DisplayTitle

Effect of a Select Group of Seed Protectant Fungicides on Growth of Sclerotinia minor In Vitro and Its Recovery from Infested Peanut Seed

Potato-dextrose agar containing 100 μg of streptomycin sulfate per milliliter of medium (SPDA) was amended to establish levels of 0, 2, 4, 6, 8, and 10 μg/ml of the fungicides thiophanate-methyl, carboxin, dicloran, captan, pentachloronitrobenzene (PCNB), or thiram. Fresh mycelial plugs, dry mycelial fragments, and sclerotia of Sclerotinia minor were placed onto the amended media, and mycelial growth and sclerotial germination were determined for 7 days. Thiophanate-methyl was the most effective chemical in inhibiting growth of S. minor, followed by PCNB and dicloran. Thiophanate-methyl was the only chemical that prevented germination of sclerotia of S. minor. Peanut seed naturally infested with S. minor was treated with the fungicides alone or in various combinations; control seed was treated with talcum powder. Seed was stored in polyethylene bags for 12 weeks at 24°C. To determine the incidence of viable S. minor in treated seed, seed was removed from bags, washed for 1 min in 0.2% unscented, liquid soap solution, rinsed twice in distilled water, and then dried for 15 min prior to plating on SPDA. The incidence of S. minor in talcum and thiophanate-methyl treated seed was 3.68 and 0.0%, respectively. Incidence of S. minor in seed treated with the other compounds ranged from 0.40 to 0.56%. Subsequent tests were performed using thiophanate-methyl and some of the above chemicals, in combinations or alone. These tests confirmed that thiophanate-methyl was the only compound that consistently reduced recovery of S. minor from infested seed. Germination of thiophanate-methyl treated seed equaled that of seed treated with talcum.