How to Manage Pests

UC Pest Management Guidelines

Alfalfa

Ground Mealybug

Scientific Name: Rhizoecus kondonis

(Reviewed 11/06, updated 11/06)

In this Guideline:


DESCRIPTION OF THE PEST

Ground mealybug is a small, whitish insect found on the roots of alfalfa and other crops. It is restricted to the heavier soils of the Sacramento Valley and is not found in the San Joaquin or Imperial Valleys.

The ground mealybug has slender, waxy filaments that form a sort of netting over some individuals. The ground mealybug also secretes a small amount of wax, which can give the soil a somewhat bluish appearance when the mealybugs are abundant. There are three generations per year with populations peaking in the early winter, spring and mid-summer periods. The eggs, nymphs and adults all occur in the soil.

DAMAGE

The ground mealybug feeds on alfalfa roots and can cause severe damage. Feeding interacts with stressful environmental conditions resulting in greatly reduced plant growth that is particularly evident during summer. Infestations in alfalfa fields generally occur in "circular" patches and spread slowly.

MANAGEMENT

There are no thresholds or control measures for this pest. Crop rotation may help, but this pest appears to survive on several crop plant and weed species. Because there is differential survival across species, rotation to a less preferred host may aid in management. In a greenhouse study, greatest survival was on potato, tomato, safflower, and alfalfa, followed by cotton, cantaloupe, dryland rice, sugarbeets, and wheat. There was only slight survival on field corn and kidney beans. However, there were no plant species without some level of survival.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430

Insects and Mites

  • C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
  • L. D. Godfrey, Entomology, UC Davis
  • M. Rethwisch, UC Cooperative Extension, Riverside County (Blythe)
  • D. R. Haviland, UC Cooperative Extension, Kern County
  • P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier
  • R. F. Long, UC Cooperative Extension, Yolo County

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