þ STRAW INCORPORATION VS. STEM ROT

Stem-rot inoculum for following crops is greater with present incorporation methods than with burning - not only in the following season but even after a year of fallow (because the inoculum lasts well in fallow). (RP2)

Complete coverage of straw and stubble with soil in the fall may help control stem rot, plant pathologists believe. So studies are seeking methods of more complete coverage of residue. (RM11)

Thus, where stem rot is already established, spread the straw well behind the harvester and burn as completely as possible in the fall. Weather permitting, follow burning with stubble-discing or moldboard plowing. (RP2)

þ STEM ROT FUNDAMENTALS

Studies continue on the stem rot organism, Sclerotium oryzae, covering its epidemiology; factors affecting inoculum level, production, and survival; determination of rot strains; and the role of the ascomycete stage, including mating capacity, mating-type distribution, and the virulence of the various strains.

The rice plant itself is being studied for resistance to the organism, and how resistance is inherited. Hope of biological control centers on finding fungi antagonistic to the stem rot organism. (RP2)

þ FERTILIZER TIMING AND STEM ROT

Stem rot is aggravated by improper timing in applying phenoxy herbicides (MCPA), and excessive use of nitrogen fertilizers. (RP2)

þ STAND DENSITY AND STEM ROT

A dense rice stand increases stem rot much more than it increases yield: So studies continue to determine the optimum stand in terms of minimum stem rot. (RP2)

STEM ROT RESISTANCE SOUGHT

All advanced experimental varieties were evaluated for damage from stem rot. Twenty-one selections showed less tissue injury than California varieties. Tests continue. (CCRRF)