Biological control of an agricultural pest protects tropical forests

K A G Wyckhuys,K A G Wyckhuys,K A G Wyckhuys,K A G Wyckhuys,J-P Deguine,L Reymondin,A C Hughes,A C Johnson,C Buamas,D Sheil,L Vasseur,L Vasseur,L Vasseur

doi:10.1038/s42003-018-0257-6

Abstract

Though often perceived as an environmentally-risky practice, biological control of invasive species can restore crop yields, ease land pressure and thus contribute to forest conservation. Here, we show how biological control against the mealybug Phenacoccus manihoti (Hemiptera) slows deforestation across Southeast Asia. In Thailand, this newly-arrived mealybug caused an 18% decline in cassava yields over 2009–2010 and an escalation in prices of cassava products. This spurred an expansion of cassava cropping in neighboring countries from 713,000 ha in 2009 to > 1 million ha by 2011: satellite imagery reveals 388%, 330%, 185% and 608% increases in peak deforestation rates in Cambodia, Lao PDR, Myanmar and Vietnam focused in cassava crop expansion areas. Following release of the host-specific parasitoid Anagyrus lopezi (Hymenoptera) in 2010, mealybug outbreaks were reduced, cropping area contracted and deforestation slowed by 31–95% in individual countries. Hence, when judiciously implemented, insect biological control can deliver substantial environmental benefits.

Highlights

Though often perceived as an environmentally-risky practice, biological control of invasive species can restore crop yields, ease land pressure and contribute to forest conservation
Our surveys, conducted across mainland Southeast Asia between 2014 and 2017 (i.e., 6–9 years and 5–8 years following the initial P. manihoti detection and A. lopezi introduction, respectively), showed that P. manihoti was present in 37.0% of the fields (n = 549) and comprised 20.8% abundance within a speciose mealybug complex[18] (Fig. 1)
In low-input, smallholder-managed systems, parasitism varied between 17.1 ± 14.8% (n = 18; Ba Ria Vung Tau – BRVT, Vietnam) to 46.7 ± 27.8% in central Cambodia (n = 10)

Summary

Introduction

Though often perceived as an environmentally-risky practice, biological control of invasive species can restore crop yields, ease land pressure and contribute to forest conservation. Modern biological control, centered on a careful selection and subsequent introduction of a specialized natural enemy (obtained from the pest species’ region of origin), can offer an effective solution for invasive species problems[11]. This approach is useful in smallholder farming systems in the tropics, as biological control is self-propagating and requires little involvement from local stakeholders[12]. One response was the 2009 introduction of the host-specific parasitoid wasp Anagyrus lopezi De Santis

Methods

Results

Conclusion