Catch me if you can: is bagrada bug able to escape its parasitoid?

Authors: MARTEL, GUILLAUME - Montpellier Supagro – International Center For High Education In Agricultural Sciences; SFORZA, RENE - European Biological Control Laboratory (EBCL)

Submitted to: International Insects Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/5/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Originating from Asia and Africa, the pentatomid bug Bagrada hilaris Burmeister (Hem.: Pentatomidae) was firstly reported in California in 2008. This severe invasive pest of crucifer crops is now expanding to several southern U.S. states and South America. We recently described the basic life history traits of Gryon gonikopalense Sharma (Hym.: Scelionidae), an egg parasitoid evaluated as a candidate for a biological control program against B. hilaris. With an average fecundity of 60 progenies over a lifespan of more than a month, the parasitoid looks efficient to control the pest. Nevertheless, in its environment, B. hilaris exhibit a unique oviposition behaviour among the Pentatomidae: females lay their eggs individually and can naturally bury them in the soil, which must limit access for predators. An issue therefore remains: How does G. gonikopalense deals with these buried eggs? Does it affect its development or its parasitism rate? We present here the first record of a parasitoid able to attack buried B. hilaris eggs since the first description of parasitoids emerging from the soil in India in 1949. Depending on the foraging time allowed, the parasitoid reaches 75% success, though the number of parasitized eggs is lower than with non-buried eggs. The emergence rate of the parasitoid progeny is 87% on average, similarly to eggs without sand. Interestingly, G. gonikopalense is also able to find eggs manually buried under clean sand, though the success rate is only 22% which indicates a high level of host eggs detection. Furthermore, we show that this behavior should be relevant against B. hilaris as the pest can lay over 80% of its eggs in the soil under laboratory conditions, depending on its host plant and its population density. Our first investigations show that the parasitoid would therefore get access to 100% of its host locations, increasing its impact on the pest. However, considering that the soil limits the host access for the parasitoid, it is likely that the choice between «free eggs» and «buried eggs», would depend on several biotic and abiotic factors that remains to describe.