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Phytoseiids were collected March through November, 2006 and 2007, from leaf samples of avocados, cherimoya, caneberry, grape, and strawberry from a combined total of 24 sites. The most diverse collection of phytoseiids was identified on grape with seven different genera and 12 different species followed by caneberry with 7 genera and 7 species. Strawberry was the least diverse with three genera and three different species. The most significant presence of type I and type II phytoseiids were located on caneberry and strawberry while avocado, cherimoya and grape were dominated by type IV species. Reasons for the difference in diversity could be attributed to the availability of preferred hosts, alternate food sources, and the effectiveness of augmentative releases and pesticide applications.

No description available.

There is a need for effective and environmentally sensitive methods of controlling vertebrate pest problems in agriculture and urban environment. Nonlethal natural repellents may meet this need where more traditional methods of control, such as scaring, shooting, and trapping, are either ineffectual or unacceptable. Neem (Azadirachta indica A Juss) extracts: oil, seed and leaf powder and chemicals from cockroach (Blaberus giganteus L.) were tested for their repellent properties. In addition defensive volatiles from B. giganteus were tested in an arena based on choice by smell (cheese or insect volatiles). This arena test used laboratory rats (Rattus norvegicus Berk.); females were more active than males. Both sexes visited the holes with cheese more than holes containing insect's volatiles. However in a feeding test with one choice of food the control did not differ from the treatment. Neem products seem to act as antifeedant on rats: neem seed oil, neem seed powder and neem leaf powder reduced rats feeding respectively at concentration of 15 ml of oil/kg, 15--50 g of seed powder/kg, and 25--50 g of leaf powder/kg of rat chow. Overall neem leaf powder was less effective than seed powder and oil. Neem and insect products may have potential in controlling rats particularly in storage situation, which could lead to an important reduction of post-harvest loss of grains in Sahelian and Asian countries.

This study investigated effects of insect growth regulators (IGRs), recommended for use on citrus in southern Africa, on non-target organisms, particularly species of Coccinellidae in and around three citrus estates in the lowveld region of Swaziland, i.e. Tambuti, Tambankulu and Tunzini estates. Some of the species are important predators of citrus pest insects. The distribution of coccinellids within an agricultural land mosaic and factors affecting this distribution pattern were also investigated. Results showed that coccinellid densities and species diversity were lowest in the natural veld surrounding the orchards. In contrast, citrus orchards had the highest coccinellid densities and diversity. River borders, along the Great Usuthu river, had intermediate densities and diversity. While temperature, relative humidity and ground insolation had no significant effect on coccinellid population densities, the presence / absence of prey (host plant), on the other hand, was an important factor. This was the case both for phytophagous and predatory coccinellid species. These showed close patterns of distribution with their respective host plants or prey species. Economically important species, such as Rodolia spp., were restricted to the orchards, while other species, especially those whose economic role is uncertain, such as Cheilomenes lunata and Scymnus spp., were found in most habitat types. Coccinellid population densities were assessed during four treatment programmes: 1) an integrated pest management (IPM) programme where no IGRs were used, 2) a programme where any of the recommended IGRs were to be applied, 3) conventional pesticide programme, and 4) an orchard which did not receive any chemically treatment over the last four years (at Tambankulu estate only). Significant differences between treatment programmes were observed at all three estates, when only economically important coccinellid species were assessed. Orchards under an IPM programme (with no IGRs) were found to have significantly higher population densities compared to those in IGR-treated or under a conventional pesticide regime. The untreated orchard at Tambankulu, however, had significantly higher coccinellid densities of economically important species and higher overall population densities than any of the managed orchards. Of the three estates assessed, Tunzini had significantly higher population densities of all beneficial coccinellids, (excluding the untreated orchard at Tambankulu). Natural vegetation around Tunzini and Tambuti contributed to the higher coccinellid densities compared to Tambankulu, which was surrounded by other agricultural land. Laboratory and field experiments on two non-target species, the ladybird Chilocorus nigritus (Fabricius) (all stages) and the moth Bombyx mori (Linnaeus) (larval stage) assessed specific IGR effects, if any. Three IGRs, buprofezin, teflubenzuron (both chitin synthesis inhibitors) and pyriproxyfen (a juvenile hormone analogue) were used. All three pesticides are currently recommended for use on citrus in southern Africa and were tested at the recommended dosages. Laboratory experiments showed that all three IGRs have a negative impact on both non-target species. When B. mori received direct applications, there was larval mortality as a result of the failing to complete moulting or dying immediately after moulting. In addition, no larvae were able to pupate after having fed on contaminated leaves. In the case of C. nigritus, larvae fed IGR-treated scale or sprayed with buprofezin suffered significantly higher mortality than controls, while IGR effects on those sprayed with, or fed scale-treated with, pyriproxyfen or teflubenzuron were not significant. No adults however, emerged from any pupae in any of the treatment groups. All three IGRs had ovicidal activity on C.nigritus eggs. Adult fecundity in both field and laboratory experiments was not affected significantly after exposure to any of the three IGRs. In field experiments, the proportion of larvae of the moth and ladybird that developed up to the reproductive adult stage, after exposure to buprofezin, was not significantly different from the control. This was not the case for pyriproxyfen and teflubenzuron. Buprofezin was therefore found to be the least detrimental of the three IGRs tested. Minimal drift was observed when a knapsack sprayer was used. However, there was spray drift up to 32m (the furthest distance assessed here) where commercial sprayers were used. This suggests that pesticide drift from orchards to adjacent areas would have serious implications for biological diversity in the river borders and rivers adjacent to the estates. The sensitivity of the non-target species to the IGRs tested needs serious consideration, as it indicates a broader spectrum of activity for the compounds than what is promoted. Additionally, natural control may be affected. This is because the timing of IGR applications and increasing coccinellid populations coincide, resulting in a reduced pool of coccinellid predators. This study emphasised the importance of an appropriately heterogenous landscape to maximise habitat availability for the coccinellids. Although the economic role of the multihabitat coccinellid species recorded here is unknown, they nevertheless clearly contribute to citrus pest control. Such a mosaic landscape, in conjunction with IPM, with no IGR use, promotes ecological diversity and controls pests with minimum disruption to biodiversity. The use of IGRs in citrus thus needs carefiil reconsideration in light of the non-target effects observed on the two species, especially the valuable predatory species, C. nigritus. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1998.

Cyperus rotundus L. CYPRO (purple nutsedge) and Cyperus esculentus L. CYPES (yellow nutsedge) are problematic weeds on every continent. At present there is no comprehensive means of controling these weeds.. The primary means of control is herbicides, although the weeds are becoming more resistant. Bioherbicide control of purple and yellow nutsedge is an important avenue of research, with much of the focus being to increase the virulence of current fungal pathogens of C. rotundus and C. esculentus. The primary aim of this study was to increase the virulence of a fungal pathogen of C. rotundus and C. esculentus, with the objective of creating a viable bioherbicide. A possible means of increasing the virulence of a pathogen would be to increase the amount of amino acid produced by the fungus. This was proposed as a means of increasing the virulence of Dactylaria higginsii (Luttrell) M. B. Ellis. Overproduction of amino acids such as valine and leucine result in the feedback-inhibition of acetolactate synthase (ALS), an enzyme which is a target for many herbicides currently on the market. By applying various amino acids to tubers of purple nutsedge and comparing the results with a reputable herbicide, glyphosate, it was possible to determine the success of the amino acid applications. Only glutamine treatment at 600 mg.r1 resulted in significantly less (P<O.OOI) germination compared with the water control, while the glyphosate application resulted in no germination. Four treatments were significantly different (P<O.OOI) from the water control in terms of shoot length, but no pattern or conclusion could be drawn from the results. Injecting amino acids and glyphosate into the leaves of the plants gave similar results to those obtained with the tubers, with no visible damage on those plants injected with the amino acids and complete plant death of those injected with glyphosate. Amino acids had little effect on the growth of the C. rotundus plant or tuber. It was later determined by a colleague (Mchunu1 , unpublished) working on the same project, that D. higginsii does not infect the local ecotypes of C. rotundus in Pietermaritzburg, South Africa. A second fungus, Cercospora caricis Oud., was isolated from C. rotundus growing in the region, and confirmed as a Cercospora species by conidial identification. Like many Cercospora species, C. caricis produces a phytotoxin, cercosporin. An increase in production of cercosporin would theoretically lead to an increase in virulence of C. caricis. Mutation of hyphae by i J Makhosi Mchunu: Address: National department ofAgriculture; Private Bag 3917; Port Elizabeth; 6056 Email: Makhosimc@NDA.agric.za ultraviolet-C light was perfected on C. penzigii Sacc., where 5 min exposure to DV-C light resulted in approximately 99% cell death. Surviving colonies were analysed by spectrophoresis, and the surviving mutant gave an absorbance value of approximately 5% more than the median. Samples were analysed by high-performance liquid chromatography (HPLC) to determine the presence of cercosporin. No definitive result was obtained. Exposure of C. caricis to DV-C for 5 min. resulted in approximately 65% hyphal cell death, with 20 min. resulting in approximately 95% death. A spontaneous mutant was observed in a colony that had been exposed to DV-C. This mutant showed sectored growth with red and grey growth patterns. The red section of the mutant was subcultured and analysed by spectrophoresis and HPLC. The red C. caricis gave an absorbance reading of approximately 140 on HPLC compared with about 22 from the grey colony. HPLC analysis of the wild-type C. caricis did not produce a peak corresponding to that of the cercosporin standard, although no conclusion could be obtained on the presence or absence ofthe toxin. The virulence of the mutant C. caricis could not be determined as inoculation experiments were unsuccessful, and had to be discontinued due to time constraints. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Water lettuce, Pistia stratiotes Lamarck (Araceae) is a South American plant that has the potential to be a very damaging and important aquatic weed in many tropical countries, including South Africa. It has the potential to rapidly multiply vegetatively and completely cover watercourses in a very short space of time outside of its natural range under ideal conditions and without its natural enemies. In such instances, the weed may cause hindrances to water transport and fishing, increasing chances of malaria, as well as affecting the natural ecology of the system. Water lettuce can also set seed, which may lay dormant for long periods, germinating when conditions are favourable. It is therefore very necessary to adopt control methods against the weed where it is a problem. However, water lettuce has also been effectively and completely controlled in many countries by the leaf-feeding weevil, Neohydronomus affinis Hustache. High nutrient levels in the form of nitrates and phosphates have been shown to have largely negative effects on biological control in several studies, with control being incomplete or taking longer than in similar areas with lower nutrient levels. The effectiveness of N. affinis on the biological control of water lettuce was investigated in a laboratory study, growing P. stratiotes plants with and without insects at different nutrient concentrations. In these studies biological control of water lettuce with N. affinis was found to be complete under eutrophic nutrient conditions, although control took longer when higher nutrient levels were tested. A field site study was conducted at a sewage settlement pond in Cape Recife Nature Reserve near Port Elizabeth, South Africa. This highly eutrophic system was used as a field example for the effectiveness of biocontrol of P. stratiotes by N. affinis under eutrophic conditions. The weevils at Cape Recife caused a massive and rapid crash in the percentage coverage of the weed, from 100% in May 2003, to approximately 0.5 % in September 2003. Plant growth parameters were also found to decrease considerably in size correspondingly with this crash from May 2003 until spring 2003. Plant size only again started to increase gradually but steadily through spring 2003 and into summer. In the laboratory studies, the fecundity of weevils was shown to be much higher on plants grown under higher nutrient concentrations than on plants grown in lower nutrient concentrations. The results from the wing-muscle analysis under different nutrient concentrations were not easy to interpret, and there were few differences in wing muscle state between most of the concentrations. From these findings it is suggested that nutrient concentration, particularly high levels of nitrates and phosphates is not a limiting factor in terms of effective biological control of P. stratiotes with N. affinis, but that under high nutrient conditions biological control might take longer.

In 1985 the Diama Dam was built near the mouth of the Senegal River to regulate flows during the rainy season and prevent the intrusion of seawater during the dry season. This created ideal conditions upstream of the dam wall for invasion by two highly invasive aquatic weeds, first by water lettuce Pistia stratiotes Linnaeus (Araceae) in 1993, and then by salvinia Salvinia molesta D.S. Mitchell (Salviniaceae) in 1999. This study was focused on the management of P. stratiotes and S. molesta. Following successes that were achieved elsewhere in the world, biological control programmes involving two weevil species were inaugurated against both weeds and research was focused on several aspects. These included pre-release studies to determine the weevils' host-specificity and impact on the plants in the laboratory, their subsequent mass-rearing and releases at selected sites and post-release evaluations on their impact on the weed populations in the field. Both programmes, which reprepresented the first biocontrol efforts against aquatic weeds in Senegal, proved highly successful with severe damage inflicted on the weed populations and complete control achieved within a relatively short time span. A laboratory exclusion experiment with N. affinis on P. stratiotes showed that in treated tubs, the weevil strongly depressed plant performance as measured by the plant growth parameters: mass, rosette diameter, root length, number of leaves and daughter plants whereas control plants were healthy. Field releases started in September 1994 and water coverage by P. stratiotes at Lake Guiers was reduced by 25% in January 1995 and 50% in April 1995. A general decline of 65% in water coverage by P. stratiotes was observed in June 1995 and by August 1995, eight months after releases P. stratiotes mats were destroyed. Further, although no releases were made there, good results were obtained within 18 months at Djoudj Park water bodies, located 150 km NW from Lake Guiers indicating the potential of the weevil to disperse long distances. In 2005, P. stratiotes reappeared and the weevil N. affinis has located and controlled all of these P. stratiotes recurrences after new releases. In 1999, S. molesta covered an estimated area of 18 000 ha on the Senegal River Left Bank and tributaries (Senegal) and 7 840 ha on the Senegal River Right Bank (Mauritania). Military and Civil Development Committee (CCMAD) and community volunteers made an effort to control S. molesta using physical removal, but this costly and labour-intensive approach was unsustainable. Hence, biological control was adopted by Senegal and Mauritania to manage the weed. Host range tests to assess feeding by C. salviniae on S. molesta and non-target plants and carried out on 13 crop species showed that no feeding damage was observed on the latter and weevils only fed on S. molesta. Field releases of some 48 953 weevils at 270 sites were made from early January 2002 to August 2002. Within one year, weevils were established and were being recovered up to 50 km from the release sites. In a case study conducted at one of the release sites, the S. molesta infestation was reduced from 100% to less than 3% 24 months after release. These results are discussed in the context of the weeds’ negative impact on aquatic systems and riverside communities, and in the involvement of these communities in the programmes.