بررسی زمان و الگوی رسیدگی بذر علف‌هرز مهاجم دودندان (Bidens subalternans DC.) در باغات استان فارس

Greater beggarticks (Bidens subalternans) is one of the new invasive and problematic weeds in the gardens of some areas of Fars province. This plant spreads by barbs on the awns seed and sticking to human clothes or wool and animal hair (Ectozoochory). Investigating the time and pattern of seed ripening of this weed can help to prevent and reduce its seed production and reduce its spread in new areas. In 2023, the pattern of flowering and seed production of this weed was investigated in two regions with different climates in the cities of Eqlid (cold climate) and Marvdasht (temperate climate) in pomegranate garden (two hectares), 195 km away from each other by sampling 40 plants. At the time of observing the first flowering with two-week intervals (2, 4, 6 and 8 weeks after the appearance of the first flower), the number of five plants was randomly selected and the capitula in the bud stages, the beginning of flowering, the beginning of seeding, the average number of seeds produced by the plant and the height of the plant were counted based on descriptive statistics. The results of this study showed that the lack of ripening and simultaneous opening of the capitula in greater beggarticks causes intermittent seed production in this plant from the beginning of flowering (late August) to two months after that, which highlights this point. It can be considered as a mechanism in the success of greater beggarticks. The average number of capitula with ripe or ripening seeds in two, four, six and eight weeks after the beginning of flowering in Marvdasht is 0.2, 2.5, 5.7 and 17.3 respectively and in Eqlid was 1.4, 4.9, 19.3 and 32.8 respectively. The average number of seeds produced in each capitula in Marvdasht and Eqlid regions was 42 and 35.66, respectively. According to the number of capitula produced by the plant and the average seed production per capitula, the number of weed seeds produced in each plant varied from 1037 to 4679 and on average 2864 seeds were estimated. The height of the plant is considered as an important feature in the competition of weeds with nearby plants and the results of this study showed that the average height of the plant at the time of ripening of the greater beggarticks plant in the pomegranate garden of Marvdasht and Eqlid was 134.4 and 121.8 respectively. According to the obtained results, greater beggarticks as a weed with competitive characteristics through tall plant height, large number of seeds and ectozoochory dispersal mechanism has a high potential to infect new areas and spread. Regarding its management by preventing the production of seeds, it should be fought with appropriate methods until the time before flowering.