It causes damping off and root rot diseases of hundreds of diverse plant hosts including maize, soybean, potato, wheat, fir, and many ornamental species.

Contributing to the widespread distribution and persistence of P. ultimum is its ability to grow saprotrophically in soil and plant residue.

[4] One major distinguishing feature between these two genetically distinct organisms is the production of zoospores (swimming spores) -- which are produced only rarely by P. u. var.

ultimum do not release zoospores, instead, they undergo a process called "direct germination", during which the sporangia themselves form invasive hyphae that serve as the primary inoculum source.

Generation of these infectious hyphae is initiated once the free sporangia have made contact with susceptible plant tissues.

Once attached, they form appressoria; specialized infection structures that can generate enough turgor pressure to punch through the plant cuticle.

[6] From there, both variants engage in necrotrophy, a process by which pathogenic organisms kill host cells in order to access and incorporate their contents to meet their nutritional needs.[7]P.

ultimum in particular, is known to release a cascade of unique effector proteins to break down and degrade various cellular components of plant tissues.

Biological control agents include the bacteria Bacillus subtilis, Enterobacter cloacae, Streptomyces griseoviridis, and the fungi Candida oleophila, Gliocladium catenulatum, Trichoderma harzianum, and T.

These results stress the importance of sanitation and encourage greenhouse growers to improve their scouting of all incoming plant material to prevent additional root rot.

[26][27] The method of microbe-mediated suppression of Pythium remains uncertain, however, these and other studies suggest that competition in the rhizosphere for carbon and nitrogen resources could play a role.

[28] Another theory suggests that at high enough concentrations, bacteria can quickly coat and protect susceptible plant tissues, leaving no room for Pythium adherence and subsequent infection.