Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 27-31). Also available via Humboldt Digital Scholar.

In order that the citrus industry in South Africa may be commercially developed to the greatest possible extent it is of importance that certain basic ecological problems should be investigated. Until the complex relationships between the host plant, the insect pests and their parasites and predators are known, the results of applications of either chemical or biological control must be largely a matter of chance. A certain amount of rather generalised work in this connection has already been done in South Africa, principally by Carnegie (1955), Smithers (1953) and Whitehead (1948) in the Eastern Cape Province and by Steyn (1954) in the Transvaal. The first three of these workers were content to determine which species of insects occurred in citrus orchards and made some attempts to study the biology of certain predators. Steyn went a little further when he correlated ant activity with scale insect infestations. Without doubt the most economically important insect pests of citrus are the scale insects (Homoptera: Coccoidea). Introduction, p. 1.

[Introduction] In the Western Cape Province the mealybug, Planococcus citri (Risso), was first reported on vines in 1930 by Joubert (1943a). By 1935 this mealybug had spread to the Hex River Valley, and subsequently to all the main table grape producing areas of the Western Cape Province. At present Pl. citri is the most important insect pest of the table grape industry and can, if not effectively controlled, result in a loss of at least five per cent of the export table grape crop (Kriegler, 1954). Some preliminary work on the natural enemies of Pl. citri on vines was carried out by Stubbings in 1948, but no further work of this nature has been undertaken in this area since then. The fact that the natural enemies can be an effective check to this mealybug on vines in the Western Cape Province has been known for a number of years (Potgieter, 1937; Hattingh, 1943; Joubert, 1943a; Myburgh, 1951). The present work is an attempt to obtain some basic knowlege of the population fluctuations of the insects concerned in this biological control. Surveys undertaken have shown that there is a complex of primary, secondary and possibly tertiary Hynenopterous parasites associated with Pl. citri. The presence of hyperparasites reduces the efficiency of the primary parasitic Hymenoptera. The usefulness of these primary parasites is further reduced as they only occur in effective numbers for a short period of the year. On the other hand, although attacked by some parasites, the numerous coccinellids found preying on Pl. citri are of more importance in reducing the mealybug populations, as they are present on the vines in effective numbers for the greater part of the year.

No description available.

This report includes the determination of activity and possible mode of action for a group of potential new insecticides. The biological screening procedure was developed using Drosophila melanogaster as the test organism while Musca domestica was used for mode of action assays. The percent kill for each compound is based on the number of eggs placed on media containing the insecticide minus the number of adults enclosed as compared to the control media reared flies. Observations were made on all stages from eggs through adults to determine time of death and if any malformations were present. These observations aided in the mode of action studies as did preciously published work on diflurbenzuron. The mode of action studies encompassed chitin synthesis, chitin breakdown and DNA synthesis. Cuticle deposition was determined gravimetrically on pupal instar reared on media with and without DOWCO 416. Chitin synthesis and DNA synthesis were followed by measuring the incorporation of radiolabeled precursors by pupal instars reared on media with and without DOWCO 416. Chitin breakdown was followed through the measurement of chitinase activity spectrophotometrically on all stages of larvae which were reared on media with and without DOWCO 416. Direct inhibition of chitinase was investigated by incubation of the purified chitinase from Staphlycoccus griseus with varying concentrations of the test compound.

Thesis (M.S.)--University of Tennessee, Knoxville, 2010. / Title from title page screen (viewed on July 20, 2010). Thesis advisor: Gary McCracken. Vita. Includes bibliographical references.

Thesis (MSc)--Stellenbosch University, 2000. / Full text to be digitised and attached to bibliographic record. / ENGLISH ABSTRACT: The cultivation of citrus in the Vaalharts region is a fairly recent development. With the introduction of this crop, an insect pest complex has also developed in this region. The presence of these pests was studied in eleven orchards, planted with three citrus cultivars and of varying ages, distributed in the 300 square kilometer cultivation area. Each orchard was inspected for the presence of pests by making use of two weekly sampling techniques. Ten of the most important insect pests of citrus in the Vaalharts region are briefly described by refering to their general appearance, life cycles, feeding and pest status and economic threshold. For every pest various control options, including operational systems, crop cultivation, biological and chemical control, are discussed and, where applicable, illustrated by means of graphic presentations. The seasonal presence of the cirtrus pests in the Vaalharts region is tabulated and discussed individually. With these details as background, an insect pest management programme for citrus in the Vaalharts region is compiled. / AFRIKAANSE OPSOMMING: Die verbouing van sitrus in die Vaalhartsgebied is 'n redelik onlangse ontwikkeling. Gepaard met die nuwe gewas het daar ook 'n insekplaagkompleks in die gebied ontstaan. Die voorkoms van die plae is in elt .boorde, beplant met drie sitruskultivars en van verskillende ouderdomme, verspreid in die 300 vierkante kilometer verbouingsareaal, bestudeer. Elk van die boorde is weekliks ondersoek vir die aanwesigheid van plae deur van twee moniteringstegnieke gebruik te maak. Die tien belangrikste insekplae van sitrus in die Vaalhartsgebied word kortliks beskryf deur na hulle algemene voorkoms, lewenssiklus, voeding en plaagstatus en ekonomiese drempelwaardes asook die moniteringsmetodes wat gebruik is, te verwys. Vir elke plaag word beheeropsies, wat operasionele stelsels, gewasverbouing, bloloqlese en chemiese beheer insluit, bespreek wat, waar toepaslik, aan die hand van grafiese voorstellings gemustreer word. Die seisoenale aanwesigheid van die sitrusplae word in 'n tabel aangedui en individueel bespreek. Met die gegewens as agtergrond is 'n insekplaagbestuurprogram vir sitrus in die Vaalhartsgebied opgestel.

Many organisms, especially animals like insects, which depend on the environment for body heat, have growth stages and life cycles that are highly dependent on temperature. To better understand and model how insect life history events progress, for example in the emergence and initial growth of the biogeographical research subjects, we must first understand he relationship between temperature, heat accumulation, and subsequent development. The measure of the integration of heat over time, usually referred to as degree-days, is a widely used science-based method of forecasting, that quantifies heat accumulation based on measured ambient temperature. Some popular methods for calculation of degreedays are the traditional sinusoidal method and the average method. The average method uses only the average of the daily maximum and minimum temperature, and has the advantage that it is very easy to use. However, this simplest method can underestimate the amount of degree-day accumulation that is occurring in the environment of interest, and thus has a greater potential to reduce the accuracy of forecasting insect pest emergence. The sinusoidal method was popularized by Allen (1976, [1]), and gives a better approximation to the actual accumulation of degree-days. Both of these degree-day accumulators are independent of typical heating and cooling patterns during a typical day cycle. To address possible non-symmetrical effect, it was deemed prudent to construct degree-day accumulators to take into account phenomena like sunrise, sunset, and solar noon. Consideration of these temporal factors eliminated the assumption that heating and cooling in a typical day during the growth season is symmetric. In some tested cases, these newer degree-day integrators are more accurate than the traditional sinusoidal method, and in all tested cases, these integrators are more accurate than the average method. After developing the newer degree-day accumulators, we chose to investigate use of a logistic phenology model similar to one used by Onsager and Kemp (1986, [54]) when studying grasshopper development. One reason for studying this model is that it has parameters that are important when considering pest management tactics, such as the required degree-day accumulations needed for insects in immature stages (instars) to be completed, as well as a parameter related to the variability of the grasshopper population. Onsager and Kemp used a nonlinear regression algorithm to find parameters for the model. I constructed a simplex algorithm and studied the effectiveness when searching for parameters for a multi-stage insect population model. While investigating the simplex algorithm, it was found that initial values of parameters for constructing the simplex played a crucial role in obtaining realistic and biologically meaningful parameters from the nonlinear regression. Also, while analyzing this downhill simplex method for finding parameters, it was found there is the potential for the simplex to get trapped in many local minima, and thus produce extraneous or incorrectly fitted parameter estimates, although Onsager and Kemp did not mention this problem. In tests of my methods of fitting, I used an example of daily weather data from Onefour, AB, with a development threshold of 12 ±C and a biofix day of April 1st, as an example. The method could be applied to larger, more extensive datasets that include grasshopper population data on numbers per stage, by date, linked to degree accumulations based on the non-symmetrical method, to determine whether it would offer significant improvement in forecasting accuracy of spring insect pest events, over the long term. / xii, 106 leaves ; 29 cm

Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Lucerne is the most important pasture and fodder crop in the winter rainfall area of South Africa. Various pests are known to cause damage to this crop. The use of the sweep net for monitoring pests is a cheap, easy and quick technique. If the sweep net is suitable for the lucerne pests in South Africa, potential pest status can be determined easily and quickly and the necessary precautionary measures taken to prevent crop losses. From a managerial point of view, it is also important to know the composition of the insect community in order to follow practices in which the number of beneficial insects can be increased and the injurious insects decreased. Therefore a study was done to quantify the use of the sweep net as a survey technique for monitoring pests on established lucerne stands. Insect diversity was also determined to obtain information on the insect families and guilds on lucerne. The redlegged earth mite, due to its importance as a pest, and the Anystis mite, important as a predator, were also included. The sweep net proved to be suitable for the sampling of the main lucerne pests. If a 29 cm diameter sweep net is swiped once per pace for six long paces, twelve systematically chosen sampling units are recommended for the lucerne earth flea and aphids. It is not necessary to differentiate amongst the three aphid species, or between the winged and unwinged aphids. Actual counts should be used instead of absence-presence data. Instead of counting all the insects in a sample, sub-samples can be taken. Operational characteristic curves can be used to determine the risk involved in the decision not to intervene, for example by spraying or grazing. Recommendations for monitoring and the accuracy of control decisions for the redlegged earth mite, Sitona weevil and lucerne butterfly can only be made after threshold values have been determined. The pea aphid, bluegreen aphid and lucerne earth flea showed peaks in their population levels during spring. Peak numbers of the spotted alfalfa aphid occurred during late summer and autumn. The Sitona weevil and lucerne butterfly numbers reached peak levels during late spring and early summer. For all pests population levels were dramatically reduced after grazing or cutting of the plantings. Therefore, these cultivation practices provided good control. The herbivores made up more than 85% of the insect community in lucerne. The largest herbivorous families, in terms of the number of individuals per family, were the Aphididae and Sminthuridae. These two families contain the main lucerne pests, the pea aphid, bluegreen aphid, spotted alfalfa aphid and the lucerne earth flea. The largest predatory family was the Anystidae, represented by the Anystis mite, the most important predator of the red legged earth mite and lucerne earth flea. Another well represented predatory family was the Coccinellidae, containing natural enemies of the aphids. The dryland plantings had a higher percentage of predators than the irrigated lucerne. The most important parasitaids were those in the superfamily Chalcidoidea and in the family Braconidae. The main detritivores were springtails in the suborder Arthropleona, insects in the families Mycetophilidae on irrigated lucerne, and Mycetophagidae on dryland lucerne. The most abundant visitors were in the families Chironomidae, Drosophilidae and Tephritidae. The dryland plantings had a lower percentage of visitors than the irrigated plantings. The number of insect families, as well as the number of individuals per family, was lower at the dryland plantings than at the irrigated plantings. The vast majority of insect families found on lucerne were collected during the one-year sampling period. A lower diversity was found where grazing was more severe, and there was a negative relationship between diversity and evenness. / AFRIKAANSE OPSOMMING: Lusern is die belangrikste wei- en voergewas 10 die winterreëngebied van Suid- Afrika. Hierdie gewas word deur 'n verskeidenheid plae aangeval. Die gebruik van die swaainet vir die monitering van plae is 'n goedkoop, maklike en vinnige tegniek. lndien die swaainet geskik is vir die betrokke plae in Suid-Afrika, kan potensiële plaagstatus van die plae dus maklik en vinnig bepaal word en die nodige voorsorgmaatreëls getref word om verliese te voorkom. Vanuit 'n bestuursoogpunt is dit ook belangrik om te weet wat die samestelling van die insekgemeenskap is sodat praktyke gevolg kan word waardeur die getal voordelige insekte verhoog en nadelige insekte verlaag word. Gevolglik is 'n studie uitgevoer om die gebruik van die swaainet te kwantifiseer as 'n monsternemingsmetode vir die monitering van plae op gevestigde lusernstande. Insekdiversiteit is ook bepaal ten einde inligting te bekom oor die insekfamilies en -gildes op lusern. Die lusernerdvlooi en swartsandmyt, vanweë hul belang as plae, en die Anystis-roofmyt, vanweë sy belang as predator, is ook ingesluit. Die swaainet blyk geskik te wees vir die monitering van die. vernaamste lusernplae. Wanneer 'n 29 cm deursnee swaainet vir ses lang treë een keer per tree geswaai word, word 12 sistematies gekose steekproefnemingseenhede vir die lusernerdvlooi en plantluise aanbeveel. Daar hoef nie onderskeid tussen die plantluisspesies en tussen gevleuelde en ongevleuelde plantluise getref te word nie. Daar moet gebruik gemaak word van werklike insektellings en nie van aanwesigheid-afwesigheid data nie. In plaas van om al die insekte in 'n monster te tel, kan submonsters geneem word. Operasionele karakteristieke kurwes kan gebruik word om die risiko verbonde aan die besluit om nie op te tree, deur byvoorbeeld te spuit of bewei nie, te bepaal. Vir die swartsandmyt, Sitona-snuitkewer en lusernskoenlapper moet drempelwaardes eers vasgestel word voordat aanbevelings vir monitering en die akkuraatheid van besluite rakende beheer, gegee kan word. Vir die ertjieluis, blougroenluis en lusernerdvlooi het die bevolkingsvlakke 'n piek in die lente bereik. Die gevlekte lusernluis se piekgetalle was hoofsaaklik in die laat somer en herfs. Die Sitona-snuitkewer en lusernskoenlapper het piekgetalle gehad in die laat lente en vroeë somer. Vir al die plae het bevolkingspieke drasties afgeneem nadat die aanplantings bewei of gesny is. Hierdie verbouingspraktyke blyk dus goeie beheer te verskaf. Die herbivore op lusern het meer as 85% van die insekgemeenskap beslaan. Die grootste herbivoorfamilies, in terme van aantal individue per familie, was die Aphididae en Sminthuridae. Hierdie twee families bevat die vernaamste lusernplae, naamlik die ertjieluis, blougroenluis, gevlekte lusernluis en lusernerdvlooi. Die grootste predatoriese familie was die Anystidae, wat verteenwoordig is deur die Anystis-roofmyt. 'n belangrike predator van die swartsandmyt en lusernerdvlooi. Nog 'n predatoriese familie wat goed verteenwoordig was, was die Coccinellidae, natuurlike vyande van plantluise. Die droëland aanplantings het 'n hoër persentasie predatore gehad as die besproeide lusern. Die belangrikste parasitoïede aanwesig was dié in die superfamilie Chalcidoidea en familie Braconidae. Die vernaamste detritivore was erdvlooie in die suborde Arthropleona, insekte in die families Mycetophilidae by besproeide lusern, en Mycetophagidae by droëland lusern. Die volopste besoekers was lede van die families Chironomidae, Drosophilidae en Tephritidae. Die droëland aanplantings het 'n laer persentasie besoekers gehad as die besproeide lusern. Die aantal insekfamilies, asook die aantal individue per familie, was laer by die droëland aanplantings as by die besproeide aanplantings. Die oorgrote meerderheid insekfamilies wat op lusern voorkom, is gedurende die een jaar opnameperiode waargeneem. 'n Laer insekdiversiteit is gevind waar beweiding strawwer was, en daar was 'n negatiewe verband tussen diversiteit en gelykmatigheid.