Diseases of fruit plantation medicinal and aromatic crops (2+1)

Flower and fruit spot

Causal organism: Phytophthora nicotianae
Symptoms

• Diseased spots on flower result in premature shedding.
• Lesions are also formed on fruits.
• Twigs in the trees are also infected.
Mode of survival and Spread

• Oospores are spherical, sporangia are broadly turbinate with spherical basal portions and apical part prolonged into a break or papillate
Life cycle

• Oospores are thick walled, sexual diploids spores present in the infected debris
• When conditions are congenial, the oospore germinates as a sporangium and releases zoospores
• After their release the zoospores encyst (Short period resting phase) and the zoospores looses their flagellum.
• Soon after landing on the host surface, encysted zoospore germinates to produce germ tube and enter inside the host through stomata.
• The mycelium multiplies by producing intracellular haustoria and absorbing nutrients which causes infection by producing sporangium and thus continues the life cycle.
• In adverse conditions, it undergoes sexual reproduction with gematangial contact type of reproduction between oogonium and antheridium followed by Plasmogamy, Karyogamy mitosis, meiosis and oospore formation.
Management

• Clean cultivation.
• Spray nitrogen solution (Urea) or bleaching powder to enhance degradation of fallen leaves or infected plant parts.
• Prune and burn infected branches and pruned material and the pruned branches should be treated with Bordeaux paste or COC paste.
• Spray thiophenate methyl ( 0.1%) or mancozeb ( 0.2%) or cardendazim (0.1%)