As their common name implies, adult green lacewings are green, with four clear wings. Adult female lacewings live for approximately three or four weeks and lay up to 600 eggs. Each egg sits on the end of a slender stalk, which elevates it from the ground and decreases the chances of predation by ants. The eggs take approximately four days to hatch.
Larvae range in size from 1 mm at first emergence up to 8 mm just before they pupate. They have small spines on their backs upon which they impale the remains of prey. This provides a form of camouflage and allows the larvae to appear inconspicuous amongst the prey. Larvae pass through three moults over a period of 12 days before pupating inside a silken cocoon. Adults emerge after nine days and start laying eggs seven days after emergence.
- Aphids (various species)
- Twospotted mite Tetranychus urticae
- Greenhouse whitefly Trialeurodes vaporariorum
- Scales (various species)
- Mealybugs (various species)
- Moth eggs and small caterpillars
The green lacewing is one of the most common and widely distributed native lacewings in Australia. It is well suited to a wide variety of crops and habitats, including greenhouses, and is most active in warm climates. Lacewings are probably best suited to tree and shrub crops. Adult lacewings feed on nectar and pollen, so the presence of flowers after release will assist in keeping the lacewings within the crop. Cool temperatures slow down green lacewing activity and may induce diapause (hibernation).
Lacewings should be released before pests can reach damaging levels. As with other beneficial insects, it is better to release them earlier rather than later. Do not use residual pesticides within three weeks of release.
Lacewings are despatched as eggs and should hatch into the larval stage during transit. Eggs are packed with shredded paper to allow them a surface area, in lots of 100 or 500. The package includes a small quantity of sterilised moth eggs for food. Lacewings should be released when they reach the second stage of larval development. If the package is checked daily from arrival it should be quite easy to notice the sudden significant increase in size that indicates that the second stage has occurred. To ensure that the lacewings remain in the crop it is best if the shredded paper and containers with larval stages are distributed within the crop. The Lacewing larvae can also be sprinkled into our small release boxes and suspended on twigs or branches. This allows the larval stages ready access to the protection of foliage and to their food source. At this critical stage of release it may be necessary to control the ant population. Refer to the ant control blog.
Recommended release rates
- Field crops: Release rates vary considerably depending on the crop, the pest to be controlled and its density. A minimum of 2000-5000 lacewings per hectare should be released. Aim for 10,000 per hectare if possible.
- Nurseries: A minimum release rate of between one and five lacewing larvae per plant is recommended.
- Other situations: The number of lacewings needed for an individual situation can be determined after consultation with the suppliers. It is best to release larvae in pest hot spots, to ensure larvae have an immediate food supply.
It is preferable to make two or three releases 10 to 14 days apart to improve establishment of green lacewings in the field. Larvae take about 12 days to develop before they pupate in cocoons. After this time, there will be few lacewing larvae in the field, as it takes 16 days before adults emerge and lay eggs.
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.
Since lacewing larvae camouflage themselves with dead prey items, some practice is needed to find them in the field. Normally they are more mobile than the pest, and can often be seen moving over plant leaves and stems. The lacewing cocoons are usually well hidden and difficult to find. Adults fly at night and are attracted to lights, so avoid leaving lights on at night.
Lacewing eggs can readily be seen on their distinctive long slender stalks. Start scouting for eggs approximately 30 days after releasing larvae.
Cultural practices to aid establishment
Adult lacewings will persist in the crop if nectar and pollen are present. Practices such as strip intercropping and encouraging flowering plants will give best results.
Little is known about insecticide toxicities to lacewings. It is reasonable to assume that unless the pesticide is specific to one particular group, for example a miticide, it will have some sort of harmful effect on lacewings.
Lacewings are despatched by express post or overnight courier and should be received within 48 hours. Lacewing should not be released until the eggs have hatched and developed into the second stage larvae (see above). If necessary they can be stored as eggs or young larve for several days in a cool, dark place. If storage is required, containers should be turned upside-down daily to allow re-distribution of their included food supply. If lacewings are held for too long such that their food supply becomes depleted they may start to cannibalise each other.
Now available our new garden pack consisting of 300 lacewing eggs, 6 release boxes and 2 yellow sticky traps. Great for the home garden or vegetable plot on the balcony.