Lecanicillium lecanii

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Lecanicillium lecanii
Fruiting bodies and Spores[1]
Taxonomic Position
Super Kingdom Eukaryota
Kingdom Fungi
Phylum Ascomycota
Subphylum Pezizomycotina
Class Sordariomycetes
Order Hypocreales
Family Hypocreaceae
Genus Lecanicillium
Species lecanii
Binomial name
Lecanicillium lecanii
Authority : Zare and Gams (2001)[2]
Direct Penetration of Lecanicillium lecanii into target pest
Direct Penetration of Lecanicillium lecanii into target pest[3]
Lecanicillium lecanii on hemlock woolly adelgid cadaver
Lecanicillium lecanii on hemlock woolly adelgid cadaver[4]

Lecanicillium lecanii, commonly know as White-Halo Fungus, is a fungal species that acts as an insect biopesticide which commonly used in pest management. Insects targeted by L. lecanii are sap feeding insects such as aphids, whiteflies, scale insects, thrips and mealy bugs[3].


[edit] Mode of Action

L. lecanii uses two strategies to kill insects; mechanical pressure and the release of mycotoxins[3].

[edit] Mechanical Pressure

L. lecanii applies mechanical pressure inside insects by growing within them[3]. The process begins when L. lecanii conidia land on an insect and adhere themselves[3]. The conidia begin to germinate forming an appressorium[5]. The appressorium leads to the growth of a penetration peg which breaks through both the epicuticle and procutile of the insect[3]. This is accomplished by mechanical pressure exerted by the appressorium and by the secretion of enzymes which break down the cuticle layers[5]. Finally, a blastospore will form within the inner tissues of the insect[3]. L. lecanii has now sucessfully infected the insect and it will begin colonizing the insect. As L. lecanii grows within the insect, it will eventually crush it from the inside out[3]. Eventually, L. 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[3]. The conidiophores release conidia and the process starts over.

[edit] Toxins

L. lecanii releases secondary metabolites, known as mycotoxins, which are harmful to the target insect [6]. The mycotoxins released L. lecanii include beuvericin, bassianolide, dipicolinic acid, decenedioic and 10-hydroxy-8-decenioc which aid in successful infection[3].

[edit] Factors Affecting Lecanicillium lecanii Performance

The success of L. lecanii as an insecticide depends on many factors.

Genetic Variability L. lecanii strains target various insect species with different efficiency[3].
Tritropic interaction L. lecanii efficiency is mediated by the tritropic interaction between the it, the target insect species and the host plant on which the insect lives. [3]. As a result, changing the host plant will affect the efficiency of L. lecanii. For example, when greenhouse whitefly is treated with L. lecanii, 50% mortality occurs when the host plant is cucumber but only 20% when the host plant is poinsettia[3].
Environmental Conditions Spore germination, growth and sporulation are essential for the infection and colonization of entire population of a target species. As a result, environmental conditions, such as humidity and temperature, that favour these events will enhance the effectiveness of L. lecanii as an insecticide[3]. For example, in L. lecanii strains 6543, 6541, and 4078 no germination occured at 10°C or 35°C, with optimal germination occuring at 25°C to 30°C [7].
Inoculum level Inoculum concentrations can be modified to change the performance of L. lecanii[3]. For example when mustard aphid was treated with 108 condidia/ml, 107 condidia/ml and 106 condidia/ml, insect mortality was 40%, 33.3% and 23.3%, respectively[3].
Stage of Target Insect Host During the life cycle of an insects, in experiences multiple life stages[3] which are not equally susceptible to L. lecanii. For example, Western Flower thrips are more susceptible in the adult life stage than the larval life stage to L. lecanii[3].
Compatibility with Chemical Pesticides Chemical pesticides can either enhance or reduce the effect of L. lecanii.[3]. For example, copper oxychloride, copper sulphate and chlorothalonil inhibited the growth of L. lecanii by 79.24%, 68.53% and 28.39%, respectively[3]. Chemical pesticides that inhibit the growth of L. lecanii should be avoided so that target species is efficiently colonized.
Effect on non-target Organisms The effect of L. lecanii must be evaluated to ensure it des not adversely affect native or beneficial non-target organisms.[3].

[edit] References

  1. Svetlana Y. Gouli, University of Vermont, Bugwood.org
  2. Zare, R., and Gams, W. (2001) Nova Hedwigia, 73:1-50.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 Shinde, S. V., Patel, K. G., Purohit, M. S., Pandya, J. R., & Sabalpara, A. N. (2010). "LECANICILLIUM LECANII (ZIMM.) ZARE AND GAMES" AN IMPORTANT BIOCONTROL AGENT FOR THE MANAGEMENT OF INSECT PESTS -- A REVIEW. Agricultural Reviews, 31(4), 235-252.
  4. Svetlana Y. Gouli, University of Vermont, Bugwood.org
  5. 5.0 5.1 Moore, D., G. D. Robson, and A. P. J. Trinci. 21st Century Guidebook to Fungi. Cambridge: Cambridge UP, 2011. Print.
  6. Sharma, P. D. (2005). Fungi and allied organisms / P.D. Sharma. Oxford, U.K. : Alpha Science International, c2005.
  7. Vu, V., Hong, S., & Kim, K. (2007). Selection of Entomopathogenic Fungi for Aphid Control. Journal Of Bioscience And Bioengineering, 104(6), 498-505. doi:10.1263/jbb.104.498
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