Optimizing pyrethrum planting dates to enhance productivity in a changing climate: A case of southern Highlands in Tanzania

Pyrethrum has excellent potential for growing and industrial production in Tanzania, offering an environmentally friendly alternative to synthetic pesticides and reducing pest and disease incidence without altering the natural balance. Planting date and seeding rate are critical for the productivity of pyrethrum; however, farmers in recent years have been experiencing climate change, resulting in unreliable planting periods. This study seeks to optimize the planting date for increased crop production. The study was conducted in the Umalila Highlands in the Mbeya region, with demonstration plots established in three villages (Iyunga Mapinduzi, Santilya, and Pashungu) and planted at monthly intervals from January to April. A randomized complete block design with three replications was used. The highest flower yield was achieved with early planting dates, particularly in January, with yields progressively decreasing from February to April. Sowing in January produced a yield of approx. 550 kg ha-1, significantly more than the April control with approx. 122 kg ha-1. The survival rate of Pyrethrum plants was highest at about 75% when planted in January and decreased to 72% in February, 67% in March and 57% in April. Pyrethrum planted in January had the most significant plant height, rosette size, and number of stems at all three sites, while April plantings had the worst performance and higher disease scores. Positive correlations were observed between yield and plant traits, such as height, rosette size, and number of stems, with negative correlations between yield and disease scores.
The study shows that planting pyrethrum in January results in the highest flower yields, optimal plant growth, and survival rates, with yields progressively decreasing in the later months and disease incidence increasing. It is recommended that pyrethrum farmers in the southern highlands of Tanzania plan pyrethrum planting in January to maximize yield, plant health, and profitability.