# Wanted egg parasitoids: Ooctonus vulgatus parasitizes Philaenus spumarius in Corsica and is probably widely distributed in Europe

Xavier Mesmin, Marguerite Chartois, Guénaëlle Genson, Jean-Pierre Rossi, Astrid Cruaud, Jean-Yves Rasplus

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Xavier Mesmin, Marguerite Chartois, Guénaëlle Genson, Jean-Pierre Rossi, Astrid Cruaud, et al. "Wanted egg parasitoids: Ooctonus vulgatus parasitizes Philaenus spumarius in Corsica and is probably widely distributed in Europe." 3rd European conference on Xylella fastidiosa and XF-ACTORS and final meeting, Apr 2021, Online Event, France., 10.5281/zenodo.4680103. hal-03844595

HAL Id: hal-03844595

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Submitted on 16 Nov 2022

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# Wanted egg parasitoids:
Ooctonus vulgatus parasitizes
Philaenus spumarius in Corsica and
is probably widely distributed in
Europe

Mesmin X.; Chartois M.; Genson G.; Rossi J.-P.; Cruaud A.; Rasplus J.-Y

CBGP, INRAE, CIRAD, IRD, Montpellier SupAgro, Univ Montpellier, Montpellier, France
# INTRODUCTION – MATERIALS & METHODS

Although this research field has been overlooked, **vector biological control** could be an interesting environmentally friendly lever to help **lower vector density**. Ultimately, it could slow down *Xylella fastidiosa* propagation.

## M&M

- 5-10 handfuls of 8 **top branches of Cistus monspeliensis** collected per site.

- Sample collection in **Corsica** in early **February**.

- **2019** (4 sites) and **2020** (5 sites), total of **1107 eggs**.

- Leaf cuttings with **P. spumarius eggs** set on moistened filter paper inside Petri dishes (Fig. 1).

- Daily monitoring of **insect emergence**.

<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

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<figure><img src="image_7.png" /><figcaption>Fig. 1 Illustration of the hatching experiment set to identify emerging insects and quantify parasitism rates of *Philaenus spumarius*</figcaption></figure>
## OOCTONUS VULGATUS PARASITIZES PHILAENUS SPUMARIUS WITH VARIABLE PARASITISM RATES THROUGHOUT CORSICA

Morphological and molecular identifications converge on:

*Ooctonus vulgatus* Haliday, 1833
(Hymenoptera, Mymaridae)

<figure><img src="image_8.png" /><figcaption>Fig. 2 *Ooctonus vulgatus*, habitus</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 3 Parasitism rates of *P. spumarius* by *O. vulgatus*</figcaption></figure>

**Parasitism rates** are highly variable and range from 0 % (2 sites) to 69 %
SPECIES DISTRIBUTION MODELS PREDICT THAT THE
PARASITOID IS WIDELY DISTRIBUTED IN EUROPE

M&M

Species distribution models
fitted on all available
occurrences of *O. vulgatus*
(Fig. 4) to **predict habitat
suitability of this
parasitoid in Europe.

<figure><img src="image_10.png" /><figcaption>Fig. 4 Occurrences of *O. vulgatus*
used to predict habitat suitability</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Fig. 5 Predicted habitat suitability of *O. vulgatus* in Europe</figcaption></figure>

- *O. vulgatus* occurs or is likely to occur in **many** EU regions where **P. spumarius** also occurs (Fig. 5).

- **Mass release** could **increase** natural parasitism rates of eggs of *P. spumarius*.
# EGG PARASITOIDS ARE PROMISING BIOCONTROL AGENTS

* Known *P. spumarius* natural enemies include **egg parasitoids**, **adult parasitoids** <fnref n="1" /> and **adult predators** <fnref n="2" />

* Egg parasitoids have a unique combination of features that probably makes them promising biocontrol agents for **inundative vector control**:

They kill the pest **before the adult stage**

<figure><img src="image_12.png" /></figure>

**Short term effect** on vectors (and on Xf propagation if parasitism is massive) are expected

Host **eggs** are **immobile**

<figure><img src="image_13.png" /></figure>

Inundative release can be **restricted to egg laying sites** which increases practical feasibility and reduces costs

Egg parasitoids usually exhibit a **high level of specialization**

<figure><img src="image_14.png" /></figure>

**Side effects** on the local entomofauna are **unlikely**

Provided that host specificity is confirmed and that mass rearing is possible, *O. vulgatus* could contribute to **IPM of P. spumarius**, and more generally, of Xf pathosystem

## References:

<footnote n="1">¹ G. Molinatto et al., *Insects*. **11**, 607 (2020)</footnote>

<footnote n="2">² A. Liccardo, A. Fierro, F. Garganese, U. Picciotti, F. Porcelli, *PLOS ONE*. **15**, e0232363 (2020). Part of the work presented in this poster is published in X. Mesmin et al., *PeerJ*. **8**, e8591 (2020).</footnote>