The sorghum plant bug Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae) is a major seed pest of rice in Japan. Male S. rubrovittatus were previously shown to be attracted to traps baited with unmated females. The solvent extract of unmated females was analyzed by GC-MS using HP-INNOWax and HP-5ms columns, and retention index data and mass spectra of peaks detected in the female extract were compared with those of authentic samples. Three compounds, hexyl butyrate (ϭbutanoate), (E)-hex-2-en-1-yl butyrate and (E)-4-oxohex-2-enal, were identified from the female extract. Contents of these compounds in solvent extract of females were ca. 18.6, 8.6 and 1.0 mg/female, respectively. In a field experiment, a blend of three compounds showed potent attractant activity to male S. rubrovittatus, although no binary combinations of the three components were attractive. These results suggested that these compounds are components of the female sex attractant pheromone of S. rubrovittatus.

Three components, hexyl butyrate (ϭbutanoate) (6:nBu), (E)-4-oxohex-2-enal (E2O4-6:Ald) and (E)-hex-2-en-1-yl butyrate (E2-6:nBu), were identified as sex attractant pheromone components of the sorghum plant bug Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae) in a previous study. The optimum ratio and amount of the three components loaded into rubber septa for male attraction were investigated. A 5:10:1 blend of 6:nBu, E2O4-6:Ald and E2-6:nBu at 64 mg per rubber septum was most effective for male attraction and regarded as an 'optimized blend'. The attractiveness of the optimized blend lures did not differ between lures with and without a sunshade and was equal to that of 10 unmated females. The attractiveness of optimized blend lures after weathering for 14 d did not differ from fresh lures, whereas the attractiveness of optimized blend lures weathered for more than 21 d was lower than fresh lures. Female extracts of S. rubrovittatus contain 13 minor components; however, the attractiveness of lures impregnated with female extracts did not differ from optimized blend lures. This result suggests that minor components at the amounts contained in the female extract do not strongly enhance its attractiveness.

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Seasonal changes in egg diapause induction and the effects of photoperiod and temperature on the sorghum plant bug, Stenotus rubrovittatus (Matsumura), were investigated. Female bugs were collected approximately every five days from fields in Azuchi, Shiga Prefecture from mid-August to early October for three years, from 2004 to 2006. The proportion of diapause eggs produced by the collected females increased rapidly in mid-September, reaching approximately 100% in October. Bugs were reared from egg to adult at three temperatures: 20, 25 and 30°C, combined with eight photoperiods, ranging from 11.5L12.5D to 15L9D. The critical photoperiod for egg diapause induction fell between 13L11D and 14L10D at 25°C; however, the critical photoperiod for females reared at 20°C became slightly longer, and females reared at 30°C tended to lay non-diapause eggs. The percentage of diapause eggs produced by the females reared at 30°C was 73.0, 41.9 and 80.1% under 12.5L11.5D, 12L12D and 11.5L12.5D, respectively.

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