ABSTRACT
The cassava mealybug Phenacoccus manihoti Mat.-Ferr. (Hemiptera: Pseudococcidae) is a globally important pest of cassava (Manihot esculenta Crantz), a crop that is cultivated on nearly 25 million ha across the tropics. Following its continent-wide invasion of Africa during the 1970s and early 1980s, P. manihoti was inadvertently introduced to Southeast Asia in late 2008, where it caused important yield drops in local crops. Guided by the widely-acclaimed biological control successes against this mealybug in Africa, the endophagous parasitoid Anagyrus lopezi De Santis (Hymenoptera: Encyrtidae) was introduced to Thailand in 2009. Subsequent introductions of A. lopezi were made into neighbouring countries, and an integrated campaign was launched to scale-up mealybug biological control. Multi-country field surveys were carried out to map P. manihoti geographic distribution, field-level abundance and extent of parasitoid-mediated suppression, and innovative extension programmes were deployed to raise farmer awareness of mealybug pests and associated natural enemies. Survey work from nearly 600 fields throughout mainland Southeast Asia revealed that P. manihoti occurred at abundance levels of 14.3 ± 30.8 individuals per tip in the dry-season, and A. lopezi parasitism averaged at 38.9%. An applied research programme yielded critical insights into various determinants of A. lopezi establishment, spread and biological control efficacy. In close collaboration with national partners, research was carried out on the eventual effects of soil fertility and plant nutrition, landscape composition, and a plant’s phytopathogen infection status, amongst others. Our work shows how the host-specific A. lopezi effectively suppresses the cassava mealybug across a range of agro-climatic, biophysical and socio-economic contexts in tropical Asia, and constitutes a central component of area-wide integrated pest management (AW-IPM) for this global pest invader. This study also underlines the need for holistic, transdisciplinary approaches to (invasive) pest management, and the tangible yet (largely) untapped potential of coupling social and biological sciences to address crop protection problems in the developing-world tropics.
