Natural Enemies Gallery

Vedalia

Hosts or Prey

Egg-sac producing mealybugs and scales and especially cottony cushion scale, Icerya purchasi

Identification

Adult vedalia (lady beetles, also called ladybugs or ladybird beetles) are about 1/8 inch (3 mm) long and irregularly marked with black and red. Black predominates on some individuals and red on others. Overall this lady beetle can appear grayish because it is covered with fine hairs. Adults are dome shaped (convex) on top, flat on the bottom, and oval when viewed from above.

Eggs are oblong and red. They are most readily observed when laid on the white egg sac of cottony cushion scale.

First instars (immatures) have a red body, red legs, and no obvious antennae. Second instars have dark reddish to black legs and black tubercles (slightly raised bumps) on the abdomen and thorax. Third and fourth instars have black legs and more apparent black tubercles. Their body is dark pink, but can appear bluish to gray overall. Fourth instars grow to about 1/4 inch (6 to 7 mm) long before pupating.

The mature, fourth instar glues itself to a leaf or twig before pupating. The pale skin of the fourth instar splits over the back to reveal the developing, oblong pupa. A healthy pupa is reddish and moves slightly when touched.

Lookalikes

Adults because of their unique coloration are unlikely to be confused with other lady beetles in California. First instars resemble the crawlers of cottony cushion scale; both are reddish and oblong and can be observed on the egg sacs of cottony cushion scale. However, cottony cushion scale crawlers have black legs and black antenna that commonly project forward; vedalia first instars have red legs and no obvious antennae.

Life Cycle

Vedalia develops through 4 life stages: egg, larva, pupa, and adult. Females can lay several hundred eggs during their 1 to 3 month lifespan. Larvae develop through 4, increasingly larger instars. Vedalia can develop throughout the year in coastal areas. Development from egg to adult occurs in 4 to 6 weeks when temperatures are warm. Vedalia has multiple generations per year.

Habitat

Adult females lay eggs singly or in a scattered group attached to the egg sac of cottony cushion scale. The first instars dig their way into the egg mass and feed mostly hidden on the eggs. Second through fourth instars are active searchers that move on leaves and up and down branches searching for and feeding on all stages of the scale.

Vedalia is the most important natural enemy of cottony cushion scale in California's Central Valley. In coastal locations a tiny, parasitic, black fly Cryptochaetum iceryae is the most important natural enemy of cottony cushion scale. Both natural enemies can be common at intermediate locations, such the delta regions of the Sacramento and San Joaquin Rivers.

If its populations are not disrupted by pesticide application or hot weather, when vedalia adults arrive in Central Valley citrus orchards in March to April they can control a serious cottony cushion scale problem in 4 to 6 weeks. Vedalia halts egg production and larval development slows when daily temperatures exceed 90°F, usually in June in the San Joaquin Valley.

Species

Vedalia was introduced from Australia in the 1888. It successfully controlled cottony cushion scale that was killing trees in commercial citrus orchards. No other Rodolia species or similarly colored lady beetles occur in California.

More Information

Scientific classification:

  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Coleoptera
  • Family: Coccinellidae
Adult vedalia, Rodolia cardinalis, a red and black lady beetle, and a female cottony cushion scale, Icerya purchasi. Red eggs and a first instar of vedalia are shown on the scale.
Adult vedalia, Rodolia cardinalis, a red and black lady beetle, and a female cottony cushion scale, Icerya purchasi. Red eggs and a first instar of vedalia are shown on the scale. Credit: Jack Kelly Clark, UC IPM Program
Adult, female cottony cushion scale, Icerya purchasi, with eggs of vedalia, Rodolia cardinalis, a lady beetle on the scale's fluted, white egg sac.
Adult, female cottony cushion scale, Icerya purchasi, with eggs of vedalia, Rodolia cardinalis, a lady beetle on the scale's fluted, white egg sac. Credit: Jack Kelly Clark, UC IPM Program
Last-instar vedalia, Rodolia cardinalis, lady beetle larva feeding on a nymph of cottony cushion scale, Icerya purchasi.
Last-instar vedalia, Rodolia cardinalis, lady beetle larva feeding on a nymph of cottony cushion scale, Icerya purchasi. Credit: Jack Kelly Clark, UC IPM Program
Vedalia, Rodolia cardinalis, lady beetle adult and pupa (top center) on a twig infested with cottony cushion scale, Icerya purchasi.
Vedalia, Rodolia cardinalis, lady beetle adult and pupa (top center) on a twig infested with cottony cushion scale, Icerya purchasi. Credit: Jack Kelly Clark, UC IPM Program