Similar worldwide patterns in the sex pheromone signal and response in the oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae)

Abstract

The response of Grapholita molesta (Busck) males to three-component sex pheromone blends containing a 100% ratio of the major sex pheromone component, (Z)-8-dodecenyl acetate and a 10% ratio of (Z)-8-dodecenol, but with varying ratios of (E)-8-dodecenyl acetate (0.4, 5.4, 10.4, 30.4, and 100.1% E-blends) was tested with populations in eight stone and pome fruit orchards in Europe, Asia, and North and South America. Traps baited with the 5.4% E-blend caught significantly more males than traps with any other blend with all populations. Significantly more males were caught in traps baited with the 10.4% E-blend than in traps with the remaining blends, except with the 0.4% E-blend in Turkey. Significant differences in male moth catches occurred between the other blends with the 0.4>30.4% E-blend, and the 30.4>100.1% E-blend. Male moth catches with the 100.1% E-blend only differed from the hexane control in Chile. No apparent differences were noted to these blends in populations collected from pome or stone fruits. Flight tunnel assays to synthetic blends with a subset of populations were similar to the field results, but the breadth of the most attractive E-blends was wider. Flight tunnel assays also demonstrated a high level of male-female cross-attraction among field-collected populations. Female gland extracts from field-collected populations did not show any significant variation in their three-component blends. The only exceptions in these assays were that long-term laboratory populations were less responsive and attractive, and produced different blend ratios of the two minor components than recently collected field populations.

Role of plant volatiles and hetero-specific pheromone components in the wind tunnel response of male Grapholita molesta (Lepidoptera: Tortricidae) to modified sex pheromone blends

“…Male G. molesta responses peaked at optimal pheromone concentrations and optimal ratios of the two acetate isomers, as reported in earlier studies (Baker et al, 1981;Linn & Roelofs, 1983;Willis & Baker, 1988;Knight et al, 2015). We have shown previously that plant volatiles synergize male response to a below-optimal pheromone dose (Varela et al, 2011); however, in the present study we failed to observe plant synergism to an above-optimal pheromone dose.…”

Improved monitoring of oriental fruit moth (Lepidoptera: Tortricidae) with terpinyl acetate plus acetic acid membrane lures

“…Moth catches with this binary lure compared with the 2-PH lure alone increased from <twofold to >100-fold, and the proportion of females caught in traps baited with this binary lure ranged from 0.24 to 0.71 across the various studies. At present, we have no hypothesis to explain this high degree of variation in the relative performances of these lures, and further studies might address lure efficacy in different host crops (stone fruits, apple and pear) or possible geographical differences in these behavioural responses among G. molesta populations (Knight, Barros-Parada, et al, 2015). Clearly, the TA/AA membrane lure has not yet been optimized.…”

Response profile of pheromone receptor neurons in male Grapholita molesta (Lepidoptera: Tortricidae)

“…Male G. molesta behaviorally discriminate small variations in the ratio of the two acetate isomers Baker et al, 1981;Knight et al, 2014a), so they should have a detection system that reports the relative abundance of the two isomers in the blend. In the majority of moths this is achieved by having specific receptor neurons to each of the main pheromone components (De Bruyne and Baker, 2008).…”

“…Z8-12:OH is 10% of the pheromone blend, so it probably has few dedicated ORNs that were missed in our sampling of 176 sensilla, or these neurons were not very specific or housed in sensilla other than trichodea (e.g., sensilla auricillica in Cydia pomonella (L.), Ebbinghaus et al, 1997;Ansebo et al, 2005), which were not sampled in our study. Whereas narrow variations in the ratio of the two acetates have a strong effect in male behavioral response (Baker et al, 1981;Knight et al, 2014a), males accept wide variations in the quantity of Z8-12:OH in the blend Linn and Roelofs, 1983;Linn et al, 1986), and in some locations Z8-12:OH is produced in trace amounts by females (Lacey and Sanders, 1992), or does not seem to play a role in attraction (Han et al, 2001;Jung et al, 2013). Furthermore, other alcohols affect the response of male G. molesta to the two acetates Cardé et al, 1975aCardé et al, ,b, 1979, including the sex pheromone of C. pomonella (Knight et al, 2014b), and Z8-12:OH inhibits males of closely related species (Grapholita funebrana (Treitschke) and Grapholita prunivora (Walsh)), that use a similar ratio of the Z/E acetates as G. molesta Guerin et al, 1986), so a reinvestigation of the role of alcohols in the olfactory communication of G. molesta is warranted.…”