Thesis (PhD (Agric))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: During a survey in the greater Cape Flats Heterodera schachtii was found to be widespread on cauliflower, Brussels sprouts, beetroot and cabbage. The numbers present were above two eggs and juveniles per gram of soil, generally regarded as the economic threshhold level of infestation and requiring control. The damage potential of H schachtii on vegetables, as well as the ability of certain weeds to serve as a source of infection on subsequent crop plantings was studied under greenhouse conditions and resulted in a reduction of yield and root weight of crops. Population densities of H schachtii increased significantly under favourable hosts like cabbage where densities of 198 eggs and juveniles per gram of soil were reached. The most commonly occurring weeds maintained nematode development and increased their population densities. They can thus serve as alternative hosts in the absence of susceptible hosts and should be routinely controlled. The life cycle and biology of H schachtii was also studied. Penetration of plant tissue and subsequent development on vegetables, weeds and trap crops were observed. Penetration was successful on all crops tested reaching 37% and 52% at inoculum levels of 22 and 11 juveniles per gram of soil, respectively. Subsequent development of H schachtii on weeds and vegetables was similar, but in the case of cauliflower and black nightshade as hosts, their life cycle was shorter in comparison to other crops. The possible existence of varying susceptibility of crops to different populations of H schachtii was examined by comparing the rates of penetration in crops and reproduction of geographically isolated populations of H schachtii in the greater Cape Flats. When root penetration, virulence and juvenile emergence were examined, populations from Lynedoch and Philippi were distinct from the other populations. Subsequently, representative individuals of these populations were subjected to PCR-RFLP, but with these techniques real differences between the various populations could not be adequately detected. The environmental parameters such as soil texture, temperature and pH on H schachtii were investigated as to their influence on the root weight and yield of crops. Reductions in the yield of beetroot and cabbage were observed with soil temperatures ranging between 15 to 30°C. Migration and penetration of H schachtii juveniles declined with an increase in clay and silt content of the soil. Above a 34% silt and clay content of soil, no migration and penetration took place. Root penetration levels of 30% and higher were reached with pH varying between 4.5 and 7.4. This resulted in a significant reduction in yield of crops. Crop rotation is an essential component of non-chemical control. In the case of H schachtii, it required one host crop in four non-host rotational cycles to maintain the population of the nematode in the soilless than three eggs and juveniles per gram of soil. The inclusion of a trap crop reduced the population densities to below two eggs and juveniles per gram of soil. It therefore also forms an integral part of a control strategy. Solarization proved successful as a physical control method. Best results were obtained in summer with clear polyethylene which led to a 97% reduction of infective juveniles. This method can be applied during the late summer in the greater Cape Flats, just before the onset of winter. This may safeguard future spring plantings. The need for effective control strategies in order to reduce the numbers of H schachtii is of the utmost importance to ensure vegetable production in the future. Small-scale farmers should therefore be educated in this respect. / AFRIKAANSE OPSOMMING: Heterodera schachtii het wydverspreid in 'n opname in die groter Kaapse Vlakte voorgekom op beet, blomkool, Brusselse spruite en kopkool. Die nematode getalle by alle lokaliteite was bo die algemeen aanvaarbare ekonomiese drempelwaarde van twee eiers en larwes per gram grond wat beheer regverdig. Die skadepotensiaal van H schachtii op groente, sowel as die vermoë van sekere onkruide om as infeksie bronne te dien vir opvolgende gewasse, is in glashuise ondersoek en het tot 'n verlaging in opbrengs en wortelmassa by gashere gelei. Die populasie digthede van H schachtii het met die aanplant van geskikte gashere tot vlakke van 198 eiers en larvae per gram grond gestyg. Die mees algemeen voorkomende gasheeronkruide het nematode ontwikkeling in stand gehou en selfs tot 'n populasie verhoging gelei. Hierdie onkruide is 'n beperkende faktor vir die verbouing van groente aangesien die onkruide as alternatiewe gasheer kan dien in die afwesigheid van gashere en onkruidbeheer moet dus op 'n gereelde basis toegepas word. Die lewenssiklus en biologie van H schachtii is ondersoek deurdat die penetrasie van gasheer wortels en die daaropvolgende ontwikkeling op groente, onkruide en vanggewasse vergelyk is. Penetrasie, vyf dae na inokulasie, is met alle gashere verkry met 37% en 52% penetrasie met inokulum vlakke van 22 en 11 larwes per gram grond onderskeidelik. Daaropvolgende ontwikkeling van H schachtii was soortgelyk op groente en onkruide, maar blomkool en nastergal het as gashere 'n verkorte lewenssiklus tot gevolg gehad. Die moontlikheid van verskille in die virulensie van H schachtii is ondersoek deur die penetrasie van gewasse en reproduksie vlakke van nematodes van nege verskillende geografies geskeide populasies in the groter Kaapse Vlakte te vergelyk. Die Lynedoch en Philippi populasies het onderskeibare resultate gelewer ten opsigte van die populasies uit die ander lokaliteite, maar geen verskille kon met PKR-RFLP aangetoon word nie. Die invloed van omgewings parameters, grondtekstuur, temperatuur en pH, is op H schachtii ondersoek ten opsigte van opbrengste en wortelmassa van gewasse. Grondtemperature tussen 15°C - 30°C het tot die grootste daling in opbrengs gelei op kopkool en beet. Migrasie en penetrasie het afgeneem met 'n toename in klei en slik inhoud tot en met 'n klei en slik inhoud van 34%, waarna geen penetrasie en migrasie voorgekom het nie. Wortelpenetrasie van 30% en hoër het voorgekom by pH vlakke van tussen 4.5 - 7.4 met die gepaardgaande verlaging in opbrengs van gewasse. Afwisseling van gewasse is 'n essensiële metode van nie-chemiese beheer van nematode getalle in die grond. Die mees optimale rotasie ten opsigte van H schachtii beheer is met die aanplanting van een gasheer gewas in vier gewas aanplantings verkry. Die insluiting van 'n vanggewas in die gewas rotasie siklus het die nematode populasievlakke tot onder twee per gram grond laat daal. Solarisasie is suksesvol uitgevoer met deurskynende poli-etileen in die groter Kaapse Vlakte gedurende die somer met gevolglik 'n 97% vermindering van die getalle infektiewe nematodes. Effektiewe beheermaatreëls ten opsigte van H schachtii moet in die groter Kaapse Vlakte ingestel word om groente-produksie in hierdie gebied te verseker. Kleinboere moet in hierdie tegnieke opgelei word.

The control of the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) in sugarcane fields of KwaZulu-Natal, South Africa has proved problematical. Researchers at the South African Sugarcane Research Institute (SASRI) have since 1974 been intensively investigating various means of controlling the pest. Among the methods of control currently being investigated are biological control, chemical control, production of more resistant varieties and crop management. These investigations, however, require many years of experimentation before any conclusions can be made. In order to aid the research currently being carried out in the Entomology Department at SASRI (to investigate biological control strategies, insecticide application strategies and the carry-over decision), a simulation model of E. saccharina growth in sugarcane has been formulated. The model is cohort-based and includes the effect of temperature on the physiological development of individuals in each life-stage of the insect. It also takes into account the effect of the condition of sugarcane on the rate of E. saccharina infestation, by making use of output from the sugarcane growth model CANEGRO. Further, a crop damage index is defined that gives an indication of the history of E. saccharina infestation levels during the sugarcane’s growth period. It is linked to the physiological activity of the borer during the period spent feeding on the stalk tissue. The damage index can further be translated into length of stalks bored and hence the percentage of the stalk length bored can be calculated at each point in the simulation using the total length of stalks calculated in the CANEGRO model. Using an industry accepted relationship between percent stalks damaged and reduction in sucrose content of the crop, reductions in losses in the relative value of the crop when the various control measures are implemented can be compared. Relationships between the reduction in percent stalk length bored (and hence gains in the relative value of the crop) and the various control strategies are obtained. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermartzburg, 2008.

Two ant species, Pheidole megacephala (Fabricius) and Anoplolepis custodiens (Smith) reach pest status in citrus orchards through precipitating outbreaks of homopterous pests. However, predacious ants, including these two ant species, play an important role in pest suppression in agroecosystems and are therefore beneficial to these systems. If A. custodiens and P. megacephala are important natural control agents in citrus, using ant bands to break the mutualism between the ants and the Homoptera as a method of ant control is preferable to poisoning. Ant communities were sampled by pitfall trapping in three experimental subunits of 2-, 4-, 15- and 30-year-old citrus orchards, in the Grahamstown area of the Eastern Cape. In one subunit in each orchard, populations of P. megacephala and A. custodiens were suppressed by poison applications. In a second subunit, trees were banded with trunk barriers so that ants were prevented from foraging in the trees and a third subunit served as the untreated control. Bait pupae of bollworm, false codling moth and fruit fly were planted in bait trays in all of the subunits to investigate predation on these citrus pests in the relative absence of predacious ants and where they were excluded from the trees. Pheidole megacephala dominated exclusively in all of the plots. Community composition did not change dramatically with increasing age of the trees, but species diversity and species abundance did. Rank-abundance curves showed that community diversity was highest in the 2-year-old plots and lowest in the 30-year-old plots. The Simpson and Shannon-Wiener diversity indices and their evenness measures indicated that diversity and equitability were highest in the poisoned subunits and lowest in the banded subunits. Principle component analysis revealed that the poisoned subunits were similar and distinct in species composition, that there was significant monthly variation in species composition and that community stability increases with an increase in orchard age. The presence of P. megacephala was significantly negatively correlated (rs = -0.293; p < 0.001) with pest pupal survival. Pupal survival was significantly higher for bollworm (p < 0.001), FCM (p < 0.001) and fruit fly (p < 0.001) in the poisoned subunits, than in the banded and control subunits. There was a general trend for survivorship to increase with an increase in the age of the trees. A significant difference (p < 0.001) was found between the months in which the trials were carried out. Pupal survival was significantly lower (p < 0.001) for FCM than for bollworm and fruit fly. In citrus orchards, ant communities are organised by ecological processes and interactions and are influenced by methods of ant control. Ant bands are preferable to poisoning as a method of ant control, so that beneficial species are left on the ground to prey on pests that pupate in the soil. Maintaining high ant species diversity in citrus orchards would be beneficial as predation on the pupae was more effective where ant species diversity was higher.

Please read the abstract in the section 00front of this document / Dissertation (M Inst Agrar (Sustainable Insect Management))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

MSc (Zoology) / Department of Zoology / See the attached abstract below

Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae) (obscure mealybug), is a common and serious pest of apples and pears in South Africa. Consumer and regulatory pressure to produce commodities under sustainable and ecologically compatible conditions has rendered chemical control options increasingly limited. Information on the seasonal occurrence of pests is but one of the vital components of an effective and sustainable integrated pest management system needed for planning the initiation of monitoring and determining when damage can be expected. It is also important to identify which orchards are at risk of developing mealybug infestations while development of effective and early monitoring tools for mealybug populations will help growers in making decisions with regards to pest management and crop suitability for various markets. It is also essential to determine the presence and efficacy of naturally occurring biological control agents in orchards so as to ascertain the potential of biological control as a viable alternative in orchards. However, under the current integrated pest management protocol, it has been difficult to determine this, due to the sporadic and relatively low incidence of mealybug infestations in some orchards, or by simply relying on naturally occurring field populations of biocontrol agents. Knowledge of the environmental conditions under which P. viburni population levels may become destructive is also essential for timing the release of insectary reared natural enemies as well as understanding the population ecology of this pest and its natural enemies. Information was gathered regarding the seasonal phenology of P. viburni and its natural enemies in pome fruit orchards in the Western Cape Province during the 2007/08 and 2008/09 growing seasons. Seasonal population studies showed that P. viburni has multiple overlapping generations with all life stages present throughout the year. The highest orchard infestations occurred during the summer period until early winter (January to early June). This was followed by a decrease in population from late June to November, before another increase in December. Presence-absence sampling of mealybugs on the host plant revealed that woody parts of the tree, such as the trunk and old stems were the most preferred sites for mealybug habitation, due to the availability of protected refuge sites. Migration of mealybug populations to newer growth and the upper sections of the tree crown, such as the new stems, leaves and eventually the fruit, was observed from December throughout the summer period until the early winter in June. Fruit colonization in both apples and pears commenced in January, when the fruit had developed a size sufficient for P. viburni to penetrate and occupy spaces such as the fruit core, calyx and stem end. There was no evidence of P. viburni occurring beneath the soil surface or on the roots of host trees. Two natural enemies of mealybugs, namely Pseudaphycus maculipennis (Mercet) and Coccidoxenoides perminutus (Girault), were found to be active in apple and pear orchards in the Western Cape. However, the status of C. perminutus as a parasite of P. viburni still needs to be verified despite evidence of emergence from P. viburni mummies, which was not sufficient enough to suggest that it is a useful biological control agent. Seasonal abundance trends of the two natural enemies revealed that their lifecycle is synchronized with that of the host. However, there was no evidence of P. maculipennis activity in Ceres. No predators were found during the course of this study. The rate of P. viburni parasitism at harvest was 46.52%, with P. maculipennis and C. perminutus constituting 98.966% and 1.034% of the parasitoids recovered from mealybug mummies, respectively. Studies on the use of pheromone traps as early monitoring tools for P. viburni showed that there was a positive and significant relationship between the fruit infestation and number of P. viburni adult males caught in pheromone-baited traps (r2 = 0.454). The action threshold level was estimated to be 2.5 male P. viburni caught per trap per fortnight at an economic threshold of 2% fruit infestation. / AFRIKAANSE OPSOMMING: Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae) (ligrooswitluis), is ‘n algemene en ernstige plaag van appels en pere in Suid-Afrika. Druk deur verbruikers en regulasies om kommoditeite onder volhoubare en ekologies verenigbare toestande te produseer het chemiese beheeropsies toenemend beperk. Inligting oor die seisoenale voorkoms van plae is een van die essensiële komponente van ‘n effektiewe en volhoubare geïntegreerde plaagbestuurprogram. Dit is in die aanvanklike beplanning van monitering en om te bepaal wanneer skade verwag kan word. Dit is ook belangrik om boorde vroegtydig te identifiseer wat die risiko het om witluisbesmettings te ontwikkel. Die ontwikkeling van effektiewe en vroeë moniteringstegnieke vir witluisbevolkings sal produsente help met besluitneming rakende plaagbestuur en die geskiktheid van gewasse vir verskeie markte. Dit is ook noodsaaklik om die teenwoordigheid en effektiwiteit van biologiese beheer agente wat natuurlik in boorde voorkom te bepaal ten einde die potensiaal van biologiese beheer as ‘n lewensvatbare alternatief vas te stel. Onder die huidige geïntegreerde plaagbestuurprotokol was dit egter moeilik om laasgenoemde te bepaal weens die sporadiese en relatiewe lae voorkoms van witluisbesmettings in sommige boorde of deur bloot staat te maak op die veldpopulasies van biologiese beheer agente wat natuurlik voorkom. Kennis van die omgewingstoestande waaronder P. viburni bevolkingsvlakke skadelik raak is ook noodsaaklik vir die beplanning van vrylating van biologiese beheer agente, asook om die bevolkingsekologie van hierdie plaag en sy natuurlike vyande te verstaan. Inligting oor die seisoenale fenologie van P. viburni en sy natuurlike vyande in sagtevrugte boorde in die Westelike Kaapprovinsie is gedurende die 2007/08 en 2008/09 groeiseisoene versamel. Seisoenale bevolkingstudies het getoon dat P. viburni verskeie oorvleuelende generasies het met alle stadia teenwoordig regdeur die jaar.

The objectives of this study were to establish the effectiveness of chlorpyrifos in suppressing H. armigera population in oranges and to determine the effect chlorpyrifos had on the health of farm pesticide operators. Experiments showed that by applying chlorpyrifos on orange trees, H. armigera larvae population was suppressed significantly. High fruit yields were realized from trees that were sprayed with chlorpyrifos. Visual observation of personnel involved in pesticide related duties, revealed that judicious use of pesticides was not practiced by farm workers in all three farms. Data analysis from questionnaires, health records and interviews proved that farm workers suffered from illnesses that were pesticide related. It was mainly those farm workers in the age group of 31 to 35 years who suffered the most from pesticide related illnesses. / Agriculture and Life Sciences / M. Sc. (Agriculture)

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / The South African table grape industry exports approximately 60% of the table grapes produced. A major threat to the export of these grapes is the phytosanitary risk that insect pests pose. This study was conducted in the Hex River Valley, South Africa’s main table grape producing area. The aim of this study was to reduce the number of phytosanitary rejections from insects on table grapes from the Hex River Valley. Thus the main objectives of the study were to identify the most important phytosanitary pests in the Hex River Valley; the determination of their presence in the vineyards with possible means to control them; and to assess the possibility of using postharvest quarantine treatments in the Western Cape. Further aims were to determine the effect of different colour harvesting crates on the phytosanitary pests and whether the phytosanitary pests infested the grapes via packhouses. The most important phytosanitary pests of table grapes of the Hex River Valley are in order of importance: Phlyctinus callosus (Schonherr) (Coleoptera: Curculionidae), Epichoristodes acerbella Walker (Lepidoptera: Tortricidae), Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), Gonocephalum simplex Fabricius (Coleoptera: Tenebrionidae) and Dysdercus fasciatus Signoret (Hemiptera: Pyrrhocoridae). 12.71% of rejections were from species that were not identified, while a further 33% of the rejections were possibly identified incorrectly. Phytosanitary control of P. callosus appeared to be far more effective using Plantex® than pesticides. Weather conditions appeared to affect the abundance of P. callosus, especially warm weather, while bunches harboured less P. callosus later in the day. Control of E. acerbella with DiPel® (Bacillus thuringiensis var. kurstaki) appeared to at least reduce the population within the vineyards, and so its use is recommended. P. ficus is a non-actionable species for the USA market and is not listed as a phytosanitary pest for the Israeli market and so should not be causing any phytosanitary rejections. C. capitata appeared to be successfully controlled by the fruit fly sterile release program and the cold sterilisation it currently undergoes. G. simplex caused few rejections. It is still unclear where this pest infests the grapes, as it was found in both the field and in the packhouses. D. fasciatus occurrence on grapes was probably accidental. It was shown that picking during the early and late parts of the day, when this species was less active, reduced its occurrence in bunches. Gryllus bimaculatus (De Geer) (Orthoptera: Gryllidae), although not reported as a reason for rejections in table grapes for the past two years, was an actionable species that was present in large numbers in the Hex River Valley. There was a strong correlation between increasing quantities of pesticides and higher abundances of G. bimaculatus. It appeared to be an indicator of the overuse of pesticides. Results of this study showed that infestation by the phytosanitary pests came from neighbouring vineyards. The creation of barriers to prevent the movement of these pests between vineyards is suggested. Methyl bromide is the most commonly used postharvest quarantine treatment. Owing to the ozone-depleting properties of methyl bromide, it is scheduled to be outlawed in many countries from 2005. Alternative postharvest treatments are irradiation, extreme temperatures, forced air, vapour-heat treatments and the use of controlled atmospheres. Irradiation treatments appeared to control the pests at doses that do not damage the grapes. Controlled atmosphere treatments also have a high probability of success, although more research is required on this treatment. Low temperature treatments are relatively cheap as most exported fruit already undergoes cold storage, and appears to control species in the families Pseudococcidae and Tephritidae, although further research is required for the other pest. Colour or location of the harvesting crates in the vineyards appeared not to influence the number of phytosanitary pests collected, as they were not attracted to these crates.

Soybean rust (SBR), caused by the fungus Phakopsora pachyrhizi Syd., is a real threat to soybean crops in South Africa. Its ability to spread rapidly and its potential to severely reduce yields have earned it the reputation as the most destructive foliar disease of soybeans. SBR has been reported in South Africa every year since its arrival in 2001. While extensive research had been done on the epidemiology and fungicide application requirements in South Africa, no work into the long term climatic vulnerability of soybean production areas to SBR had been done. This meant soybean producers do not know whether SBR is a threat in their areas. Through this research a SBR algorithm was developed using readily available climate data, viz. temperature and rainfall, to create a daily index specifying the climatic vulnerability of SBR infection. The algorithm was applied to a 50 year historical climate database, and a series of maps was created illustrating the long term vulnerability of different areas to SBR infection. These maps allow soybean producers to understand the climatic vulnerability of their area to SBR infection. Time series graphs were created for selected key soybean production areas to allow soybean producers to distinguish periods of high and low climatic risk during the season. This may help with decisions regarding the planting times, the maturation rate of different cultivars as well as the timing and application of fungicides. The framework for a near real time forecasting system was created outlining how the system could amalgamate recently recorded and forecasted weather data, run it through the SBR algorithm and provide a near real time, as well as forecasted vulnerability, based on the climatic conductivity for SBR infection. Anticipated limitations and difficulties on developing the forecasting system are also outlined. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

The backbone of this study was a systems thinking based analysis of the management and control of predators as practiced in South Africa since the advent of Europeans in 1652. The first bounties were introduced for a variety of animal species in 1656. Many species became labeled as vermin and were persecuted, often with the intention of eradication. A variety of controls have been applied, of which many have not kept pace with contemporary thinking or technology, and which by simply killing predators fail to address the crux of the issue of predator – livestock conflict. Many of the methods used cannot be applied to specifically remove an individual damage-causing animal. Considerable collateral ecological damage is inflicted by the killing of animals regarded as innocent bystanders. The objective of the analysis was to highlight the futility of temporary solutions which fail to resolve the conflict in the long term. These quick fixes frequently perpetuate an ecological imbalance which exacerbates the predator – livestock conflict. The analysis used raw data from a questionnaire survey conducted by the Poison Working Group of the Endangered Wildlife Trust (EWT-PWG) (2003). The EWT-PWG intended to assess pesticide abuse as toxicant for predators by farmers, and to identify all control methods used. The data forthcoming was Cartesian in nature and a fixed snap-shot in time. This study sought to identify the root cause of the conflict by applying systems thinking which added the dimension of cause and effect interrogation. The study categorised and described predator conflict management methods as lethal or preventative, and assessed each category in archetypal terms from a systems thinking perspective. It also sought to identify leverage points, or small changes which have profound effects, to stimulate a change in approach to humanpredator conflict management. In order to assess and illustrate the positive change brought about by application of preventative methods, a small group of farmers who had initiated changes in their predator conflict management over the five years subsequent to the EWTPWG survey were selected from the original group for reassessment. Through evaluation of predator conflict management methods from a systems thinking perspective, and by probing learning processes, the shortcomings or failure of inappropriate management responses to conflict situations were shown to exacerbate conflicts. Contrarily, it was illustrated that application of systems thinking and a process of addressing the root cause of conflict issues in predator conflict management, was a longer term solution. The study illustrated that application of long term proactive prevention and conflict avoidance principles, can offer long term solutions for predator conflict managers. / Thesis (M.Env.Dev.) - University of KwaZulu-Natal, Pietermaritzburg, 2008.