Diversity and population of thrips species on legumes with special reference to Megalurothrips sp. / Zafirah Zakri

Zafirah, Zakri (2017) Diversity and population of thrips species on legumes with special reference to Megalurothrips sp. / Zafirah Zakri. Masters thesis, University of Malaya.

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Abstract

Thrips (Thysanoptera) are a common pest on legume plants, yet little is known about their ecology or diversity in Peninsular Malaysia. In legumes, thrips are typically found in the flowers, where their feeding activity causes malformations that eventually lead to crop damage. The aim of this study is to examine the diversity and population of thrips species, particularly Megalurothrips usitatus, in three selected legume farms around Peninsular Malaysia (Janda Baik, Pahang; Bestari Jaya, Selangor and Jelebu, Negeri Sembilan). Depending on growing season, legume flowers were inspected monthly for thrips in five random plots from each farm for 6 to 12 months. Sampling was performed six times in Bestari jaya and Jelebu, and twelve times in Janda Baik. The most abundant thrips species on legumes was M. usitatus (89.97%) followed by Thrips parvispinus (9.77%), Thrips hawaiiensis (0.13%) and Ceratothripoides brunneus (0.12%). Differences in legume species, which is i.e. long bean, French bean and winged bean, did not affect the abundance of M. usitatus, and the species was equally distributed among different arbitrary strata on legume plants. Temperature and light intensity were found to be positively correlated with the abundance of M. usitatus, but relative humidity showed negative relationship. M. usitatus was found in large numbers during the hot and dry months, but in lower numbers during the raining season. This suggests that the wet season may help to reduce populations of M. usitatus on legume plants. The doubtful female individuals of M. usitatus were obtained from the field and from the unmated female of lab rearing. There are 15.4% of doubtful female of M. usitatus were produced from the unmated female. The molecular analysis showed the doubtful females with several M. usitatus females belong to the sub clade 2 which is in the same clade of M. typicus. Hence, at this stage, the doubtful female could be considered as a cryptic species and a by-product from the unmated female. Thus, the present study is important for obtaining more information of M. usitatus on legume crops in Malaysia, and thus to improve effective management strategies for this pest.

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