Responsible hobby gardeners first use all biological means to combat pests in their garden before resorting to chemicals. In this way, you can make your green area inviting for beneficial insects such as hedgehogs, ground beetles or birds. It is less well known that there is also helpful support from nature for the home to combat pests such as aphids, mites or whiteflies. This is the lacewing, a greenish shimmering lacewing that is becoming increasingly important in biological pest control because its larvae feed exclusively on plant pests.

The impact in pest control

The brownish larvae with their elongated body devour the largest number of pests in the course of their approximately two-week development stage up to pupation. The information provided by the various researchers varies somewhat, but the benefits and the lacewing larvae can be clearly seen from the following rough figures:

  • 1 female lays 350 eggs
  • 1 larva eats about 450 aphids
  • results in 157,500 aphids killed per female.

Depending on the pest occurrence in the home, a lacewing larva feeds alternatively on up to 12,000 mite eggs, which can lead to the destruction of up to 4,200,000 mite eggs per lacewing female. The adult lacewings feed mainly on pollen and honeydew. In view of these roughly estimated numbers, it is not surprising that research into the promotion of the lacewing population is constantly being pushed forward.

Get to know the life cycle

Lacewings are active at dusk and spend most of the day on the underside of leaves. The males and females find their partners with the help of ultrasonic sounds. After mating, the females prefer plants inhabited by aphids to lay their eggs. Each individual egg is attached to a small handle to protect it from predators. Depending on the weather, the larvae hatch after 2 to 10 days and go in search of their favorite food, aphids, white flies or spider mites. They feed on these in the 2 weeks until pupation. The lacewings leave the corresponding cocoon after about 1 week and the process begins again.

In total, 2 to 3 generations develop each year until it gets colder from the end of August. Then the lacewings look for winter quarters in the foliage, in tree cracks, in attics and in buildings. Here they fall into a state of torpor, in the course of which any form of heat, for example in heated rooms, is fatal to them.

Purchase and use lacewings

The life cycle of the lacewing shows that these insects are not suited to being permanently settled indoors. For this reason, specialist companies have started to breed lacewing larvae , which can be bought in the 1st or 2nd instar in a suitable packaging. The packaging consists of a honeycomb system so that each larva is housed individually so that the animals do not eat each other, as they tend to cannibalize.

They are simply tapped out of this packaging over the infested plants, where they immediately attack the aphids, spider mites, whiteflies and mealybugs. Since the larvae do this activity for a maximum of 10 to 14 days, it is sometimes necessary to repeat this process after 14 days. So that the larvae do not fall to the ground when they are knocked out of the honeycomb, experts advise first knocking them on a kitchen towel or paper fleece, which is then hung in the plant. From there, the larvae quickly find their way to the pests.

It is also an advantage if the infested plants touch each other so that the lacewing larvae can switch to the next feeding station. It is very important to observe the instructions for dosing the larvae used per plant or per square meter in the room. Overdosing creates overkill, causing the larvae to eat each other. The result is that they no longer have an appetite for aphids and spider mites, but immediately switch to pupation.

The process after the release of the larvae

As with most biological pest control agents, success is not immediately apparent. In order for the use of lacewing larvae in the home to be effective at all, no chemical agents may have been used at least 6 weeks beforehand. If products from the plant extract of the neem tree were previously used, this is harmless.

The lacewing larvae live through a total of 3 stages. In the first larval stage, they are not particularly active and are only 2 mm in size. They are therefore usually delivered in the 2nd larval stage, so that they start hunting for the pests right away. The little animals, which are only 5 mm in size, are active at dusk and prefer to move on the underside of the leaf. Therefore, they are difficult to see with the naked eye. When they reach a size of 7 mm after 3 to 4 days, they are in the 3rd instar larvae and develop an activity whose effects can be seen. A significant reduction in pest infestation on the plants in the apartment can therefore be seen after a week at the earliest. Then the pupation begins, which can be recognized by the cocoons that are located on different parts of the plant.

Anyone who makes the apartment inviting for the hatched lacewings will, with a bit of luck, get a second generation of lacewing larvae; provided female and male specimens hatch. Since the lacewings – in contrast to the larvae – feed on pollen and nectar, there should be some flowering plants in the apartment. As several experienced hobby gardeners report, lacewings also accept sugar water or diluted honey as food. They place their eggs in the plants that have not been completely cleared of aphid infestation during the first round. If there are not enough aphids or other pests, it can happen that the lacewing larvae starve and pupation does not even occur.

The visual appearance

Scientists have determined that the mortality rate among beneficial lacewings ranges from 60% to 90% because many people are unaware of what the lacewings and their larvae look like. Therefore, they are often viewed as annoying insects that are killed with the fly swatter or bug spray.

The lacewing owes its name to the filigree, fabric-like wings, which are transparent and have a subtle iridescent shimmer. The species occurring in Central Europe are greenish to brownish in color and have a wingspan of between 10 mm and 40 mm. The lacewing owes its colloquial name golden eye to its compound eyes.

A total of 2,000 species of lacewings have been discovered worldwide, 35 of which are native to Central Europe. In Germany, the common lacewing is the most common and was voted insect of the year in 1999. Their body color is a striking light green, with a wingspan of up to 35 mm. The larvae of the common lacewing are also referred to as aphid lions, which is quite accurate given the numbers presented.

Encourage lacewings

If you make the garden inviting for the useful lacewings, the hobby gardener will definitely have his own stock of lacewing larvae there during spring and summer, which you can use tweezers to carefully transport to the apartment on a piece of paper. The following measures serve to promote lacewings:

  • do not use chemical pesticides;
  • plant flowering plants in the kitchen garden;
  • Lacewings love catnip;
  • plant deciduous trees;
  • let lacewings hibernate in the attic;
  • leave the autumn leaves behind;
  • Hang up lacewing houses.

If the beneficial insects feel comfortable in the garden, they produce enough eggs and larvae, which not only devour the pests outdoors, but can also be used on the plants in the apartment. Then, in the worst case, in winter it is necessary to fall back on the offer of specialist dealers who offer lacewing larvae for sale. Under certain circumstances, this procedure saves a gratifying amount of money, because the minimum purchase quantity of larvae costs from 15 euros and upwards.

Build lacewing houses yourself

These small insect hotels can be ordered from specialist retailers. If you are skilled with your hands, you can also build a lacewing house yourself:

material list

  • Wooden panels: thickness 1 cm
  • Back panel 25cm x 25cm
  • Side walls 26 cm high at the front, 25 cm at the back, width 25 cm
  • Roof 30cm x 30cm
  • 2 Fugenleisten 25 cm x 2 cm x 2 cm
  • 12 strips for the front and the bottom 25 x 4 x 1 cm
  • wooden pole
  • screws
  • red-brown color
  • wheat straw

First, the two joint strips are screwed to the rear wall, followed by the two side walls. The battens on the front and on the bottom are attached to the side walls at an angle of 45°, protruding by about 1 cm. This creates a slatted wall as an entrance for the lacewings to their home during the cold season. Attach the stake to the back. Now paint the little house with the red-brown color and fill it with wheat straw. The wheat straw is pressed together as tightly as possible. In the last step, the roof is screwed on and also painted. The lacewing house is placed in a wind-protected spot in the garden, as close as possible to herbaceous borders and catnip.

Depending on the size of the garden, it can make sense to hang several of these insect hotels. Here they spend the winter in a sheltered environment and will start busy producing lacewing larvae in the spring. If necessary, the hobby gardener can collect some of these specimens and expose them to plants infested with pests in the apartment.

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