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Growing
natures army
Left on its own, nature has enough predatory species to limit the population of and the crop damage
caused by insect pests to a minimum. But the misuse of pesticides kills off these benecial species and
tips the balance heavily in favor of major pests such as rice planthoppers. In 2011, IRRI launched an
action plan to stop devastating planthopper outbreaks by focusing on nurturing natures army of pest killersand reducing the use of pesticides.
Each species on our planet
plays a role in the healthy
unctioning o natural
ecosystems, on which humans de-
pend, said Dr. Will iam Schlesinger,
president o the Cary Institute o Eco-
system Studies, about the complex
interactions that govern the naturalworld. This mantra is embraced and
advocated by IRRI through its ecologi-
cal engineering strategy in which the
little things count in the rice ecosys-
tem: the owers in the felds, the spi-
ders, the wasps, among many other
lie orms.
Through this strategy, armers
work efciently with natural processes
and the natural-born protectors o
rice rather than against them to keep
pests at bay. IRRI discovered that car-
ing or biodiversity helps in overcom-
ing even the pest that many rice arm-
ers ear the mostplanthoppers.
Little grim reapers
The degree o havoc that planthop-
pers are capable o has been grimly
shown in a series o inestations
across Asia. In 2010, Indonesias West-
ern, Central, and Eastern Java lost
more than 25,000 hectares o rice to
hopperburn (drying o crops and with-
ering o shoots as i scorched by the
sun caused by the eeding o plant-
thoppers) and the viral diseases they
transmitted. In Thailand, brown plan-
thopper damaged more than 3 million
hectares o rice area and more than
1.1 million tons o paddy with an ex-
port potential o US$275 million rom
2009 to 2011. In China, rice armerslose 1 million tons o rice annually to
planthoppers.
One o the most devastating
planthopper outbreaks took place
in 2005 when Vietnam lost about
400,000 tons o rice paddy. As the
problem persisted, the country sus-
pended its exports in 2007 to protect
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its domestic supply, and this contrib-
uted to the 2007-08 rice crisis.
Ecosystem breakdown
What triggers planthopper outbreaks?
IRRI entomologist K.L. Heong has
identifed one o the main culprits:misuse o pesticides. One o the
consequences o using pesticides
is the indiscriminate killing o pest
predators. The resilience o the eco-
system to fght o pests starts to get
o-balance the moment chemicals are
sprayed.
A rice feld is rich in diversity, in
which natural enemies o pests such
as spiders, aquatic bugs, parasitic
wasps, and predatory bugs thrive,Dr. Heong said. These natural en-
emies keep the pest population under
check.
The practice o managing arms
so that they harbor sufcient popula-
tions o pest predators that happily
east on crop pests is an eective
control technique. Rice scientists are
learning to make better use o these
invisible yet powerul allies by creating
sae habitats or them within the riceecosystem, thus encouraging them to
stay and reproduce.
Weaning away from pesticides
The Planthopper Project, a collabora-
tive research network with scientists in
Asia co-unded by IRRI and the Asian
Development Bank, campaigns
or less dependency on using chemi-
cals to control pests. This advocacy is
not an easy eat or the planthopper
project team because advertising has
conditioned armers to believe they
need chemicals to solve their pest
problems.
In 2011, brown planthopper
inestation in several provinces o
Thailand destroyed 104,000 hectares
o rice area. To control the pests in a
sustainable manner, Thailands min-
ister o agriculture came up with a
$12.8-million initiative to stop the use
o two insecticidescypermethrin and
abamectinwhich actually causes
planthopper outbreaks. Instead, the
agency promoted a campaign to im-
prove pest management practices in
rice. The move was viewed as interna-
tionally signifcant because Thailand is
the worlds largest exporter o rice and
a leader in the global rice industry.
An eco-friendly counterstrike
In 2011, IRRI launched an action plan
seeking to solve the hopper problem
in a sustainable manner. IRRI proposed
the restoration o biodiversity in rice
felds, as well as building ecologicalresilience.1 IRRI came up with more
detailed ecological engineering ap-
proaches, which include the ollow-
ing:
Planting owers and other plants
to promote the buildup and suste-
nance o a healthy population o
natural enemies o planthoppers.
Using resistant varieties, or a
combination o varieties, that are
tolerant o the local or invadingplanthopper populations. (Farm-
ers are advised against using
the same variety or more than
2 years to prevent the hoppers
rom developing resistance to the
variety.)
Synchronous planting and allow
periods o 1 month in between
1Action Plan: Preventing planthopper outbreaksin rice. IRRI (2011).
successive crops o rice, as well as
crop diversifcation schemes.
Controlling chemical control
Furthermore, to support armers in
their on-the-ground activities, IRRI is
also calling on its partners in nationalgovernments and the private sector to
regulate the marketing and improve
the use o insecticides.
The advocacy is to re-classiy pes-
ticides rom consumer goods to regu-
lated materials, and to ban or restrict
the use in rice o broad-spectrum pes-
ticides that contain active ingredients
known to contribute to planthopper
outbreaks such as cypermethrin, del-
tamethrin, abamectin, and chlorpyri-os.
IRRI also recommends that pesti-
cide retailers be certifed and trained
to prevent sales o ake, banned, or
unapproved products, and to promote
integrated pest management and
proper pesticide use.
The ecological engineering ap-
proaches, which put a premium on
biodiversity with its natural protec-
tors, ensure more sustainability in rice
production or armers, Dr. Heong
said. And a healthy rice ecosystem
can better withstand and recover rom
disasters brought by pests.
With a healthy biodiversity in the
rice ecosystem, armers will not end
up losing twice: paying the high costs
o pesticides and yet still becoming
victims o pest outbreaks.
Welcome sign. Planting owers is one way o encouraging biodiversity. Enhancing the habitat attracts benefcial insects and other species that are essential to natural pest control.
Growing natures army
IRRI Annual Report 2011 31