Pythium oligandrum is an
Oomycete. It is a parasite of many fungi and other oomycetes including
Botrytis,
Fusarium and
Phytophthora. It has been licensed as a
biocontrol agent in the form of an oospore soil treatment, which reduces pathogen load and concomitant plant disease.
P. oligandrum can grow within the roots of certain plants, including tomato and sugar beet. Production of
auxin-like substances stimulate plant growth. Defense responses can be induced in the plant, which primes the plant from further infection by pathogenic fungi, oomycetes or bacteria.