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Mealybug destroyer

Also known as Cryptolaemus montrouzieri, Crypts, Mealybug ladybird

Beneficial or harmlessBeneficial
Adult mealybug destroyer: dark wing cases, orange head and thorax Photo: Quoted from source:"Image Citation: Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org" "Image Use: You must attribute the work in the manner specified (but not in a · CC BY 3.0 us

In short

The mealybug destroyer is a small Australian ladybird whose adults and larvae eat mealybugs, including their eggs. It is reared commercially and released in greenhouses and conservatories. Its fluffy white larvae look like large mealybugs, so growers sometimes kill them by mistake.

How it looks

Adults are dome-shaped ladybirds about 3–4 mm long with dark brown to blackish wing cases without spots, and an orange-brown head, thorax and legs. Larvae grow to about 12–15 mm (about half an inch), more than twice the size of an adult mealybug, and are covered in long white waxy filaments; unlike mealybugs they move quickly and have visible legs and mouthparts. Eggs are yellow and laid in or among mealybug egg sacs.

Signs

Mealybug colonies shrinking; fluffy, fast-moving white larvae among the mealybugs.

Life cycle

Egg, four larval stages, pupa and adult; development takes roughly 24 days to six weeks in warm conditions. Females live about two months and lay roughly 200–400 eggs among the egg masses of their prey.

What favours it

Develops fastest at about 22–25 °C and 70–80% relative humidity; reproduction slows markedly below about 20 °C. Needs plenty of mealybugs to establish.

Prevention

  • Release when mealybugs are a known problem, so there is enough prey to feed the beetles and their larvae.
  • Avoid broad-spectrum insecticides around released beetles.

Treatment

Start with the first step and move down only if the problem persists.

  1. Release beetles on or near infested plants following the supplier's rate (the UC IPM guide suggests several beetles per square foot in greenhouses).
  2. Leave the white, fast-moving larvae in place; do not wipe them off with the mealybugs.
  3. Combine with hand removal of the worst colonies.

Pros and cons

Pros

  • Both larvae and adults eat mealybugs, their eggs and crawlers.
  • Also eat soft scale insects and scale insect eggs, and occasionally aphids.
  • Long history of successful use, including in citrus.

Cons

  • Needs warm, fairly humid conditions and a good supply of prey to breed.
  • Larvae are easily mistaken for mealybugs and removed.
  • Only egg-laying females contribute much to control.

Look-alikes

Mealybugs
Mealybugs are smaller, slow, with hidden legs and mouthparts; destroyer larvae are larger, fast and have visible legs.
Other small ladybirds (Scymnus, Nephus)
Their waxy larvae are about half the size or less.

Where you find it

Greenhouse and conservatory plants, citrus and other plants with mealybug infestations.

Sources

  1. Mealybug destroyer — UC IPM Natural Enemies Gallery
  2. Cryptolaemus montrouzieri — Wikipedia

Written in our own words from these sources. Check a product label before using any treatment.