Biological control means ‘control of an organism by using another living organism’. Classical biological control covers the recognition, assessment and introduction of a natural enemy from elsewhere, the maintenance of indigenous usual enemies and the expansion of the biocontrol agents. Biocontrol agents are generally slower-acting, but cause longer-lasting biotic suppression of a specific pest population. Ticks are important vectors of disease-causing pathogens of humans, wildlife, and livestock. Reducing tick abundance is an important but elusive goal.
Chemical pesticides applied to habitats occupied by ticks can be effective but appear to have significant negative effects on nontarget organisms. Reducing tick abundance is likely to remain the most effective method for preventing tick-borne diseases. Several methods of bio-control of ticks, including parasitoids and some bird predators, have been shown to reduce tick numbers in some situations.
Perhaps the most promising method of bio-control is the targeted use of fungal pathogens, which has been shown to reduce tick numbers both directly (through mortality) and indirectly (through reductions in fitness).
These preliminary successes demonstrate the importance and potential of rigorous research into novel and existing methods of biological control of ticks.The most promising alternatives to chemical pesticides are biological control (bio-control) agents, which are species that consume target pest organisms via predation, herbivores, or parasitism. Bio-control agents typically are nontoxic to humans and to non target wildlife (for a few exceptions, see below). Moreover, bio-control agents are expected to co-evolve with their target organisms, reducing the likelihood that resistance will evolve. Biological control of ticks or mites means controlling them with natural organisms that are their natural enemies.
There are three major types or organisms that are natural enemies of those ticks and mites that affect livestock:
• Predators: They just eat the ticks; either those still attached to the host, or engorged females
that have dropped to the ground: mainly birds, ants and a few mite species.
• Parasitoids: These are wasps that deposit their eggs on ticks. The larvae of the wasps feed on
the tissues of the ticks that are ultimately killed. They can be considered as
"parasites" of the ticks.
• Pathogens: Mainly bacteria, fungi and nematodes (roundworms) that infect and kill the ticks or
mites or their larvae. They can be considered as "diseases" of the parasites.
So far there are no biological control methods against ticks and mites of dogs and cats.
Why biological control is preferred?
Pest biocontrol is becoming one of the most hopeful replacements to chemical pesticides.
This technique is used:
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To minimize the chemical residues on our planet
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To minimize the growing problem of arthropod resistance to pesticides
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To balance rising prices of new chemical pesticides
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To create friendly environment(chemical free)
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Due to longer effect of this techniques compared to other methods
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To overcome the drawback of broad spectrum insecticide
Significance of ticks
Ticks are economically the most important pests of cattle and other domestic species in tropical and subtropical countries. Why it should be preferred for the control of Ticks?
Fungi are the most reliable source of tick control due to the following reasons.
1. The ability of entomic-pathogenic fungi to penetrate the cuticle of arthropods
2. The ability of a strain to kill several stages of ticks.
3. The relatively specific virulence of a single strain to one or agents.
Mechanism of Action:
EPNs penetrate engorged female B. annulatusticks almost solely via the anus or genital pore. Heterorhabditid nematodes killed engorged B. annulatus females in Petri dishes after less than 2.5 hof exposure, whereas steinernematid nematodesneeded more than 4 h to penetrate into ticks. The injection of a single heterorhabditid nematode into a tick can cause mortality.
Parasitoids
Most parasitoids used in the biological control of insect pests of plants belong to the order Hymenoptera. Only a few species of hymenopteran parasites are known to affect ticks. It has been described that two species of chalcidoid wasps collected from ticks in Texas. These are now both included in the genus Ixodiphagus of the family Encyrtidae, which includes seven species, all tick parasites. The most widespread species is I. hookeriwhich has been recorded from Asia, Africa, North America and Europe. The EPNs are known to be pathogenic to over 3000 insect species, whereas each strain may often be relatively specific to a small group of hosts and thus their effects on most beneficial insects have been found to be negligible.
What the end result is?
The development of anti-tick biological control agents (BCAs) is still in its infancy. Furthermore, the various steps required for commercialization of these products, including adaptation by companies (production, storage and delivery) and education of consumers (storage, application and evaluation of results), are still in the future. Nevertheless, we believe that the need to develop alternative control methodswill yield useful results.
The fact that some BCAs and particular strains are far more specific in their selection of target pests than are acaricides and that many strains are effective only under specific ecological conditions, provide considerable advantages over pesticides, because harmful ecological effects are minimized. Partial or total replacement of chemical acaricides with extra use of tick pathogens and/or parasitoids would require considerable changes in the techniques of producers and suppliers. Biological control of plant pests, by means of parasitoids, predatory mites, viruses, B. thuringiensis, bugs, beetles, and others, has had several striking successes.
These include the use of several enemies/ pathogens simultaneously or in a pre-determined order. However, only about 5% of all pest problems are treated with biological control methods and many problems have to be solved in order to increase their use. Relatively fewstudies have been performed on the existence of promising natural enemies of ticks, or on their use against ticks in most parts of the world. Collaboration between biocontrol experts who have experience in managing plant pests and tick experts could lead to valuable developments in tickbiocontrol.In India, there are nature gifted biological agents, which can be used for the control of ticks. These include sparrows, crows, chickens and parrots. But for this we have to move towards the nature, so that balance of nature cannot be disturbed.
Similarly, we can purchase birds like oxpecker, can develop anti-tick bacterial and fungal sources. A lot of research is still needed until reliable products based on these nematodes become commercially available for the control of ticks or mites of veterinary importance.
Ticks have numerous natural enemies, but only a few species have been evaluated as tick biocontrol agents (BCAs). Most predators of ticks are generalists, with a limited potential for tick management. Biological control is likely to play a substantial role in future IPM programmes for ticks because of the diversity of taxa that show high potential as tick BCAs.
By- Pramod Prabhakar and M.K. Bharti
Assistant Professor -cum- Jr. Scientist
Animal Husbandry, MBAC, Agwanpur, Saharsa
(BAU, Sabour, Bhagalpur)
T.V.O. Saharsa
Email: ppmbac@gmail.com
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