Rhyzobius lophanthae
A tiny Australian lady beetle, about 1/12 inch (2 mm) long, with a reddish-brown head and a dark back covered in fine grey hairs. Adults and larvae eat scale insects. They can chew through the cover of armoured scales, and they eat the eggs and young of soft scales. It is sold as Rhyzobius or under its old name, Lindorus, and works best released into dense patches of breeding scale. It is easy to overlook, because it is small and dull and its larvae feed hidden under the scales.
At a glance
- Mode
- Predator — adults and larvae
- Rate
- 2–6 /m² or 2–5 per plant
- Ships as
- Adults, 10–500 per vial or tube
- Temp
- Best 59–82 °F (15–28 °C)
- Humidity
- 20–90 % RH (Arbico, Rincon-Vitova)
- Setting
- Orchards, landscapes, greenhouses, interiors
How it works
Adults and larvae eat all stages of armoured scale. They chew an irregular hole in the cover, and small scales are eaten whole. They also eat the eggs and crawlers of soft scales, though Rincon-Vitova says they favour soft scale only until honeydew builds up, because sticky leaves hinder them. UC puts a female's lifetime intake at about 100 soft scale nymphs or 200 soft scale eggs, and about twice that for armoured scales. Rincon-Vitova says a flush of scale crawlers stimulates egg laying, and the female tucks one or two eggs under a scale.
UC gives about a month from egg to adult in warm weather and about three generations a year in California. Adults live about two months and overwinter as adults, although Rincon-Vitova says they can live up to a year. UC counts 200–400 eggs per female and Rincon-Vitova 60–100. The beetle was brought to California from Australia in the 1890s against black scale. Rincon-Vitova notes that ants do interfere, but the beetle can keep its numbers up on ant-infested trees by feeding on the scale along the trunks and branches where ants trail.
Is it established?
The adults you release are only the start. What you want to see is larvae of the next generation working the same scale patches.
- DAY 1Small dark beetles with reddish heads walking over the scale; they may not fly at once
- WEEKS 1–2Scales with ragged holes chewed in their covers
- WEEKS 3–4Dark grey larvae up to 4 mm, with pale bands, moving among the scales
- AFTERBeetles spreading out from the release patches to find more scale
Release & handling
Beetles arrive as adults in a vial or tube with a carrier. Release them as soon as possible, and until then keep them cool and dark but out of a household fridge, because Rincon-Vitova warns they are susceptible to freezing. Wash honeydew off the leaves first, because it gums up adults and larvae.
Release within a day
Arbico says to use them within 18 hours. Koppert allows 1–2 days at most.
42–59 °F, dark, no fridge
Arbico gives 42–50 °F (6–10 °C) and Koppert 50–59 °F (10–15 °C).
Evening, on dense scale
Tap them onto the heaviest patches of breeding scale. Those patches become field insectaries for their offspring.
Rinse off honeydew
Spray the leaves with water to remove honeydew before you release the beetles.
Pesticide sensitivity
No product-specific toxicity data was found for this beetle. Natural Enemies suggests neem as a knockdown before release, and says to let oil or soap residues dry before the beetles go out. UC advises avoiding broad-spectrum, persistent insecticides wherever scale natural enemies are relied on. Check a product →
When to choose something else
Rhyzobius is a slow-building predator for scale that is breeding. Choose something else when:
- Armoured scale is heavy on citrus or ornamentals: add the parasitoid Aphytis melinus. Koppert and Rincon-Vitova both pair the two
- The problem is mealybugs: the beetle eats some, but Rincon-Vitova says it needs scale to reproduce, so use the mealybug destroyer
- Leaves are coated in honeydew from soft scale: wash them first, or the beetles cannot move over them
- It is a few scaly twigs on a small plant: UC says pruning them off works when the scale is limited to a few parts of the plant
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics (Purple Scale Predator)100 / 250US
- Evergreen Growers Supply50 / 100 / 250US
- Koppert (Rhyzobug)500GLOBAL
- Natural Enemies (Rhyzobug)500US
- Nature's Good Guys10 / 25 / 50 / 100US
- Rincon-Vitova25 / 50 / 100 / 250US
Rhyzobius lophanthae by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.