Soils containing sclerotia of Sclerotium rolfsii were covered with transparent plastic and exposed to sunlight in an experiment to study the effect of soil solarization on the growth of the fungi and its pathogenicity to peanut. Soil solarization for 3 to 4 weeks significantly suppressed the sclerotial germination up to 44% and reduced hyphal growth and pathogenicity of S. rolfsii placed at 0.5 cm below the soil sulfate, but did not have any gects when the sclerotia were placed at the depth of 15 cm. Among ungerminated sclerotia, 88.0 and 82.7% of them were physically damaged by 3 and 4 weeks of soil solarization, respectively. Some of the damaged sclerotia were colonized by microorganism. The most frequent colonizing microorganisms observed were Asagillus spp, Trichodenna spp., and bacteria. Increased soil temperature as direct effect of soil solarization and the role of some soil microbes might be responsible for the suppression.
Resistance of peanut varieties to phytoplasm. Recently, witches' broom disease on peanut is becoming more important in Indonesia The use of resistant varieties is very potential to overcome the yield loss caused by the disease. Ten peanut varieties were evaluated for their response to phytoplasma using insect vector transmission. Three categories of plant response were observed during the experiment, i.e. moderate resistant (var, Macan, Zebra, and Simpai), susceptible (var. Biawak, Treggiling, Pelanduk, and Kidang), very susceptible (var. Gajah, Tupai, and Banteng). The average seed weight decrease per plant due to the phytoplasma infection was 40.99 - 100%.