The Effect of Seed-Borne Pathogens on Emergence of Globe Amaranth, Calendula and Tagetes and the Methods of Control

Nimbya gomphrenae, Stemphylium vesicarium and Alternaria tagetica were isolated for the ®rst time from seeds of diseased globe amaranth (Gomphrena globosa), pot marigold (Calendula ocinalis) and marigold (Tagetes erecta), respectively, in Taiwan. The amount of seed-borne N. gomphrenae or Colletotrichum dema- tium was positively correlated (Pˆ0.05) with the amount of the abnormal seedling and unemergent seed of globe amaranth. Similarly, the amount of seed-borne Alternaria alternata or S. vesicarium was negatively correlated (Pˆ0.05) with the emergent rate of pot marigold. Treating the fungi-contaminated globe ama- ranth seeds with Bacillus megaterium [1.3 ´ 109 colony- forming units (CFU)/ml] or 1% NaOCl signi®cantly (Pˆ0.05) increased seed emergence over control whereas 10 p.p.m. pyrifenox could control N. gomphre- nae on globe amaranth. Stemphylium-contaminated pot marigold seeds responded to 200 p.p.m. iprodione treatment by increasing signi®cantly (Pˆ0.05) in seed emergence over untreated control. For seed-borne A. tagetica, treating marigold seeds with Bacillus azot- oformanis (1 ´ 109 CFU/ml) was found e€ective and mancozeb highly e€ective