Abstract
Biological control, a globally-important ecosystem service, can provide long-term and broad-scale suppression of invasive pests, weeds and pathogens in natural, urban and agricultural environments. Following (few) historic cases that led to sizeable environmental up-sets, the discipline of arthropod biological control has—over the past decades—evolved and matured. Now, by deliberately taking into account the ecological risks associated with the planned introduction of insect natural enemies, immense environmental and societal benefits can be gained. In this study, we document and analyze a successful case of biological control against the cassava mealybug, Phenacoccus manihoti (Hemiptera: Pseudococcidae) which invaded Southeast Asia in 2008, where it caused substantial crop losses and triggered two- to three-fold surges in agricultural commodity prices. In 2009, the host-specific parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae) was released in Thailand and subsequently introduced into neighboring Asian countries. Drawing upon continental-scale insect surveys, multi-year population studies and (field-level) experimental assays, we show how A. lopezi attained intermediate to high parasitism rates across diverse agro-ecological contexts. Driving mealybug populations below non-damaging levels over a broad geographical area, A. lopezi allowed yield recoveries up to 10.0 t/ha and provided biological control services worth several hundred dollars per ha (at local farm-gate prices) in Asia’s four-million ha cassava crop. Our work provides lessons to invasion science and crop protection worldwide. Furthermore, it accentuates the importance of scientifically-guided biological control for insect pest management, and highlights its potentially large socio-economic benefits to agricultural sustainability in the face of a debilitating invasive pest. In times of unrelenting insect invasions, surging pesticide use and accelerating biodiversity loss across the globe, this study demonstrates how biological control—as a pure public good endeavor—constitutes a powerful, cost-effective and environmentally-responsible solution for invasive species mitigation.
Highlights
Biological control is a globally-important ecosystem service, and plays a pivotal role in the functioning and broader resilience of agricultural and natural ecosystems alike (Costanza et al, 1997)
When examining P. manihoti parasitism rates from a select set of sites, A. lopezi was present in 96.9% of mealybug-affected fields (n = 97) in mainland Southeast Asia, yet were only found in 27.5% sites (n = 40) across Indonesia
In Indonesia, A. lopezi was found in 22.0% fields in Lombok (n = 9) and was absent from prime growing areas in Nusa Tenggara Timur (NTT)
Summary
Biological control is a globally-important ecosystem service, and plays a pivotal role in the functioning and broader resilience of agricultural and natural ecosystems alike (Costanza et al, 1997). For US agriculture alone, insect-mediated biological control is conservatively valued at $4.5–17 billion per year, and a diverse community of natural enemies helps alleviate pressures from herbivores and other crop antagonists (Losey & Vaughan, 2006). Arthropod pests reduce agricultural productivity by 10–16% and constitute key impediments to food security and (indirectly) poverty alleviation (Oerke, 2006; Bebber, Ramotowski & Gurr, 2013). Though native pests continue to pose major problems for the world’s agriculture, non-native species are of increasing significance as a result of trade globalization and human movement (Bradshaw et al, 2016; Paini et al, 2016). Importation biological control (IBC; known as ‘classical biological control’), or the judicious selection and subsequent introduction of a specialized natural enemy
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