ENTOMOPATHOGENIC FUNGI – Lecanicillium lecanii

ENTOMOPATHOGENIC FUNGI – Lecanicillium lecanii

General Characteristics of Lecanicillium lecanii

• Lecanicillium lecanii (Order – Hypocreales; Family - Cordycipitaceae) commonly known as “White Halo Fungus” is known to cause Mycosisin insects.
• Lecanicillium lecanii is now an approved name of an Entomopathogenic fungus species, that was previously widely known as Verticillium lecanii.
• Lecanicillium lecanii acts as an insect biopesticide which commonly used in pest management.
• Lecanicillium lecanii are important entomopathogenic fungi ubiquitously distributed in soils, although these fungi are mainly isolated from insects.
• The entomopathogenic fungus Lecanicillium lecanii has been developed as biopesticides and used widely for biological control of several insects in agricultural practice. Due to the lack of isolation/count methods for Lecanicillium lecanii in soil, the persistence of this fungus in soil appears to have attracted no attention.

Target Insects of Lecanicillium lecanii

• Lecanicillium sp. have a broad host range including insects, phytopathogenic fungi and plant-parasitic nematodes.
• The common target pests are Soft scale insects, Whiteflies, Thrips, Aphids and Mealy bugs.
• Lecanicillium lecanii is primarily marketed for the control of greenhouse Aphids, Whiteflies and Thrips. However, products are also available for the control of Lepidopteran, Homopteran, and Dipteran pests of flowers, vegetables, and other crops. 

Mode of action of Lecanicillium lecanii

• Lecanicillium lecanii uses two strategies to kill insects

a)     Mechanical pressure

b)     Release of Mycotoxins

a) Mechanical pressure

• Lecanicillium lecanii applies Mechanical pressure inside insects by growing within them.
• The process begins when Lecanicillium lecanii conidia land on an insect and adhere themselves.
• The conidia begin to germinate forming an Appressorium (A flattened and thickened tip of a hyphal branch, formed by some parasitic fungi, that facilitates penetration of the host).
• The Appressorium leads to the growth of a penetration peg which breaks through both the epicuticle and procutile of the insect. This is accomplished by Mechanical pressure exerted by the Appressorium and by the secretion of Enzymes which break down the cuticle layers.
• Finally, a Blastospore will form within the inner tissues of the insect. Lecanicillium lecanii has now successfully infected the insect and it will begin colonizing the insect.
• As Lecanicillium lecanii within the insect, it will eventually crush it from the inside out. Eventually, Lecanicillium lecanii consumes all the nutrients within the insect. As a result, the hyphae grow outwards and begin to grow on the outside surface of the target organism forming conidiophores. The conidiophores release conidia and the process start over.

b) Release of Mycotoxins

• Lecanicillium lecanii releases secondary metabolites, known as Mycotoxins, which are harmful to the target insect.
• The Lecanicillium lecanii proliferates throughout the insect’s body, produce Mycotoxins (Beuvericin, Bassianolide, Dipicolinic acid, Decenedioic and 10-hydroxy-8-decenioc), draining the insect of nutrients, and eventually killing it in around 48 - 72 hours.

Figure – 1: Insects affected with Lecanicillium lecanii

Cultural characteristics of Lecanicillium lecanii

• Lecanicillium lecanii colonies incubated for 10 days on PDA were white to cream, and thin cottony with reverse colorless to pale or deep yellow.
• The conidiophores of Lecanicillium lecanii were erect and verticillate with loose whorls of phialides conidiogenous cells, which mostly awl-shaped and sometimes to some extent inflated at the base. Conidia were hyaline, single-celled, produced in slimy heads, and smooth-walled

Figure – 2: Colony morphology of Lecanicillium lecanii

Uses of Lecanicillium lecanii

• Lecanicillium lecanii has been used to control insect pests of plants grown for the production of Ornamentals and vegetable crops in greenhouses; nurseries, lawns and landscape perimeters.

Advantages of Lecanicillium lecanii

• Non-toxic to beneficial insects, humans and animals.
• Used for Integrated Pest Management (IPM) by many organic farmers.
• Reduce the use of chemical insecticide sprays, which are extremely toxic and expensive.