Detection and monitoring of Drosophila suzukii in raspberry and cherry orchards with volatile organic compounds in the USA and Europe

Spotted wing drosophila captures within the United States

Comparison between the raspberry field and wooded area, during pre-harvest and harvest periods to account for presence of developing and fully ripened fruit, SWD captures and selectivity per QB dry sticky trap is found in Fig. 1A,B. No difference was found in average capture per trap between either area during the pre-harvest period, nor was there a difference between these and the field during the harvest period. The wooded area during the harvest period captured the greatest amount of SWD/trap (F_1,209 = 7.335, P = 0.007) (Fig. 1A). Dry sticky traps baited with QB had a significantly higher selectivity during the pre-harvest period in the raspberry field than in the wooded area but was not significantly different from the trap selectivity in the wooded area during the harvest period. The pre-harvest wooded area trap selectivity was not different from the harvest field trap selectivity. While the harvest field trap selectivity was lower than that of the wooded area trap selectivity during the same period (F_1,203 = 23.6, P < 0.0001) (Fig. 1B). Average SWD capture per trap and average selectivity per trap within a raspberry field and nearby wooded area in Maryland, can be found within Fig. 2A–D. In the raspberry field, dry sticky traps baited with QB had the lowest capture (Pre-harvest: F_2,82 = 13.94, P < 0.0001; Harvest: F_2,139 = 62.22, P < 0.0001) and selectivity (Pre-harvest: F_2,81 = 12.83, P < 0.0001; Harvest: F_2,137 = 46.46, P < 0.0001) rates compared to the other two liquid systems in both the pre-harvest and harvest periods (Fig. 2A,B). Liquid traps baited with QB had higher selectivity than ACV during the pre-harvest period. Within the wooded area dry sticky traps baited with QB had the lowest capture (Pre-harvest: F_2,122 = 26.36, P < 0.0001; Harvest: F_2,172 = 110.8, P < 0.0001; Post-harvest: F_2,54 = 10.97, P < 0.0001) and selectivity (Pre-harvest: F_2,120 = 22.79, P < 0.0001; Harvest: F_2,169 = 108.6, P < 0.0001; Post-harvest: F_2,54 = 23.79, P < 0.0001) rates in all trapping periods except with the exception of pre-harvest where ACV baited traps had a similar selectivity. During pre-harvest QB baited liquid traps had the highest selectivity, but then in the remaining trapping periods selectivity rates between ACV and QB baited liquid traps did not differ. Average weekly capture and selectivity for both the raspberry field and wooded area can be found in Fig. S1A–D.

First capture of spotted wing drosophila captures within the United States

Within the United States the ACV baited liquid trap and QB baited dry sticky trapping systems caught male SWD during the first week of deployment in the wooded area (Table1). Traps were placed on May 7, 2019 and were picked up on May 14, 2019 for processing. Within the raspberry field ACV liquid traps were initially deployed on the ground on May 7, 2019, as the raspberry bushes were not developed enough to support hanging traps. The QB baited dry sticky traps were not deployed until June 4, 2019. Once placed the QB dry sticky traps captured a single SWD male compared to the ACV trapping eight SWD males. Liquid traps baited with QB were placed on June 19, 2019 and immediately captured SWD males and females during the first week of trapping.

Comparison of QB baited dry sticky traps in France, Germany, Italy, and Spain

A comparison of the QB baited dry sticky traps average SWD captures and selectivity from France, Germany, Italy, and Spain can be found within Fig. 3. Germany had significantly lower average trap captures compared to the other countries within both trapping periods, while the remaining countries showed no difference between each other during the same periods. (Spring: F_3,147 = 18.8, P < 0.0001; Fall: F_3,128 = 10.5, P < 0.0001. B) (Fig. 4A). Germany and Italy had significantly lower average selectivity per trap ratios compared to the ratios of France and Spain during the spring trapping period (Spring: F_3,147 = 18.8, P < 0.0001) (Fig. 4B). However, during the fall the average selectivity ratio for traps within Italy increased to be significantly greater than the other selectivity ratios from the other countries (F_3,128 = 10.5, P < 0.0001).

Spotted wing drosophila captures within France

Sticky traps baited with QB dispenser typically caught lower numbers of SWD per trap on average (Fig. 4A) compared to ACV baited traps (Spring: t = 1.25, df = 70, P = 0.22; Fall: t = 5.33, df = 62, P < 0.0001), however the selectivity of dry sticky traps baited with QB dispenser was not significantly different from ACV baited traps (Spring: t = 0.54, df = 70, P = 0.59; Fall: t = 1.64, df = 62, P = 0.12) (Fig. 4B). Trapping averages during the fall period, when the cherry fruits were absent, showed a small increase in the number of SWD caught per trap in both ACV and QB baited system, though only the average capture for the QB dispenser baited system significantly increased compared to spring capture (t = 4.52, df = 78, P < 0.0001). The average number of males caught per trap baited with QB dispenser nearly doubled during fall, however, this was still significantly lower than the average number caught by traps baited with ACV. The selectivity for the trapping systems during the spring trapping period was relatively low and not significantly different. The selectivity of the two trapping systems increased significantly during the fall trapping period compared to the spring trapping period (QB: t = 2.14, df = 66, P = 0.036; ACV: t = 2.63, df = 66, P = 0.011), however they again were not significantly different from each other. Average weekly capture and selectivity for France can be found in Fig. S2A,B.

Spotted wing drosophila captures within Germany

In the spring there was not a significant difference between ACV baited traps and the QB baited dry sticky traps in the average number of SWD caught per trap. However, there was a significant difference between those trapping systems and liquid traps baited with the QB dispenser with boric acid (QB + BA) added to the liquid solution (F_2,162 = 10.72, P < 0.0001) (Fig. 4C). All trapping systems saw an increase in the average number of SWD caught per trap during the fall trapping period from the spring period. Traps baited with QB saw a 11-fold increase (F_54,39 = 1.86, P < 0.0001) in average capture which made it significantly greater than the average capture in ACV baited traps that only increased by 4.9-fold (F_54,39 = 1.97, P < 0.0001). JKI QB traps baited with QB + BA saw a 14-fold increase in capture during the fall (F_39,54 = 2.7, P < 0.0001), however, the average capture continued to be significantly lower than either of the other trapping systems (F_2,117 = 59.54, P < 0.0001). As with the results from France, there was no significant difference in selectivity between the trapping systems during the spring or fall trapping periods (Spring: F_2,159 = 1.868, P = 0.1579; Fall: F_2,117 = 0.3514, P = 0.7044) (Fig. 4D). However, each system did see an increase in selectivity from spring to fall. ACV baited traps increased three-fold (F_54,39 = 1.16, P < 0.0001), QB baited dry sticky traps increased four-fold (F_54,39 = 3.58, P < 0.0001), and QB + BA baited traps increased six-fold (F_39,52 = 1.4, P < 0.0001). Average weekly capture and selectivity for Germany can be found in Fig. S2C,D.

Spotted wing drosophila captures within Italy

Data collected from cherry trees in Italy show that there was statistically no difference between ACV baited liquid traps and the QB baited dry sticky traps in average number of SWD caught per trap (Spring: t = 0.362, df = 38, P = 0.72; Fall: t = 1.49, df = 38, P = 0.26) or selectivity per trap (Spring: t = 0.36, df = 38, P = 0.15; Fall: t = 0.71, df = 38, P = 0.48) in the spring or fall (Fig. 4E,F). During the spring trapping period traps baited with QB caught on average half of the amount of SWD individuals that traps baited with ACV caught. During the fall trapping period, average capture for ACV baited traps increased by 1.6-fold per trap (t = 3.66, df = 38, P = 0.0008), while the average capture of QB baited dry sticky traps increased by 4.7-fold (t = 5.47, df = 38, P < 0.0001). Selectivity of traps baited with QB was about three-fold lower than the selectivity of traps baited with ACV in the spring, however the values were not significantly different. Both trapping systems saw an increase in selectivity from the spring trapping period to the fall trapping period. Traps baited with ACV had an average selectivity increase of 5.4-fold (t = 7.4, df = 38, P < 0.0001) while traps baited with QB had a selectivity increase 19-fold (t = 10.78, df = 38, P < 0.0001). Average weekly capture and selectivity for Italy can be found in Fig. S2E,F.

Spotted wing drosophila captures within Spain

Trapping within cherry trees in Spain revealed that there was not a significant difference in average trap capture between ACV baited traps and QB baited dry sticky traps in the spring (t = 1.47, df = 78, P = 0.15) (Fig. 4G). There was a significant difference found between the two systems within the fall trapping period with ACV baited traps capturing 3.2-fold more SWD than traps baited with QB (t = 6.38, df = 78, P < 0.0001). The selectivity of traps baited with ACV during the spring trapping period was 3.3-fold greater than traps baited with QB (F_2,117 = 8.165, P < 0.0001) (Fig. 4H). However, as the ACV baited capture zero “other insects” likely due to trap design, adjusting the selectivity of the QB traps by removing the “other insects” captured from the analysis will provide an idea of what could be achieved utilizing a trap system similar to what was used for the ACV lure. This increases the selectivity of the QB baited dry sticky traps by 1.5-fold making the selectivity value not significantly different from that of the ACV baited traps. The selectivity of the trapping systems during the fall trapping period were not significantly different (F_2,117 = 1.405, P = 0.2495). Comparing the selectivity between the spring and fall trapping periods the selectivity of QB baited dry sticky traps was increased by 1.3-fold (F_39,39 = 4.19, P = 0.0075), while the selectivity of ACV baited traps decreased slightly (F_39,39 = 2.16, P < 0.0001). The adjusted value of the QB traps remained approximately the same between trapping periods (F_39,39 = 6.85, P = 0.71). Average weekly capture and selectivity for Spain can be found in Fig. S2G,H.

First capture spotted wing drosophila captures within France, Germany, Italy, and Spain

First capture, for the European data, are found within Table 2. In Spain, France, and Italy both trapping systems caught male and female SWD within the first week of deployment. Traps placed in Germany however found that the QB baited dry sticky traps caught SWD a week earlier than the ACV baited liquid traps. Traps placed in Germany were deployed on April 30, 2019 and first detection of male SWD was made by the QB baited dry sticky traps at the May 7, 2019 collection day. ACV baited traps did not detect male SWD until June 11, 2019, five weeks after the first male detection made by the QB baited dry sticky traps. ACV liquid traps had the first female detection a week later than the male detection by the QB liquid trap, i.e., on May 14, 2019 collection day. The QB baited dry sticky traps did not have a female detection until May 28, 2019 collection, 2 weeks after the ACV traps. The modified JKI QB traps had their first female SWD detection on June 25, 2019, three weeks after the QB baited dry sticky traps had their first female detection, and five weeks after the ACV baited traps. These traps additionally did not capture any male SWD until the fall trapping period.

Source: Ecology - nature.com