Cryptolaemus are Australian native ladybird beetles. They are very efficient natural enemies of mealybugs and several closely related pests. Cryptolaemus have been exported to many other countries and are recognised as powerful predators of mealybugs worldwide.
The adult beetle is about 4mm long with an orange head and black wing covers. The larvae grow to 13mm long and are covered in waxy filaments. The larvae look very much like mealybugs and are often confused with them. Adult female beetles lay up to ten eggs per day directly into mealybug egg masses. They can lay up to 500 eggs in total. Adult beetles and young larvae feed on mealybug eggs and young stages. Large cryptolaemus larvae can also consume adult mealybugs. The life cycle takes from 4 to 7 weeks depending on temperature.
In addition to mealybugs, cryptolaemus will also feed readily on many species of soft scales including black scale, pulvinaria scale and cottony cushion scale.
This video clip shows cryptolaemus feeding on mealybug.
- Pulvinaria scales
- Cottony cushion scale
- Soft scales
Mealybugs are serious pests of orchards and vineyards. They also attack many indoor and glasshouse plants. They thrive in the protected areas between clustering fruit, in the growing tips of many ornamental plants as well as flower buds and leaf axils. Mealybugs feed by sucking sap.
All mealybugs produce large amounts of honeydew on which sooty moulds grow. They take about four weeks to reach maturity in summer, producing up to 500 eggs in a white woolly egg mass.
Mealybugs are difficult to control with pesticides. This is largely due to their waxy covering, their habit of infesting sheltered plant parts, and the consequent difficulty in achieving effective spray coverage. Mealybugs also readily develop resistance to pesticides.
Cryptolaemus can be used to control mealybugs in a range of crops and environments. Like many other predatory beetles, cryptolaemus are most efficient when the host is plentiful. Both the adult beetles and the larvae prey on mealybugs. They survive at temperatures of 16 to 33°C but do best in temperatures around 28°C. Adult beetles are most active in sunny weather.
Cryptolaemus work well in field, glasshouse and indoor atria. Our new rearing method means that we can now supply cryptolaemus as larvae. This means that they can be strategically placed directly on mealybug ‘hotspots’. This reduces the risk of adult beetles taking flight before laying their eggs. It also means that after pupation the next generation is more likely to remain in the environment due to ‘habituation’.
In indoor or nursery environments, cryptolaemus are best released whenever mealybugs are present. Best results are obtained when a full release is made early in the season, followed by smaller top- up releases at intervals of between three and six weeks. In orchard environments, cryptolaemus should be released when active mealybugs are present but preferably before the population has built up to high and damaging levels.
Like other beneficial insects, cryptolaemus should be protected from extremes of heat and low humidity. Avoid using insecticides for at least two weeks before release.
Recommended release rates
- Orchards: minimum 1,000 larvae or beetles per hectare. For persistent mealybug infestations continue releasing at 7-14 day intervals until evidence of establishment and control are noted.
- Enclosed situations: minimum one or two larvae or one adult beetle per square metre.
Higher rates of release may be required where there is a history of mealybug problems. Regular dribble releases of cryptolaemus are encouraged in nurseries and glasshouses to keep mealybugs at low levels.
A note on release rates: Unlike chemicals which generally exhibit a clearly defined dose response curve, with beneficial insects, more is always better. However, they are costly to produce and the goal should be to achieve the best results at minimal cost. We are constantly trying to strike a balance between cost and efficacy. There are many factors that should be considered including the value of the crop, the magnitude of the pest population and the activity (or otherwise) of naturally occurring beneficial species. Also unlike chemicals, where it is common to respond to pest populations that have already exceeded some ‘economic threshold’, we recommend establishing beneficials early in the life of the crop before pest populations reach threatening levels. In most cases our releases are inoculative and we anticipate that our beneficials will establish and breed up within the crop to give long term control. As a general principle, 2-3 releases of modest numbers is better than a single large release – this reduces risk, improves establishment and accelerates the development of multiple overlapping generations of the beneficial species.
After release, larvae should commence feeding on mealybug egg masses and immature stages immediately. It will take around 2 weeks for them to complete their development (at 25°C). They will pupate nearby and adult beetles should emerge to continue the cycle in another 2-3 weeks.
Regular monitoring by an experienced scout is recommended following release to check that the cryptolaemus have established. Because the younger larvae of cryptolaemus look similar to those of mealybugs, care should be taken not to confuse the two.
Significant control is possible within one generation of cryptolaemus (about four weeks). However, high pest populations may take longer to control and may require booster releases.
Cultural practices to aid establishment
Ant control: Ants are often associated with mealybug infestations. Controlling or reducing ant numbers can make a big difference to the success of biological control of mealybug pest populations. See our ant control blog article for more details.
Sleeve cages: When releasing adult ladybird beetles, we recommend the use of sleeve cages to aid in the establishment of a local breeding population. You can purchase our beetle bag sleeve cage product or view our tips for establishing a ladybird population blog article for details about how to make your own sleeve cage.
Pesticide residues may slow or prevent the establishment of cryptolaemus. Copper and nutritional sprays are generally not harmful and many miticides are also quite safe. Organophosphate, carbamate and synthetic pyrethroid insecticides are very toxic and should be avoided where possible. If these sprays are applied, a minimum of four weeks should elapse before cryptolaemus are released. Prevent drift of pesticides from neighbouring areas. Some insect growth regulators (IGRs) are also harmful to predatory beetles.
Cryptolaemus are often released with green lacewings to improve prospects for biological control of mealybugs.