Following the outbreak: preliminary findings on the landscape effect on Dasineura oleae and its parasitoids in Central Italy

Abstract

Dasineura oleae (Angelini, 1831) (Diptera: Cecidomyiidae), the olive leaf gall midge, is a pest of olive crops that has never been problematic in Italy since 2016, when a massive infestation of this pest was reported in a small region of Central Italy. We selected infested olive orchards through farmers’ reports aiming at quantifying the pest infestation level and the parasitism rate in each site. Also, we aimed at exploring the landscape effect in both pest and parasitoids, using proportion of olive crops and semi-natural habitats, as well as the Shannon index as a measurement of the landscape diversity, estimated at four different scales (250m, 500m, 750m and 1000m buffers around the sampling points). Results showed different landscape effect depending on the organism and on the scale. We underlined a small-scale effect on the parasitism rate and a large-scale effect on the olive leaf midge mediated by the Shannon Index. Moreover, some preliminary results showed that the parasitism rate was high in sites where plants associated with D. oleae parasitoids were present in the adjacent semi-natural habitat. Further study should deepen and validate our findings on the effect of landscape and of the vegetation on natural enemies of D.oleae. These results should stimulate new approaches in the studying of the olive gall leaf midge as well as new suppression strategies.

Climate Change and Major Pests of Mediterranean Olive Orchards: Are We Ready to Face the Global Heating?

“…Picchi et al (2021) [108] stressed the importance of pest monitoring in the outbreak areas to provide useful information concerning pest control strategies for olive growers. In this way, farmers may have an overview of pest population abundance and its natural enemies, offering the chance to study the effect of climate change on crop-pest synchrony over a long period [108].…”

“…The recent outbreaks of Dasineura oleae (Angelini) (Diptera: Cecidomyiidae) in several Mediterranean regions prompted the consideration of this gall pest as a serious threat for the olive grove [ 100 , 105 , 106 , 107 , 108 ]. Little is known about this species, since before these outbreaks it has never been assumed as problematic [ 108 ].…”

“…The recent outbreaks of Dasineura oleae (Angelini) (Diptera: Cecidomyiidae) in several Mediterranean regions prompted the consideration of this gall pest as a serious threat for the olive grove [ 100 , 105 , 106 , 107 , 108 ]. Little is known about this species, since before these outbreaks it has never been assumed as problematic [ 108 ]. However, leaves attacked by D. oleae are physiologically compromised, and premature foliar dropping is recorded when serious infestations occur, prompting yield losses to be hypothesized [ 106 , 107 ].…”

“…This may lead to an alteration of the tritrophic interaction concerning D. oleae , its parasitoids and the olive tree [ 2 ], resulting in unpredictable D. oleae outbreaks [ 2 , 100 ] ( Figure 2 ). Picchi et al (2021) [ 108 ] stressed the importance of pest monitoring in the outbreak areas to provide useful information concerning pest control strategies for olive growers. In this way, farmers may have an overview of pest population abundance and its natural enemies, offering the chance to study the effect of climate change on crop–pest synchrony over a long period [ 108 ].…”

Infestation of the gall midgeDasineura oleaeprovides first evidence of induced plant volatiles in olive leaves

“…The olive leaf gall midge, Dasineura oleae (Angelini, 1831) (Diptera: Cecidomyiidae), is an endemic monophagous species of Mediterranean countries hosted by olive trees ( Olea europaea L.) (Dogănlar et al ., 2011). In recent years, several outbreaks have been reported in the Mediterranean (Simoglou et al ., 2012; Caselli et al ., 2021; Picchi et al ., 2021). In particular, the Tuscany region (Italy) has registered a dramatic increase in infestations throughout its area, with large outbreaks recorded in Grosseto Province (i.e., Gavorrano and Capalbio) and Massa-Carrara Province since 2013 (Tondini and Petacchi, 2019).…”