Effects of calliterpenone and GA(3) on the growth, yield, and pyrethrin contents of pyrethrum [Tanacetum cinerariifolium (Trevir.) Sch Bip.] planted on different dates

Studies on the effects of calliterpenone and gibberellic acid (GA(3)) on the growth, yield, and pyrethrin contents of pyrethrum Tanacetum cinerariifolium (Trevir.) Sch. Bip.] planted on three separate dates at Lucknow, India indicated that plant height, the number of shoots per plant, the percentage of flowering plants, the number of flowers per plant, and the pyrethrin contents of flowers declined significantly with a delay in planting. Pyrethrum seedlings planted on 3 November, without any plant growth regulator (PGR) treatment, produced the highest dry weight (DW) of flowers and the greatest yield of pyrethrins (159.5 kg ha(-1)). Delays in planting to 23 November or 13 December caused 34% and 42% reductions in flower DWs, and 48.5% and 73.1% reductions in pyrethrin yields, respectively, compared to the 3 November planting. Two sprays of either PGR, at 60 d and 75 d after planting (DAP), resulted in significant reductions in floral DWs and in the yield of pyrethrins in pyrethrums planted on 3 November. However, spraying with 3.2 mg l(-1) calliterpinone resulted in 21.2% and 24.1 A) increases in flower yields in the 23 November and 13 December plantings, respectively, compared to the non-sprayed controls. Spraying with 3.2 mg calliterpenone resulted in a significant increase in pyrethrin contents in the 3 November planting, but reduced pyrethrin contents in the later (3 December) crop. Spraying with 0.32 mg l(-1) calliterpenone resulted in significantly higher concentrations of pyrethrins [0.28% (w/w) and 0.24% (w/w), respectively] in the 23 November and 13 December plantings. Spraying 3.2 mg l(-1) calliterpenone on the 23 November plantings, and 0.32 mg l(-1) calliterpenone on the 13 December plantings resulted in significantly higher yields of pyrethrins (107.6 and 79.7 kg ha(-1), respectively) compared to the non-sprayed controls. Planting pyrethrum seedlings during the first week of November is normally recommended to obtain maximum flowering and pyrethrin yields under the sub-tropical climatic conditions of the northern Indian plains. Alternatively, spraying pyrethrum seedlings planted on 23 November or on 13 December twice with calliterpenone at 3.2 mg l(-1) or 0.32 mg l(-1), respectively, at an interval of 10 - 12 d starting 60 DAP can also be recommended to achieve higher yields of pyrethrins.