Landscape context does not constrain biological control of Phenacoccus manihoti in intensified cassava systems of southern Vietnam

T. T.N. Le, I. Graziosi, T. M. Cira, M. W. Gates, L. Parker, K. A.G. Wyckhuys

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

In 2008, the cassava mealybug, Phenacoccus manihoti (Homoptera: Pseudococcidae) was inadvertently introduced to Southeast (SE) Asia, where it inflicted severe damage on cassava crops, and impacted countless farming families and rural agro-industries. The host-specific endophagous parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae) was imported into Thailand in 2009, and subsequently released in neighboring countries. At present, nothing is known about the degree to which A. lopezi establishment, in-field colonization and impact on P. manihoti populations is shaped by local agro-landscape context. In this study, we contrasted temporal population fluctuations of P. manihoti, A. lopezi, and associated hyperparasitoids within low- and high-diversity landscapes in Tay Ninh (Vietnam). Across years and landscape types we found 24.8 ± 17.7% (mean ± SD) plants infected with P. manihoti and on average 5.6 ± 5.3 mealybugs per cassava tip. High parasitism levels were attained across both years, with season-long averages of 49.9–52.1% in either low- or high-diversity settings. Hyperparasitism levels were on average 2.8 ± 5.4%, and a total of three hyperparasitoid species were recorded. Cassava age was a significant predictor of P. manihoti incidence, abundance, parasitism rate and hyperparasitism rate. Landscape type significantly affected P. manihoti incidence and hyperparasitism rate (at particular ages), but not P. manihoti abundance or parasitism rate. At the scale of individual cassava tips and entire fields, A. lopezi exhibited a strong density-dependent response to P. manihoti during the early season. This work constitutes the first, comprehensive assessment of A. lopezi establishment, parasitism rates, and parasitoid x host dynamics from a key cassava-growing region in SE Asia. Our study underlines how this exotic parasitic wasp effectively suppresses a globally-important insect pest in its newly invaded range, thus providing cost-free, environmentally-sound and lasting control across the developing-world tropics.

Original languageEnglish (US)
Pages (from-to)129-139
Number of pages11
JournalBiological Control
Volume121
DOIs
StatePublished - Jun 2018

Bibliographical note

Funding Information:
This manuscript presents original datasets that result from collaborative research, with trials jointly conceptualized, defined and executed by Vietnamese counterparts, CIAT personnel and international cooperators. We would like to thank Drs. Nguyen Van Liem, Trinh Xuan Hoat and Le Xuan Vi at Vietnam’s Plant Protection Research Institute (PPRI-VAAS), for their support to field staff and for facilitating this 2-year insect survey. We are grateful to collaborators from Hung Loc Research station and staff from the Provincial office of Vietnam’s Plant Protection Department (PPD-MARD) in Tay Ninh for facilitating access to a field laboratory and providing backstopping to site selection, grower interactions and insect sampling. A short-term stay of Dr. Theresa Cira was facilitated by an Interdisciplinary Center for the Study of Global Change (ICGC) Global Food Security Fellowship and a Graduate School Thesis Research Travel grant from the University of Minnesota – United States. This initiative was conducted as part of an EC-funded, IFAD-managed, CIAT-executed programme (CIAT-EGC-60-1000004285), with additional funding through the CGIAR Research Program on Roots, Tubers and Banana (CRP-RTB).

Keywords

  • Arthropod biological control
  • Ecosystem services
  • Landscape fragmentation
  • Landscape simplification
  • Natural enemy
  • Tropical agriculture

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