Mating Disruption of the Olive Moth Prays oleae (Bernard) in Olive Groves Using Aerosol Dispensers

The olive moth (OM), Prays oleae (Bern.) (Lepidoptera: Yponomeutidae), is a major olive grove pest worldwide; however, until now, very few studies have investigated the effectiveness of mating disruption (MD) techniques against this pest. Experiments were carried out for two successive years (2019 and 2020) in three different olive groves in Andalucía (Southern Spain) to evaluate mating disruption’s efficacy in controlling the OM from the first to the third generation. The effectiveness of MD formulations against the three generations of OM was assessed by determining the percentage of infested olive fruits, the reduction of pheromone trap catches, and the number of affected inflorescences in both MD-treated and untreated control olive groves. The number of release points (one or two aerosol devices per ha) was also evaluated. In all years and trials, the mean number of males caught in traps placed in the MD-treated plots was significantly lower than untreated sites. Mating disruption registered a high suppression of male captures (>75%) in treated plots for two consecutive seasons. Concerning infested olive fruits, substantial reductions (about 80%) were observed in the MD plots of locations B and C, and a reduction of about 40% was detected in location A, compared to the control plot. Results showed that the installation of two aerosol devices/ha reduced fruit damage below 20% of infested olive fruits except for one site where a reduction of about 71% in the MD plot was recorded in 2019. Although few significant differences were associated with OM male catches and infested olive fruits between plots treated with one aerosol/ha and two aerosols/ha in most of the comparisons, significant differences in the number of olive inflorescences infested by P. oleae were found, suggesting a similar performance between the two tested aerosol densities. Results of two-year field trials in Andalucía demonstrated the potential of Mister P X841 aerosol devices as an effective tool for controlling the olive moth, P. oleae.

Ground cover presence in organic olive orchards affects the interaction of natural enemies against Prays oleae, promoting an effective egg predation

The olive moth, Prays oleae, is one of the most common insects that damages olives in the circum-Mediterranean region. The establishment of ground cover within olive orchards has been promoted in this region in recent years to avoid erosion and soil degradation. Nevertheless, its role as a shelter for natural enemies of pests has been controversial. In this study we have investigated the effectiveness of the biological control of P. oleae in organic olive orchards with ground cover (mowed) and without ground cover (tilled). For this (1) we assessed the relationship between predated eggs and the abundance of natural enemies in both types of orchards; (2) we compared both the potential damage of the pest and the egg hatching in the two types of orchards; and (3) we examined the interaction amongst families of natural enemies and P. oleae (as adults and as predated eggs). The results showed that there is a high rate of predation in the studied olive orchards, 81% of the eggs were predated, 12.2% hatched, and 6.9% were live eggs. However, mowed orchards were more effective for controlling P. oleae by means of egg predation rather than tilled orchards, i.e., in mowed orchards, whilst the potential damage of the pest was higher, egg hatching was rather low. The structure of the adult arthropod community, i.e., the composition and abundance of families of natural enemies did not differ between the orchards, but the abundance of the families Anthocoridae, Miridae and Scelionidae was significantly higher in the mowed orchards. Finally, the interaction amongst natural enemies and P. oleae showed that the families that better explained the effects on egg predation were Aeolothripidae, Anthocoridae, Miridae, Chrysopidae (predators), and Formicidae (omnivore). We discuss the results in terms of ecological interactions of trophic guilds and we conclude that the establishment and maintenance of ground cover in organic olive orchards, at least in June and July, is of great significance because it positively affects the egg predation of P. oleae. This effect is especially significant when there is a low abundance of natural enemies in the olive orchards.

Land-Use Effect on Olive Groves Pest Prays oleae and on Its Potential Biocontrol Agent Chrysoperla carnea

Olive growing has been intensified through the simplification of agricultural landscapes. In order to rethink the environmental drawbacks of these practices, conservation biological control techniques have been examined. In this work, Prays oleae and its natural enemy Chrysoperla carnea were monitored to account for the effects of the amount and diversity of different land-uses. We found that C. carnea showed an attraction to areas with high abundances of P. oleae but this predator did not display any affection by the different land-uses. Inversely, P. oleae abundance was lower in diverse landscapes and higher in simplified ones. Importantly, higher abundances of C. carnea were related to lower infestation levels of P. oleae in the late part of the season. These results corroborate the attraction of C. carnea to the olive moth, highlighting the potential of C. carnea as a biological control agent of this pest, assert that the promotion of land-use diversity can reduce P. oleae and confirm that landscapes dominated by olive groves can promote this pest. The present study aims at contributing to the discussion about the management of agricultural ecosystems by providing farmers with sustainable alternatives that do not have harmful effects on the environment and public health.

Do non-crop areas and landscape structure influence dispersal and population densities of male olive moth?

The permeability of the crop surroundings to pests and the landscape structure can influence pest dispersal between crop patches as well as its abundance within the crop. In this work, we analyzed the dispersal of the olive moth Prays oleae (Bernard) throughout the olive grove surroundings and their abundance within the crop following three approaches: (i) pollen grains settled on bodies of olive moths collected in olive groves were identified and compared with flora occurring on the surrounding patches; (ii) the capability of P. oleae males to penetrate non-crop patches was analyzed (iii) the effect of the landscape structure on the abundance of the three generations of the olive moth was studied. Pollen grains of scrubs and other trees occurring in the crop surroundings, such as Cistus sp., Quercus sp., Juniperus-type or Pinaceae were identified on P. oleae bodies suggesting that P. oleae penetrates into non-crop habitats. Additionally, woody and, to a lesser degree, herbaceous patches, did not constitute barriers for P. oleae. Finally, more complex and heterogeneous patches presented lower numbers of captures of P. oleae. These results give new insights into the movements of the olive moth in the olive grove surroundings and suggest that the management of non-crop areas could influence this pest abundance.

Hidden Genetic Variability, Can the Olive Moth Prays oleae (Lepidoptera: Yponomeutidae or Praydidae?) be a Species’ Complex?

Prays oleae is the second most important pest in Mediterranean olive groves, causing substantial damage on olive production. We used mitochondrial [cytochrome c oxidase subunit I (COI), and NADH dehydrogenase subunit 5 (nad5)] and nuclear [ribosomal protein S5 (RpS5)] amplicons to assess the population variability in five main olive producing regions from Tunisia, to support or dismiss the existence of two non-monophyletic groups within the species, as found within Portugal. Our phylogenetic analysis with cytochrome c oxidase subunit I (COI) indeed displayed two distinct and well-supported clades of P. oleae, which were corroborated by the haplotype network reconstructed with both mitochondrial and nuclear amplicons. We were also able to dismiss the hypothesis that one of the clades would not develop on olive fruits. No correlation was observed between clades differentiation and geographic distribution. The existence of cryptic species can impact on the management of agroecosystems and on the perception of how these moths responds to environmental changes.