water. Spraying with water may have to be repeated regularly, every bit needed.

As a result of their phenomenal reproductive rate, aphids are very difficult to control with insecticides. If a single aphid survives, a new colony can be produced in a short period of time. In addition, using insecticides ways that benign predators will likewise be killed. If information technology is determined to be absolutely necessary, various insecticides are labeled for use by homeowners confronting aphids on crape myrtles. These include insecticidal soap, horticultural oil, pyrethrins, neem oil, permethrin, cyfluthrin, cyhalothrin, acephate, or malathion. Soil drenches of imidacloprid in the spring will control aphids and terminal longer within the establish to prevent future infestations by aphids and other insect pests (run across Table ane for specific products). As with all pesticides, read and follow all characterization instructions and precautions.

Japanese Beetles: Developed Japanese beetles are nearly ½ inch in length and coppery-brown in color with metallic green heads. They emerge from the soil and feed from May to Baronial. They lay their eggs in the soil. Grubs hatch from the eggs and feed on grass roots. Equally the weather cools, the grubs move more securely into the soil to overwinter.

Both adult beetles and their larvae (grubs) can seriously damage plants as a result of their feeding. Adult Japanese beetles swallow flowers and skeletonize leaves (eat leaf tissue between the veins, resulting in a lacy skeleton remaining). The grubs feed on the roots of plants, peculiarly on the roots of grasses.

Command: Multiple approaches are necessary for controlling Japanese beetles. Adults can be handpicked and drowned in a pail of soapy water. Japanese protrude traps are available commercially or can be homemade. They may be effective at reducing adult populations.

Keep traps at least 50 anxiety from the crape myrtle tree, or you may create more of a trouble past attracting them to the area. Milky spore, Paenibacillus popilliae, is a disease-causing bacterium that is constructive against grubs of Japanese beetles that live in the soil and feed on turfgrass roots, but non the adults. It is commercially available for homeowner utilize. Many products containing neem oil, cyfluthrin, permethrin, cyhalothrin, or acephate are labeled for use past homeowners against Japanese beetles on crape myrtles. Soil drenches of imidacloprid in the spring will profoundly reduce damage by Japanese beetles and final longer within the constitute to prevent future infestations by additional pests (encounter Table ane for specific products). As with all pesticides, read and follow all label instructions and precautions.

Crapemyrtle Bark Scale: This crape myrtle pest is a more recent arrival. For information on this insect pest and command measures, please see HGIC 2015, Crapemyrtle Bark Scale.

Sooty mold completely covers these crape myrtle leaves.

Sooty mold completely covers these crape myrtle leaves.
Prototype from John Herbert, University of Florida

Other Problems

Sooty Mold: Leafage and stalk surfaces are covered with a black sooty substance, causing them to appear black and dirty. Sooty mold indicates that in that location is an insect trouble on the establish. These common molds are caused by fungi that grow on the sugary substance called honeydew, produced past various insects that suck sap from the plant. Aphids, scales, mealybugs, and whiteflies near commonly cause this problem.

Prevention & Treatment: Sooty molds are cruddy only are relatively harmless since they do not directly set on the found. Controlling the insect problem can reduce excessive amounts of sooty mold. Reduce aphid numbers by allowing beneficial insects, such equally lady beetles, to inhabit the found. Aphids can be removed from the constitute with a stiff spray of water.

Although not necessary, sooty mold can exist washed from the leaves by spraying leafage with a dish lather solution (four ounces per gallon of water), waiting three to 4 minutes, then rinsing the leaf with a strong stream of water.

These harmless lichens are growing on an older crape myrtle.

These harmless lichens are growing on an older crape myrtle.
Karen Russ, ©2007 HGIC, Clemson Extension

Lichens: A lichen is an unusual organism equanimous of a fungus and a green alga and/or a cyanobacterium living together in the aforementioned body. Lichens often appear as greenish to grayness-green leafy or crusty growths on the trunks or branches of plants. Typically, they occur in affluence on plants that are failing in health or vigor. They are harmless to the plant and are in no way responsible for the poor health of the plant. Less vigorous plants tend to exist more open with less foliage, which increases sunlight penetration and subsequent lichen growth.

Prevention & Treatment: Controls are non necessary. Lichens volition gradually disappear if the wellness of the plant is restored. Nevertheless, there are a few consumer products with lichen control listed on their labels. They are:

  • Bonide Moss Max RTS
  • Bayer BioAdvanced 2-in-1 Moss & Algae Killer & Cleaner RTS
  • Scott's MOSS-EX three-in-i RTS

All products say to employ only to the hardened bark of trees. They should be practical but to the bark and with no foliar contact. These products do non say for use on shrubs. All iii are identical and contain 22.11% potassium salts of fat acids. RTS means they are in a hose-finish sprayer bottle.

Table 1. Insecticides & Fungicides for Crape Myrtle Insect Pest & Disease Control.

Insecticides & Fungicides Examples of Brand Names & Products
Acephate Bonide Systemic Insect Control Concentrate
Copper-based Fungicides Bonide Liquid Copper Concentrate
Bonide Copper Fungicide
Camelot O Fungicide/ Bactericide Concentrate
Monterey Liqui-Cop Fungicide Concentrate
Natural Guard Copper Soap Liquid Fungicide Conc.
Southern Ag Liquid Copper Fungicide Concentrate
Cyfluthrin Bayer BioAdvanced 24 Hour Lawn Insect Killer RTSane
Bayer BioAdvanced Consummate Insect Killer for Soil &Turf I RTSi
Bayer BioAdvanced Insect Killer for Lawns RTSone
Horticultural Oil Bonide All Seasons Spray Oil Concentrate
Ferti-lome Horticultural Oil Spray Concentrate
Monterey Horticultural Oil Concentrate
Safer Brand Horticultural & Dormant Spray Oil Conc.
Southern Ag Parafine Horticultural Oil
Top Year Circular Spray Oil Concentrate
Imidacloprid Bayer BioAdvanced 12 Month Tree & Shrub Insect
Control Landscape Formula (soil drench)
Bonide Annual Tree & Shrub Insect Control with
Systemaxx (soil drench)
Ferti-lome Tree & Shrub Systemic Insect Deluge
Martin'southward Rule Tree & Shrub Insecticide (soil drench)
Monterey In one case A Year Insect Control Ii (soil drench)
Insecticidal Soap Natural Guard Insecticidal Soap Concentrate
Safer Brand Insect Killing Soap Concentrate
Cyhalothrin, Lambda or Gamma Martin's Cyonara Lawn & Garden Concentrate; & RTS1
Spectracide Triazicide Insect Killer for Lawns &Landscapes Conc.; & RTSi
Malathion Bonide Malathion 50% Insect Control Concentrate
Gordon'south Malathion 50% Spray Concentrate
How-do-you-do-Yield 55% Malathion Insect Spray
Martin's Malathion 57% Concentrate
Ortho MAX Malathion Insect Spray Concentrate
Southern Ag Malathion 50% EC
Spectracide Malathion Insect Spray Concentrate
Tiger Brand l% Malathion Spray
Milky Spore St. Gabriel Organics Milky Spore Granular Grub Control
Myclobutanil Spectracide Immunox Multi-Purpose Fungicide Conc.
Ferti-lome F-End Lawn & Garden Fungicide Concentrate
Monterey Fungi-Max (Concentrate)
Neem Oil Bonide Rose Rx 3-in-1 Concentrate
Bonide Neem Oil Concentrate
Business organisation Garden Defence force Multi-Purpose Spray Conc. Ferti-lome Rose, Flower & Vegetable Spray Concentrate
Garden Prophylactic Fungicide 3 Concentrate
Garden Safe Neem Oil Excerpt Concentrate
Monterey 70% Neem Oil Fungicide/Insecticide/Miticide
Natria Neem Oil Concentrate
Natural Guard Neem Concentrate
Safer Brand Neem Oil Concentrate
Southern Ag Triple Action Neem Oil Concentrate
Permethrin Bonide Eight Insect Control Vegetable Fruit & Flower
Concentrate
Bonide Total Pest Control – Outdoor Concentrate
Bonide Eight Yard & Garden Ready To Spray (RTS1)
Hi-Yield Indoor/Outdoor Broad Apply Insecticide Conc.
Southern Ag Permetrol Lawn & Garden Insecticide Conc.
Tiger Brand Super 10 Concentrate
Propiconazole Banner Maxx Fungicide
Bonide Infuse Systemic Disease Control Conc.; & RTS1
Ferti-lome Liquid Systemic Fungicide 2 Concentrate
Martin's Laurels Baby-sit PPZ
Quali-Pro Propiconazole
Pyrethrin Bonide Pyrethrin Garden Insect Spray Concentrate
Monterey Bug Blaster-O
PyGanic Ingather Protection EC 1.iv
Southern Ag Natural Pyrethrin Concentrate
Thiophanate-methyl Cleary's 3336-WP Turf & Ornamental Fungicide
Southern Ag Thiomyl Systemic Fungicide
Note: Command of diseases and insects on large trees is usually not feasible since adequate spray coverage of the leafage with a pesticide cannot exist achieved.
1RTS = Fix to Spray (a hose-end sprayer)