Once released, oospores germinate on the host and infect target host tissues. Production of sporangia, oospores, and zoospores were observed on "Phytophthora kernoviae". Zoospores are produced in wet conditions by either oospores or sporangia. Sexually, they reproduce with structures called antheridia, oogonia, and oospores. Hormonal communication triggers the formation of the sexual spores, called oospores. "Phytophthora sojae" overwinters in plant debris and soil as oospores. Oospores and mycelium can survive on dead leaves. The pathogen can persist in the soil for several years as oospores. Mycelia and oospores in soil can infect seeds or roots. Improving soil tillage can help eliminate oospores from the soil. "P. fragariae" survives in the soil in the form of oospores. "P. colocasiae" is an oomycete and is thus characterized by oospores and coenocytic hyphae. "Pythium aphanidermatum" overwinters in the soil as oospores, hyphae and/or sporangia. The oospores germinate to form usually one sporangia. The fungus spreads by oospores on diseased leaves and/or on infected seed.