Molecular identification of mealybug species (Hemiptera: Pseudococcidae) affecting Theobroma cacao for improved pest management

Authors: Puig, Alina; Wurzel, Sarah; SUAREZ, STEPHANIE - Mars, Inc; NIOGRET, JEROME - Mars Australia; MARELLI, JEAN-PHILIPPE - Mars, Inc

Submitted to: Entomology International Congress Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2021
Publication Date: 6/30/2021
Citation: Puig, A.S.; Wurzel, S.; Suarez, S.; Niogret, J.; Marelli, J.-P. Molecular identification of mealybug species (Hemiptera: Pseudococcidae) affecting Theobroma cacao for improved pest management. In Proceedings of the 1st International Electronic Conference on Entomology, Online, 1–15 July 2021; MDPI: Basel, Switzerland, 2021, doi:10.3390/IECE-1039 DOI: https://doi.org/10.3390/IECE-10399
DOI: https://doi.org/10.3390/IECE-10399

Interpretive Summary: Theobroma cacao is affected by viruses on every continent where it is grown commercially. Most are transmitted by several mealybug species. Mealybugs belong to a diverse group known as Pseudococcidae, and each geographic region has different species composition. Due to the specificity of commonly used biological control organisms (ex: parasitoids), effective management of mealybugs requires accurately identifying the species present. To enable more rapid identification of these important insects, scientists at the USDA-ARS (Miami, FL) collaborated with Mars Inc. to develop a molecular approach that can be completed in a few days. This study compares the usefulness of the COI, ITS2, and 28S gene regions using various primer pairs to identify mealybugs, without the need for specialized taxonomic skills. Molecular protocols are described for identifying mealybugs associated with cacao plants in North America, and detecting the presence of certain parasitoids. These results will contribute to the selection of effective pest management strategies.

Technical Abstract: Theobroma cacao is affected by viruses on every continent where the crop is cultivated, with the best-known ones belonging to the Badnavirus genus. Badnaviruses are transmitted by several species of Pseudococcidae, a large, taxonomically diverse group of insects collectively known as mealybugs. Effective management of mealybugs depends on accurate identification of species present, as even closely related species have distinct life cycles and are vulnerable to different biological control organisms. This study compares the usefulness of the COI, ITS2, and 28S markers using the primer pairs (MFCO1/MRCO1, ITS2-M-F/ITS2-M-R, D10F/D10R, and D2F/D2R) to identify mealybugs associated with cacao plants in North America. All markers were informative for Pseudococcus comstocki (n=4) and Maconellicoccus hirsutus (n=8), but only CO1 provided unambiguous identification for Pseudococcus jackbeardsleyi (n=11). Primer pair D2F/D2R is not recommended for mealybug identification, as it frequently yielded sequences of Anagyrus sp., an Encyrtid parasitoid wasp commonly used for biocontrol. This study describes molecular diagnostic protocols for identifying cacao-associated mealybugs and detecting the presence of certain parasitoids. This information is essential for selecting the most effective interventions as part of an integrated pest management program.