The process begins when L. The conidia begin to germinate forming an appressorium . 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 .
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PLoS One. Published online Sep Competing Interests: The authors have declared that no competing interests exist. This article has been cited by other articles in PMC.
Associated Data All relevant data are within the paper. Abstract The entomopathogenic fungus L. A selective medium and count method for L. The results showed that the rate of recovery for L. The minimum CFUs for L. The L. The colony growth, conidia yield and germination rate on plates, as well as the median lethal concentration or times LC50 or LT50 to aphids, mycelium growth in aphids and sporulation on aphids of L.
In general, the count method developed here was a very useful tool for monitoring the dynamics of natural or introduced L. Introduction Entomopathogenic fungi EPF play a crucial role in the control of pest insect populations in nature [ 1 — 2 ], and have been considered as an important supplement or attractive alternative to chemical insecticides [ 3 — 4 ]. Several species of EPF have been formulated, registered and used as mycoinsecticides in the world [ 5 ]. However the mycoinsecticides often do not match the efficacy of cheaper chemical pesticides in the field application, which is the primary obstacle to their commercialization and large-scale application [ 6 — 8 ].
The inconsistent performance of biological control agents is often associated with an incomplete understanding of the ecological constraints of the biological system in which they are placed. Most biological control agents need a threshold population level and certain survival period for efficient pest control [ 9 ].
In addition, the persistence of introduced microorganisms in the environment is also crucial for the assessment of risks that may result from their applications [ 10 ]. Thus the assessment of the post-application persistence of a biological control agent is important with respect to its biocontrol potential and performance [ 11 ]. Many laboratory studies conducted with Beauveria spp. In the last two decades, several semi-field or field studies had been conducted with Beauveria spp.
These studies showed that the persistence time varied among EPF after the application, ranging from a few months to several years. The persistence depends largely on the environmental conditions of each area and the fungal isolate used. Hence, the extrapolation of results to other regions is not straightforward. In addition, the viability of EPF during the persistence in soil appears to have attracted no attention.
The entomopathogenic fungus L. However, there is no report about the persistence of L. Unlike Beauveria spp. Although the molecular techniques based on PCR provide the necessary tools to undertake environmental sampling to monitor EPF e. In the present study, we developed an efficient selective medium for L. At the meantime, the viability of recovered L. These results were important for us to understand the possible constraints of using EPF and to optimize its application strategies.
Materials and Methods The study presented no ethical issue. Fungal isolates Nine isolates representing nine fungal species L. Details on all fungal isolates are provided in Table 1.