Managing flower-visiting insects is essential in Castanea: Enhance yield while ensuring quality

Abstract

The role of insects in the agriculture of plants that can rely on wind for successful pollination has been a mystery. We studied the contributions of wind-, insect-, and self-pollination in Castanea henryi (which can receive fruits relying on the wind). The fruit set under open pollination was significantly higher than other treatments. Insects contributed 40% of fruit by their indirect or direct pollination and did not decrease fruit quality. When the stigma was receptive, floral fragrance attracted numerous insects to visit male flowers and carry pollen; however, insects rarely visit female flowers and hardly transport pollen by contacting the stigma. The flower-visiting insects density was positively correlated with air pollen density. Therefore, insects, as facilitators of wind pollination, enhance orchard fruit production. Not emphasizing the importance of wind pollination to chestnut but reminding us that insect management is also extremely important for the agriculture of plants that can be harvested by the wind.

Keywords: Agricultural science; Horticulture; Interaction of plants with organisms.

Graphical abstract

Figure 1

Castanea henryi description (A and B) branches at flowering; (C) male-only inflorescences; (D) mixed inflorescences; (E) fruits.

Figure 2

Effects of wind-, insects- and self-pollination on the chestnut fruit set (A) fruit sets of different pollination treatments; (B) the contribution rates of wind, insects, and self-pollination in 2018 and 2019; (C) influence of mesh bag (40 mesh size) on wind speed. CK stands for natural treatment, T1 for treatment excluding insects, and T2 for self-crossing. The different letters indicate significant differences at p < 0.05. Data are represented as mean ± SEM.

Figure 3

Quality of nuts harvested from three treatments in 2018 and 2019 (A) nut weight; (B) transverse diameter; (C) longitudinal diameter; (D) water content; (E) Reducing sugar content; (F) soluble sugar content; (G) starch content; (H) sucrose content. CK stands for natural treatment, T1 for treatment excluding insects, and T2 for self-crossing. The different letters indicate significant differences at p < 0.05. Data are represented as mean ± SEM.

Figure 4

The relationship between insects and flowers (Ⅰ) flower-visiting insects (A–O) and the number visiting male vs. female flowers (a–o); (Ⅱ) pollen load of six species of insects with visiting number greater than 50 and frequent contact with female flower stigma; (Ⅲ) the attractive ability of floral substances to insects.∗∗ indicate significant differences at p < 0.01, ∗∗∗ indicate significant differences at p < 0.001. Data are represented as mean ± SEM.

Figure 5

The relationship between visitors, wind speed, and air pollen density (A) air pollen density, flower-visiting insect density, and wind speed for Castanea henryi, (B) the correlation analysis of each factor. Data are represented as mean ± SEM.