Diamondback moth (Plutella xylostella L.) ; toxicological database, resistance monitoring techniques, and intraplant distribution

The diamondback moth (Plutella xylostella L.) is a major pest of crucifer crops worldwide. It is a particularly important problem in Southeast Asia where climatic conditions favor a short generation time and rapid proliferation. In countries such as Thailand, the diamondback moth has apparently become resistant to all classes of insecticides, even the newest ones. The first part of this thesis is the development of a computer database of all the available information on diamondback moth toxicology. About 1,550 records were extracted from more than 235 published or unpublished documents. These records include information on the geographical location of experiments, the insecticide evaluated, the testing method and the results observed. Most records in the database are from the last decade, and are predominantly from Taiwan, Thailand, the USA and Japan. Trends in the use of various classes of insecticides can easily be followed. Thirty three records have been found of insecticide resistance of more than a thousandfold. An the known mechanisms of resistance are found, and the diamondback moth has become resistant to all the classes of insecticides, including Bacillus thuringiensis but excluding abamectin. Case studies made possible by the use of the database showed a rapid succession in the use of 29 insecticides in the last 26 years in a single country (Thailand). Although this rapid succession is usually ascribed to the development of resistance, a case study on the regional differences in resistance to five insecticides showed marked variations in the level of resistance over distances of 20 miles or more. The possibility of managing insecticide resistance at the local level, already suggested by studies in Hawaii, is thus supported by this analysis. In the second part of this thesis, the toxicity of Bacillus thuringiensis var. aizawai and of the bacterial toxin abamectin was tested by two bioassay techniques on populations of the diamondback moth from two Chinese kale fields at locations in Thailand at which the highest levels of resistance to most insecticides have been reported. The leaf-dip bioassay was found to be superior to a residue-vial assay or to the FAO-recommended assay. More than 70-fold resistance to Bacillus thuringiensis var. aizawai was observed in the populations of DBM collected from these two fields, suporting the theory that resistance resulted in the control failures reported by growers. Resistance did not explain control failures with abamectin as no resistance to this compound could be detected. The third part of this thesis analyzes the intraplant distribution of the diamondback moth larvae in an effort to explain the control failures with abamectin on Chinese kale. Extensive sampling of the various larval instars of the diamondback moth revealed that a majority of second instar larvae were sheltered on the young folded leaves of Chinese kale. The majority of fourth instar larvae and pupae were found on mature (lower) leaves. Inefficient spraying practices observed in the field with high volume, low pressure hydraulic pump sprayers may allow the young larvae to escape pesticide exposure possibly explaining control failures in the absence of physiological resistance. This study shows that resistance in the diamondback moth is a worldwide problem of major proportions. The rapid development of resistance to Bacillus thuringiensis in the field is of practical concern. Resistance management programs in developing countries should include mechanisms to optimize insecticide delivery to the protected habitats of diamondback moth on Chinese kale

Candida sp. infections in patients with Diabetes mellitus

Candidiasis has increased substantially worldwide over recent decades and is a significant cause of morbidity and mortality, especially among critically ill patients. Diabetes mellitus (DM) is a metabolic disorder that predisposes individuals to fungal infections, including those related to Candida sp., due to a immunosuppressive effect on the patient. This review aims to discuss the latest studies regarding the occurrence of candidiasis on DM patients and the pathophysiology and etiology associated with these co-morbidities. A comprehensive review of the literature was undertaken. PubMed, Scopus, Elseviers ScienceDirect, and Springers SpringerLink databases were searched using well-defined search terms. Predefined inclusion and exclusion criteria were applied to classify relevant manuscripts. Results of the review show that DM patients have an increased susceptibility to Candida sp. infections which aggravates in the cases of uncontrolled hyperglycemia. The conclusion is that, for these patients, the hospitalization periods have increased and are commonly associated with the prolonged use of indwelling medical devices, which also increase the costs associated with disease management.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of: the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020-Programa Operacional Regional do Norte, financially supported by project UID/EQU/00511/2019 - Laboratory for Process Engineering, Environment, Biotechnology and Energy – LEPABE funded by national funds through FCT/MCTES (PIDDAC), and by Célia F. Rodrigues’ [SFRH/BD/93078/2013] PhD grant and M. Elisa Rodrigues [SFRH/BPD/95401/2013] post-doc grant.info:eu-repo/semantics/publishedVersio