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Title: Biological, ecological and phylogenic studies of Pseudoligosita babylonica viggiani, a native egg parasitoid of Dubas bug Ommatissus lybicus de Bergevin, the major pest of date palm in the Sultanate of Oman
Author: Al-Khatri, Salim Ali Humaid
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2011
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Abstract:
Seasonal fluctuations, development and phylogeny of Dubas bug Ommatissus lybicus de Bergevin (Hemiptera: Tropiduchidae) and its native natural enemy Pseudoligosita babylonica Viggiani (Hymenoptera: Trichogrammatidae) were studied on date palm Phoenix dactylifera Linnaeus (Arecales: Arecaceae) in the Sultanate of Oman. P. babylonica emergence and 0. lybicus egg hatching were significantly influenced by temperature whereas relative humidity had no significant effect. P. babylonica developed successfully at temperatures between 22.3°C and 32.4°C with an optimum at 30.0°C whilst no development occurred at temperatures of 17.6,34.4 and 37.2°C. 0. lybicus eggs developed at temperatures between 17.6°C and 32.4°C with an optimum at 27.5°C, whereas no development occurred at 34.4 and 37.2°C. Linear regression estimated the lower thermal threshold (Tzower) and thermal constant (DD) whereas non-linear models (Briere l " and Briere 2nd equations) estimated TZowen upper (Tmax) and optimum thermal threshold (Topt). P. babylonica successfully parasitised 0. lybicus eggs of 1 to 42 days old with embryogenesis of 1.3% to 57.2%. There was a negative response of P. babylonica female density on parasitism %. P. babylonica showed arrhenotokous parthenogenesis where male progeny developed from unfertilised eggs and females from fertilised eggs. Three sex forms were recorded (female, normal kale and deformed male). Deformed males successfully mated with females and this resulted in the production of all three forms. The results of phylogenic analysis on samples of 0. lybicus and P. babylonica collected from four different geographical locations in Oman revealed 98.1-100% nucleotide similarity among 0. lybicus samples with 8 different genotypes of which two were dominant based on sequences of the Cytochrome Oxidase Subunit I (COl) and showed 85% nucleotide similarity with Hemiptera species. P. babylonica samples shared 96.8-100% nucleotide similarity among each other with 10 different genotypes based on sequences of Cytochrome B (CytB) and shared 86% nucleotide similarity with Achrysocharoides sp. Predictive models were developed and tested for P. babylonica emergence and 0. lybicus egg hatching and showed promise for increasing the efficiency of P. babylonica in suppressing 0. lybicus populations and suggested improved timings for the applications of non-persistent insecticides used in an rPM programme. VI.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.558806  DOI: Not available
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