Includes bibliographical references (leaves 152-164) Microscopy investigations into the oil glands, localisation of the rind oils and the development of oleocellosis have been carried out in Washington navel orange (Citrus sinensis [L.] Osbeck). Aims to develop an improved understanding of the physiological basis of the rind disorder.

Microxeromagna armillata ( Lowe, 1852 ) is a snail introduced snail to Australia which has established populations in the Riverland and Sunraysia citrus growing regions. Citrus exported from these regions to the USA has been rejected due to contamination with M. armillata, causing significant economic losses. The life history, phenology and activity of Microxeromagna armillata has not been studied in Australia : this forms the basis of this thesis. Microxeromagna armillata employs an iteroparous egg laying strategy in semi - field conditions and lays approximately 500 eggs per year. Field populations can reach high densities ( ∼ 4000 snails / m ² ), particularly during the winter months when juvenile recruitment occurs. Snails reach sexual maturity at ∼ 6mm in shell diameter and can grow to this size from a juvenile stage ( 2mm ) within six weeks. Microxeromagna armillata can reproduce successfully by self-fertilisation, and juveniles are able to aestivate with little reduction in subsequent fecundity. These traits make control of this pest a significant challenge. Leaf litter is the preferred habitat of M. armillata, but snails do move in the tree canopy. Cues for snail activity in the leaf litter and canopy appear to differ, as does the size of active snails in these areas. Microxeromagna armillata activity was low in the tree canopy during harvest compared to post harvest, intimating that fruit contamination is either occurring infrequently or post - harvest. Copper trunk bands were shown to minimise snail movement into the canopy and may be an important preventative measure. These findings have changed the recommendations for M. armillata management in citrus groves of south eastern Australia. / Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2007.

Includes bibliographical references (leaves 152-164) / x, 165 leaves : ill. (chiefly col.), plates ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Microscopy investigations into the oil glands, localisation of the rind oils and the development of oleocellosis have been carried out in Washington navel orange (Citrus sinensis [L.] Osbeck). Aims to develop an improved understanding of the physiological basis of the rind disorder. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002

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.

False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is considered the most important indigenous pest of citrus in southern Africa. Major concerns such as progressive insecticidal resistance, the negative impact of insecticides on the environment, as well as the influence of consumers opposed to chemical residues on fruit, created opportunities for biological control methods such as Sterile Insect Technology (SIT). This technology is now established in the Western and Eastern Cape provinces of South Africa as an effective, sustainable alternative to conventional FCM control methods. Due to the prevalence of the pest in all citrus producing areas of South Africa, potential for SIT to expand is enormous. Success of an SIT programme is highly dependent on efficient application of the technology to achieve its objectives in a timeous manner. The aim of this study was to advance the application of SIT for control of FCM on citrus in South Africa, by investigating the effect of certain critical stages in the process. The effect of long-distance transportation on fitness of irradiated FCM was determined, showing reduced performance with cold-immobilized transport. A significant decrease in flight ability and longevity of irradiated FCM was found, although critically, realized fecundity was not affected. The effect of two different insecticides in the pyrethroid and organophosphate chemical groups were investigated for their residual effect on mortality of released irradiated FCM, to determine if these pest control programmes could be integrated. Both chlorpyrifos and tau-fluvalinate were effective in killing irradiated FCM for a number of days after application, after which degradation of the active ingredient rendered it harmless. This effect was found to be similar for irradiated and non-irradiated males, consequently ratios of sterile : wild male FCM should be retained regardless of whether sprays are applied or not. The modes for release of sterile FCM in an SIT programme were investigated. Efficacy of ground and aerial release platforms were tested by evaluating the recovery of released irradiated male FCM in these orchards. More irradiated FCM were recovered in orchards released from the ground compared to air. However, an economic analysis of both methods shows application of irradiated insects over a large geographical area is more cost-effective by air. Depending on the terrain and size of the target area, a combination of both methods is ideal for application of SIT for control of FCM in citrus. Development of application technology for advance of the programme is discussed and recommendations for future research and development are offered.

False codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyr) (Lepidoptera: Tortricidae), is one of the most important pests on citrus. The Cryptophlebia leucotreta granulovirus (CrleGV) has been developed into a successful biological control agent, registered under the name Cryptogran, and is currently the preferred product for the control of FCM on citrus in South Africa. A prerequisite to the continued success of Cryptogran as a means of controlling false codling moth is to understand the factors affecting field persistence of the virus, and to find ways to improve it. The aim of this study was to gain a clearer understanding of the product and the abiotic and biotic factors affecting its persistence in the field, and to investigate methods to improve this persistence. The effect of UV-irradiation on the virus was determined, and various products were tested as UV protectants in laboratory bioassays. Lignin was the most effective additive, and was tested in several field trials, where it also enhanced the efficacy of Cryptogran. Laboratory trials indicated that Cryptogran is rainfast. Cryptogran applications early in the season had a longer period of residual activity than sprays applied closer to harvest. Daytime applications were less effective that evening sprays. Sprays applied coinciding with peaks in pheromone moth trap catches were more effective than those applied between peaks. Biotic factors influencing persistence were investigated. Residual efficacy was longer when treatments were applied to blocks than as single tree treatments. Attempts were made to quantify the effect of the navel end of a navel orange on the field persistence of Cryptogran. Cryptogran was shown to be compatible with many agricultural chemicals used on citrus. Economic thresholds and various cost-benefit analyses are discussed. A list of practical recommendations to growers was drawn up, and possibilities for future research are presented.

The study examined the larval parasitoids of Cryptophlebia leucotreta (Meyrick) on citrus in South Africa and aimed to improve the existing rearing techniques of C. leucotreta with a view to mass rearing of biological control agents. The biological characteristics of Agathis bishopi Nixon (Hymenoptera: Braconidae) were studied, with an emphasis on parasitism rates in the field, host stage preference, developmental rate, life span and offspring sex ratios. Two larval parasitoids, A. bishopi and Apophua leucotretae (Wilkinson) (Hymenoptera: Ichneumonidae), and an egg parasitoid, Trichogrammatoidea cryptophlebiae Nagaraja (Hymenoptera: Trichogrammatidae), were recorded on C. leucotreta on citrus. A. bishopi was the more abundant of the larval parasitoids and exhibited density dependent parasitism. The highest parasitism rates were observed in December with up to 38% in Sundays River Valley and 34% in Gamtoos River Valley, at a time when the highest false codling moth infestations were observed. Agathis bishopi was recorded only in the Eastern Cape Province. The sex ratio of A. bishopi was biased towards females throughout the study (77% in Gamtoos River Valley and 72% in Sundays River Valley). Agathis bishopi is a solitary, koinobiont, larval-pupal endoparasitoid. The species showed a preference for 1st and 2"d instar hosts. Females regulate the sex of their progeny according to the size and larval stage of the host, ovipositing unfertilised eggs in younger, smaller larvae (1st instars) and fertilised eggs in older, larger larvae (2nd instars). The developmental rate of A. bishopi is in synchrony with that of the moth and adults emerge when adult moths that have escaped parasitism emerge. Agathis bishopi and T. cryptophlebiae compliment each other because they have different niches and strategies of attack. Integrating A. bishopi and T. cryptophlebiae into the management of citrus orchards has potential to suppress false codling moth. Larger rearing containers seemed ideal for large-scale rearing of false codling moth. A higher percentage of adults was obtained from larvae reared in larger containers than in smaller ones. The width of the sponges used as stoppers prevented escape of the larvae. Media prepared in larger containers are easier and simpler to prepare than in smaller ones, thus eliminating many precautions otherwise necessary to prevent contamination. Moth production was greatly reduced by the high concentration of Sporekill used for egg decontamination.

Made available in DSpace on 2014-06-11T19:26:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-15Bitstream added on 2014-06-13T19:33:26Z : No. of bitstreams: 1 dallacqua_fc_me_jabo.pdf: 321125 bytes, checksum: 095ba41139dc507b26139c5c4897dd6c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As bactérias pertencentes ao gênero Xanthomonas constituem um dos grupos de fitopatógenos mais importantes na natureza, com capacidade de infectar aproximadamente 120 tipos diferentes de plantas monocotiledôneas e 270 dicotiledôneas. A bactéria Xanthomonas citri subsp. citri (Xcc) é o agente causal do cancro cítrico, uma das principais doenças dos citros. Restrita à Flórida, a mancha bacteriana dos citros, causada por Xanthomonas alfalfae subsp. citrumelonis (Xacm), afeta principalmente o citrumelo ‘Swingle’. A bactéria Xanthomonas fuscans subsp. aurantifolii (Xfa) é o agente causal das cancroses B e C, encontradas apenas na América do Sul. As técnicas mais utilizadas na diferenciação e caracterização dos patógenos bacterianos, hibridização DNA-DNA (DDH) e sequenciamento da região do DNA que codifica o RNA ribossomal 16S (rRNA 16S), são onerosas, trabalhosas, lentas e de resultados restritos, não permitindo a comparação dos resultados obtidos entre diferentes estudos laboratoriais. Por isso, a técnica de análise de sequências multilocus (MLSA), considerada rápida, barata e confiável, tem sido recomendada para a caracterização e delimitação de espécies de patógenos bacterianos, tais como as do gênero Xanthomonas, permitindo o estabelecimento das relações filogenéticas por meio de genes housekeeping. Portanto, o objetivo do trabalho foi caracterizar os isolados de Xanthomonas (Xcc-A, Xfa-B, Xfa-C e Xacm) por meio da técnica MLSA. Foram utilizados 27 isolados de Xanthomonas patogênicas a citros, sendo quatro de X. citri subsp. citri (Xcc), três de X. fuscans subsp. aurantifolli B (Xfa-B), dezenove de X. fuscans subsp. aurantifolli C (Xfa-C) e um de X. alfalfae subsp. citrumelonis (Xacm). Os genes atpD, dnaK e fusA foram utilizados como genes housekeeping e para a reação da PCR... / Bacteria belonging to the genus Xanthomonas are one of the main groups of phytopathogens in nature, capable to infecting about 120 different monocots and 270 dicots plants. Xanthomonas citri subsp. citri (Xcc) is the causal agent of bacterial citrus canker, one of the major diseases of citrus. Restricted to Florida, citrus bacterial spot, caused by Xanthomonas alfalfae subsp. citrumelonis (Xacm), affects mainly citrumelo 'Swingle'. Xanthomonas fuscans subsp. aurantifolii (Xfa) is the causal agent of canker B and C, found only in South America. The most widely used techniques for the differentiation and characterization of bacterial pathogens, DNA-DNA hybridization (DDH) and analysis of DNA sequences coding for small subunit ribosomal RNAs (16S rRNA), are costly, cumbersome, slow and give limited results, do not allowing the interlaboratorial comparisons of the results. Therefore, the technique of multilocus sequence analysis (MLSA), which is considered fast, cheap and reliable, has been recommended for characterization and delineation of species of bacterial pathogens, such as the genus Xanthomonas, allowing the establishment of phylogenetic relationships between them through housekeeping genes. Therefore, the objective of this study was to characterize strains of Xanthomonas (Xcc-A, Xfa-B, Xfa-C and Xacm) using the MLSA technique. We used 27 strains of Xanthomonas pathogenic to citrus, being four Xcc, three Xfa-B, 19 Xfa- C and one Xacm. The PCR reaction was performed using the specific primers to amplify the atpD, dnaK and fusA genes. PCR products were purified, sequenced and the sequences were analyzed using the software CodenCode Aligner version 3.7.1. Phylogenetic analysis was performed using Maximum Likelihood based on the model of Tamura-Nei and using the software MEGA 5. Analyses ... (Complete abstract click electronic access below)

The false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is one of the major pests of citrus in South Africa, the others being mealybug, Mediterranean fruit fly, bollworm and some mites. Due to problems such as the expense of pesticides, insects evolving pesticide resistance (Hogsette 1999), chemical residue on the skin of export fruit and the negative impact of pesticides on the environment, it became necessary to find alternative methods for pest control (Viggiani 2000). Agathis bishopi (Nixon) (Hymenoptera: Braconidae), a larval parasitoid of false codling moth known only from the Sundays River Valley area (Sishuba 2003), offers a means of control for the pest. A total of 11 389 navel oranges were collected from various orchards in the Addo/Kirkwood area, and false codling moth larvae infested 36.09% of the fruit. A single parasitoid species, A. bishopi, was reared from these larvae. In 2006 the highest parasitism rate, 11.43%, was recorded in May and in 2007, the highest parasitism rate, 13.27%, was in April. Agathis bishopi parasitizes larvae in instars 2 and 3, possibly due to the accessibility of these younger instars to the female parasitoid and possibly due to the length of the life cycle of this koinobiont. Second instar hosts yielded the highest number of parasitoids, and there was no emergence of parasitoids from fifth instar larvae. Females of A. bishopi live for 18.5 days (n = 20; S.E. = 3.1) and males for 8.25 days (n = 20; S.E. = 1.23). Females produce an average of 23 offspring in a lifetime, while female false codling moths produce about 800 eggs each. A high number of parasitoids will be required per hectare to reduce the population of false codling moth. Captive rearing of A. bishopi proved difficult due to viral and fungal contamination. Agathis bishopi has potential for use in an integrated pest management programme once the hurdle of mass-rearing has been overcome.

A granulovirus isolated from Cryptophlebia leucotreta larvae was shown through restriction endonuclease analysis to be a novel strain (CrleGV-SA). No more than one isolate could be identified from a laboratory culture of C. leucotreta. However, a preliminary examination of restricted DNA profiles of isolates from different geographical regions indicated some minor differences. In surface dose bioassays on artificial diet, LC50 and LC90 values with neonate larvae were estimated to be 4.095 x 103 OBs/ml and 1.185 x 105 OBs/ml respectively. LT50 and LT90 values with neonate larvae were estimated to be 4 days 22 h and 7 days 8 h, respectively. Detached fruit (navel orange) bioassays with neonate larvae indicated that virus concentrations that are likely to be effective in the field range from 1.08 x 107 to 3.819 x 1010 OBs/ml. In surface dose bioassays with fifth instar larvae LC50 and LC90 values were estimated to be 2.678 x 107 OBs/ml and 9.118 x 109 OBs/ml respectively. LT50 and LT90 values were estimated to be 7 days 17 h and 9 days 8 h, respectively. A new artificial diet for mass rearing the host was developed. Microbial contamination of diet was significantly reduced by adding nipagin and sorbic acid to the diet and by surface sterilising C. leucotreta eggs with Sporekill. Almost 20 % more eggs were produced from moths reared on the new diet compared to moths reared on the old diet. A further 9 % improvement in egg production and a reduction in the labour required to produce eggs, was made with the development of a new oviposition cage attached to the moth eclosion box. Virus was mass produced in fifth instar C. leucotreta larvae by surface inoculating diet with the LC90. When 300 individuals were placed onto inoculated diet, 56 % of them were recovered six to 11 days later as infected larvae. Mean larval equivalents was 1.158 x 1011 OBs/larva. When larvae and diet were harvested together, highest yields of virus were achieved at eight days after inoculation. Microbial contamination in semi-purified preparations of CrleGV ranged from 176211 to 433594 (OB:CFU ratio). Half-life of CrleGV in the field was estimated to be less than 1 day on the northern aspect of trees and between 3 - 6 days on the southern aspect. Original activity remaining (OAR) of the virus dropped below 50 % after 5 days on the northern aspect of trees and was still at 69 % on the southern aspect of trees after 3 weeks. In field trials, CrleGV reduced C. leucotreta infestation of navel oranges by up to 60 % for a period of 39 days. CrleGV in combination with augmentation of the C. leucotreta egg parasitoid, Trichogrammatoidea cryptophlebiae, reduced infestation by 70 %. The integration of CrleGV into an integrated pest management (IPM) system for the management of C. leucotreta on citrus is proposed.