priciples of insecticide use in rice ipm

Insecticides in Rice IPM (DRR)
insecticides like phorate and carbofuran were recommended for application in the nursery as well as in
the main field. The dosages are in the range of 1000 to 1500 g a.i. /ha. The application was done in
standing water and the water was inundated for three to four days to enhance the uptake of the active
principles of the insecticides into the rice plant, thereby, GLH feeding on the foliage is controlled effectively.
In many of the cases, this was helpful for containing the multiplication of GLH but not the virus transmitting
ability of the virulent insects living in rice fields.
ORGANOPHOSPHATES AND CARBAMATES
During late 70’s and 80’s sprays of organophosphates like monocrotophos, acephate and carbamates
like carbaryl were extensively employed for the management of vector in RTD endemic areas. These
insecticides also can contain the multiplication of the vector but cannot prevent the transmission ability
from one plant to other. Moreover, the sprays in general are less persistent than granular insecticides.
Hence, more frequent applications of these insecticides were necessary. All the above insecticides do not
have the quick knockdown kill of the vector, which is very much essential for successful prevention of the
transmission of RTD viruses into healthy plants.
SYNTHETIC PYRETHROIDS
During 90’s, a thorough search was made to observe the effectiveness of later groups of insecticides
available during those periods. Synthetic pyrethroids possess good knockdown kill as well as excellent
persistent toxicity against GLH. The notable among the synthetic pyrethroids were the deltamethrin,
cypermethrin, fenvalerate, chlothianidin, beta-cyfluthrin and lambda-cyhalothrin. These can be applied at
dosages as low as 10 to 25 g a.i./ha. This strategy was economical and effective in tungro epidemic
situations where outbreaks can be contained in the localized pockets. But later studies revealed that
synthetic pyrethroids invariably cause resurgence of BPH and WBPH. This acted as a great deterrent for
recommendations of synthetic pyrethroids for routine management of the vector and RTD in endemic
areas. Hence, there was search for other groups of insecticides, which can contain GLH but do not cause
BPH resurgence.
ETHOFENPROX DOES NOT CAUSE BPH RESURGENCE
During late 1990’s and early years of 21 st century there were new groups of insecticides like ether
derivatives, neonicotinoids and phenyl-pyrazoles. The evaluation of the ether derivative ethofenprox
revealed that this insecticide is effective at 50 g a.i./ha against green leafhopper, the vector of RTD but at
the same time almost equally effective against BPH and WBPH and does not cause the resurgence of
plant hoppers. Hence, this became an ideal choice for rice entomologists and pathologists for
recommendation against GLH and RTD for routine application in endemic areas. This insecticide has
extreme mammalian safety and also safety to predators of leaf- and planthoppers like spiders and mirid
bugs.
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