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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Natural enemies and mortality factors of the coffee leafminer Leucoptera coffeella (Guerin-Meneville) (Lepidoptera: Lyonetiidae) in Chiapas, Mexico

Lomeli-Flores, Refugio 15 May 2009 (has links)
Through field surveys and laboratory experiments, this study assessed in part the impacts of host plant, natural enemies, and weather variables on coffee leafminer Leucoptera coffeella distribution and abundance at two elevations and two rainfall levels in coffee farms in Chiapas, Mexico. In addition, a checklist of Neotropical coffee leafminer parasitoids was assembled from field collections and literature review. Coffee leafminer field incidence was positively correlated with leaf nitrogen content and age, but in laboratory experiments coffee leafminers grew larger, developed faster, and had higher survivorship on leaves with moderate (2.9±0.01%) versus low (2.5±0.04%) or high (3.4±0.01%) nitrogen level, and on tough versus soft leaves. Ovipositional preference was not generally for leaves that maximized offspring performance. Coffee leafminer incidence was higher during the rainy versus dry season, and at low versus high elevation. Shade cover reduced ambient temperatures within coffee farms, but did not significantly affect coffee leafminer incidence. The coffee leafminer predator complex included 16 morphospecies, ~88% of them ants (Formicidae), and contributed >58% of real mortality. Predation rates were higher at high versus low elevation, and under high versus low rainfall. Predation was the main source of coffee leafminer mortality throughout the year, and was highest during the rainy season, when coffee leafminer incidence was highest. Neotropical coffee leafminer parasitoids included 23 species of Eulophidae and seven of Braconidae. In Chiapas, 22 larval parasitoid morphospecies were collected. Egg and pupal parasitoids were not recovered. Parasitism accounted for <10% of real mortality, and rates were 8-10-fold higher at low versus high elevation. Parasitism rates were not significantly influenced by temperature or rainfall. Coffee leafminer oviposited mostly during the night, and less under low versus high temperatures. Average monthly temperature minima, which occur during the night, were generally lower at high (~18 oC) versus low (~20 oC) elevation farms. The incidence and abundance of coffee leafminer may differ between elevations due to differences in temperature, because at high elevation lower temperatures likely reduced coffee leafminer oviposition, and may have increased its mortality rate as a consequence of longer development time and exposure to natural enemies.
2

Natural enemies and mortality factors of the coffee leafminer Leucoptera coffeella (Guerin-Meneville) (Lepidoptera: Lyonetiidae) in Chiapas, Mexico

Lomeli-Flores, Refugio 10 October 2008 (has links)
Through field surveys and laboratory experiments, this study assessed in part the impacts of host plant, natural enemies, and weather variables on coffee leafminer Leucoptera coffeella distribution and abundance at two elevations and two rainfall levels in coffee farms in Chiapas, Mexico. In addition, a checklist of Neotropical coffee leafminer parasitoids was assembled from field collections and literature review. Coffee leafminer field incidence was positively correlated with leaf nitrogen content and age, but in laboratory experiments coffee leafminers grew larger, developed faster, and had higher survivorship on leaves with moderate (2.9±0.01%) versus low (2.5±0.04%) or high (3.4±0.01%) nitrogen level, and on tough versus soft leaves. Ovipositional preference was not generally for leaves that maximized offspring performance. Coffee leafminer incidence was higher during the rainy versus dry season, and at low versus high elevation. Shade cover reduced ambient temperatures within coffee farms, but did not significantly affect coffee leafminer incidence. The coffee leafminer predator complex included 16 morphospecies, ~88% of them ants (Formicidae), and contributed >58% of real mortality. Predation rates were higher at high versus low elevation, and under high versus low rainfall. Predation was the main source of coffee leafminer mortality throughout the year, and was highest during the rainy season, when coffee leafminer incidence was highest. Neotropical coffee leafminer parasitoids included 23 species of Eulophidae and seven of Braconidae. In Chiapas, 22 larval parasitoid morphospecies were collected. Egg and pupal parasitoids were not recovered. Parasitism accounted for <10% of real mortality, and rates were 8-10-fold higher at low versus high elevation. Parasitism rates were not significantly influenced by temperature or rainfall. Coffee leafminer oviposited mostly during the night, and less under low versus high temperatures. Average monthly temperature minima, which occur during the night, were generally lower at high (~18°C) versus low (~20°C) elevation farms. The incidence and abundance of coffee leafminer may differ between elevations due to differences in temperature, because at high elevation lower temperatures likely reduced coffee leafminer oviposition, and may have increased its mortality rate as a consequence of longer development time and exposure to natural enemies.

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