Ecology, invasion history and biodiversity-driven management of the coconut black-headed caterpillar Opisina arenosella in Asia

Abstract

The coconut black-headed caterpillar (BHC), Opisina arenosella Walker (Lepidoptera: Xyloryctidae) is an important herbivore of palm trees that originates in South Asia. Over the past decades, O. arenosella has spread to several countries in Eastern and Southeast Asia. BHC larval feeding can cause severe defoliation and occasional plant death, resulting in direct production losses (e.g., for coconut) while degrading the aesthetic value of urban and rural landscapes. In this review paper, we systematically cover taxonomy, bio-ecology, invasion history and current management of O. arenosella throughout Asia. Given that O. arenosella is routinely controlled with insecticides, we equally explore options for more sustainable management through agroecological and biodiversity-based tactics e.g., cultural control or biological control. Also, recent advances in chemical ecology have unlocked lucrative opportunities for volatile-mediated monitoring, mating disruption and mass-trapping. Substantial progress has been made in augmentation biological control, with scheduled releases of laboratory-reared parasitoids lowering BHC infestation pressure up to 95%. Equally, resident ants provide 75-98% mortality of BHC egg masses within the palm canopy. Biological control has been effectively paired with sanitary measures and good agronomy (i.e., proper fertilization, irrigation), and promoted through participatory farmer training programs. Our comprehensive listing of non-chemical preventative and curative tactics offer bright prospects for a more environmentally-sound, biodiversity-driven mitigation of a palm pest of regional allure.

Keywords: agroecology; biological control; coconut black-headed caterpillar; crop protection; ecological intensification; invasion biology; natural enemies.

Figure 1

BHC larval and pupal abundance following augmentative releases of Habrobracon hebetor and Chouioia cunea in a coconut plantation. The following release rates were adopted: C. cunea were released at 10,000 individuals and H. hebetor at 5,000 individuals every two weeks. Releases were only conducted during January-June 2018 in Baodao village, Danzhou City, Hainan, China. Average BHC larval and pupa abundance (± SEM) per coconut tree is plotted on a monthly basis for the entire year (Wu, 2019). (A, B) (GLMM poisson,***p < 0.001). The abundance values are expressed per tree. The error bars are SE. The lines are loess curve line. (C) Linear regression captures the relationship between temperature and quantity (R² _non-release=0.45, p <0.001; R² _release=0.23, p = 0.55). (D) Linear regression explains the correlation between temperature and quantity (R² _non-release=0.41, p <0.001; R² _release=0.21, p = 0.89).

Figure 2

Potential geographic distribution of Opisina arenosella as predicted through climate-based niche modeling. Suitable areas are delineated using Maxent (Phillips and Dudik, 2008), using occurrence records drawn from Lyu et al. (2018), Wu (2019), and the Centre for Agriculture and Bioscience International (CABI; www.cabi.org). Nineteen bioclimatic variables, averaged over 1950-2000 and with a spatial resolution of 2.5 arc min (c. 5 km), were downloaded from the WorldClim database (http://www.worldclim.org). A digital elevation model at 1 km² (∼30 arc s) resolution was obtained from the National Geophysical Data Center (www.ngdc.noaa.gov).