Effects of Trap Color and Placement Height on the Capture of Ambrosia Beetles in Pecan Orchards

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in the tribe Xyleborini are economically important pests of woody ornamentals, tree nuts, and fruit orchards, including pecans in the United States. Among them, the granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), is the most common species in pecan orchards in Georgia. Various traps, including ethanol-mediated Lindgren multi-funnel traps, panel traps, bottle traps, sticky cards, and ethanol-infused wooden bolts, are used in ambrosia beetle monitoring programs. Trap color and placement height are important factors that increase trap effectiveness. To improve trap effectiveness for ambrosia beetles, we conducted a color and height preference experiment under field conditions using six different colored sticky cards, including black, blue, green, red, transparent, and yellow, placing them at three different heights (15, 60, and 120 cm from ground level). The results show that red and transparent sticky cards consistently captured a higher number of ambrosia beetles, whereas yellow-colored sticky cards consistently captured a lower number of ambrosia beetles compared to all other tested colors of sticky cards. A similar trend was observed with X. crassiusculus in field and laboratory settings. Among the evaluated trap heights, more ambrosia beetles, including X. crassiusculus, were consistently captured in the sticky cards placed at a height of 60 cm from the ground surface. Additionally, we monitored natural infestations of ambrosia beetles in commercial pecan orchards in Georgia and found more damage to pecan trees near the ground surface (45 cm) compared to the upper parts. We also recorded three ambrosia beetle species, X. crassiusculus, the black stem borer, X. germanus (Blandford), and the Southeast Asian ambrosia beetle, Xylosandrus amputatus (Blandford). Among them, X. crassiusculus (90.50%) was the most abundant species in the pecan orchards. Therefore, red and transparent sticky cards placed at a height of 45 to 60 cm could improve the trap efficacy and can be used for monitoring ambrosia beetles in pecan orchards.