Inclusion/exclusion field experiments demonstrated that the red imported fire ant, Solenopsis invicta Buren, did not affect the abundance of 49 groups of insects and spiders collected in pitfall traps. However, arthropod diversity was significantly greater (H' = 2.829) in exclusion plots relative to inclusion plots (H' = 2.763). Moreover, this study demonstrated that S. invicta can have an important impact upon cotton arthropod communities, including key predator species. Densities of ground beetles (Carabidae), spiders, lacewings (Chrysoperla spp.), and minute pirate bugs (Orius spp.) were significantly lower in the presence of S. invicta. However, populations of aphidophagous insects such as Hippodamia spp. and Scymnus spp. increased with cotton aphid (Aphis gossypii Glover) density early in the season. Abundance of cotton aphids was ca. 5x greater in inclusion plots, likely due to protection and tending by S. invicta. This increase was observed early in the season, though aphid populations did not reach economic levels. Predation of sentinel bollworm [Helicoverpa zea (Boddie)] and beet armyworm (Spodoptera exigua Hubner) eggs increased 20-30%, when S. invicta was present. Most predation of sentinel beet armyworm egg masses, measured via direct nocturnal observations, was due to S. invicta (68%) and cotton fleahopper [Pseudatomoscelis seriatus (Reuter)] (21%) in plots with S. invicta, and by the mite Abrolophus sp. (52%), spiders (13%) and minute pirate bug (13%) in plots without S. invicta. The frequencies of minute pirate bug, cotton fleahopper, S. invicta and native ants in beat bucket samples did not accurately reflect the frequency with which they were observed feeding on sentinel noctuid eggs. Overall, the results of these studies demonstrated that S. invicta was associated with declines in the abundances of minute pirate bug, spiders, and lacewing and with an increment in cotton aphid populations, though they did not reach the economic threshold. Moreover, S. invicta significantly increased predation of bollworm and beet armyworm eggs. All together, the results suggested that S. invicta has a net positive impact on cotton pest management.

No description available.

There is very low tolerance for blueberry maggot (Rhagoletis mendax Curran) in blueberries making it a serious pest in eastern North America. Control is focused on eliminating flies with insecticides before oviposition in fruit. Organic mulches may improve highbush blueberry production, but their effects on this pest are largely unknown. The research in this thesis evaluated compost and pine needle mulches on blueberry maggot (mature maggots, pupae, emerging flies) and predatory beetles that may consume these stages. Mulches affected fly emergence and maggot pupation. Fly emergence was reduced by 80-100% and delayed ~8 days from pupae covered with 20 cm of pine needles compared to 1 cm of soil. Emergence from 20 cm of compost was lower in wet conditions, and 5 cm of mulch did not limit emergence in the field. Pupation at increased depth reduced emergence because flies did not eclose or, if eclosed, were unable to crawl to the surface. The delay was likely due to lower temperatures at depth. No flies emerged from 1 cm in pine needles in the field probably due to high temperatures. In the laboratory, maggots pupated more deeply in pine needles than other substrates, but ~30% did not pupate in dry pine needles. Saturated soil caused ~50% of maggots to pupate on the surface. Mulching altered beetle diversity and activity/density and affected beetle predation on maggots and pupae. Compost plots in a highbush blueberry field attracted predatory carabids and staphylinids, although some staphylinids were frequent in pine needles and phytophagous carabids preferred unweeded compost plots. Attraction to compost, particularly for Pterostichus melanarius (Illiger), was due primarily to higher prey densities - earthworms and millipedes - than other treatments. This beetle consumed some maggots or pupae in soil or compost, but predation rates decreased when alternative prey was abundant. Blueberry bushes in weedy compost plots attracted many flies, but infestation rates were higher in composted bushes only in the year mulch was applied. Overall, thick mulching with pine needles contributes most significantly to blueberry maggot management. Future research should explore integration of mulch with other tactics for R. mendax control.

Chaoborus americanus larvae were used in laboratory experiments to assess their efficiency at decreasing mosquito larval populations. Third and fourth instar Chaoborus americanus larvae were independently fed assemblages of single prey species to test hunger and several prey species to test preference. Prey species included Daphnia and the four Aedes aegypti larval instars. The results show that Chaoborus americanus larvae will choose early instar mosquito larvae over Daphnia, however, this preference decreases as the mosquito larvae become older. Third instar Chaoborus americanus larvae will choose first instar mosquito larvae over Daphnia 76% of the time, whereas they will select third instar mosquito larvae only 30% of the time. Fourth instar Chaoborus americanus larvae will choose first instar mosquito larvae 94% of the time, and select fourth instar mosquito larvae only 3% of the time. Crowding also has an effect on feeding times; individual Chaoborus larvae take more time to ingest their prey items than do individuals within a group. Chaoborus americanus larvae are good biological control agents within a laboratory setting.

No description available.

Control of Taraxacum officinale (dandelion) and other broadleaf weeds in turfgrass has been readily achieved with phenoxy herbicides, but the herbicide option has been revoked in many regions, necessitating alternative weed control strategies. One biological alternative is Sclerotinia minor, an Ascomycete fungus. The impact of S. minor on broadleaf weed dynamics and biotic interactions were studied in a turfgrass environment. The goal was to maximize effectiveness of a S. minor formulation as a biocontrol of dandelion using an ecological approach. S. minor efficacy was not affected by turf microenvironments and was similarly efficacious with spring or fall application. All accessions from a worldwide collection of dandelion and 32 turfgrass broadleaf species were susceptible to S. minor. Biocontrol efficacy was inversely correlated with dandelion age, but efficacy on all ages was enhanced in the presence of grass competition. When combined with regular mowing at 7-10 cm, the S. minor suppressive effect on dandelion was similar to the herbicide effect, particularly in the following season. Weed suppression was less with close mowing at 3-5 cm due to increased dandelion seedling recruitment. While spring herbicide application was effective to suppress dandelion population, the S. minor treatment has no residual activity, necessitating a second application to suppress seedling recruits. Root regrowth after S. minor infection was minimal and was further reduced in superior quality turf after season-long mowing, and after spring applications. S. minor infected dandelion seeds, reduced the dandelion seedbank, and reduced dandelion seedling emergence by 98%. S. minor did not affect the emergence or the total biomass of cool season temperate turfgrass species. Turfgrass quality was improved following S. minor application and populations of other broadleaf weeds were also controlled by S. minor. Understanding the biotic interactions within the turfgrass environment has rewardingly lead to successful integration of the S.minor biocontrol with the common management tools of mowing and over-seeding to achieve excellent control of dandelion and a healthy thriving turf.

Delairea odorata Lem., an asteraceous perennial vine indigenous to southern Africa, has become naturalised and invasive in many subtropical regions including California, South Australia and Hawaii. Biological control offers a potential long term solution to the management of this species in exotic locations. This study analysed aspects of the biology of D. odorata in its native environment to determine its suitability to classical biological control. To this end an examination of the reproductive biology and natural enemies of D. odorata was made. A study of the pyrrolizidine alkaloid profile was also conducted. Reproductive biology: Delairea odorata reproduces both sexually by seeds and asexually by stolons. The flowering season occurs over the autumn months from April to June. Results of the pollination trials indicate that D. odorata is a cross compatible species and an obligate outbreeder. There is no specialised pollination system and the predominant pollinators belong to the families Apidae, Syrphidae and Calliphoridae. Following pollination, numerous small achenes are produced. Laboratory trials indicate that these achenes germinate readily between 10 and 25 °C and, although germination occurs in both the light and dark, light clearly stimulates seed germination. Greenhouse trials conducted to determine the effect of light on growth and reproduction indicate that D. odorata is a shade tolerant species which shows plasticity in terms of growth form and deployment of biomass in response to changes in light intensity. Growth rate and allocation of biomass to vegetative and sexual reproduction are highest at an intermediate light level. However, greatest allocation of biomass is to stem growth regardless of light level. Natural enemies: Surveys for potential biological control agents against Delairea odorata were conducted in KwaZulu-Natal and several phytophagous species were associated with the plant. However, only one potentially suitable control agent was identified, a stem galling tephritid fly, Parafreutreta regalis Munro. Preliminary studies indicate this species to be fairly host-specific, a valuable asset if it is to be considered as a control agent. Furthermore, as D. odorata proliferates extensively by means of stem regeneration and elongation, galling of these growing points by P. regalis may limit stolon spread in exotic locations. Two species of parasitic wasp (Braconidae) were found to parasitise P. regalis pupae. If P. regalis is to be used as a control agent the likelihood of parasitisation in the new environment must be determined. Pyrrolizidine alkaloids: Host-specificity in insects is often dependent on host-plant chemistry (e.g. alkaloids or essential oils). Thus prior to any biological control programme it is important to determine if there are ecotypes of the host plant present. An investigation to determine the specificity of the pyrrolizidine alkaloid profile of D. odorata, occurring across KwaZulu-Natal, was made. The results indicate the presence of nine retronecine based pyrrolizidine alkaloids which occur in similar proportions in locally distributed plants. However, these alkaloid profiles differ considerably from those published for D. odorata occurring in California. This is an interesting and important result which indicates that chemotypes of D. odorata may exist, a factor which must be considered in the initiation of any biocontrol. If chemotypes of D. odorata are present this may affect the behaviour of natural control agents on the exotic plant populations. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

No description available.

No description available.

Ineffective biological control of the Eucalyptus pest Paropsis charybdis Stål (Coleoptera: Chrysomelidae: Paropsini) in cold areas of New Zealand was believed to be caused a climatic mismatch of the egg parasitoid Enoggera nassaui Girault (Hymenoptera: Pteromalidae). Two Tasmanian strains of the parasitoid were introduced to test climate-matching theory in 2000, with approximately 7000 wasps released. Establishment of the Florentine Valley strain was detected in 2002 using the Mitochondrial (mtDNA) gene Cytochrome Oxidase I (COI) as a strain specific marker. The hyperparasitoid Baeoanusia albifunicle Girault (Hymenoptera: Encyrtidae) and primary parasitoid Neopolycystus insectifurax Girault (Hymenoptera: Pteromalidae) were detected for the first time in New Zealand.
As paropsines have proven highly invasive internationally, a risk assessment of the paropsine threat to New Zealand was undertaken by evaluating the host range of E. nassaui and a reproductive assessment of 23 paropsine species in the genera Dicranosterna Motschulsky, Chrysophtharta Weise, Paropsis Olivier, Paropsisterna Motschulsky and Trachymela Weise. Enoggera nassaui proved polyphagous, but bioassay results proved that Paropsis species were significantly more susceptible to the egg parasitoid than Chrysophtharta species. Resistance within Chrysophtharta was attributed to spine-like chorion modifications. A COI derived Chrysophtharta phylogeny divided the genus into two distinct groupings, which was supported by chorion morphology.
Paropsine reproductive output was tested for key parameters indicating pest potential. Pest species displayed fecundity exceeding 600 eggs at an oviposition rate above 10 eggs per day⁻¹. Several non-pest species were identified as potential pests based on these parameters. The Chrysophtharta phylogeny suggested a moderate relationship between genetic relatedness and reproductive output. The Acacia defoliating paropsine Dicranosterna semipunctata (Chapuis) was evaluated for its susceptibility to E. nassaui and reproductive output. Egg parasitism occurring in bioassay did not translate into biological suppression following a specifically targeted release of E. nassaui, and the fecundity and oviposition rates fell below the thresholds predicted for a pest paropsine species.
Despite establishment of Tasmanian E. nassaui, hyperparasitism has now rendered this control agent ineffective in New Zealand. Neopolycystus insectifurax offers the best hope for future biological control of paropsine species in New Zealand.