Biological Plant protection
What is biological plant protection?
Biological plant protection in the broad sense is defined as the use of biological processes,
to improve plant growth and the plant's resistance against diseases or to suppress plant pests.
With the increasing awareness of health and environmental risks involved with the use of chemical
pesticides, biological control agents have recently gained significance, because they pose no risk
to humans and nature. Furthermore biological control agents often have a sustainable control effect,
meaning that they only need to be applied once and hence protect the plants for a long period,
sometimes over several years. The increasing number of organic growers in agriculture, horticulture
and forestry completely refrain from using chemical pesticides but are very successful with using
biological means. Since the range of chemical pesticides is also restricted by law, a further
increase of the use of biological control agents can be expected.
Biological pest control - A part of biological plant protection
Besides boosting the plants defence against diseases, the use of beneficial Organisms to control pestsis a central part of biological plant protection. The term 'pest' covers plant-feeding or
plant-damaging Organisms which by rapid proliferation and high population densities cause
economic damage to crop-plants. These pests mostly become abundant when the natural diversity
of species is reduced by man, which is the case in any cultivation of plants and most evident
in large monocultures. The lack of naturally occurring predators, parasites and other antagonists
combined with a huge amount of food enables an almost unlimited proliferation of the pest Organism.
In biological control, the natural antagonists are deliberately applied, to decrease the number of pestOrganisms. Since the beneficials can reproduce, they can adapt to the population density of the pest,
which is a distinctive advantage compared to chemical control measures: Those efficacy is diluted with
and increasing population density of the pest, whereas the opposite can often be observed for biological
control agents. The efficacy increases with the pest population density. Since many of the benenfical
antagonists can enter into enduring stages and can therefore survive without nourishment, a sustainable
control of the pest over years is achievable, which is impossible when using chemical pesticides.
How does biological pest control actually work?
The garden chafer is common and widespread on lawn and pastures. It can be a serious threat to turf.
Female beetles lay their eggs end of May into the soil. After 2 weeks, the larvae, often called white
grubs, hatch. Tese larvae do the prinicpal damage. Grown up to a certain size, these larvae start cutting
the roots of grass-plants thus disconnecting the water supply to the grass. The consequence of this is a
yellowing turf mat, which can be rolled off the soil. To reduce this damage eel-like worms (nematodes)
are used in biological control. Like the white grubs, nematodes are soil living animals. The beneficial
nematodes enter the white grubs and penetrate into their 'blood' system, the haemocoel. The grubs are
killed and subsequently, the nematodes proliferate inside the dead grubs. Whereas a few nematodes(2 to 10) are sufficient to kill a grub, around 100,000 will leave the cadaver after reproduction. These
nematodes can then infect living grubs. Ths chain reaction continues until the number of grubs is
significantly decreased and the nematodes have difficulties finding their source of nutrients. Depending
on the grub, the number of beneficial nematodes decreases. The population size of both, the grub and the
insecticidal Nematode is hence mutually controlled in a typical prey-predator pattern.
Biological control - a sustainable investment in nature conservation!
Despite all the advantages the efficacy and the use of biological control agents is still viewed sceptically.
The reasons for this are manifold. Due to the lacking or insufficient understanding about the use and the
efficacy they are often considered to be unreliable. The storage and the transport of living Organisms for
biological control is, in contrast to chemical products, difficult and challenging for distributors.
Furthermore the immediate, albeit quickly fading, action of chemical pesticides is also expected from
biological agents. However, biological agents usually exert a slow, but more sustainable efficacy. The use
of biological control agents requires more attention from the user; handling living Organisms needs practice.
Some Organisms, for example, need specifc temperatures, sufficient aeration or darkness, to survive. This,
in turn, requires a more intensive assistance by the distributors and therefore more time.
Alltogether, the use of biological means requires a change in thinking. In the context of environmental
protection, conservation and sustainable production systems, biological plant protection is an indispensable element.
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