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How to Manage Pests

UC Pest Management Guidelines

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Ground mealybug nymphs.

Floriculture and Ornamental Nurseries

Root Mealybugs

Scientific name: Rhizoecus spp.

(Reviewed 3/09, updated 6/10)

In this Guideline:

DESCRIPTION OF THE PESTS

Root mealybugs are belowground dwelling mealybugs that feed on the roots of plants. These mealybugs have a thin, uniform waxy coating and lack the terminal wax filaments typical of their foliar-feeding relatives.

DAMAGE

The only outward sign of root mealybug feeding may be a decline in the health of infested plants. When plants are removed from the pot, the whitish mealybugs feeding on the roots are then observed.

MANAGEMENT

Biological Control
Biological control has not been investigated.

Cultural Control
Discard infected and surrounding plants. Control ants.

Monitoring and Treatment Decisions
Examine plant root balls when monitoring and when plants are declining. The presence of ants climbing on the plant can also indicate a problem with mealybugs. Rogue and discard infected plants. Treat with a soil drench or discard the surrounding plants.

TREATMENT

Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.

Class   Pesticide
(commercial name) 		Manufacturer R.E.I.1 Mode of action2 Comments
  Calculate impact of pesticide on air quality
botanical A. pyrethrin/PBO3
(PT Pyrethrum TR) 		Whitmire
MicroGen 		12 3/— An aerosol.
B. pyrethrin/rotenone
(Pyrellin EC) 		Webb Wright 12 3/21B  
neonicotinoid A. imidacloprid
(Marathon 1G)
(Marathon II) 		OHP 12 4A Not to be used more than once every 16 weeks. Do not apply to soils that are water logged or saturated. Do not apply to bedding plants intended to be used as food crops.  
  (Marathon 60 WP)       As above, but apply only as a drench.  
organophosphate A. acephate
(Acephate 97UP) 		United Phosphorus 24 1B  
B. acephate
(Orthene T,T&O Spray) 		Valent 24 1B A number of chrysanthemum varieties have exhibited phytotoxic reactions. In greenhouse, only labeled for use on anthurium, cacti, carnation, rose, orchids, some foliage plants, young poinsettia and some varieties of chrysanthemum. Can stunt new growth in roses.
pyrethroid A. bifenthrin
(Talstar Professional) 		FMC 12 3 Label permits low-volume application.
B. cyfluthrin
(Decathlon 20 WP) 		OHP 12 3 Label permits low-volume application.
C. fenpropathrin*
(Tame 2.4 EC Spray) 		Valent 24 3 Label permits low-volume application.
D. fluvalinate
(Mavrik Aquaflow) 		Wellmark 12 3 Label permits low-volume application. Also labeled as a cutting dip at 5 fl oz/100 gal.
E. permethrin
(Astro) 		FMC 12 3 Direct application to blooms may cause browning of petals. Marginal leaf burn may occur on salvia, diffenbachia and pteris fern. Label permits low-volume application. Do not apply more than 2 lb a.i./acre/year.
pyrethroid/
neonicotinoid 		A. cyfluthrin/imidacloprid
(Discus) 		OHP 12 3/4A  
1  Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
2 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
3 PBO = piperonyl butoxide.
* Restricted use material. Permit required for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Insects and Mites
J. A. Bethke, Entomology, UC Riverside
Acknowledgment for contributions to Insects and Mites:
K. L. Robb, UC Cooperative Extension, San Diego County
H. S. Costa, Entomology, UC Riverside
R. S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT
M. P. Parrella, Entomology, UC Davis

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