Increasing introductions of non-native terrestrial slugs (Mollusca: Gastropoda) are a concern to North American regulatory agencies as these generalists impact the yield and reduce the aesthetic value of crop plants. Understanding how the increase in diversification in North American cropping systems affects non-native gastropods and finding effective biological control options are imperative for pest management; however, little research has been done in this area. This study tested the hypothesis that dietary diversification affects the biological control capacity of a generalist predator and allows the slug pest Deroceras reticulatum (Müller) (Stylommatophora: Agriolimacidae) to more effectively fulfill its nutritional requirements. Results showed no significant correlations between dietary diversification and slug development; however, this was likely due to the addition of romaine lettuce to all treatments. The study also showed that dietary diversification had no significant effect on D. reticulatum egg production, with self-fertilizing slugs consistently having significantly higher egg production than outcrossing slugs. Most significantly, this research demonstrated reductions in plant damage by D. reticulatum in treatments containing the North American carabid beetle Scarites quadriceps Chaudoir (Coleoptera: Carabidae) with the presence of alternative prey having no effect, supporting its use in biological control efforts in spite of its generalist feeding habits.

Erynia neoaphidis Remaudiere and Hennebert (Zygomycetes: Entomophthorales) is an obligate pathogen of invertebrates, especially aphids, and has therefore been studied as a possible biological control agent for a number of years. However, a number of important physiological and ecological questions regarding optimal conditions for conidial production and transmission 0 f the fungus through an aphid population had to be answered. This thesis investigated some of these aspects. Solid and liquid media were used to culture the fungus, and E. neoaphidis was cultured on a fully defined medium for the first time. A sporulation monitor and digital image analysis was used to quantify conidial production from E. neoaphidis biomass produced in vivo and in vitro. This was a completely novel method and is useful for gathering data on large numbers of conidia, 50 that size distributions can be constructed and the physiological status of the conidia inferred from this. E. neoaphidis infected aphid cadavers produced more, smaller conidia when grown in vitro. Biomass harvested from exponential growth phase in fed batch culture produced significantly more conidia than biomass harvested from any other growth phase although further work on the nutritional requirements of E. neoaphidis in vitro is required. The duration of the conidial discharge was also greatest from biomass harvested at the exponential phase and therefore. biomass harvested from the exponential phase should be used if the fungus is to be applied as a control agent. E. neoaphidis biomass kept at low humidity during simulated winter conditions produced infective conidia after 24 weeks, indicating that mycosed cadavers may act as a reservoir to infect the next season's hosts. Pesticides adversely affected the growth and production of conidia by E. neoaphidis, with herbicides having the least deleterious effects, and therefore being most compatible in an integrated pest management program. Laboratory and field studies were used to assess the transmission of E. neoaphidis through aphid populations. Position of the inoculum on the host plant affected the primary transmission of the fungus through aphid populations in the laboratory and in the field, and secondary transmission of the fungus in the laboratory. It is therefore important to apply the fungus to where it will maximally spread. There was some evidence for effects of host and inoculum density on the transmission of the fungus, especially in the laboratory, indicating that, in practice, the fungus is unlikely to spread rapidly through low densities of aphids and therefore to achieve control of such populations, a high inoculum density may be required. There was also very Iittle transmission of the fungus via aphid vectors to susceptible aphid populations on different host, although as a general observation, vectoring of conidia by the wind may be very important. The smaller conidia produced by in vivo biomass may be vectored more easily by wind than the large conidia produced in vitro.

Wolbachia are bacteria that infect and induce reproductive alterations in a large number of arthropods. The present study was undertaken to improve our understanding of the effects that Wolbachia have on the reproductive biology of the leaf beetle Chelymorpha alternans Boh, in Panama. Two strains of Wolbachia occur in C. alternans, both of which induce some degree of cytoplasmic incompatibility (CI), a reproductive problem occurring when individuals bearing different infection status are mated together resulting in lowered levels of egg fertility. I attempted to localize where Wolbachia occurs in highest density in male reproductive tissues and to see if variation in Wolbachia density was associated with levels of CI in crossing experiments involving males (1) differing in age, (2) carrying different strains and (3) belonging to different populations previously known to vary in their levels of CI. Wolbachia were found to occur only in the somatic cells surrounding the testis, rather than in the germ cells, and yet were capable of inducing strong CI. Male age, infection status and provenance all were factors affecting the level of CI induced.

A three-year (1991-1993) investigation was done in the field and laboratory to study the bionomics of Smicronyx guineanus Voss and Sm. umbrinus Hustache and the spatial distribution of Striga hermonthica (Del.) Benth. Studies on the life history of the weevils were undertaken. Seasonal activity and habits were established by monitoring life stages in the field. A behavioral Time Budget of Smicronyx adults was established in semi-field conditions. Dispersion patterns and the optimum sample size for Smicronyx and Striga were determined. Smicronyx adults as well as Striga plants were aggregated in the field. Smicronyx larvae were located in the upper stratum of the witchweed (93.2%) where they make galls and destroy large number of seeds. The effect of precipitation on emergence of Smicronyx adults was investigated in the insectary. The optimum rainfall required for Smicronyx adult emergence ranged from 30 to 40 mm. Good synchrony and positive association of Sm. guineanus and Sm. umbrinus with S. hermonthica were observed. There are good prospects for augmentation and/or conservation of Smicronyx populations as part of an integrated control strategy of S. hermonthica.

Stachybotrys elegans (Pidopl.) W. Gams is a destructive mycoparasite of the soilborne plant pathogen Rhizoctonia solani. It colonizes effectively all types of cells of R. solani, and is considered as an effective biological control agent (BCA). Monitoring the presence of this mycoparasite in the field trials requires the development of a reliable and sensitive diagnostic assay that is able to detect and differentiate the BCA from their target host. To achieve this, designed SCAR (sequenced characterized amplified regions) primers designated as SE-13F and SE-13R were generated from informative RAPD markers. They were tested in conventional PCR assays alone or in conjunction with the recently developed SCAR primers (SBU-177/336) designed for Rhizoctonia solani (Kuhn) on several types of DNA. These included DNA extracted from pure cultures, co-cultures of the BCA and the pathogen, plant tissue and several types of soils inoculated with both the BCA and the pathogen. Irrespective of the type of the biological samples from which the DNA was extracted, the primers SE-13F/SE-13R successfully amplified only S. elegans. No cross-reaction was observed when the primers were used to amplify DNA of other fungi, bacteria and plant tissues. Likewise, the primer pair SBU-177/336 detected only its target organism, i.e., R. solani. The detection limit using these primers on amplified DNA was as little as 1 pg DNA extracted from pure cultures of S. elegans, 100 pg DNA extracted from greenhouse soil and 33 pg DNA extracted from natural soil. This work is the first report on the development of SCAR markers for the BCA, S. elegans. These molecular markers offer not only an alternative diagnostic assay to conventional detection methods, but also the possibility of being used in ecological studies.

From 1991 to 1994 inclusively, a field and laboratory study was undertaken on egg parasitoids of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) to determine their potential in controlling their host. Five species were found to parasitize Lygus eggs in southwestern Quebec. They were three mymarids: Anaphes iole Girault, Polynema pratensiphagum (Walley), and Erythmelus miridiphagus Dozier (Mymaridae) and two scelionids: Telenomus nysivorus Huggert and Telenomus n.sp. (a new species near strelzovi Vasiliev) (Scelionidae). The maximum levels of field parasitism by these parasitoids were 20, 70, 35, and 70% (for both species of Telenomus), respectively. The field parasitism was determined on Lygus eggs inserted in Contender green beans, Phaseolus vulgaris L., Irish cobbler potatoes, Solanum tuberosum L., and alfalfa, Medicago sativa L. P. pratensiphagum and Telenomus were the most abundant parasitoid species recorded. / In 1991 and 1992 the seasonal occurrences of these parasitoids were investigated in three different habitats: mixed weeds, alfalfa, and crown vetch, Coronilla varia L. In both years Telenomus n.sp. was the most numerous parasitoid in all three habitats throughout the season, and had a strong synchrony with L. lineolaris populations. / The laboratory and field monitoring experiments on the overwintering of A. iole, P. pratensiphagum and E. miridiphagus indicated that the presence of an alternative host is essential for the overwintering of these parasitoids. The eggs of the alfalfa plant bug, Adelphocoris lineolatus (Geoze) were the most common overwintering host for all three mymarids and Canada fleabane, Erigeron canadensis L. sustained more Adelphocoris eggs and egg parasitoids than other weed hosts. / In the laboratory the parasitoid survival, mortality, fecundity, and adult longevity were determined for P. pratensiphagum, A. iole and Telenomus n.sp. The females of all three species lived longer than males, but males emerged 24 hours before females, and all are solitary parasitoids. Telenomus n.sp. showed a higher rate of survival (93%) and a higher rate of parasitism (87%) than other species under laboratory conditions. / For rearing L. lineolaris, potato sprouts, S. tuberosum were found to be the medium preferable to potato slices and Patana artificial diets. This medium is worthy of further investigation for use in augmenting the egg parasitoids of L. lineolaris.

No description available.

After a wild-type isolate of Epicoccum purpurascens was exposed to shortwave ultraviolet light, several new strains were recovered which were improved in sporulation, fungicide tolerance, and performance in suppression of white mold caused by Sclerotinia sclerotiorum. The efficacy of E. purpurascens in controlling white mold of snap bean (Phaseolus vulgaris) was assessed in greenhouse and field trials. White mold was significantly reduced in both greenhouse and field trials when 2-4 sprays of E. purpurascens conidial suspensions (in 1% malt extract) were sprayed onto the plant surface during the flowering period. Germination of E. purpurascens conidia on senescent petals was greater than on younger flowers. Addition of malt extract to conidial suspensions improved germination on flowers and increased colonization of emerging flowers. Application of E. purpurascens did not accelerate senescence of bean leaves or affect pod yield of bean in greenhouse trials. Mycoparasitism of S. sclerotiorum by E. purpurascens was found only rarely in in vitro tests and was not observed on flower disks. Production of inhibitory compounds by E. purpurascens was the most important mechanism in suppression of white mold but competition for nutrients also appeared to play a role in biocontrol. The influence of nutrients on conidial germination, growth, sporulation and production of antifungal compounds by E. purpurascens were also investigated.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 71-87) / Microfiche. / x, 87 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 167-173) / Microfiche. / xxiv, 212 leaves, bound 29 cm