Entymology aspect
Rice bugs (Hemiptera: Alydidae: Leptocorisa oratorius (Fabricius),
Leptocorisa chinensis (Dallas) and Leptocorisa acuta
(Thunberg)).
Both sexes of adults and nymphs can reduce grain quality and seed
viability through feeding.
How rice bugs damage grain Flowering or preflowering spikelets - feed on the ovary, resulting
in partially filled or empty grain.
Milk stage rice - feed on liquid endosperm, resulting in reduced
weight of grain and misshapen, discolored grain.
Dough stage - feed on solid endosperm, resulting in pecky
grain (i.e. stained and lacking glossiness).
Pathology aspect
The diseases connected with grain quality are: Sheath rot, Brown spot,
and Leaf scald in the order of decreasing importance. Click here
to view the reference guide, Fungal Diseases of Rice.
To manage water, fields must be level and
bunds or levees maintained. Uniform water depth (2-5 cm) across
the field will contribute to:
a more uniform crop
higher grain yields
consistent moisture content in the grain
Good water management helps reduce weed
competition, increases yields, and improves grain quality by
reducing dockage (impurities) levels.
If water is scarce, intermittent irrigation
can be practiced only during the vegetative phase, up to panicle
initiation. Thereafter, maintaining a uniform water level is
critical for good grain filling.
Building bunds.
The right application levels of suitable
fertilizers for the variety and growing conditions is essential.
Prudent application of nitrogen is essential to get an evenly
maturing crop with full grain size and high protein levels.
NOTE: Excessive or uneven application
of nitrogen can stimulate late tiller production which results
in heads on the main culm ripening a number of days faster than
the tillers. This results in more immature and green heads as
well as higher moisture content that increases the chance of
fissuring and spoilage.
Conversely insufficient nitrogen can lead
to reduced grain size and protein content.
Farmers using the Leaf Color Chart (LCC) for determining appropriate
Nitrogen application.
Establishing the correct plant population
during planting is essential to maximize:
Water efficiency
Nutrient efficiency
Ideally, planting will result in 400
to 500 panicles per square meter. This means establishing
at least 70 to 100 seedlings per square meter when transplanting.
Planting single seedlings will maintain varietal purity. Broadcasting
or row seeding 80kg to 120kg of seed per hectare will be sufficient
for direct seeding.
If necessary, the seeds should be treated
with appropriate fungicides to control seed-borne diseases.
The following table describes what can happen
if your plant population is not ideal:
If
then
the
plant population is too low,
the yield
and quality of the variety can be reduced due to:
increased tillering which increases
variation in panicle maturity.
increased weed populations.
the
plant population is too high,
the yield
and quality of the variety can be reduced due to:
competition
for water and nutrients, resulting in reduced grain
size.
mutual
shading resulting in reduced photosynthesis.
lodging
(falling over of the plant).
Appropriate plant density is essential
to maximizing a variety's yield potential.
Early and thorough weed control is essential
to obtain greater yields of higher quality grain. Controlling
weeds through either cultural, mechanical, or through the use
of herbicide is equally effective.