180 Agroecology and Sustainability
IPM in rice seeks to optimize production and to maximize profits through its
various practices. To accomplish this, however, decision making must always con-
sider both the costs of inputs and the ecological ramifications of these inputs. A
particular characteristic of Asian rice ecosystems is the presence of a potentially
damaging secondary pest, the rice brown planthopper (BPH), Nilaparvata lugens
(see Box 9.1). This small but mighty insect has in the past occurred in large-scale
outbreaks and caused disastrous losses (IRRI, 1979). These outbreaks were pesti-
cide-induced and triggered by pesticide subsidies and policy mismanagement
(Kenmore, 1996). BPH is still a localized problem, especially where pesticide over-
use and abuse is common, and therefore can be considered as an ecological focal
point around which both ecological understanding and management are required
for profitable and stable rice cultivation. BPH also becomes the major entry point
for all IPM educational programmes since it is always necessary to prevent its out-
break during crop management. Other pests which interact strongly with the
Box 9.1 The brown planthopper (BPH)
The brown planthopper (BPH), Nilaparvata lugens Stål (Delphacidae, Homoptera),
is an insect that has been associated with rice since the crop was grown for food in
Asia. This insect is known to survive well only on rice and in evolutionary terms has
co-evolved with the rice plant.Rice fields are invaded by macropterous adults. Upon finding a suitable host, female
BPH will lay eggs into the stem and leaf stalks. The egg stage lasts from six to eight
days. Nymphs resemble adults except for size and lack of wings. There are five
nymphal stages. The complete life cycle lasts 23–25 days. When food is suitable, the
next generation of adults are often brachypterous or short winged. Both nymphs
and adults prefer to be at the base of rice plants. BPH feeds by removing sap from
rice plants, preferably from the phloem.Usually, populations of BPH are kept low by the action of a wide range of natural
enemies indigenous to tropical rice ecosystems in Asia. Outbreaks reported in the
tropics during the 1970s were associated with regular use of insecticides. The more
effective the insecticide, the faster the resurgence of BPH populations which led to
a large-scale dehydration of rice plants, a symptom known as ‘hopperburn’. Insecti-
cides removed both BPH as well as their predators and parasitoids. However, eggs
laid inside the stem are relatively unharmed by spraying and, when these hatch,
BPH nymphs develop in an environment free of predators. In unsprayed fields, the
population of BPH did not increase to any significant level, suggesting the impor-
tance of biological control. Today, farmers learn about predators by carrying out
experiments and when they discover the role of these natural enemies, they are less
likely to use insecticides. In Indonesia, Presidential Decree 3/86 provided the frame-
work and support for farmers to understand and conserve natural enemies and this
has in turn helped rice fields in Indonesia to be relatively free of BPH in the last ten
years. This has coincided with an extensive programme to educate farmers based
on the Farmer Field School model.