Maclean et al. - 2002 - Rice almanac source book for the most important e

engineering is being employed to introduce
resistance to stem borers and sheath blight, two
pests for which limited resistance has been found
in rice germplasm. Details are given in the
section on “Biotechnology issues”.
More sustainable integrated weed
management technology is also being developed
by investigating and promoting rice cultivars
with superior weed competitiveness, biological
control, rice allelopathy, and a thorough
understanding of the biology and ecology of
weeds, and of the socioeconomics of weed
management practices of farmers. Integrated
weed management, promoting biological and
cultural control, and minimizing the use of
herbicides are seen as keys to sustainable ricefarming
systems.
Friends
As mentioned, most of the organisms in a rice
field are not harmful. Control of insect pests, for
example, depends on the activities of a whole
array of their natural enemies, through a complex
and rich food web of generalist and specialist
predators and parasites that live above, below,
and at the water surface as well as in flooded and
aerated soil habitats (Fig. 8). In tropical rice
fields, levees or bunds also form refuges for
early season predators of rice pests, such as ants
and spiders, as do bordering grasses and other
nearby habitats.
Predators are the most conspicuous group of
rice “friends,” that is, the natural enemies of rice
pests. They are the most abundant forms and are
often confused with pests. Some, such as spiders,
predatory crickets, longhorned grasshoppers,
damselflies, ants, wasps, and beetles, search the
plant for prey such as leafhoppers, planthoppers,
moths, caterpillars, and larvae of stem borers.
Some predators eat eggs of pests. Others, such as
water bugs and beetles, live on the surface of and
in the water in the rice field and attack pests that
fall from the plants.
Canopy
Neuston
Plankton
Epibenthos
Benthos
Fig. 8. Habitat zones and dominant taxa of an irrigated rice farmer’s rice field in Calauan, Laguna,
Philippines. Canopy taxa are Stilbus sp. adults (1), Chironomidae adults (2), Cardiochiles philippinensis adults
(3), and Egadroma sp. adults (4). Neustonic (water surface) taxa are Microvelia atrolineata adults (5),
Ephydra sp. immatures (6), Entomobryidae adults (7), and M. atrolineata immatures (8). Planktonic and
benthic taxa are Heterocypris luzonensis (9), Eucyclops serrulatus adults (10), Chironomidae immatures (11),
and Hydrophilidae adults (12).
28 Rice almanac