Brown leaf spot disease and fertilizer interaction in irrigated rice growing on different soil types
Studies have been undertaken in a 1000 ha area of irrigated rice (Oryzica sativa) at Caroni (1975) Limited to determine the effect of the fertilizer programme on the incidence of important diseases. Over a period of three years higher levels of brown leaf spot (Cochliobolus miyabeanus) on rice varieties Oryzica 1 and Oryzica 5 on three different soil types were associated with increasing levels of leaf P, from a low of 0.149% of dry matter (DM) to a high of 0.396% DM. On the Washington silty clay loam series (Inceptisol) brown leaf spot incidence was lowest when leaf P was between 0.135% and 0.149% of DM. However, disease incidence was higher when leaf P levels fell to 0.133% of DM or rose above 0.149%, under conditions where N was more than adequate. The moderate levels of the disease experienced over the period had no effect on yield, as grain infection was minimal. The results support the conclusion that the incidence of brown leaf spot on irrigated rice at Caroni is influenced by sub-optimal levels paticularly of P. Careful monitoring and managememt of P nutrition is seen as an important part in the overall strategy for controlling the disease.
Effect of calcium silicate on blast and brown spot intensities and yields of rice.
Rice production in the subtropical climate of Florida is on Histosols, which are high in organic matter content and low in plant-available silicon (SI). broadcast rates of calcium silicate slag were 0, 5, 10, and 15 Mg/ha in 1987 and 1988. In 1987, applications of calcium silicate slag reduced blast by 30.5% and brown spot by 15.0% over the control. In 1988, blast and brown spot were reduced by 17.4 and 32.4%, respectively, over the control (...)
A petri-dish moist chamber
An improved moist chamber, for encouraging fungi to grow from pieces of infected plant tissues, can be made by adding strips of compressed paper pulp to Petri dishes containing the usual moistened filter-paper. The strips absorb sufficient water to keep the filter-paper moist for 3–4 weeks.