Browsing by Author "Serfontein, Adriaan Jacobus"

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    Development of handling and transport protocols for Eldana saccharina (Lepidoptera: Pyralidae) sterile insect technique (SIT) programme
    (Stellenbosch : Stellenbosch University, 2021-04) Serfontein, Adriaan Jacobus; Conlong, D. E.; Addison, Pia; Desmond, Edward; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Eldana saccharina Walker (Lepidoptera: Pyralidae), is indigenous to sub-Saharan Africa and is a serious economical pest of sugarcane in South Africa. Recent area-wide integrated pest management (AW-IPM) efforts have proven to be effective in lowering infestations and better predicting population growth and spread into new areas. The sterile insect technique (SIT) promises to provide great benefit as a component of the AW-IPM strategy. This study aimed to establish parameters for collection, packaging, and transport of recently emerged E. saccharina adult males, within a maintained cold chain conjointly with methodologies for the routine assessment of the performance and competitiveness of sterilized insects. These treatments should not impact the fitness nor mating ability of the adults exposed to them. Several major outcomes were realized, summarized as follows: Parental male and female pairs exposed to 100 Gy irradiation prior to mating provided an 83.3 % male biased first filial generation. Thus, a male biased, semi sterile generation could be reared for collection and release using this technique; difference between average male (0.0700 g) and female (0.133 g) pupal weights (as an indication of adult weight) were identified as a morphological trait that could be exploited to obtain a high degree of sex separation; and the plenum collection box was effective in collecting male and female adult E. saccharina (a mean of 80.67 % ± 4.56 % adults were collected when placing 200 adult moths (male : female = 1:1) into the prototype collection system overnight for 12 hours replicated three times). Furthermore, the effect of exposure of virgin E. saccharina males to 5 °C for 24, 48 and 72 hours on male mating frequency and longevity was measured to determine the impact of prolonged periods of cold exposure to male fitness. The 72 hour treatment showed a significant decrease in male mating frequency (average of 4.4 females mated at 48 h versus 2.7 females mated at 72 hours). It is therefore possible to hold E. saccharina at 5 °C for 48-hours without impacting on moth fitness in terms of mating frequency. Bran was identified as a good temperature insulating material to use as a packaging substrate for adult males, as it buffered temperature fluctuations over time inside a transportable freezer set at 5 °C (1.5 °C to 5.5 °C) when fully stocked with bran, versus being empty (0 °C to 6 °C). Bran’s effect as a packaging substrate on male fitness during high density packaging and exposure to 5 °C for 24, 48 and 72 hours showed no significant decrease in male mating frequency (mean mating frequency of 2.8889 females mated). Males did have a decreased mating frequency (1.4667 females mated) after 72 hours for the no bran packaged adults. A visual rating system was tested to measure the difference in loose scale cover - on the eyes, dorsal surface, ventral surface, as well as scale loss from the pronotum - between bran and no bran packaged moths. There was a clear improved visual quality with bran packaged adults compared to no bran packaged adults with less scale loss from the pronotum and less loose scales covering the eyes and ventral and dorsal surfaces, indicating that this visual rating system could be valuable as a quality control check at the point of elease.