and Integrated Pest Management - part - usaid

106 PETlCIDE MANAGEMENT AND IPM INSOUTIIEAST ASIA
would be willing to take the trouble of sampling for pests following the
time-consuming
often
and complicated methods suggested by crop protection
researchers for the sake of saving a few bahts, pesos, or rupics. To make matters
worse, the farmers' perception of missing one insecticide application per season
is quite different from that of the researcher's "objective" loss assessment. While
the magnitude of yield losses due to insects are in the order of 10%, farmers,
average,
on
attribute a loss of more than 40% to one missed spraying (Waibel
1986b) or even expect total loss (Brunold 1981). This, in the eyes of
makes
farmers,
spraying a highly profitable undertaking and makes not spraying a rather
risky affair.
INDIRECT CONTROL MEASURES IN THE CONTEXT OF IPM
Agronomic or cultural practices (we include varietal selection) with regard to
pest control are measures which aim at reducing the probability of pest attack by
creating unfavorable conditions for pest development (Heitefuss 1975). Since
agronomic practices affect both the pest and beneficial complex, as well as crop
yield, their adoption always requires a judicious compromise between plant
protection and plant production (Heinrichs et al. 1979).
In Table 3, we have tried to investigate possible negative effects of IPMbased
agronomic practices on the economics of rice production. Only those
practices that are supposed to have an influence on the pest and beneficial
complex, referred to as 'potential loss', were selected. Following Table 3, the
more interactions between agronomic practices and economic factors, the more
conflicting the adoption of practices would be.
The only IPM practice with supposedly no negative impact on economic
factors is the use of economic thresholds (not an agronomic practice), making it
the easiest to adopt. Practices most conflicting are variety, planting date and
planting method. In varieties, pest resistance is a trait which mostly goes with
high yield, although there are cases where these do not match. For example, in
Thailand, RD], a highly susceptible variety, has a potential yield of almost 750
kg/rai, while the later-developed varieties which were more resistant could not
reach this yield level (Anonymous 1985). Furthermore, highly resistant
varieties do not always command a price as high as susceptible varieties. Also,
if new certificd seeds need to be purchased from seed producers, additional cash is
required in comparison to the regular practice of using owner exchanged seeds.
Another example of conflicting agronomic practices is the change of the
planting method due to pest reasons. In the intensive rice areas in Thailand,
direct seeding is widely practiced. To change back to the transplanting method
would severely affect labor and, consequently, cash resources as more
transplanters would have to be hired.
An important question to address is what quantitative basis exists for the
IPM recommendations currently being made. Undoubtedly, research has achieved
a lot in the past in identifying the influence of cultural practices on the pest and
beneficial complex. On the other hand, how valid such results are beyond a
given area and a given year is yet to be determined. Inthe surveillance system in