Effective biological control of an invasive mealybug pest enhances root yield in cassava

Insects provide critical ecosystem services to humanity, including biological control of pests. Particularly for invasive pests, biological control constitutes an environmentally sound and cost-effective management option. Following its 2008 invasion of Southeast Asia, biological control was implemented against the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae) through the introduction and subsequent release of the host-specific parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae) in Thailand. In this study, we quantify yield benefits of mealybug biological control in Thailand's cassava crop by using two different types of manipulative field trials: i.e., 'physical exclusion' cage trials and field-level 'chemical exclusion' assays. In cage trials with two popular cassava varieties, root yield and total dry matter (or 'biological yield') were a respective 4.0-4.2 times and 3.5-3.9 times higher in the presence of biological control. Extrapolating results from cage trials, biological control thus ensured an approximate yield gain of 5.3-10.0 T/ha for either variety. Under chemical exclusion trials, P. manihoti populations attained levels of 3266 +/- 1021 cumulative mealybug-days (CMD) over a 10-month time period, and no longer impact yields. Moreover, under effective P. manihoti control, both root yield and biological yield increased with season-long CMD measures, and pest management interventions-including insecticide sprays-led to notable reductions in yield. This study is the first to show how biological control effectively downgrades the globally invasive P. manihoti to non-economic status and restores yields in Thailand's cassava crop. Our work emphasizes the economic value of biological control, reveals how current P. manihoti populations do not necessarily cause yield penalties, and underlines the central importance of nature-based approaches in intensifying global agricultural production

Firefly tourism: Advancing a global phenomenon toward a brighter future

10.1111/csp2.391Conservation Science and Practice3

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

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

International scientists formulate a roadmap for insect conservation and recovery

Plant science