The ladybug is one of those quite popular insects because its appearance is rarely considered repulsive. In our gardens, we often come across the seven-spotted ladybug. But did you know that in reality there are more than 130 species in the USA? Each of these species lives in a particular biotope and has its own diet. So you may be surprised to learn that not all ladybugs eat only aphids!
The biological control method
It is with the ladybug that the method of biological control was initiated. It was at the end of the nineteenth century, in California. Citrus fruits were then invaded by mealybugs. The idea then came to use Rodolia cardinalis, a species native to Australia, particularly voracious. It was a real success because it quickly put an end to the invasion. The ladybug is a particularly interesting auxiliary because it adapts to the amount of food: the more prey it ablaces, the more voracious it is, and the greater the number of eggs it lays.
Today the agents mobilized for biological control have multiplied: predatory insects, parasites, pathogens, and fungi. Obviously, for this to work, it is essential to stop using chemicals. The agents are carefully selected according to the target to be eradicated, pest, disease, or unwanted plant. Biological control makes it possible to envisage a return to the balance between pests and auxiliaries in a defined ecosystem and not to eliminate the pests entirely, otherwise, it could cause other negative consequences.
There are several methods of biological control. The ladybug is most often mobilized in what is called conventional control, by acclimatization. This involves introducing eggs or adult ladybugs into an environment infested by disruptors. But the ladybug can also be involved in the so-called soft method: it consists of improving an environment to attract ladybugs to a given place so that they can then develop.
Now let's look at the categories of ladybugs, identified according to their diet.
Aphidiphagous ladybugs
Aphidiphagous ladybugs are the best-known because they are the ones that feed mainly on aphids. They are all the more useful as aphids attack many plants in the garden by sucking nutrients from the sap but also the roots of plants. These ladybugs may also be interested in other insect pests such as mealybugs and mites. Some are specific predators of certain aphid species, while others will be more generalist.
Ladybugs are known to eat hundreds of aphids a day. Their mandibles allow them to grasp them effectively. They can also eat the eggs of other insects and larvae, as well as moths, mites, and other small insects.
Aphidiphagous ladybugs are divided into three families:
- The Coccinellini, brightly colored, they measure more than 3 mm;
- The Hippodamini, with similar characteristics;
- And the Scymnini, dark in color, their size does not exceed 3 mm.
Phytophagous ladybugs
Phytophagous ladybugs are species of ladybugs that feed mainly on plants. As a result, some of them can cause damage to crops and are considered agricultural pests in some areas. This is the case with the Mexican bean ladybug (Epilachna varivestis). Phytophagous ladybugs feed on the leaves, flowers, stems, and roots of plants. They have a particular preference for beans, cucurbits, and potatoes. There are still species of phytophagous ladybugs considered beneficial for agriculture: they feed on weeds and can help control their growth in crops.
In the family of phytophagous ladybugs, mycophagous ladybugs have been identified that delight in the spores and mycelium of certain fungi found in the garden.
Some species, such as the Asian lady beetle (Harmonia axyridis), can also feed on fruits and vegetables. Damage caused by phytophagous ladybugs of course varies depending on the species and host plant, but common symptoms include spots and holes on leaves, malformations, and reduced plant growth.
There are also so-called floricultural ladybugs because they feed mainly on pollen and flower nectar. They are often attracted to Asteraceae and dandelions, and daisies and chrysanthemums have their preferences. However, they can also feed on flowering plants such as carrots, celery, and fennel, and consume insects, especially during the breeding season.
White-eating lady beetles
White-eating lady beetles are among the carnivorous species. They prefer whiteflies, insects of the whitefly family. These are significant agricultural pests that suck sap from plants, which can cause significant damage to crops and reduce crop yields. In our gardens, they are found on tomato, eggplant, squash, cabbage, strawberry, mint, geranium, or rhododendron plants. The larvae and adults of aleurodiphagous ladybugs feed on the eggs, larvae, and adults of whiteflies. Some species are particularly effective at controlling pest populations because, laying eggs on their eggs, reduces hatchability.
These ladybugs are also used in the biological control of other agricultural pests such as aphids, spider mites, and mealybugs.
Carishing ladybugs
Carishing ladybugs specialize in mites like red spiders that are frequently found in plum trees, lindens, raspberries, conifers, strawberries, eggplants, beans, grass, and even some houseplants. Mites can cause significant damage to crops and ornamentals because they feed on plant sap and can cause deformations, necrosis, and leaf spots, as well as reductions in plant growth.
It is both larvae and adults that feed on mites. Some species of carpophagous ladybugs lay their eggs directly on the mites, limiting their lifespan and the havoc they can cause. These ladybugs may also be interested in aphids and whiteflies.
Some species of ladybugs as examples
Adalia bipunctata is one of the most used species in biological control in gardens because it preys on many species of aphids. And even if its preferences are towards aphids, it can also consume mites, mealybugs, pollen, or even mushrooms. It also colonizes many environments. This makes it an effective predator because it is versatile. The same applies to Coccinella septempunctata. Adalia decempunctata is more suitable for action in broadleaves, conifers, and hedgerows.
Cryptolaemus montrouzieri is a ladybug that eliminates mealybugs and pulvinus by laying its eggs inside the pest's eggs.
Delphastus pusillus is a tiny black ladybug that feeds on whiteflies at all stages. Its larvae and adults are very voracious: they consume 10,000 eggs or 700 larvae during their lifetime. If whiteflies are lacking, they will turn to spider mites and aphids. Females are especially attracted to whitefly homes in which they lay their eggs. They are able to differentiate between a parasitized larva and a non-parasitized larva. Another important asset, this species does not enter diapause (a term that designates the state of hibernation in insects): it remains active whatever the season.
Stethorus punctillum is another small, black ladybug. It feeds exclusively on phytophagous mites such as the weaver spider mite. Larvae and adults attack all stages of development of these pests.
Promote the presence of ladybugs in the garden
There are several ways to promote the presence of ladybugs in your garden. The tricks we present are quite easy to implement.
First of all, you can plant flowers that are favored by ladybugs. Marguerite, cosmos, marigold, or sunflower are well suited.
Then, even if it's tempting, you have to stop using pesticides. Ladybugs are very sensitive to their action and this destroys their food sources. It is therefore essential to make clear choices!
If you like ladybugs, you can also plant plants that attract aphids! Roses, sunflowers, and dahlias are ideal. However, you must be sure to attract ladybugs in number, otherwise, your plants will not be beautiful. In this case, it may be useful to buy ladybugs in addition to what nature can provide you for free.
The life cycle of the ladybug
The ladybug is a beetle, and as a beetle, during its lifetime, it goes through what is called a complete metamorphosis, which means that the baby ladybug looks nothing like the adult ladybug.
The larval stage
Ladybugs are oviparous insects, which means they lay eggs, 4 to 5 days later and the young come out of their egg. This is the first stage of the ladybug, the so-called 'larval' stage, the larva has a non-extensible external skeleton, in order to evolve, so it will have to separate from it, this is called the 'molt'. Ladybugs molt 3 times, so there are 4 larval stages, each lasting between 4 and 5 days. Depending on the species to which the ladybug belongs, it will feed on what it likes the most as we saw earlier in our article.
The nymph stage
Once the larva has reached its maximum size, it stops and puts its back on a leaf, and curls up on it to form a nymph that will allow the formation of the adult ladybug.
The adult stage
A few days pass and the adult ladybug breaks the nymph, it will reproduce in turn, continuing the life cycle of the ladybug.
Finally, the creation of habitats dedicated to ladybugs is also an interesting strategy. Ladybugs need shelter to rest and lay their eggs. Ladybug hotels, piles of dead leaves, stacked stones, or branches in your garden will please them.
Where do ladybugs live in winter?
It is normal that you do not see ladybugs in winter. But what do ladybugs do that, all at once, disappear in winter? Do they spend the winter in the sun to avoid the harsh winter temperatures?
Well, no! Ladybugs are among the animals that hibernate, which means that during the coldest months, their body works in slow motion and they enter a body torpor that will make them sleep during the coldest months. During their hibernation, ladybugs shelter where they can and it is not uncommon to see ladybugs sheltering in house facades, holes in trees, etc.
And now, you know where ladybugs live in winter, you can see that they never really leave you, these beautiful beetles.
Predator of the ladybug
The life of a ladybug is not so quiet, many predators watch for it to make their lunch ... Among the main predators of the ladybug are:
- Insectivorous birds are attracted to red.
- Spiders
- Ants
- Bedbugs
Flies as well as some species of wasps can parasitize the ladybug by laying their eggs in its body.
The Asian lady beetle, an invasive species in Europe, is considered a super-predator because it attacks the larvae of its congeners.
Bibliography
Stethorus punctillum (March 26, 2020) Available on: https://anatisbioprotection.com/produits-lutte-biologique/stethorus-punctillum-predateur-tetranyque.html
Technical data sheet of breeding. Aphidiphagous ladybug: Coccinella septempunctata (March 26, 2020) See on: http://www.insectes.org/opie/pdf/1129_pagesdynadocs4b508b17b83df.pdf
On the menu of ladybugs. Consult on: https://www.zoom-nature.fr/au-menu-des-coccinelles/
Lounes Saharaoui. Algerian lady beetles (Coleoptera, Coccinellidae): faunal analysis and community structure. Biodiversity. Paul Sabatier University - Toulouse III, 2017. French. ffNNT: 2017TOU30246ff. fftel-01914941f Available from: https://tel.archives-ouvertes.fr/tel-01914941/document
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