priciples of insecticide use in rice ipm

Insecticides in Rice IPM (DRR)
GREENHOUSE STUDIES
Orientation and settling behaviour
Neem oil possesses a strong repellance activity to brown planthopper (BPH). Only a very low number of
BPH settled on treated plants. Even at 3% concentration of oil, the spray treated plants attracted not
more than 36% of insects (Saxena et al., 1980a). There was a progressive decrease in arrivals of BPH
and WBPH to treated plants with an increase in concentrations of neem oil. When neem oil treated leaves
were offered to leaf folder in a choice test, it significantly lowered the number of larvae that arrived on
treated leaves, particularly at 12% or higher concentration (Saxena et al., 1980b). However, similar
effects were not observed in case of green leafhopper females (Heyde et al., 1983).
In a comparative study (Krishnaiah and Kalode 1988b), with other non-edible oils, neem oil and pinnai oil
applied as spray exhibited more or less similar repellency to BPH adults while mahua oil was inferior.
However, neem cake applied to soil did not restrain BPH settling response on TN 1 in a choice test.
(Saxena et al., 1984). The soil applied neem cake might not have released sufficient voaltiles to show
repellency to insects arriving on leaves.
Feeding behaviour
Feeding deterrency of neem oil was observed in many insect pests. On treated plants, BPH adults were
restless, took longer time to locate feeding sites and ingested smaller quantities of food. Such effects
were not observed in vegetable oil treated plants (Saxena et al., 1980a). Significant reduction in quantity
of food ingested by BPH, WBPH and GLH occurred even at 1% concentration of neem oil (Heyde et al.,
1983). Custard apple oil was relatively more effective as antifeedant than neem oil against BPH, WBPH
and GLH (Saxena et al., 1983). Among others, pinnai and mahua oils were comparable to neem oil in
reducing BPH feeding as indicated by significantly less honeydew excretion on TN 1 plants even at 3%
concentration (Krishnaiah and Kalode, 1988b). Reduced phloem feeding increased xylem feeding, repeated
probing and profuse salivation of Nephotettix virescens on plants sprayed with 10% neem oil was
demonstrated by Saxena and Khan (1985).
Significant reduction in duration of phloem feeding by GLH was observed with neem seed bitters (NSB) at
2500 ppm (Kareem et al., 1988). On neem oil (50%) treated plants feeding duration in BPH also was
decreased to 6 min. in contrast to 53 min in control (Rajasekharan et al., 1987).
Antifeedant activity of neem oil against leaf folder was higher with an increase in concentration of neem
oil spray on plants, as measured by quantum of excreta. However, even neem oil spray at 25% was
similar to control when treated plants were exposed to 2 to 4 days light (Saxena et al., 1980b). Reduced
feeding period of leaf folder on NSB treated leaf cuts was shown by Kareem et al., (1988).
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