Seed pests and their effect on quality of Caragana microphylla seeds in semi-arid sandy land

Seed pests have severely hindered afforestation with and the industrial utilization of Caragana shrubs in North China. Therefore, in the initial (June 9), middle (June 18), late (June 27), and last (July 6) bearing phases of Caragana microphylla grown in Horqin Sandy Land, we investigated damage induced by seed pests in these plants while the latter were under different orientations (east, south, west, and north) and examined the effect of the damage on seed quality. Next, we analyzed the occurrence characteristics of seed pests and formulated a specific prevention measure. The results showed that there was no significant difference (P > 0.05) between the seed-set amount, pest rate, and seed quality at different plant orientations. The seed-set amount decreased significantly (P < 0.05) in the initial bearing phase and tended to stabilize in the middle bearing phase. The successful seed set rate stabilized at 89.17%. The pest rate increased sharply from 7.4% in the initial bearing phase to 19.3% in the last bearing phase before stabilizing at 22.8% in the late bearing phase. Pests reduced seed quality significantly (P < 0.05), causing the thousand-seed weight, germination rate, and germination potential to decrease by 30.7%, 17.2%, and 34.7%, respectively, but there was no significant difference (P > 0.05) between seedling emergence and germination rate. This study clarified the degree of damage caused by seed pests and occurrence characteristics of seed pests in C. microphylla, contributing to the investigation and prevention of seed pest infestation in Caragana shrubs in the arid and semi-arid areas of northern China.