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Ladybirds (lady beetles)

Also known as Ladybugs, Lady beetles, Coccinellidae

Beneficial or harmlessBeneficial
Adult seven-spot ladybird (Coccinella septempunctata) Photo: Luc Viatour · CC BY-SA 3.0

In short

Ladybirds are small, domed beetles whose adults and larvae eat aphids and other soft-bodied sap-feeders. Their spiky, dark larvae look nothing like the adults and are often squashed by mistake as pests. A few leaf-eating relatives (Epilachna) are pests in their own right, so it pays to look closely.

How it looks

Adults are dome-shaped on top and flat underneath, roughly round from above, and range from under 1 mm to about 18 mm; the familiar seven-spot ladybird is about 8 mm long with seven black spots on orange-red wing covers. Colours are usually red, orange, yellow or brown with darker markings, and some species are plain or black. Eggs are spindle-shaped, yellow to orange, about 1 mm long and stand upright in clusters of roughly 10–30, usually close to an aphid colony. Larvae are elongated, "tiny alligator" shapes with legs, up to about 8 mm, dark grey, brown or bluish-black with orange or yellow spots and often bumps or bristles. Pupae (about 6 mm) are glued to leaves or stems where the larva fed, starting orange and developing black blotches.

Signs

Clusters of yellow eggs on leaf undersides near aphids, dark spiky larvae walking over aphid colonies, orange pupae stuck to leaves, and aphid numbers that fall without any spraying.

Life cycle

Egg, four larval stages, pupa and adult. For the seven-spot ladybird, development from egg to adult takes about six weeks in the growing season, with up to five generations a year; adults shelter in protected places over cold periods. A single female can lay a few hundred eggs.

What favours it

They follow food: ladybirds gather where aphids, scale, mealybugs, whiteflies or psyllids are plentiful and where nearby flowers provide pollen and nectar. Ants tending aphids drive them off.

Prevention

  • Learn to recognise ladybird larvae and pupae so you do not remove or spray them.
  • Grow a few flowering plants that offer nectar and pollen near your collection, keep ants off infested plants, and avoid broad-spectrum, persistent insecticides.
  • Tolerate a small aphid colony on outdoor plants for a while: it is what keeps ladybirds breeding nearby.

Treatment

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

  1. No control is needed for predatory ladybirds; leave adults, larvae and pupae in place.
  2. If a leaf-eating Epilachna ladybird (hairy adult, pale spiny larva, scraped "window" damage) is chewing solanaceous, cucurbit or bean plants, hand-pick adults and larvae early and remove related weeds nearby.
  3. Bought ladybirds mostly fly away: studies found about 95 percent left within 48 hours. If you do release them, water the plants first, mist the beetles and release in the evening.
  4. If a spray is unavoidable, prefer a short-residual option such as insecticidal soap or horticultural oil applied directly to the pest, away from larvae and pupae, and follow the product label.

Pros and cons

Pros

  • Adults and larvae both eat aphids; an Asian lady beetle adult can eat more than 100 aphids a day and a larva roughly 600–1,200 during its development.
  • Different species target different pests: some eat scale, some spider mites (Stethorus), some whiteflies.
  • They multiply where prey is plentiful, so they help without any cost or effort.

Cons

  • Purchased beetles tend to disperse within a day or two, so releases rarely help small gardens or indoor plants.
  • The multicoloured Asian (harlequin) lady beetle has displaced native ladybirds in some regions and can gather in houses over winter, where it leaves smelly, staining secretions.
  • Ladybirds exude foul-tasting defensive fluid from their leg joints when handled (reflex bleeding).
  • Some ladybirds (Epilachna, such as the 28-spot ladybird) eat leaves of eggplant, potato, cucurbits and beans and are pests.

Look-alikes

28-spot ladybird and other Epilachna beetles
Dull orange with many black spots and covered in short downy hairs; they chew leaves rather than eat aphids, and their pale yellow larvae carry long branched spines.
Mealybug destroyer larvae
A ladybird too, but its larva is covered in white waxy filaments and looks like a large mealybug.
Mealybugs
Slow, oval, sap-sucking insects coated in white wax that stay in clusters; ladybird larvae move quickly and are dark.
Lacewing larvae
Also alligator-shaped predators, but flatter, cream to tan with prominent sickle-shaped jaws.

Where you find it

Any plant carrying aphids, soft scale, mealybugs, whiteflies or psyllids, outdoors or on a balcony; less relevant for sealed indoor collections.

Sources

  1. Coccinellidae — Wikipedia
  2. Sevenspotted lady beetle — UC IPM Natural Enemies Gallery
  3. Multicolored Asian lady beetle — UC IPM Natural Enemies Gallery
  4. Releasing Ladybugs in the Garden — UC ANR Pests in the Urban Landscape
  5. Eggplant 28-spot ladybird beetle — Pacific Pests, Pathogens and Weeds (Lucid)

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