Isolation and Identification of The Fungal Pathogen Aspergillus aflatoxiformans Strain and Its Role in Controlling The Two-Spotted Spider Mite Tetranychus urticae (Koch) عزل وتعريف المسبب المرضي Aspergillus aflatoxiformans ودوره في مکافحة أکاروس العنکبوت الأحمر ذي البقعتين Tetranychus urticae (Koch)

Abstract

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is the major mite pest infesting many cultivated crops. The fungus, Aspergillus aflatoxiformans Frisvad, Ezekiel, Samson & Houbraken produces aflatoxins where it considered as secondary polyketide metabolites, which cause the death of pests. Therefore, this work aimed to isolate and identify this fungus by amplify the internal transcribed spacer (ITS) region of the rDNA, as well as to evaluate the efficiency of this fungus to control T. urticae. Results showed 300bp DNA product corresponding to the omt-A gene. The existence of omt-A gene in A. aflatoxiformans reflected its ability to produce aflatoxin, which may be responsible of mite control. The efficacy of A. aflatoxiformans against T. urticae recorded the highest reduction percentage of eggs hatch at concentration of 1x108 conidia/ml within the 5th and 6th day after exposure. These percentages were 99.42 and 100%, respectively. The highest mortality percentage was recorded on the 4th, 5th and 6th day at higher concentration of 1x108. No eggs and larvae of T. urticae were observed within the 5th and 6th day after treatment at 1x108. There were not observed nymphs at all tested concentrations. Microelectronic photos showed fungal conidia with cluster shaped which were developed at all T. urticae body surface 6 days after treatments at 1x107 and 1x108. Results also confirmed that A. aflatoxiformans could be used successfully to control T. urticae eggs, immature stages and adults. Therefore, this fungus could be involved in any IPM programs of the two-spotted mite.