PS 20-21 - The use of floral strips increases floral visits by wild insects, mainly, Coleoptera and improves fruit set in cherimoya orchards in Central Chile.

Abstract: Recent decades have witnessed a sharp decline in the richness and abundance of pollinators, threatening the stability of the pollination service in crops. One way to deal with pollinator loss is to incorporate flower strips into orchards, as studies have shown. A crop highly dependent on pollination by wild insects is cherimoya (Annona cherimolla Mill.) This crop is not pollinated by Apis mellifera, but by small insects, mainly Coleoptera. In Chile, cherimoya is grown conventionally, and the soil is generally kept free of herbaceous plants, which is probably the reason for the low abundance of floral visitors. Therefore, it is usually manual pollination, which represents 50% of production costs. Thus, our goal was to evaluate the use of floral strips to increase the richness and abundance of floral visitors and fruit set in cherimoya.
The study was carried out in three cherimoya orchards in central Chile. In each orchard, a sector was delimited in which we established flower strips and another sector without it. The flower strips were established in the spring of 2019 and were a mix of seeded ornamental flowers and free-growing herbaceous flower. Floral visitors sampling was performed in all three orchards during cherimoya bloom flowering in 2020 and only in one orchard in 2021, as the other two orchards were affected by drought. The number of visits of each morpho-species of floral visitors and the number of flowers and fruit set on 3 twigs per tree was counted. Data were analysed with generalized linear mixed models (GLMMs) in R, with flower strips treatment as a fixed factor and orchards and trees as random factors.
We found 9 species of beetles visiting cherimoya flowers (6 native, 1 endemic and 2 exotics). The richness and abundance of floral visitors and fruit set were greater in the treatment with floral strips than without flower strips. Although the fruit set was higher with the presence of floral strips, studies are needed to test whether this can replace hand pollination of cherimoya. For now, our study only suggests that the incorporation of flower strips can complement hand pollination. However, it is necessary to design flower strips that are more resistant to drought.