Beauveria bassiana General Information

Beauveria bassiana, formerly also known as Tritirachium shiotae, is an entomopathogenic fungus (parasitic to insects) that grows naturally in soils throughout the world.  It acts as a parasite on a very wide variety of arthropods, including, whiteflies, termites, thrips, aphids, beetles,caterpillars, weevils, grasshoppers, ants, mealybugs, bedbugs and even malaria-transmitting mosquitoes. Insects vary in susceptibility to different strains. Strains have been collected from different infected insects and cultured to create a particular product for commercial use. The product is made via a bio-fermentation process. The spores (conidia) are extracted and made into a sprayable form. Beauveria bassiana was named after the Italian entomologist Agostino Bassi. He first found B bassiana in 1835 as the cause of the muscardine disease of the domesticated silkworms.

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Beauveria bassiana Mode of Action

Beauveria bassiana kills arthropods as a result of the insect coming into contact with the conidia (fungal spores). contact is made in several ways. The most common and effective is the spray droplets landing on the pest or by walking on a treated surface.  Once the fungal spores attach to the insect’s cuticle, the fungus spores germinate sending out threaded hyphae which penetrate the insect’s body and proliferate. It takes 3 to 5 days for an infected insects to die. The dead insect may serve as a source of spores for secondary spread of the fungus. An infected adult male will also transmit the fungus during mating. (Long et al. 2000).

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  • The conidia of Beauveria. bassiana adhere to the insect cuticle by means of hydrophobic interaction between the spore wall and epicuticle lipids.
  • The conidia germinate, and the germ tube penetrates the cuticle, using a specific series of enzymes, which in turn degrade the lipids, protein and chitin in the insect cuticle.
  • In the insect body, the fungus multiplies in the haemocoel as a blastospore, or yeast-like cell, and enzymes begin to destroy the internal structures of the host insect causing morbidity within 36 – 72 hours.
  • Reduced feeding and immobility are rapidly evident,
  • The insect dies within between 4 to 10 days post-infection. The time to death will depend on the insect species, age and conidial dose.
  • After death, the blastospores transform into mycelia, which emerge through the cuticle and form spores.
  • These cover the cadaver as a characteristic white growth.
  • Sporulation occurs only in conditions of high humidity.

Beauveria bassiana Mode of Application

The liquid spray should have a concentration of at least 2.5X109 viable spores. High humidity and water amplify the activity of the conidia and the infection. Fungal spores are readily killed by solar radiation. It is best to spray the plants with the anthropoid pests in the morning or late afternoon, in cool to moderate temperatures (Goettel et al. 2000, Wraight and Ramos 2002). Apply the Beauveria bassiana liquid spray to the top as well as the undersides of the leaves or wherever the arthropod primarily occurs. Good coverage is a must. The spores have a relatively short life cycle, so it is important that the spray has sufficient opportunity to contact the insect. For insects that bore into a plant, control is difficult. For best results, applications should be made during the early growth stages of the insect before much damage has occurred. Speed of kill depends on the number of spores contacting the insect, insect age, susceptibility and environmental conditions.

Beauveria bassiana has a wide host range and should be considered a non-selective biological insecticide. These should not be applied to flowers visited by pollinating insects