Primary parasitoids of Aulacaspis tubercularis Newstead (Hemiptera: Diaspididae) occurring in Spanish mango orchards

Abstract

The white mango scale (WMS), Aulacaspis tubercularis, is the main pest of mango crops in Southern Spain. Field surveys were carried out from July 2019 to May 2022 to investigate the identity, seasonal abundance and active parasitism rates of A. tubercularis primary parasitoid species, using yellow sticky traps and periodic leaf sampling. The combination of morphological characters and DNA sequences of the mitochondrial cytochrome c oxidase subunit 1 (mtCOI) and 28S ribosomal (28S rDNA) genes allowed the identification of only two parasitoid species belonging to the genus Encarsia Förster (Hymenoptera: Aphelinidae). The most prevalent, E. citrina (Crawford), is a widespread species and proved to be the dominant species in the sampled mango orchards. Next, Encarsia sp., is an unidentified species genetically close to E. lounsburyi Berlese but significantly differs in the sequences of the mtCOI and 28S rDNA regions. Population abundance and active parasitism rates of Encarsia parasitoids depended on the presence of susceptible WMS stages for parasitism and on the abiotic conditions. The seasonal abundance of these parasitoid species fluctuated around the year, being lower during the winter but it increased in late spring, reaching the highest values at the end of summer. The average percentage of active parasitism was 12.48% for female scales and 13.97% for male scales but reached maximum values of 38.56 and 43.52%, respectively at specific seasons in the year. The highest rates of parasitism for female scales were observed in summer, while for male scales were observed in winter. The natural occurrence of parasitoids was unable to control the WMS populations and, consequently, complementary measures should be implemented to reduce its density levels.