Entomopathogenic nematodes for controlling Lobesia botrana in vineyards: fine-tuning of application, target area, and timing

Resumen

Lobesia botrana (Lepidoptera: Tortricidae), also known as the European grapevine moth, is one of the majar harmful pests detectad in worldwide vineyards. The current control methods have limitations, and expanding the available biological control agents can provide new strategies in both 1PM and organic viticultura. Entomopathogenic nematodes (EPN) are well-known biological control agents far numerous soil pests. Thanks to the current application systems, such as the use of adjuvants, their implementation against aerial pests is now possible. Previous laboratory experiments probed the control capability of the EPNs Steinemema fe/tiae and S. carpocapsae against L. botrana at various larval stages and pupae. We hypostatized that by selecting the best combination of EPN-adjuvant, target area in the grapevine and the timing (season/temperatures), we can enhance EPN efficacy as a biocontrol agent against L. botrana. The aim of this study was to screen far the best EPN-adjuvant mix and to determine the best ecological scenarios far their use against L. botrana. We investigated (i) survival, viability, and adherence on leaves of EPNadjuvant mix, (ii) protection capability (mortality of L. botrana and reduction of its damage) in leaves, grapes, and trunk bark, and (iii) EPN activity against L. botrana at low temperaturas as a proxy of the overwintering period. The screening of five adjuvants (Multi-Us, Maximix, Dash HC, Nu-Film-17 and Adrex) and a subsequent combination (Multi-Us+Maximix), showed generally high compatibility with all the adjuvants, resulting Maximix as the best candidata far the EPNs S. feltiae and S. carpocapsae. Comparad with the noapplication treatment, Maximix combinad with EPN increased their killing against L. botrana L3 on grapes and leaves with significant reduction of the damage. The study of the pupae in the trunk bark system at 22ºC, 14°C, and 10°C showed that mortality caused by EPNs decreased with temperatura, from ~60% at 22ºC to values ~20% at 1 0ºC, and the use of Maximix in this scenario did not improve their efficacy. Overall, the results showed that the combination with Maximix can enhance the survival, infectivity, and adherence of the EPN S. feltiae and S. carpocapsae. In addition, these species combinad with Maximix reduced the damage caused by L. botrana L3 in leaves, and grapes. However, this combination did not improve their efficacy against pupae. Finally, we suggest their application at sunset and late spring/ealy autunm (March/September) to target mid-temperatures (22ºC-15°C). Further validation in field conditions is necessary far their full implementation.