Effects of sublethal doses of insecticides on the mirid predator, Cyrtorhinus lividipennis (Reuter) (Heteroptera: Miridae)
1993
Raschanee Suvaparp
Toxicities of chlorpyrifos and BPMC on the adult female Cyrtorhinus lividipennis and Nilaparvata lugens were investigated using topical application. Toxicities of buprofezin on the fifth instar C. lividipennis and N. lugens were also estimated. Based on the relative potency, chlorpyrifos, BPMC and buprofezin were more toxic to N. lugens than C. lividipennis. The LD50 values for chlorpyrifos, BPMC and buprofezin on C. lividipennis were 69.2, 20.5 and 360 micro g/g, respectively. The LD50 values for chlorpyrifos, BPMC and buprofezin on N. lugens were 13.9, 6.5 and 0.1 micro g/g, respectively. Sublethal doses of BPMC was significantly affected the number of eggs laid per day of C. lividipennis. The average number of eggs laid per day were decreased from 7.86 +- 6.75 to 4.66 +- 0.78 and 5.56 +- 0.87 for the treated females paired with either treated or untreated males. While the untreated females when paired with treated males laid 5.05 +- 0.99 eggs per day. BPMC did not affect fertility, longevity and survival but showed tend to reduce the total eggs laid per female. Chlorpyrifos and acetone did not affect fecundity, fertility and survival of C. lividipennis but longevity of chlorpyrifos treated males paired with treated females was significantly reduced from 19.15 +- 1.89 to 13.7 +- 1.97 days. Insecticides and acetone appeared to affect egg laying pattern of C. lividipennis. The egg laying pattern showed highly variable. The effect of chlorpyrifos and BPMC at sublethal doses and acetone on searching efficiencies of the female adult C. lividipennis were not significant. Buprofezin reduced searching efficiencies of the fifth instar C. lividipennis. The attack rate (a') was reduced 20 times. Partially or incompletely attacked BPH eggs were always found during the observations of the predatory behavior.
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