Cocoa mirid attractiveness by different colour of trap

Cocoa mirids, Sahlbergella singularis and Distantiella theobroma, are the most economically important insect pests of cocoa in West and Central Africa, where they can cause up to 40% losses in cocoa yields. Sahlbergella singularis is the most common species in Cameroon and was therefore targeted in this study. During a two-year trial in 15 cocoa plantations in Ayos and Konye, in the Centre and Southwest regions of Cameroon respectively, the most effective colour – white, purple or green – of sex pheromone traps was examined for integration into mirid management programmes. Similar temporal patterns in S. sahlbergella male trap catches were observed with all three colours, but the green trap caught more S. singularis (Ayos: 0.968 ± 0.091 [SEM]; Konye: 0.640 ± 0.076/trap/month) compared with purple traps (Ayos: 0.674 ± 0.068; Konye: 0.441 ± 0.058), and white traps (Ayos: 0.467 ± 0.049, Konye: 0.253 ± 0.041). Trap reflectance showed wavelength peaks typical for purple in both short (approximately 380–480 nm) and long wavelengths (>650 nm), and ~530 nm for green. Reflectance peaks exceeded 100% of the incident light in the 400–450 nm range from the white, suggesting the presence of optical brighteners. Trap catches support the hypothesis that S. singularis ocelli are more responsive to light of shorter wavelengths. Despite the low attractiveness of the sex pheromone to S. singularis, a optimisation of the colour of the trap can improve S. sahlbergella monitoring, mass trapping, and other control measures which could ultimately lead to reductions of insecticide use and to conservation of beneficial arthropods, particularly cocoa flower pollinators that are critical for improving cacao tree productivity.

可可盲蝽（Cocoa mirids）包含单眼盲蝽（Sahlbergella singularis）与瘤盲蝽（Distantiella theobroma）两个物种，是西非与中非地区可可种植园中经济危害最为显著的昆虫害虫，可造成最高达40%的可可产量损失。单眼盲蝽是喀麦隆境内分布最广泛的可可盲蝽物种，因此为本研究的核心研究对象。本研究在喀麦隆中央省与西南省的阿约斯（Ayos）和孔耶（Konye）两地的15处可可种植园开展了为期两年的田间试验，旨在评估白色、紫色、绿色三款性信息素诱捕器的诱捕效果，以适配盲蝽的综合防治方案。三款诱捕器对单眼盲蝽雄虫的诱捕时序动态规律并无显著差异，但绿色诱捕器的诱捕量显著更高：阿约斯站点为0.968±0.091 [标准误（SEM）]头/诱捕器/月，孔耶站点为0.640±0.076头/诱捕器/月；而紫色诱捕器的诱捕量分别为0.674±0.068（阿约斯）、0.441±0.058（孔耶），白色诱捕器则为0.467±0.049（阿约斯）、0.253±0.041（孔耶）。对诱捕器的反射光谱检测显示，紫色诱捕器在短波（约380–480 nm）与长波（>650 nm）波段均存在典型反射峰，绿色诱捕器的反射峰则位于约530 nm处。白色诱捕器在400–450 nm波段的反射率超过入射光的100%，表明其添加了光学增白剂。诱捕结果佐证了“单眼盲蝽的单眼对短波光线更为敏感”这一假说。尽管性信息素对单眼盲蝽的吸引力较弱，但优化诱捕器配色可提升单眼盲蝽的监测、大量诱捕及其他防控措施的实施效果，最终有望减少杀虫剂的使用，并保护有益节肢动物——尤其是对可可树生产力提升至关重要的可可花传粉昆虫。