Verticillium lecanii

Verticilium lecanii (which is previously known as Cephalosporum lecanii) is a widely spread entomopathogenic fungus. It can also exist as a saprophyte or as a hyperparasite on rust fungi, the mildew and even on other entomopathogenic fungi. In nature V. lecanii is spread in the regions of moderate, subtropical and tropical climate. In tropical conditions the infestation of insects occurs regularly. It connects with humidity, which is favorable for fungus development. But in the regions of moderate climate infestation happens rarely, usually in cultivation buildings. V. lecanii is a specific parasite and it doesn't constitute danger for plants, entomophages, birds, fish and mammals. Owing to it the fungus is widely used as a component of biological systems in agricultural crop defense.

The practical application of biopesticides made on the base of V. lecanii was searched on different species of phytophages especially on aphids, mealy bugs, thrips, mites and nematodes. The greatest effectiveness is observed when the fungus is applied for the biological control of whiteflies. The fungus mainly infects larvae of the whitefly and under high humidity it also kills pupae and adult insects. But eggs are not affected. Some strains of the fungus V. lecanii are used against agricultural pests such as various aphids and thrips.

In natural conditions the fungus spreads by means of conidiospores. V. lecanii is not able to spread quickly and effectively within the confines of pest population because the spores are not transferred by wind. The spores have a sticky coat and they are spread mechanically or by water. For effective application it is necessary to use the fungus several times until all the phytophages are killed on treatable area. If the pest regenerates its population treatments should be repeated.

The entomopathogenic fungus infects phytophages by means of penetration into insect epidermis. The spores of V. lecanii germinate on insects and fungus strings (hyphae). Usually they grow on the sweet excretions of whiteflies (the products of life activity) or on carbohydrates, which are added in biopesticides. As a result of it insects commit as if autoinfection. The fungus is also able to direct its hypha growth directly to the insects escaping this external phase. Further the inside development of the fungus kills the insect. Although it is rather difficult to determine the exact cause of death the main factors resulting in lethal outcome are: the mechanical destroying of respiratory ways and hemolymph circulation, the exhaustion of nutrient reserves and the breaking of organ functions, the synthesis of specific proteins by the fungus inside the insect.

Under the infection of whiteflies they perish before than fungus development becomes evident. The dead larva and the pupa sometimes assume a dark-brown color. It is happened the fungus hypha ruptures the epidermis of the insect and forms the spores on the surface of its body. After that infection may spread to other insects.

The first symptoms of fungus infection can be displayed on the whitefly in 7–10 days. After two weeks the effect of influence is expressed exactly.

The favorable conditions for V. lecanii development are: a temperature of 15–20°C, a relative air humidity of 80% and more. The fungus needs higher air humidity during 10–12 hours (minimum). The application of fungus pesticide is the most effective under these conditions. The whitefly can be affected in glasshouses by way of natural infecting. But spontaneous epidemics occur very rarely therefore the natural biological control of the fungus is not enough effective.

There are names of biopesticides containing V. lecanii:

• Vertalec
• Mycotаl
• Verticel
• Bioline
• Verticilin