Oak Forests Infestation by Tortrix viridana and its Performance on Three Quercus Species

Abstract

The Tunisian oak forests are susceptible and sensitive to invasion of various pests, among them, the green oak leaf roller, Tortrix viridana, which is considered one of the most destructive defoliators of oak trees in the western Palearctic region. Important defoliations caused by this pest have been observed in different cork oak forests of north-western Tunisia. The study was carried out in five native cork oak (Quercus suber) forests (Ain El Baya, Bellif 1, Bellif 2, Bellif 10, and El Jouza), one zeen oak (Q. canariensis) forest Mzara and the Ain Zena forest which is a mixed cork oak, zeen oak and afares oak (Q. afares) located in the north-west of Tunisia. The average number of larvae per branch varied significantly between sites (6.6 ± 0.77 larvae/branche in El jouza and 0.11 ± 0.05 larva/branche on Q. afares in Ain Zena forest). Budburst timing did not differ between Q. canariensis and Q. afares whereas that of Q. suber occurred about 3 weeks later than the other two species. As the host plant phenology differs from species to another, the larval survival and their development are likely different across the host plant species. Feeding performance of the green oak leaf roller was determined on three host plants including Q. suber, Q. canariensis and Q. afares under laboratory conditions. Larvae grew best on Q. suber. Total larval development time from the 1st to the 5th instar was shorter on Q. suber (24.92 ± 0.26 days) than on Q. canariensis (26.69 ± 0.29 days ) and Q. afares (29.03 ± 0.39 days). Larval mortality of the three host plants did not differ significantly while for the pupal weight, data showed a significant difference where 35.52 ± 9.44, 30.43 ± 8.25, and 22.95 ± 5.34 mg of pupae from the larvae reared on Q. suber, Q. canariensis and Q. afares were noted, respectively

Keywords

• Infestation
• oaks
• performance
• Tortrix viridana
• Tunisia