Hosts or Prey
Mealybugs and other soft-bodied insects that produce waxy egg sacs
The adult mealybug destroyer is a type of lady beetle (ladybug or ladybird beetle). It is dome shaped (convex) on top, flat on the bottom, and oblong when viewed from above. The hard body is 1/8 to 1/6 inch (3–4 mm) long with short, clubbed antennae. On top the abdomen of adults is blackish to dark gray and the head and thorax are dark brown to orange.
Larvae grow up to 1/2 inch (12 mm) long and closely resemble a mealybug. However mealybug destroyer larvae are faster moving and at maturity more than twice size of an adult female mealybug.
Eggs are oblong and yellow. Eggs occur singly or in groups in the waxy egg sacs of host insects.
Most lady beetles in the taxonomic tribe Scymnini have larvae with waxy secretions. In California these include Didion and Nephus spp. and numerous species of Scymnus; the adults and mature larvae of these other lady beetles are about one-half or less the size of those of the mealybug destroyer.
The arrangement of filaments differs distinctly between lady beetle larvae and mealybugs. Cryptolaemus and other Scymnini larvae have long, wax filaments protruding from the top and sides; mealybugs have only short marginal (side, or lateral) filaments and in some species two to four relatively long filaments at the rear end. Lady beetle larvae have distinct legs and mouthparts, while legs and mouthparts are obscure in mealybugs. Cryptolaemus and other Scymnini larvae can be recognized as those of lady beetles if the wax is gently brushed away to reveal the alligatorlike body with obvious appendages.
Mealybug destroyers develop through 4 life stages: egg, larva, pupa, and adult. An adult female lives about 2 months and during her lifetime lays about 200 to 400 eggs among the egg masses of their host. The adult female's consumption of waxy eggs of egg sac-producing insects stimulates her to lay eggs. At 80ºF eggs hatch about 5 days after being laid.
Each beetle larva can consume more than 250 mealybug nymphs (immatures) or over 1,000 mealybug eggs as it develops through 4 increasingly larger instars. Larvae feed for about 3 to 4 weeks before pupating.
Development and reproduction of the mealybug destroyer occurs most rapidly at 72º to 77ºF and relative humidity of 70% to 80%. Temperatures below 68ºF and short day lengths greatly slow the reproductive rate of this predator. The mealybug destroyer is often unable to control mealybugs during winter months outdoors or in greenhouses unless they are heated and lighted.
Development time egg to adult requires about 4 to 6 weeks during warm temperatures. About 4 generations per year occur in California.
Mealybug destroyer adults and young larvae prefer to feed on mealybug eggs and young nymphs. Older larvae feed on mealybugs of any age. Mealybug destroyers also feed on egg-sac producing scale insects and sporadically other soft-bodied insects such as aphids.
The mealybug destroyer is a tropical species introduced from Australia. It does not tolerate cold temperatures. In California it overwinters poorly (at low numbers) in coastal areas and less well or not at all at interior locations.
The mealybug destroyer is reared commercially and shipped to purchasers as adults or larvae. Supplies can be limited by difficulties in maintaining production colonies.
In California citrus release of 500 Cryptolaemus per acre is recommended in spring where mealybugs have been a problem. In greenhouses and interiorscapes one or more releases of several beetles per foot square of growing area or plant can be made where mealybug egg masses are present. Placing a white (nonsticky) card each about 3 × 5 inches near infestations can attract adult Cryptolaemus to that location, apparently because adults are visually drawn to the color of waxy egg sacs.
When receiving purchased mealybug destroyers as adults, check a portion to estimate the ratio of females to males; healthy colonies should be approximately 50% each gender. Production difficulties can result in a high proportion of male beetles, which are of little value for biological control.
The gender of Cryptolaemus is distinguished by examining their underside. The front pair of legs, are black to dark brown on females and orange on males. Only the egg-laying females contribute significantly to biological control. If the beetles received are predominantly males, request a replacement shipment from the supplier.
To increase the effectiveness of resident natural enemies and any that are released
- Avoid the use of broad-spectrum and persistent insecticides and miticides (acaricides).
- Control ants and dust.
- Grow flowering plants that provide nectar and pollen for adults (insectary plants).
About 150 species of lady beetles occur in California. These include the mealybug destroyer and over 2 dozen Scymnini species with larvae that cover their body with waxy filaments.
- Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) Mealybug Destroyer, Cornell University
- Cryptolaemus montrouzieri (Mulsant) (Coccinellidae: Scymninae): a Review of Biology, Ecology, and Use in Biological Control, CAB Review
- Natural Enemies Handbook, UC Integrated Pest Management Program
- Protecting Natural Enemies and Pollinators, UC Integrated Pest Management Program
- UC IPM Pest Management Guidelines: Citrus
- Phylum: Arthropoda
- Class: Insecta
- Order: Coleoptera
- Family: Coccinellidae