Quick Guide to Cranberry Rootworm Beetle
Affected Plants: Azalea, rhododendron, camellia, blueberry, hollies, roses, redbud, oakleaf hydrangea, and other shrubs
Primary Insect Pest: Cranberry rootworm beetle (Rhabdopterus picipes)
Primary Causes: Adult beetles feed on shrub foliage, while young larvae move into the soil and feed on host-plant roots
Typical Damage: Curved, C-shaped, and elongated holes in leaves that may resemble hail damage
Most Important Prevention Strategy: Keep landscape shrubs healthy with adequate irrigation, appropriate nutrient management, and a beneficial layer of mulch
Chemical Control: After flowering, use a labeled foliar insecticide when feeding damage is detected, or apply an imidacloprid soil drench according to the product label
Cranberry Rootworm Beetle (Rhabdopterus picipes) on Landscape Shrubs in South Carolina
The cranberry rootworm beetle (Rhabdopterus picipes) is a nocturnal, leaf-feeding beetle that damages woody landscape shrubs in South Carolina.
What Is the Cranberry Rootworm Beetle?
The cranberry rootworm beetle is one of several leaf-feeding beetles and weevils that consume the foliage of woody landscape plants in South Carolina.
Identifying Cranberry Rootworm in the Landscape
These nocturnal-feeding adult beetles are:
- Shiny, dark bronze-black
- About 1/4 inch long and 1/8 inch wide
Cranberry Rootworm Beetle Behavior in the Landscape
Beetles hide in landscape mulch during daylight hours and, therefore, are seldom noticed.
The adults feed on landscape plants for several weeks in the late spring and early summer.
Cranberry Rootworm Beetle Life Cycle
Cranberry rootworm beetles complete a one-year life cycle from egg to root-feeding larva to foliage-feeding adult.
Egg and Larval Stage
After feeding, adult females lay eggs on the soil. Upon hatching, young beetle larvae move into the soil to feed on the roots of the host plant.
Overwintering, Pupation, and Adult Emergence
They feed throughout the summer and into fall, then move deeper into the soil to overwinter. The larvae pupate within the soil during early spring, and the adults emerge in late spring to begin foliar feeding and repeat the one-year life cycle.
How to Identify Cranberry Rootworm Beetle Damage
Feeding damage by cranberry rootworm beetle (Rhabdopterus picipes) on camellia foliage results in C-shaped holes.
Jim Baker, North Carolina State University, Bugwood.org
Cranberry rootworm beetle feeding results in:
- Curved holes in leaves.
- C-shaped holes in leaves.
- Elongated holes in leaves.
- Foliar damage that may appear similar to hail damage.
Damage may occur on:
- Azalea
- Blueberry
- Camellia
- Hollies
- Oakleaf hydrangea
- Redbud
- Rhododendron
- Roses
- Other shrubs
Cranberry Rootworm Beetle Prevention and Treatment on Landscape Shrubs
Management combines plant-care practices with carefully timed insecticide applications that protect pollinating insects.
Cultural Controls
Plant Health
Keep landscape plants as healthy as possible so they can tolerate the damage.
Irrigation
If rainfall is inadequate, irrigate plants weekly during the growing season, providing 1 inch of water per week.
Soil Testing
For proper nutrient management in landscape beds, have the soil tested the following fall or winter.
A soil analysis test is recommended to determine which nutrients are needed to improve plant growth and whether lime is required.
Fertilization
In the absence of a soil test, fertilize plants with slow-release tree and shrub fertilizer, such as a 12-6-6, in early spring and again 6 weeks later at a rate of 1 pound per 100 sq ft.
However, in the coastal counties of Beaufort, Charleston, and Horry, there is typically sufficient phosphorus that naturally occurs in the soil. Therefore, in these areas, apply a 15-0-15 fertilizer around the shrubs in spring.
Mulch
Although mulch provides a hiding place for adult beetles, it is quite beneficial to landscape plants in conserving soil moisture, regulating soil temperature, and suppressing weeds.
Apply a 3- to 4-inch-deep layer of mulch around woody shrubs.
Cranberry rootworm beetle (Rhabdopterus picipes) feeding on azalea foliage, resulting in curved, elongate holes.
Chazz Hesselein, Alabama Cooperative Extension System, Bugwood.org
Alt Text: Cranberry rootworm beetle feeding damage on azalea foliage, with curved and elongated holes in the leaves.
Chemical Control
Labeled contact insecticides may contain the following active ingredients:
- Bifenthrin
- Cyfluthrin
- Cyhalothrin
- Permethrin
- Spinosad (a natural insecticide)
Foliar insecticides target adult cranberry rootworm beetles after flowering by treating both the shrub foliage and the mulch or leaf litter where the beetles hide.
- When to apply: After flowering, as soon as feeding damage is detected.
- Where to apply: Spray the shrub foliage and saturate the mulch or leaf litter beneath the shrubs.
- Pollinator protection: Do not spray during bloom or while pollinators are foraging.
- Product guidance: Always follow the current product label.
See Table 1 for examples of products labeled for foliar pest control on shrubs.
How to Use Imidacloprid Soil Drenches for Cranberry Rootworm Beetle
Alternatively, control can be achieved with soil drenches containing the active ingredient imidacloprid.
Imidacloprid is a systemic insecticide that is absorbed by the roots of the shrub and moves upward into foliage and flowers. It may take one week for the insecticide to translocate throughout smaller shrubs or up to a few weeks for larger shrubs.
- Apply after flowering to reduce risk to pollinating insects.
- Water plants thoroughly the day before application.
- Drench the soil around the bases of the shrubs.
- Follow the label directions for the amount of product based on shrub height.
- Note that soil drenches will not kill grubs feeding on roots outside the treated area.
Systemic insecticide products are best applied in the spring. Protection duration varies by product. Follow the current product label for application timing and residual control.
See Table 1 for examples of products containing imidacloprid.
Cranberry Rootworm Beetle Pesticide Examples
The following insecticides are examples of products labeled for cranberry rootworm beetle control on landscape shrubs; always read and follow the current product label.
Insecticides for Cranberry Rootworm Beetle on Landscape Shrubs
Active Ingredient |
Example Product Names |
|---|---|
| Bifenthrin | Bifen I/T Bonide Eight Insect Control Flower & Vegetable Above & Below Soil Insect Granules Hi-Yield Bug Blaster Bifenthrin 2.4 Ready to Spray Hi-Yield Bug Blaster II Bifenthrin 2.4 Ready to Spray Hi-Yield Vegetable & Ornamental Insect Control Granules Martin’s FLEE Ready to Use Yard Spray Monterey Mite & Insect Control Monterey Mosquito Control Ortho Bug B Gon Insect Killer for Lawns & Gardens1 Ortho BugClear Insect Killer for Lawns & Landscapes Ortho Outdoor Insect Killer Concentrate Talstar P Professional Insecticide Up-Star Gold Insecticide |
| Cyfluthrin | BioAdvanced Science-Based Solutions 24 Hour Lawn Insect Killer Ready-to-Spray BioAdvanced Science-Based Solutions Complete Brand Insect Killer for Soil & Turf Ready-to-Spray I| BioAdvanced Science-Based Solutions Insect Killer for Lawns Ready-to-Spray BioAdvanced Science-Based Solutions Rose & Flower Insect Killer Ready-to-Use |
| Cyhalothrin | Bonide Eight Insect Control Garden & Home II Ready to Use Cutter Backyard Bug Control Spray Concentrate Cyzmic CS Controlled Release Insecticide Martin’s Cyonara Lawn & Garden Insect Control Martin’s Cyonara Lawn & Garden Insect Control Ready-to-Spray Spectracide Triazicide Insect Killer for Lawns & Landscapes |
| Imidacloprid | BioAdvanced Science-Based Solutions 12 Month Tree & Shrub Insect Control Concentrate Landscape Formula BioAdvanced Science-Based Solutions 12 Month Tree & Shrub Protect & Feed Concentrate 2-1-1 BioAdvanced Science-Based Solutions 12 Month Tree & Shrub Protect & Feed II Concentrate 2-1-1 BioAdvanced Science-Based Solutions 12 Month Tree & Shrub Protect & Feed II Ready to Use Granules 2-1-1 BioAdvanced Science-Based Solutions 12 Month Tree & Shrub Protect & Feed Ready to Use Granules 2-1-1 BioAdvanced Science-Based Solutions 2 in 1 Systemic Rose & Flower Care Ready-to-Use Granules II Bonide Annual Tree & Shrub Insect Control w/ Systemaxx Bonide Systemic Granules Insect Control Bonide Systemic Insect Spray w/ Systemaxx Ready to Spray Ferti-lome Tree & Shrub Drench Hi-Yield Systemic Insect Granules Hi-Yield Systemic Insect Spray Ready-to-Spray Martin’s Dominion Tree & Shrub Insecticide Concentrate Monterey Once A Year Insect Control II |
| Permethrin | Bonide Eight Insect Control Vegetable, Fruit, & Flower Concentrate Bonide Eight Yard & Garden Ready to Spray Hi-Yield 38 Plus Turf, Termite & Ornamental Insect Control Hi-Yield Lawn Garden Pet & Farm Insect Control Southern Ag Permetrol Lawn & Garden Insecticide Tiger Brand Super 10 Brand |
| Spinosad | Bonide Captain Jack’s Deadbug Brew Concentrate Bonide Captain Jack’s Deadbug Brew Ready to Spray Bonide Captain Jack’s Deadbug Brew Ready to Use Bonide Colorado Potato Beetle Beater Concentrate Conserve SC Turf & Ornamental Monterey Garden Insect Spray Monterey Garden Insect Spray RTU Natural Guard by ferti-lome Spinosad Bagworm, Tent Caterpillar & Chewing Insect Control Natural Guard by ferti-lome Spinosad Soap Ortho Insect Killer Tree & Shrub Concentrate Southern Ag Conserve Naturalyte Insect Control |
Definitions
RTS = Ready to Spray (hose-end sprayer)
RTU – Ready to Use (spray bottle)
Pesticide disclaimer
Always read and follow the current product label. Product names are provided as examples of labeled products and do not imply endorsement. Use pesticides only according to label directions and applicable regulations.
Pesticides are updated annually. The last updates were made on 9/26 by N. Jordan Franklin.
Originally published 02/18
