Oil from leaves of Melaleuca alternifolia consisting mainly of terpenes and terpenols, aqueous extracts of stems of Yucca shidigera containing steroidal saponin, and gels from leaves of Aloe vera and A. sapponaria were tested for their possible activity against the growth and pathogenicity of Rhizoctonia solani and Pythium ultimum. On water agar medium, both Melaleuca oil and Yucca extract were fungitoxic but Aloe extracts did not inhibit the growth of R. solani, or P. ultimum. In greenhouse tests using soil infested with R. solani, Melaleuca oil at 1% in an oil-in-water emulsion, and Yucca extract at 35% dissolved solids), applied as Boil drenches in the seed row, increased percentage survival of cotton seedlings (cv. Acala SJ-2) over the untreated control u to 40% and 53%, respectively. Using soil infested with P. ultimum, these soil drenches increased seedling survival up to 52% for Melaleuca oil (1% oil in-water emulsion) and up to 35% for Yucca extract (35% dissolve solids), over the untreated control. Priming of cotton seed (cv. Acala Si-2) either by liquid infusion or solid matrix methods using melaleuca oil (1% oil-in-water emulsion) increased seedling survival over the untreated control by up to 30% and 44%, respectively. For Yucca extract (35% dissolved solids), solid matrix priming increased seedling survival up to 55% over the untreated control.