Identification, bioecology, and mass rearing of Comperiella Calauanica Barrion, Almarinez & Amalin (Hymenoptera: Encyrtidae), a native endoparasitoid for the management of the coconut scale insect, Aspidiotus rigidus Reyne (Hemiptera: Diaspididae)

• Main Author: Almarinez, Billy Joel Mondragon
• Format: text
• Language: English
• Published: Animo Repository 2016
• Subjects: Pests > Control > Philippines; Aspidiotus destructor; Parasitoids; Scale insects; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/1187
• Institution: De La Salle University

The invasive coconut scale insect, Aspidiotus rigidus Reyne, devastated coconut plantations and stands in Southern Luzon, Philippines from 2010 to 2014. This outbreak severely impaired production in the coconut-producing areas, and led to the declaration of a state of national emergency in the mid-2014. During the peak of the pest outbreak and earlier during April of the same year, a tiny parasitoid wasp was discovered and was subsequently identified as belonging to the encyrtid genus Comperiella Howard. It was found that this encyrtid not only was a primary endoparasitoid of A. rigidus and the first native record of the genus in the Philippines, but also represents a new species due to a number of morphological features that distinguish it from other Comperiella spp. The parasitoid was later named C. calauanica after Calauan, Laguna, its type-locality. Initial field observations suggested the potential of C. calauanica as a candidate biological control agent against A. rigidus. It then became imperative that baseline information on the proper taxonomic identity, biology and ecology, and prospects for mass rearing be established in view of augmentation and conservation of C. calauanica as a biological control agent for integrated pest management. In this project, a taxonomic study which involved a very detailed morphological and morphometric examination of C. caluanica was carried out. A number of morphological and morphometric characters were found to be very different from those of other Comperiella spp., sufficient to warrant the identification of C. calauanica as a completely new species. C. caluanica is the first native Comperiella species in the Philippines and only the eleventh species described under this genus since it was established in 1906. The series of field and laboratory studies conducted herein also revealed important insights and baselines on the biology and ecology of C. calauanica and its host, A. rigidus, in the Philippines. The parasitoid's holometabolous development completed in about 21 to 22 days. A facultative thelytokous parthenogenetic mode of reproduction was confirmed. Likewise, its behavior and association with another insect species apart from its diaspidid host were examined and described. The reportedly high degree of field parasitization of A. rigidus by C. calauanica was also validated across three periods, with average percent parasitization values ranging from 44.9 to 92.4% in August 2014, 57 to 92.6% in December 2014 to January 2015, and up to 96.5% in June 2015. Host density-dependent parasitism, a hallmark of an effective biological control agent, was likewise found. These findings on the parasitism of C. calauanica on A rigidus were coincident with the recovery of coconut palms in the sampling points and areas that did not receive any emergency treatment including systemic pesticide application, suggesting the putative role of the parasitoid in the observed decline in the abundance of A. rigidus in Southern Luzon. Establishment of A. rigidus was found to be highest in a differential host plant, Garcinia mangostana L., and more satisfactory on butternut squash as compared to the native variety as substrate for indoor mass rearing. Both the seedlings of G. mangostana and squash fruits were found to be able to sustain at least two generations of A rigidus. The important baselines derived from the laboratory and field studies were subsequently used as basis to develop a mass rearing protocol for A. rigidus and C. calauanica for conservation and augmentation in areas of future pest invasion.