Continental-scale suppression of an invasive pest by a host-specific parasitoid underlines both environmental and economic benefits of arthropod biological control

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.

Geographic distribution of the invasive mealybug Phenacoccus manihoti and its introduced parasitoid Anagyrus lopezi in parts of Indonesia

“…The field survey of P. manihoti and A. lopezi was carried out during the dry season of 2017 (October-November) and 2018 (September-October) in 80 cassava fields in Lampung (n = 11 fields), Banten (n = 9 fields), West Java (n = 9 fields), Central Java (n = 9 fields), East Java (n = 12 fields), West Nusa Tenggara (n = 9 fields), and East Nusa Tenggara (n = 21 fields). Survey protocols followed those that have been used in the region (Graziosi et al 2016;Wyckhuys et al 2018a;Le et al 2018), and was focused on cassava fields having characteristics of monoculture, uniform age and a continuous planting throughout the year. We selected older fields (7-10 months of age) with a minimum size of 0.25 ha in the main cassava-growing areas of each province, with individual sites located at least 1 km apart.…”

A delay differential equation model of mealybugs and green lacewings

“…When the time delay is more than the critical value, the population of mealybugs could be controlled to lie within some certain ranges and not at any specific level as we could expect to occur. In addition, our model can also exhibit a chaotic behavior which has been observed in the field data [13]. Hence, our model might be modified further to investigate the effects of biological control, insecticide or pathogen in controlling the outbreak of mealybugs in cassava fields.…”

INFLUENCE OF HOST STAGE ON OVIPOSITION, DEVELOPMENT, AND SEX RATIO OF Anagyrus lopezi (DE SANTIS) (HYMENOPTERA: ENCYRTIDAE), A PARASITOID OF THE CASSAVA MEALYBUG, Phenacoccus manihoti MATILE-FERRERO (HEMIPTERA: PSEUDOCOCCIDAE)

“…Although the population of P. manihoti had successfully been controlled by the parasitoid A. lopezi (Le et al, 2018;Thancharoen et al, 2018;Wyckhuys et al, 2018a;Wyckhuys et al, 2018b) their presence in the newly infested region posed a potential threat to food security (Yonow et al, 2017). For example, P. manihoti had been spreading into the islands of Timor and Flores, but A. lopezi had not yet been found in these islands (Wyckhuys et al, 2018a;Fanani et al, 2019). Therefore, it would be necessary to introduce the parasitoids into the newly infested regions.…”

“…The pest was accidentally introduced into Africa in the early 1970s (Bellotti et al, 2012) and Asia in 2008 (Winotai et al, 2010;Parsa et al, 2012;Graziosi et al, 2016). In Indonesia, the pest was first detected in Bogor in 2010 (Muniappan et al, 2009), and since then has spread throughout the regions of Java and Lampung (Abduchalek et al, 2017) and eastern Indonesia (Wyckhuys et al, 2018a;Fanani et al, 2019). Severe attacks had caused yield losses of up to 80% in Africa (Bellotti et al, 2012) and 40-50% in Asia (Wyckhuys et al, 2018b).…”