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Five field experiments were conducted to evaluate the relative attractiveness of potential beneficial insectary plants to aphidophagous hover flies and parasitic Hymenoptera and the effectiveness of interplanting selected flowering plants in a broccoli field to enhance biocontrol of the cabbage aphid and green peach aphid. In 1996 we established a preliminary screening trial to begin development of our sampling methods and evaluations of the attractiveness of selected flowering plants to hover flies and parasitic Hymenoptera. In 1997, we conducted a field experiment at the Oregon State University Vegetable Research Farm near Corvallis, OR to assess the relative attractiveness of 11 selected flowering plants to hover flies and parasitic Hymenoptera. Six of these plants were also evaluated for attractiveness to aphidophagous hover flies in two on-farm trials. The experimental design was a complete randomized block design, with four replications at the OSU site, and three replications at the two on-farm sites. Attractiveness of flowering plants to hover flies was assessed by conducting weekly timed observations of feeding frequencies. Associations of parasitic Hymenoptera were assessed by weekly timed vacuum sampling from a fixed area in plots of flowering plants. Attractiveness differed by dates and sites. Among early-season flowering species, Coriandrum sativa (cilantro) was highly attractive to aphidophagous hover flies and Brassica juncea (mustard), Fagopyrum esculentum (buckwheat) and Agastache rugosa (Korean licorice mint) were most attractive to parasitic Hymenoptera. Among late-season flowers, Achillea millefolium (yarrow), Foeniculum vulgare (fennel) and Agastache rugosa (Korean licorice mint) were most attractive to hover flies, but attractiveness to parasitic Hymenoptera did not differ. An on-farm trial was conducted in 1997 at Stahlbush Island Farm near Corvallis, OR. The objective of this trial was to test the hypothesis that interplanting either alyssum (Lobularia maritima), or cilantro (Coriandrum sativa), with broccoli (Brassica oleracea) would attract aphidophagous hover fly adults and parasitic Hymenoptera, enhance oviposition in the adjacent crop, and increase larval predation and parasitism in the adjacent crop, resulting in suppressed cabbage aphid (Brevicoryne brassicae) and green peach aphid (Myzus persicae) populations in the broccoli crop. The predominate hover fly species present were Toxomerus occidentalis and T. marginatus. More adult female T. occidentalis were caught in pan traps in plots with alyssum than in cilantro or control plots. More hover fly eggs were found on broccoli leaves and a higher percent of the aphids present were parasitized by Hymenoptera in plots with alyssum than in cilantro or control plots. However, no differences in aphid intensities were found between treatment and control plots. A comparison between the mean number of hover fly eggs found per broccoli leaf and the mean number of aphid counted per broccoli leaf suggests there is an association between the two. There appears to be an aphid density threshold below which few hover fly eggs are laid. Gravid females were present in the crop from the first sampling date on, yet hover fly eggs were not found in the crop until the second to last sampling date. Our results indicate that the presence of alyssum enhanced hover fly activity, but did not result in increased larval predation on aphids in the crop. In 1997 a survey of hover flies was conducted at each of the four experimental sites. Hover flies were captured with sweep nets. Representative specimens were identified to species by Christian Kassebeer, University of Kiel, Germany and subsequent identifications were made from reference specimens and with taxonomic keys. Twenty species were identified, 16 of which are aphidophagous. At the OSU site and the two on-farm sites, where the relative attractiveness of flowering plants was assessed, the six most common aphidophagous species, collected at all three sites, were: Meliscaeva cinctella, Toxomerus marginatus, T. occidentalis, Sphaerophoria sulphuripes, S. pyrrhina, and Scaeva pyrastri. / Graduation date: 1998

The effects of pathogens, used singularly or synergistically with other pathogens on the European corn borer larvae, Ostrinia nubilalis (Hubner), were studied. Pathogens used in this research were Perezia fumiferananae, Nosema disstriae, Nosema bombycis, Bacillus thuringiensis, and Beauveria bassiana. The egg masses were dipped into a vial containing a suspension of a single pathogenic species or combination of two pathogenic species. The egg masses were then incubated and hatched in a growth chamber with a temperature of 29°C, a relative humidity of 639, and constant light conditions. Observations were made concerning the mortality rates of each pathogen group.It was observed that the known pathogens, Bacillus thuringiensis, and Beauveria bassiana, caused high mortality rates in the corn borer larvae and could serve as effective biological controls. The Microsporidia, Perezia,fumiferanae, Nosema disstriae, and Nosema bombycis caused low mortality rates in corn borer larvae and therefore would not be considered as effective biological control agents for the European corn borer.The mortality rate for Bacillus thuringiensis treated larvae or Beauveria bassiana treated larvae, used in combination with other Microsporidia was not as high as when Bacillus thuringiensis,or Beauveria bassiana was used singularly. There may have been some interference or antagonism between the two combined pathogens, whether these pathogens be fungi, bacteria, or microsporidia.

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science / Water hyacinth is one of the most invasive aquatic plants in the world. As such, there have been numerous attempts to model and predict its growth. Some of these models incorporate the influence of temperature or nutrients as the two most important determinants of water hyacinth growth. Other models include the effect of biological control on the growth of the plant, but only one model integrates environmental factors (temperature) with the effect of biological control. In this study, I attempt to incorporate temperature, and biological control effects on the growth of water hyacinth into a single model. Temperature-dependent water hyacinth and stage-structured Neochetina weevil population models were constructed in STELLA 9.1.4 and compared against an empirical dataset for two water hyacinth infested sites in South Africa for a two-year period (2004-2006). Although these models may not simulate field water hyacinth populations accurately, they suggest that Neochetina weevils can reduce water hyacinth populations, to below the assumed carrying capacity (70 kg/m2). It appears that the effects of Neochetina larvae are vital in reducing water hyacinth populations, and need to be further explored in order to simulate water hyacinth/weevil systems accurately.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Year: 2016. / Entomopathogenic nematodes in the genera Heterorhabditis and Steinernema have emerged excellent as non-chemical alternatives for control of insect pest population. They have a specific mutualistic symbioses with bacterial symbionts in the genera Photorhabdus and Xenorhabdus, respectively. Native EPN species that are able to tolerate environmental stress including desiccation are of great interest for application. The aim of this study was to isolate indigenous EPN species from soil samples collected from Brits, North West province in South Africa, and to investigate their ability to tolerate desiccation stress. The second aim was to isolate the bacterial symbiont and sequence, assemble and annotate its whole genomic DNA. Insect baiting technique and White trap method proved useful in the recovery of nematodes from collected soil samples and infected cadaver, respectively. Molecular identification based on the amplification of the 18S rDNA and phylogenetic relationships revealed high affinity of the unknown EPN isolate 10 to Steinernema species and due to variation in evolutionary divergence distance, the unknown isolate was identified as Steinernema spp. isolate 10 . Isolates 35 and 42 revealed high similarity to Heterorhabditis zealandica strain Bartow (accession number: GU174009.1), Heterorhabditis zealandica strain NZH3 (accession number: EF530041.1) and the South African isolate Heterorhabditis zealandica strain SF41 (EU699436.1). Both Steinernema spp. isolate 10 and Heterorhabditis species could tolerate desiccation. Steinernema spp. isolate 10 was tolerant up to 11 days of desiccation exposure in loamy sand and up to 9 days of exposure in river sand, causing 26, 6% and 13, 4% cumulative larval mortality after 96 hours, post resuscitation by rehydration, respectively. Heterorhabditis spp. could tolerate desiccation up to 13 days of exposure and induced 26.6% cumulative larval mortality on both loamy and river sand after 96 hours post resuscitation. Swarming, aggregation, coiling and clumping behavioural characteristics were observed when Steinernema spp. isolate 10 was exposed to desiccation and Heterorhabditis species displayed no similar behavioural characteristics associated with desiccation tolerance. Morphological characteristics of the unknown Steinernema spp. isolate 10 have been described, and the thick cuticle and sheath which are both associated with tolerance to desiccation stress have been noted. The bacterial symbiont was isolated from larval hosts infected with Steinernema spp. isolate 10 and molecular identification through NCBI Blastn based on the 16S rDNA revealed high affinity to Xenorhabdus bacterial species. Phylogenetic relationships and evolutionary divergence estimates 16 revealed genetic variation and the species was identified as Xenorhabdus bacterial isolate. The genome assembly of Xenorhabdus bacterial isolate using CLC Bio revealed a total length of 4, 183, 779 bp with 231 contigs (>=400bp), GC content of 44.7% and N50 of 57,901 bp. Annotation of the assembled genome through NCBI PGAAP annotation pipeline revealed 3,950 genes (3,601 protein coding sequences (CDS) and 266 pseudogenes), 12 rRNAs and 70 tRNAs. RAST annotation revealed 55 of virulence, disease and defense subsystem features which are involved in the pathogenicity of Xenorhabdus bacterial isolate. The ability of EPNs to tolerate environmental stress is highly crucial and one of the determining factors for biocontrol potential and successful application, thus the indigenous desiccation tolerant EPN isolate, Steinernema spp. isolate 10 holds great potential as a biological control agent. The genome sequencing and annotation reveals insight to behavioural and physiological attributes of bacterial symbionts and this study will contribute to the understanding of pathogenicity and evolution of the bacteria–nematode complex. / GR 2016

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Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Robert van Engelen, Florida State University, College of Arts and Sciences, Department of Computer Science. Title and description from dissertation home page (viewed Oct. 1, 2003). Includes bibliographical references.

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