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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

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