Introduction to integrated methods in the vegetable garden
Chapter : Biocontrols
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⇒ Imports of beneficial organisms.
According to the IBMA (International Biocontrol Manufactures Association), in france 75% of vegetable crops under cover are now protected by beneficial insects, especially for tomatoes, mainly through biological control by augmentation (increasing a population of indigenous predators of a pest). For field cereal and fruit crops, this method of controlling pests in the open by mass introduction of native or imported predators is more difficult to implement, mainly because of technical difficulties. In 60 years of research, there are few successful methods of introduction by open-air augmentation; here are the best known:
The mealybug Dactylopidae from Brazil introduced into southern India and Sri Lanka to control the development of an invasive prickly pear species;
The ladybird Rodolia cardinalis is used in more than 50 countries to control aphids after being imported to California to control the accidental introduction of a mealy bug;
Trichogramma brassicae, which are mini wasps produced in large numbers to control the corn borer, and typhlodromes, which are mites that feed on other mites infecting the vine;
The introduction of European parasitoids into northern America to control the Bombyx disparate which was ravaging hardwood forests;
The parasitoid Torymus sinensis imported from Japan to control the chestnut moth.
Importing native beneficial insects to regulate a pest population is both an effective and environmentally friendly solution. Compared to plant protection products, there is no risk of environmental pollution or overdosing. Excessive predators will disappear due to lack of food or will move to other plots. The treatment is much more targeted, sparing other insects present in the garden. Red spiders, aphids, mealy bugs, Colorado beetle larvae, ants, slugs, beetle larvae, cutworms, butterfly caterpillars are some examples of the most common pests in the vegetable garden whose development can be reduced or even stopped by importing a specific predator. This is also the case for the codling moth, which burrows into apples, pears, walnuts and peaches; fruit trees that are sometimes found in the vicinity of a home garden.
The links in the green banner at the end of the page give some examples of pests whose populations can be controlled by importing beneficial insects into the garden. Among the predators of sucking pests, ladybirds are discussed in more detail because I believe that for the home gardener they are the easiest predator to control. Other useful auxiliaries are mentioned, such as mites (against red spider mites), lacewings (against aphids, mealy bugs, Colorado beetle larvae, etc.) or nematodes (against ants, cockchafer larvae, etc.).
However, I would like to point out that it is more difficult to "treat" plants with ladybirds than to use a sprayer, because it requires a lot of attention and a certain experience. For example, it is important to determine precisely when to introduce the predators; importing them too early or too late has different consequences. Either the ladybirds will starve or they will not have time to avoid the introduction of opportunistic diseases. A too late treatment requires a massive import of predators, the quantity of which is not easy to find commercially. However, with time, this method of plant protection is appreciated and is more effective than synthetic or organic pesticides, especially when the pests become resistant to these products.
The difficulties encountered are explained so that the reader can avoid certain mistakes.
Useful auxiliaries imported from abroad are not described because of the negative environmental consequences sometimes encountered.
Click on one of the buttons below to access a folder. The useful beneficials for the pest groups are specified in each folder.