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.