Biology and management of the fruit piercing moth Serrodes partita in citrus orchards
- Authors: Mushore, Tapiwa Gift
- Date: 2024-10-11
- Subjects: Baculoviruses , Moths Monitoring , Pests Control , Insect traps , Citrus Diseases and pests South Africa Kat River Valley , Catapult moth
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466792 , vital:76779 , DOI https://doi.org/10.21504/10962/466792
- Description: The fruit-piercing moth, Serrodes partita (Fabricius) (Lepidoptera: Erebidae), is a polyphagous, multivoltine pest of citrus. This insect has a distinct geographical separation between its larval and adult stages, each with different feeding patterns. During the larval stage, it primarily acts as a forest defoliator, feeding mostly on Jacket plum, Pappea capensis Eckl. & Zeyh. (Sapindaceae). In contrast, the adult stage of this moth feeds on both tropical and subtropical fruit, including citrus and can cause serious economic losses. The adult moth uses its sclerotised proboscis to pierce the skin of ripening or ripe fruit, from which it extracts the juice. This piercing action initiates a fermentation process within the fruit, attracting other secondary-feeding moths, commonly referred to as fruit-sucking moths. As a result of the feeding activity, the affected fruit eventually rot, drop to the ground, and become unsuitable for the market. Serrodes partita exhibits an outbreak life strategy, reoccurring every 5 to 10 years. In South Africa's Eastern Cape Province, specifically in the Upper Kat River Valley, citrus growers have expressed concerns about the impact of this moth on soft citrus (Satsumas and Clementines). This raises the possibility of a shift in the population dynamics of S. partita, where these occurrences become more frequent and less sporadic. Such a trend poses a significant threat to fruit arboriculture in the Eastern Cape region. Currently, there are limited management strategies available for managing fruit-piecing moths. The use of pesticides is not a feasible option for ripe or nearly ripe fruit, and is ineffective against the adult moth. Alternative control methods, such as orchard netting and light barriers, either come with high costs or are impractical for large-scale citrus production. Given the limited range of management options, combined with the moth's tendency for sudden outbreaks, citrus growers find themselves without effective means to manage this pest. The objective of this study was, therefore, to investigate the biology of S. partita and explore various control options to effectively manage this pest. Research focused on the biology and laboratory rearing of larval stages of S. partita. The flight behaviour, feeding patterns, and preferences of adult S. partita within citrus orchards were also explored. The aim was to elucidate key fundamental aspects, including whether the same population frequents a particular orchard, and if infestations within orchards exhibit a specific direction. Lure type and lure presentation method trials were conducted to determine the most effective lure and trap design. Seasonal monitoring of S. partita in soft citrus orchards was conducted over three years to determine its outbreak status in the Committee’s Drift area and the role of weather variables in the activity of the moth. Damage assessments were also conducted alongside monitoring to determine the level of damage inflicted by S. partita. Natural enemies associated with S. partita were explored to determine the prevalence and causes of mortality in late instars during laboratory rearing. Rearing S. partita on an artificial diet was unsuccessful despite several modifications. The moth, however, completed its entire life cycle on its natural host, P. capensis in the laboratory. The total life cycle from egg to adult took 80.7 ± 3.6 days, the larval stage lasted 52.3 ± 2.8 days, and the pupal stage lasted 25.8 ± 3.6 days at 21°C. The investigation into the biology of S. partita also brought attention to the most susceptible stages of its growth, with high mortality rates recorded among neonates and late instars. The findings of the study revealed directional patterns of moth infestations, with higher numbers observed at the orchard's periphery leading towards natural vegetation. This raises the prospect of using sacrificial rows on the edge of a citrus orchard to concentrate moth feeding damage during outbreak years. Using a mark and recapture technique, the study showed that a relatively small proportion (4.5 %) of moths tended to revisit the same orchard. The moths strongly preferred damaged fruit (85 %) over undamaged fruit. Visible damage (rotting symptoms) typically became apparent within 3 to 5 days. Satsumas had a higher number of feeding scars (2.1) than Clementines (1.08), highlighting their susceptibility. The study also established that, on average, pierced soft citrus fruit takes about four days to display symptoms of decay. Synthetic proprietary Australian lures were ineffective at attracting the moth, whereas fresh bananas proved to be a successful lure. Furthermore, the addition of both Agar and Super absorbent polymer showed promise as thickening agents to enhance the longevity of fresh bananas in traps. The effectiveness of various trap designs was compared, including the funnel trap, delta trap, bucket trap, and circular trap, in capturing fruit-feeding moths. The funnel trap performed best as it captured the most moths, followed by the delta trap, Lynfield trap and disc trap, respectively. Additionally, an electronic enhancement to the funnel trap, incorporating a zapper element, improved efficiency. However, efforts to exploit both visual and olfactory cues through the inclusion of an Ultraviolet (UV) light component did not improve its effectiveness. No extensive outbreaks were recorded during the study; however, population variations of S. partita populations were recorded. Annual trends showed two population peaks, with the first peak recorded from December to March, while the second peak was recorded from April to July. The activity of the moths also differed across different months, with the highest peaks recorded in May, while no moths were recorded from August to November. Both cultivar type and farm location did not influence the occurrence of the moth. Meanwhile cumulative weather parameters (rainfall, temperature and humidity) from the four months prior to occurrence influenced the activity of S. partita. Temperature determined the timing of the outbreak, while rainfall determined the magnitude of the outbreak. Damage assessment showed very low fruit damage by S. partita throughout the monitoring period. Varying levels of infestation by a tachinid fly, 4 % and 35 %, were recorded for 2021 and 2022, respectively. The tachinid parasitoid could not be identified at the species level. A novel baculovirus, tentatively classified as S. partita NPV (SepaNPV), was identified as the larval mortality causative agent. This study enhanced our understanding of S. partita's biology and population dynamics, providing valuable insights for developing effective management strategies against this economically impactful citrus pest. Future research should focus on refining control measures and addressing the challenges of the adult moth's elusive nature. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
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- Date Issued: 2024-10-11
Evaluation of the large-scale trapping of blowflies (Lucilia spp.) for an integrated pest management program : the lucitrap
- Authors: Scholtz, Anna J
- Date: 2003
- Subjects: Blowflies -- Control , Insect trapping , Insect traps , Pests -- Control
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10972 , http://hdl.handle.net/10948/126 , Blowflies -- Control , Insect trapping , Insect traps , Pests -- Control
- Description: The results presented in this dissertation have been partially presented at scientific meetings. Chapter 2 is an exact copy of the technical contents of a paper submitted to a scientific journal. The format of this paper however has been changed to comply with the format used in this dissertation. The results of this paper were partially presented at the 36th National Congress of the South African Society of Animal Science, 5 – 8 April 1998 held in Stellenbosch. In this chapter errors occurred in the execution of the trial, but these were corrected in the follow-up trial after consulting with the manufacturers. It is discussed in the paper. Results of chapter 3 were partially presented at the 5th International Sheep Veterinary Congress 21 – 25 January 2001 held in Stellenbosch and at an International Congress (The FLICS (Flystrike & Lice IPM Control Strategies) Conference, 25 – 27 June 2001, Launceston) in Tasmania by Mr. S.W.P. Cloete in 2001. The updated results are given in this chapter. The results of chapter 4 were presented at a combined congress between the Grasslands and the Animal Production Societies of South Africa (The GSSA/SASAS Joint Congress 2002. 13 – 16 May) in Christiana in 2002. The results in this chapter represent the same experimental period as was reported upon at that congress, but additional statistical analyses were executed on the same data set. Copies of the abstracts of the contributions to these meetings are attached in chapter 6. The major objective of this study initially was to evaluate the Lucitrap® system under South African conditions. During the experimental period I had an opportunity to visit Australia and meet many role players. It came under my attention that the control of the blowfly is a rather complex problem with many facets. A current issue worldwide on the use of chemicals as a control method against insects and its hazardous influence on the environment is forcing producers to minimize chemical residues in textiles and other agricultural products. An Integrated Pest Management (IPM) approach seems to be the only option. This study has been executed to try and understand some aspects of the blowfly problem for future application in such a blowfly control program.
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- Date Issued: 2003