Phenology, biological and cultural control of the new almond pest Eurytoma amygdali (Hymenoptera, Eurytomidae) in Spain

Aim of study: Eurytoma amygdali Enderlein (Hymenoptera, Eurytomidae), the almond wasp, is a new pest detected in Spain. Although the insect is present in Europe, in Spain no damage was detected until 2016, increasing substantially in the following years. The phenology of almond wasp and the natural enemies complex were investigated and the results of the parasitism rate and cultural control measures were analyzed. Area of study: Five Spanish provinces, important regions for almond production where E. amygdali causes serious harvest losses. Material and methods: Samples of different almond varieties were taken from ecological almond plots in the Spanish provinces of Valencia, Alicante, Albacete, Murcia and Cuenca. Main results: The first almond wasp eggs were observed at the beginning of May and completely developed larvae, early in July. Wasp flight occurred from mid-March to late May. Two natural enemies were associated with the pest, Pyemotes amygdali Çobanoğlu & Doğanlar (Acari, Pyemotidae), and Opilo domesticus (Sturm) (Coleoptera, Cleridae). Pyemotes amygdali parasitized wasp larvae, adult females and males, and Opilio domesticus fed on wasp larvae. O. domesticus was very scarce, unlike P. amygdali. In the plots with parasitized wasps, the parasitism rate ranged from 0.6% to 44% for P. amygdali. Our results suggest that sanitation measure was an important cultural pest control practice, because in the plantations where mummified almonds were removed, 96% of edible almonds were harvested, compared to 18% if mummified almonds were not removed from trees. Research highlights: Cultural control could be an important measure to control the almond wasp, because it allows biological conservation control, by preserving natural enemies present in the environment and avoid the negative effect of insecticides.