Effect of short periods of heat stress during early flowering period on flower development and pyrethrin accumulation in pyrethrum
Pyrethrum (Tanacetum cinerariifolium) is a relatively new agricultural crop to Australia. This is commercially grown for the extraction of natural insecticide, pyrethrin which accumulates in the flower head achenes. Pyrethrum production in Australia currently supplies more than 70% of pyrethrin to the global market. Pyrethrum production areas are predominantly in the north-west coast of Tasmania and in the Ballarat region of Victoria. Seasonal variability in pyrethrin yield was identified as a significant problem for the pyrethrum industry in Australia. The average yield per unit area across all Tasmanian and Ballarat sites has varied significantly between seasons. Temperature effect is the main difference in Tasmanian versus Ballarat climates, including effects of heat shock. Short periods of very high temperatures (>35°C) are common during the two critical months of flowering period in pyrethrum growing areas around Ballarat. This study was designed to determine the effects of a short period of heat stress applied during early flowering period on flower development and pyrethrin accumulation in pyrethrum. Plants were exposed to a short (3 days) period of moderate heat stress (35°C maximum for 6 h each day) and severe heat stress (35°C maximum for 12 h each day) during early flowering period. Responses of flower development, pyrethrin accumulation and related plant physiological responses to heat stress were monitored and the results were compared with controls maintained at 21/12°C day/night. Exposure to short periods of heat stress during the early stages of flowering period significantly reduced flower yield and pyrethrin yield plant-1 compared to control treatments. Optimum favorable temperatures for flower development significantly reduce the rate of flower development resulting in longer flowering period and higher pyrethrin yield flower-1 due to higher rate and duration of pyrethrin accumulation.
Suraweera, D.D., Nicolas, M.E. and Groom, T. (2016). Effect of short periods of heat stress during early flowering period on flower development and pyrethrin accumulation in pyrethrum. Acta Hortic. 1125, 121-128
achene, flower head, insecticide, physiological responses, seasonal variability