Browsing by Subject "Parasitoids"
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Item Classical biological control of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), (Diptera:Tephritidae): natural enemy exploration and nontarget testing(Texas A&M University, 2006-08-16) Trostle Duke, Marcia KatherineThis work covers stages one through seven (of nine stages) of a classical biological control program for Mediterranean fruit fly (=medfly), Ceratitis capitata (Wiedemann). Major research objectives concentrate on stage five (exploration and collection of natural enemies), and stage seven (testing and selecting natural enemies for additional work). Coffee was collected monthly from three locations in Kenya from November 1997 through July 1999. Four species of tephritid flies and ten parasitoid species were recovered. Four guilds of parasitoids were recorded, and two egg-prepupal endoparasitoids, Fopius caudatus (Sz??pligeti) and F. ceratitivorus (Wharton), were discovered. The oviposition behavior of these two species is contrasted. Domination of this tropical parasitoid assemblage by koinobionts is discussed relative to the dominance of temperate fruit-infesting tephritid systems by idiobionts. Fruit handling procedures were examined for impact on overall percent emergence and specifically percent emergence of flies versus parasitoids. It was determined that stirring samples had a significant positive effect on overall emergence, however daily misting of fruit did not. The only treatment without a significant bias in fly emergence over parasitoids was the stirred/dry treatment. Effects of these results on rearing procedures are discussed. Host specificity and host suitability of parasitoids reared from coffee were examined via: (1) association of parasitoids with host flies based on characteristics of the fly puparia from which parasitoids emerged, (2) rearing of cucurbit infesting tephritids and their parasitoids in Kenya, (3) rearing of flowerhead infesting tephritids and their parasitoids in Kenya and Hawaii, and (4) host range testing of Psyttalia species in Kenya and Hawaii. These results are discussed in terms of their utility for predicting nontarget effects. Psyttalia concolor (Sz??pligeti) was shipped to Hawaii and tested against the nontarget gall forming tephritid Procecidochares utilis Stone introduced to control the weed Ageretina adenophora (Maui pamakani). Psyttalia concolor failed to attack the gall-forming P. utilis both in choice and no-choice tests, but readily attacked tephritid larvae offered in fruit in choice tests. Recommendations for further testing and release of the parasitoids from Kenya are discussed for Hawaii and Latin America.Item Hydrocarbons of pest aphids and their detection by a braconid parasitoid(Texas Tech University, 2003-05) Borth, Leahann MarieThe research here reported describes the presence and semiochemical functions of cuticular hydrocarbons of cotton aphids {Aphis gossypii Glover), corn leaf aphids (Rhopalosiphum maidis Fitch), and greenbugs (Schizaphis graminum Rondani) Potential ecological pressures that may influence the production of hydrocarbons in geographically separated cotton aphid populations were considered. Both the alarm pheromone, (E)-^- farnesene, and a total of 14 n-alkane hydrocarbons from hexane extracts of cotton aphids collected from Lubbock and Brazos Counties, Texas, and Kern County, California, were identified by GC/MS analysis. The alkanes were common to both color varieties, but the relative proportions of the compounds differed significantly within each population. Among populations, however, hydrocarbons differed significantly not only in relative concentrations, but also in their types. Next, the potential of using the hydrocarbon profiles of different aphid species in systematics was investigated. GC/MS analysis revealed 4, 5 and 14 «-alkane hydrocarbons, respectively, from the hexane extracts of corn leaf aphids, greenbugs, and both green and yellow varieties of cotton aphids collected from Lubbock and Hale Counties in Texas. Unlike the shorter chain compounds, the longer chain compounds between C25 and C29 were common to all three species, and were the most abundant hydrocarbons of each species. There were clear differences in the hydrocarbon profiles of apterous females among species and between color varieties of the cotton aphid, demonstrating that although the pests each produce many of the same compounds, when viewed as a whole, their hydrocarbon profiles are species-specific. Lastly, the attractiveness of naive female parasitic wasps (Lysiphlebus teastaceipes) to various host-associated chemical cues was measured via a series of Y-tube olfactometer bioassays to investigate the foraging strategies of Z. testaceipes as influenced by the host-associated chemical cues. Semiochemicals of cotton aphids elicited stronger responses from Z. testaceipes than semiochemicals produced by the cotton plant. All the bioassays resulting in significant preferences by the wasps were aphid-related. Finally, separating the aphid extract into smaller fractions did not elicit a response from Z. testaceipes, indicating that this wasp only responded to the entire extract profile of the aphid.Item Natural enemies and mortality factors of the coffee leafminer Leucoptera coffeella (Guerin-Meneville) (Lepidoptera: Lyonetiidae) in Chiapas, Mexico(2009-05-15) Lomeli-Flores, RefugioThrough 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.