The spiralling whitefly (SWF), Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae), is a highly polyphagous pest of horticultural and plantation crops in Nigeria. Its parasitoid, Encarsia sp. (Hymenoptera: Aphelinidae), accidentally introduced, plays a critical role in its regulation, yet its ecological suitability remains underexplored. This study investigated factors influencing SWF parasitisation by Encarsia sp. from 2014 to 2019 on four host plants—Citrus sinensis (sweet orange), Acalypha wilkensiana (red acalypha), Ficus polita (fig), and Psidium guajava (guava)—at two sites in Ibadan, Nigeria. Monthly monitoring of SWF abundance, parasitised pupae (mummification), and weather factors (temperature and rainfall) was conducted and correlated. From 2014 to 2019, SWF populations declined sharply, reaching zero by 2016 on Citrus, Acalypha, and Ficus at both sites, while Psidium maintained low, stable SWF numbers with consistent parasitism rates. Initial SWF density varied significantly (P < 0.05) across host plants, with Psidium hosting significantly higher SWF numbers than others (P < 0.05). Parasitisation rates increased annually, with peaks on Acalypha (up to 70% in January 2014) and lower rates on Psidium (stable at ~ 20–30%). Encarsia sp. abundance closely tracked SWF populations, with peak parasitism synchronized across host plants, though density-dependent parasitism was evident on Citrus, Acalypha, and Ficus (significant regression coefficients, P < 0.05), but density-independent on Psidium. Multiple regression analysis identified parasitism as the primary factor influencing SWF populations, followed by temperature, with rainfall showing a weaker but significant correlation (P < 0.05). No significant correlation was found between percent parasitism and mean temperature (P > 0.05). The polynomial relationship between SWF and Encarsia sp. was 6th degree on Psidium, 5th on Ficus, and 3rd on Citrus and Acalypha. Local extinction of SWF on Citrus, Acalypha, and Ficus, contrasted with regulated low populations on Psidium, suggests that host plant quality and Encarsia sp. parasitisation are key drivers of SWF dynamics, offering insights for integrated pest management in Nigeria.

Parasitisation of the spiralling whitefly, Aleurodicus dispersus Russell (Homoptera: Aleyrodidae), by Encarsia spp. (Hymenoptera: Aphelinidae) concerning the host plant and weather factors

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发表日期：

2025年12月22日

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Caroline Oyindamola Filani,
Olufemi Richard Pitan

摘要

The spiralling whitefly (SWF), Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae), is a highly polyphagous pest of horticultural and plantation crops in Nigeria. Its parasitoid, Encarsia sp. (Hymenoptera: Aphelinidae), accidentally introduced, plays a critical role in its regulation, yet its ecological suitability remains underexplored. This study investigated factors influencing SWF parasitisation by Encarsia sp. from 2014 to 2019 on four host plants—Citrus sinensis (sweet orange), Acalypha wilkensiana (red acalypha), Ficus polita (fig), and Psidium guajava (guava)—at two sites in Ibadan, Nigeria. Monthly monitoring of SWF abundance, parasitised pupae (mummification), and weather factors (temperature and rainfall) was conducted and correlated. From 2014 to 2019, SWF populations declined sharply, reaching zero by 2016 on Citrus, Acalypha, and Ficus at both sites, while Psidium maintained low, stable SWF numbers with consistent parasitism rates. Initial SWF density varied significantly (P < 0.05) across host plants, with Psidium hosting significantly higher SWF numbers than others (P < 0.05). Parasitisation rates increased annually, with peaks on Acalypha (up to 70% in January 2014) and lower rates on Psidium (stable at ~ 20–30%). Encarsia sp. abundance closely tracked SWF populations, with peak parasitism synchronized across host plants, though density-dependent parasitism was evident on Citrus, Acalypha, and Ficus (significant regression coefficients, P < 0.05), but density-independent on Psidium. Multiple regression analysis identified parasitism as the primary factor influencing SWF populations, followed by temperature, with rainfall showing a weaker but significant correlation (P < 0.05). No significant correlation was found between percent parasitism and mean temperature (P > 0.05). The polynomial relationship between SWF and Encarsia sp. was 6th degree on Psidium, 5th on Ficus, and 3rd on Citrus and Acalypha. Local extinction of SWF on Citrus, Acalypha, and Ficus, contrasted with regulated low populations on Psidium, suggests that host plant quality and Encarsia sp. parasitisation are key drivers of SWF dynamics, offering insights for integrated pest management in Nigeria.