Green June beetle, Cotinis nitida (L.), is an important pest of grapes, peaches, blackberries, blueberries, apples, and pears. Currently, there is no inexpensive, commercially available lure or trap that could serve monitoring green June beetle adults. The objective of this study was to develop and optimize an inexpensive bottle trap baited with isopropanol to attract and capture green June beetle adults. Bottle traps baited with 8 mm diameter cotton wicked dispensers emitted from 9 to 43 ml isopropanol in 48 h and maintained that alcohol at a fairly constant concentration compared with the prototypical bottle trap with large surface evaporation of isopropanol poured into the bottom of the trap. Over 5 d, the isopropanol in the wicked dispensers remained at the same stable concentration of 45-44.5%, whereas isopropanol concentration in the bottom of prototypical traps dropped from 45% to approximately 11% after 24 h and to 0.2% by 48 h. Bottle traps with isopropanol dispensers and cotton wicks of 4, 6, or 8 mm in diameter caught significantly more green June beetles than did prototypical bottle traps with no dispensers. Isopropanol concentrations of 45.5, 66, and 91% attracted more green June beetle adults than the lower concentrations. Significantly more green June beetle adults were attracted to traps with dispensers set at 1.3 m height than those at lower heights, and traps topped with a blue, orange, or white band captured more green June beetle adults than those with bands of other colors. The optimized bottle trap is made from recycled transparent polyethylene terephthalate beverage bottle (710-ml; 24 oz.) with a blue, orange, or white band, baited with an 8 mm cotton wick dispenser of 45.5% isopropanol and hung at a height of 1.3 m. Cost and uses for this trap are discussed.