Fitness of the European grapevine moth (Lobesia botrana)on different grape varieties

【Objective】Lobesia botrana is a newly invasive quarantine pest that has recently entered Turpan, China. This pest completes five generations per year in Turpan, damaging different parts of grapevines across generations, leading to widespread grape fruit rot and causing significant economic losses to the local forestry and fruit industry. Over 550 grape varieties are cultivated in Turpan, with Vitis vinifera‘Sultana’accounting for approximately 90% of the planting area. This experiment investigated the development and growth of L. botrana on different grape varieties, aiming to screen for varieties unfavorable to the pest’s selection and development, and to preliminarily clarify the susceptibility of different grape varieties to L. botrana.【Methods】Six major grape varieties cultivated in Turpan (V. vinifera‘Manaizi’, V. vinifera‘Bolero’, V. vinifera‘Flame Seedless’, V. vinifera‘Sultana’, V. vinifera ‘Manicure Finger’and V. vinifera‘Ribier’) were selected for the study. L. botrana larvae were reared on grape berries at different developmental stages (inflorescence, young berry, and mature berry). Developmental indicators for each insect stage were measured to compare effects on growth and population increase. Measurements included larval weight and body length at different instars, pupal length, width, and weight (with sex identification), adult longevity, and female fecundity (egg production). Developmental duration and survival rates were also recorded. Larvae were reared on three food resources (inflorescence, young berry and mature berry) from the six grape varieties, with three replicates per treatment. By comparing growth indicators, survival rates, and fecundity across insect stages, grape varieties sensitive to L. botrana were identified.【Results】Under the same food resource, multiple growth indicators for 3rd to 5th instar larvae feeding on V. vinifera‘Flame Seedless’were significantly higher than those on other varieties (P＜0.05), while larvae feeding on V. vinifera‘Ribier’showed the opposite trend. V. vinifera‘Flame Seedless’is an early-maturing variety, and the nutritional content of its young fruit stage is more conducive to larval growth compared to other varieties. When feeding on young and mature berries, pupae developed from larvae fed on V. vinifera‘Ribier’had significantly lower growth indicators than other varieties (P＜0.05); conversely, individuals feeding on V. vinifera ‘Flame Seedless’exhibited the opposite, with most growth indicators being higher, possibly related to the transformation of internal nutrients. The sex ratio of adults developed from larvae feeding on different grape varieties within the same food resource (inflorescence, young berry, and mature berry) showed no significant differences, with average sex ratios ranging from 1.019 to 1.588. Regardless of the grape variety tested, L. botrana populations consistently had more females than males, favoring population expansion; the sex ratio was more stable when feeding on mature berry compared to inflorescence and young berry. Individuals developed from feeding on V. vinifera‘Sultana’had the highest fecundity per female, significantly higher than those reared on other varieties (P＜0.05). Average fecundity per female reared on inflorescence was 18.84 eggs, approximately 20%-45% higher than other varieties; average fecundity on young and mature berries both exceeded 30 eggs per female, about 23%-48% higher than other varieties. Adult longevity was longest for those feeding on V. vinifera‘Ribier’young berry and mature berry (10.19 d and 10.48 d, respectively), significantly longer than for those feeding on the other five varieties (P＜0.05). Feeding on V. vinifera‘Sultana’at the inflorescence stage prolonged longevity, while feeding on V. vinifera‘Ribier’at the young berry stage prolonged larval developmental duration and adult longevity. When larvae fed on inflorescence, there were no significant differences among individuals feeding on different grape varieties in survival rate, pupation rate, emergence rate, or total survival rate (P＞0.05). When larvae fed on young berry, there were no significant differences in pupation and emergence rates among individuals feeding on different varieties (P＞0.05); however, larval survival rate was the lowest for those feeding on V. vinifera‘Ribier’(48.89%), significantly lower than other groups except V. vinifera‘Manaizi’(P＜0.05), and total survival rate across all stages was also the lowest (31.03%). Survival rates for larvae and total survival rates for other varieties were at similar levels. When larvae fed on mature berry, there were no significant differences in pupation rate among individuals feeding on different varieties (P＞0.05); larval survival rate was the lowest for V. vinifera‘Ribier’(56.67%). Emergence rates for individuals feeding on V. vinifera‘Sultana’and V. vinifera‘Flame Seedless’were 94.45% and 96.67%, respectively, significantly higher than groups feeding on V. vinifera‘Manaizi’, V. vinifera‘Manicure Finger’, and V. vinifera‘Ribier’(P＜0.05). Total survival rate was the highest for individuals feeding on V. vinifera‘Sultana’(66.50%), significantly higher than groups feeding on V. vinifera‘Manaizi’and V. vinifera‘Ribier’by about 20%-24%. Overall, when feeding on inflorescence and young berry, the group with the highest total survival rate was V. vinifera‘Flame Seedless’; when feeding on mature berry, the group with the highest survival rate was V. vinifera‘Sultana’.【Conclusion】Grape varieties with compact fruit clusters, such as V. vinifera ‘Flame Seedless’and V. vinifera‘Sultana’, are highly suitable for L. botrana fitness; relatively speaking, varieties with loose fruit clusters have lower suitability. Different grape varieties influence the growth, development, and reproduction of L. botrana to a certain extent. V. vinifera‘Sultana’and V. vi- nifera‘Flame Seedless’are more conducive to the growth, development, and reproduction of L. botrana, enhancing its survival rate and fecundity, which are more favorable for population expansion.