Anticipating the arrival of a new stinkbug pest in continental Europe: what can we learn from preliminary host specificity tests for biocontrol?

Authors: MARTEL, G - National Association Of Hazelnut Growers; Hogg, Brian; SFORZA, R - European Biological Control Laboratory (EBCL)

Submitted to: Entomologia Generalis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Bagrada bug or painted bug is reported as a pest of cole crops in its native range of eastern and southern Africa and the Indian subcontinent. In 2008, it was first reported in California, where it now attacks a wide range of Brassicaceae crops, including cabbage, broccoli, and radish. The bug has spread to New Mexico, Mexico, Hawaii, and Chile. Bagrada is also considered a pest in the Meditereanen basin, especially on islands. To date, no efficient monitoring tools exist to long-term manage Bagrada bug populations in North America. The massive economic loss and the lack of alternative control practices, led U.S. growers to use broad-spectrum insecticides to reduce local pest populations. As new insecticides have been shown to be less effective on crucifer crops, a program on classical biological control based on foreign exploration in the native range has been initiated in 2016. Several parasitoid wasps of Bagrada were collected in Pakistan are now under investigation at USDA-ARS-EBCL, especially the egg parasitoid G. aetherium. The aim of the present study was to evaluate the specificity of the Bagrada egg parasitoid over a range of possible non target stink bug species either natives of pests in the Mediteranean basin. This approach is of major concern for evaluating this egg parasitoid before considering its introduction into Europe as a classical biocontrol agent. The results showed that four non-target pentatomid species over the 11 tested were in the physiological host range of the egg parasitoid. As most of non-target species tested in our study are absent from the USA, we also expect our results to complement host specificity tests conducted in California with North American pentatomids

Technical Abstract: The egg parasitoid Gryon aetherium (formerly Gryon gonikopalense) is a promising candidate for biocontrol of the bagrada bug, Bagrada hilaris Burmeister (Hemiptera: Pentatomidae), in the Southwestern USA. Bagrada bug is a worldwide invasive pest of crops in the family Brassicaceae. In the present study, we aim to evaluate the parasitoid’s host range in the European range of bagrada: the Mediterranean basin. These tests should complement those currently being performed in California and provide risk information of a release of G. aetherium in southern continental Europe where bagrada could spread in the future. The results showed that four non-target pentatomid species over the 11 tested were in the physiological host range of G. aetherium, with parasitism rate ranging from 21.8 % to 61.3 %: Carpocoris mediterraneus, Dolycoris baccarum, Graphosoma italicum and Ancyrosoma leucogrammes. However, parasitism rates on these four non-target species were lower in choice than in no-choice conditions with a maximum of 26 %. Surprisingly, the three Eurydema spp. that belong to the same tribe as bagrada bug (Strachiini) and feed on plants in the family Brassicaceae were not parasitized. No parasitism was observed on the cosmopolitan invasive pentatomid Nezara viridula and Halyomorpha halys, nor on the rhopalid Liorhyssus hyalinus. The adult parasitoid size was correlated with host egg size. Parasitoids from non-target species were larger than ones developing on B. hilaris and took more time to complete development. The likely consequences of releasing G. aetherium in Mediterranean basin are discussed regarding the parasitized species A. leucogrammes and C. mediterraneus which are restricted to this region. The parasitism of non-target species is also discussed regarding the specialized foraging behavior of G. aetherium on buried B. hilaris eggs.