Effects of Weed Control Practices on Plant Diversity in a Homogenous Olive-Dominated Landscape (South-East of Italy)

Olive groves represent an important economic, agro-ecological, and cultural resource in the Mediterranean Basin. Weed management plays a fundamental role in their sustainable management. The aim of this work was to characterize and assess the plant diversity associated with different weed control practices, in a homogeneous olive-dominated landscape in the South-East of Italy. Sixty-five vegetation plots were sampled in orchards treated with different weed control practices: mowing, tillage, and use of chemical herbicides. The multi-response permutation procedure was used to test the hypothesis of no difference among the treatments. The relationships between plots were visualized by means of non-metric multidimensional scaling ordination. A generalized linear mixed model was used to analyze the relationships between weed control practices and life forms, chorotypes, and diversity indexes. The results showed that the three weed control practices determined slightly different plant communities. Chemically weeded orchards showed an impoverished floristic composition and the lowest diversity, whereas mowing and tillage yielded similar values. These latter two treatments differed for the percentages of hemicryptophytes and therophytes. Moreover, different from other studies, we did not find plant species of particular concern for biodiversity conservation. We hypothesize that this result is due to the monotonous structure of the agro-landscape we investigated, where natural elements are almost lacking. From this point of view, a correct management of agro-districts should consider both the agronomic practices at the level of the individual olive groves and the structure of the agro-landscape.

Landscape spatial configuration is a key driver of wild bee demographics

The majority of studies investigating the effects of landscape composition and configuration on bee populations have been conducted in regions of intensive agricultural production, ignoring regions which are dominated by seminatural habitats, such as the islands of the Aegean Archipelago. In addition, research so far has focused on the landscape impacts on bees sampled in cropped fields while the landscape effects on bees inhabiting seminatural habitats are understudied. Here, we investigate the impact of the landscape on wild bee assemblages in 66 phryganic (low scrubland) communities on 8 Aegean islands. We computed landscape metrics (total area and total perimeter-area ratio) in 4 concentric circles (250, 500, 750, and 1000 m) around the center of each bee sampling site including 3 habitat groups (namely phrygana, cultivated land, and natural forests). We further measured the local flower cover in 25 quadrats distributed randomly at the center of each sampling site. We found that the landscape scale is more important than the local scale in shaping abundance and species richness of bees. Furthermore, habitat configuration was more important than the total area of habitats, probably because it affects bees' movement across the landscape. Phrygana and natural forests had a positive effect on bee demographics, while cultivated land had a negative effect. This demonstrates that phryganic specialists drive bee assemblages in these seminatural landscapes. This finding, together with the shown importance of landscape scale, should be considered for the management of wild bees with special emphasis placed on the spatial configuration of seminatural habitats.

Forward selection for multiple resistance across the non-selective glyphosate, glufosinate and oxyfluorfen herbicides in Lolium weed species

BACKGROUND

In the Mediterranean area, Lolium species have evolved resistance to glyphosate after decades of continual use without other alternative chemicals in perennial crops (olive, citrus and vineyards). In recent years, oxyfluorfen alone or mixed with glyphosate and glufosinate has been introduced as a chemical option to control dicot and grass weeds.

RESULTS

Dose-response studies confirmed that three glyphosate-resistant Lolium weed species (L. rigidum, L. perenne, L. multiflorum) collected from perennial crops in the Iberian Peninsula have also evolved resistance to glufosinate and oxyfluorfen herbicides, despite their recent introduction. Based on the LD50 resistance parameter, the resistance factor was similar among Lolium species and ranged from 14- to 21-fold and from ten- to 12-fold for oxyfluorfen and glufosinate respectively. Similarly, about 14-fold resistance to both oxyfluorfen and glufosinate was estimated on average for the three Lolium species when growth reduction (GR50 ) was assessed. This study identified oxyfluorfen resistance in a grass species for the first time.

CONCLUSION

A major threat to sustainability of perennial crops in the Iberian Peninsula is evident, as multiple resistance to non-selective glyphosate, glufosinate and oxyfluorfen herbicides has evolved in L. rigidum, L. perenne and L. multiflorum weeds. © 2016 Society of Chemical Industry.