priciples of insecticide use in rice ipm

Insecticides in Rice IPM (DRR)
monocotyledonous plant the coconut. In coconut, root feeding with monocrotophos has resulted in excellent
control of black headed cater pillar, of coconut. This emphasizes the point that an insecticide may not be
truly systemic in one plant but may exercise true systemic action in another plant owing to the differences
in the molecular translocation physiology among different plants.
Chlorpyriphos has limited translocation
Chlorpyriphos has shown excellent efficacy against stem borer, gall midge and whorl maggot when given
as a seedling root dip before transplanting of rice plants. It has also shown good control of gall midge in
the nursery when sprouted seeds of rice were soaked in chlorpyriphos emulsion for 3 hours before
sowing. However, chlorpyriphos failed to check effectively the leaf feeding insects like leaf folder and rice
hispa, or the sucking pests like plant hoppers and leafhoppers. This throws the light that chlorpyriphos is
getting accumulated only in the young growing parts of the plants and thus exercising its effectiveness
against stem borer, gall midge and whorl maggot whose larvae confine to the growing portions of rice
plant.
Carbosulfan: a true systemic insecticide in rice
When several insecticides including monocrotophos, have been evaluated for their effectiveness as seedling
root dip treatments against whitebacked planthopper, brown planthopper and green leafhopper, only
carbosulfan has exercised effective control of all the leaf and plant hoppers. This reveals that carbosulfan
has excellent translocation in the plant system moving through xylem from lower to upper portions of the
plant and then disbursing into the phloem through other tissues, which alone can bring about excellent
control of BPH and WBPH which are purely phloem feeders. High innate toxicity of carbosulfan to leaf and
planthoppers might be considered as the reason for its effectiveness but monocrotophos in spite of its
high innate toxicity to BPH and WBPH failed to check leaf and planthoppers as a seedling root dip
treatment.
Downward translocation of insecticides in rice
When we talk of the systemic action in rice plant, it is not merely the upward movement or translocation of
insecticides when applied either to soil or seedling root dip but, a true systemic insecticide should also
have downward translocation as well when applied to the upper parts of foliage like leaves. This property
can be effectively evaluated by spraying the insecticides to the leaves and confining the insects to the
base of the plant, which is uncontaminated. When several insecticides have been evaluated in this manner
for their downward translocation property in rice plant, only BPMC could exercise good initial kill of BPH.
However, the persistence lasted only for five days indicating that a small proportion of BPMC applied to
the foliage has really been translocated downwards to effectively check BPH. None of the other insecticides
including monocrotophos, which have high innate toxicity to BPH, could show such a downward translocation
in rice plant.
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