Beauveria bassiana is an imperfect fungus belonging to the family Clavicipitaceae, it reproduces by conidiospores and is widely used as an entomopathogen. It is the causal agent of the white muscardina disease, which parasitizes a wide variety of pests that affect various commercial crops..
B. bassiana It is cottony in appearance, white in color, widely distributed and located on the ground, which is its natural habitat. As a biological control agent, it is highly effective thanks to its saprophytic and pathogenic phase once installed in the host..
Indeed, the conidia of B. bassiana they adhere to the surface of the hosts, penetrate, secrete toxins and cause death. Under favorable environmental conditions, the fungus continues to reproduce conidia on pest insects to infect new individuals..
This species adapts to different agroecosystems and elevational floors, with temperatures ranging between 10 and 40 ºC. In fact, once the host is infested, depending on the phase of the insect and the degree of virulence, the pest dies in four to six days..
Applications of biopesticides such as B. bassiana They are appreciated for their low effect on the environment and humans. However, disproportionate applications can have negative consequences on beneficial insects, such as pollinators..
At the commercial level, the fungus is mixed with other ingredients such as powders, micro talcs or substrates. In liquid formulations, adjuvants are added, in order that the conidia remain viable, that it is easy to manipulate and maintains a high pathogenic effectiveness..
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The mushroom B. bassiana it is one of the main pest pathogens affecting commercial crops. Due to its ability to grow in artificial media and on various hosts, it is classified as a facultative parasite..
It is common to locate it in the soil or in the remains of insects that have been colonized and invaded by the pathogen. Once the fungus has detected its prey, it proceeds to enter through the integument, the mouth or the anus.
As conidia develop, by mechanical action and the intervention of enzymes, the germ tube penetrates the host. The fungus grows and invades the insect, feeding on the hemolymph and generating toxins that destroy the prey..
The life cycle of the fungus depends on the environmental conditions and the species to be infected. Under normal conditions, the fungus develops enough mycelium, conidiophores and conidia to affect a large number of individuals.
The species Beauveria bassiana It is associated with the entomopathogenic disease called white muscardina, characterized in that the mycelium of the fungus with white cottony hyphae completely covers the surface of the host.
It is used in the biological control of various commercial crops, such as coffee, musaceae, vegetables, crucifers, forages, fruit trees, ornamentals and in floriculture. Attacking coleopteran pests, moths, flies, locusts, aphids, bedbugs, weevils, thrips, lepidopteran larvae, ants, termites, mealybugs and spider mites.
Beauveria bassiana, entomopathogenic fungus that causes white muscardina disease, was initially identified by Balsamo Crivell as Botritys bassiana (1835). In later studies based on the morphology of the fungus, Vuillemin (1912) determined the genus Beauveria Y bassiana as the species.
Subsequent descriptions of the fungus have allowed the identification of up to 14 different species, including bassiana, effusa, dense Y globulifera (Beauveri, 1914).
In 1954, McLeod unified the species into bassiana Y tenella, and later Samson and Evans (1993) included amorpha Y candle as specific entomopathogens.
The gender Beauveria is an imperfect fungus belonging to the family Cordycipitaceae, of order Hypocreales, subclass Hypocreomycetidae, class Sordariomycetes, sub-phylum Pezizomycotina, edge Ascomycota, of the kingdom Fungi.
Phylogenetically B. bassiana is linked to gender Cordyceps. B. bassiana represents the asexual phase and Cordyceps bassiana the sexual phase (Rehner and Buckley, 2005).
The entomopathogen B. bassiana classified as superior fungi or imperfect fungi, it reproduces through conidia. These conidial cells of globose or subglobose form of 2 to 3 x 2.0 to 2.5 microns have a short neck.
The conidia are smooth and hyaline in appearance, globose ellipsoidal in shape with a wavy rachis. The conidiophores are grouped in compact form constituting the sinemas where the conidia originate.
Indeed, these structures are observed as a white powder on the host when it completely covers the prey. In addition, in laboratory cultures it also appears as a white powder on the surface, with a yellowish color on the back of the plates..
The entomopathogen Beauveria bassiana presents a high degree of adaptability to live in saprophytic and parasitic conditions. This condition allows it to live freely in the soil and to maintain itself in the absence of guests for a long time..
Indeed, as a free-living organism and in the presence of organic matter, conidia generate a filamentous micellar network. However, once the host is colonized, the conidia germinate forming a network of hyphae, destroying the host and forming blastospores..
The life cycle of the fungus Beauveria bassiana on the host is carried out in four phases: adherence, germination, differentiation and penetration.
Adhesion occurs when the conidia of the entomopathogenic fungus adheres to the cuticle of the host insect. In this respect, the recognition and compatibility between the conidium membrane and the epithelial cells of the cuticle must occur..
This process is framed in two actions: one passive and one active. In the passive, hydrophobic and electrostatic forces intervene that facilitate adherence to the cuticular surface. Chemical substances that favor the development of the conidium on the insect's integument intervene in the active.
Once established, the enzymatic process between the conidia of the fungus and the host's cuticular membrane begins germination. This process depends on the conditions of the environment: humidity, temperature and nutrients; and the availability of the insect.
The differentiation process begins with the growth and introduction of the apprehensive through the cuticular membrane. This germ tube allows the exchange of protease enzymes, lipases, chitinases and estreases from the fungus to the host..
In addition to creating a mechanical pressure between the pathogen and host organisms. Migration towards the epidermis and hypodermis of the insect is accelerated.
Once the pathogen has been established within the digestive tract of the insect, the hyphae that produce the antibiotic oosporin multiply. This substance acts on the bacterial flora of the host, causing death due to toxicity, malnutrition, physical damage and subsequent mummification..
The entomopathogen Beauveria bassiana has a wide pathogenic potential to infest various insects generating a high mortality rate.
The fungus has the ability to colonize insects of the orders Coleoptera, Hymenoptera, Homoptera and Lepidoptera, which are important agricultural pests..
The conidia are located on the surface of the host adhering to the cuticle. Under favorable conditions, the appressorium or germ tube develops that penetrates the host, facilitating the infection of the fungus..
Within the digestive tract of the insect, it is dispersed by the hemolymph, and produces toxins that affect the physiological activity of the host. In a period of 4 to 6 days the host is paralyzed and its subsequent destruction.
Subsequently, the fungus completely invades the host, covering its entire surface with the characteristic white mycelium. Finally, this structure proceeds to release new infective conidia into the environment in order to contaminate new pest organisms..
Products formulated based on Beauveria bassiana they are marketed as a powdered suspension of spores of the fungus. With this bioinsecticide, a spray mixture is made at the foliar level or it is dissolved in a substrate to be applied to the soil..
Generally, the formulation of the entomopathogen is obtained in the form of a dry powder (100% pure conidia). Similarly, it is available dispersed on substrates (rice or clay) on a wet basis or on a dry basis (25 to 40%).
The mode of application depends on the pest to be controlled, the development of the crop and the environmental conditions. For the preparation of the suspension it is recommended to use clean water, equipment in good condition, recommended dose and apply at the end of the afternoon.
In the case of controlling foliage pests, a suspension should be applied that covers the host insects. For soil pests, it can be incorporated into the substrate or compost, or use a suspension that penetrates until it reaches the larvae or worms.
When it is necessary to attract the insect to be parasitized, traps with baits impregnated with the fungus are used to contaminate the pest insect. Regardless of control method, it is important to follow the manufacturer's instructions regarding dosage and mode of application..
Of the wide variety of pests controlled by the fungus Beauveria bassiana can be mentioned:
The coffee berry borer (Hypothenemus hampei) is the main pest of coffee beans in most commercial plantations. The entomopathogen B. bassiana It is currently the main natural enemy of this tiny beetle.
The drill penetrates the coffee bean, perforating it and decreasing the productivity of the plantations and the quality of the bean. Once the pest is installed in the plantation, they reproduce exponentially, reaching up to eight generations in a year..
For effective control of the pest, it is necessary to use virulent strains and make applications when insects are observed flying. In this regard, the fungus cannot attack the insect inside the grain, since the conidia cannot penetrate inside the fruit..
Indeed, it is necessary for the conidia to adhere to the body of the CBB, so that they grow and penetrate the integument of the insect. Then the mycelium begins to reproduce, the fungus feeds on the host, generates toxins that weaken it and finally eliminates it..
Field studies have shown that the effectiveness of applications with B. bassiana they report better results attacking the foci of attack. It is recommended to spray the productive branches and the tree plate.
Cutter ants, belonging to the genera Atta Y Acromyrmex they are the causal agents of damage in horticultural, fruit and forestry productions. At present, the application of baits impregnated with chemical pesticides in or around the ant hills is common..
The main damage caused by cutter ants is the defoliation of the plant, reducing the yield and generating economic losses. The use of chemical products produces high environmental pollution, so the use of B. bassiana constitutes a viable alternative.
The applications with spores of the entomopathogen are carried out directly on the ants that circulate around the affected plantations. Likewise, impregnated baits are used that the workers will take to the interior of the anthill so that the fungus reproduces..
When conidia adhere to ants, they develop and produce toxins that kill the pest. In the same way, B. Bassiana attacks the food source of ants, the fungus Attamyces sp., fulfilling two types of control.
The protection and preservation of stored grains is essential to maintain post-harvest control of different crops, especially cereals and legumes..
The corn weevilSitophilus zeamais) is a pest of high commercial value of corn grains stored in silos and granaries.
Research work has shown that B. bassiana applied in different forms and dosages it has allowed to control this pest by 100%. Pellet applications report excellent results seven days after the pest was in contact with the entomopathogen.
The corn weevilS. zeamais) is very susceptible when exposed to high concentrations of the entomopathogen B. bassiana. Studies suggest that the use of these microorganisms are an alternative for the integral management of pests in stored grains..
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