Phoenix canariensis Hort. in Carthage, Sidi Bou Saïd and La Marsa for the eradication of the red palm weevil Rhynchophorus ferrugineus. (Olivier) 1790.
Evaluation of the mechanical interventions on ornemental palms Phoenix canariensis Hort. in Carthage, Sidi Bou Saïd and La Marsa for the eradication of the red palm weevil Rhynchophorus ferrugineus (Olivier) 1790 Lilia Allouche (1), Sabrine Chihaoui (1), Bouzid Nasraoui (1) , Michel Ferry (2) and Brahim Chermiti(3) 1
National Agronomic Institute of Tunisia 2 Scientific director of the Phoenix station, Elche, Spain 3 Higher Agronomic Institute of Chott-Meriem, ,Tunisia
Introduction Since its detection in Tunisia, the red palm weevil is considered as a serious threat to the Tunisian oasis. Internal quarantine measures have been implemented to prevent the spread of this pest. Despite all the efforts made, the infested areas are still increasing. It is now present in Tunis, Carthage, Marsa, Sidi Bou Said, Goulette, Kram, Soukra but also some places at the south and the north of Tunis. The damage of the pest has been observed on ornamental palms trees Phoenix canariensis. Due to the capacity of this pest to extend quickly and given that nowhere in the world measures of containment have been successful to avoid its extension, , the Tunisian authorities in collaboration with several institutions have established a strategy aiming the eradication of the pest in order to limit its spread and prevent its installation in Tunisian oasis. One of the measures to manage the situation has been to adopt mechanical interventions on infested palms (mechanical Sanitation, pollarding and cutting down). We present the results in three sites: Carthage, Sidi Bou Said and Marsa and evaluate these actions and their effectiveness.
Materials and Methods Study areas
Plant materials: Host plant
Mechanical operations Table 1: Operations and necessary equipment used during the mechanical interventions Equipment Operation Definition Stage and gear
In Tunisia, specifically in Cutting down the northern suburbs of Tunis ( Goulette Kram, Carthage, Sidi Bou Saïd, Marsa and Soukra), two species of palms are present: Phoenix canariensis L. Pollarding and Washingtonia filifera. (André) 1879 However, R. ferrugineus prefers P. canariensis L.
Marsa Sidi Bou Saïd
Carthage
An extreme solution. Is only advisable if the palm could not recover by mechanical sanitation or not be treated after this operation
For palms at the stage 4 (all Telescopic the leaves felled down and Chain saw dried) and for palms less infested for which preventive treatments after sanitation cannot be regularly and surely implemented
Operation performed on Sunk palm trees. Idem Consists in pollarding the head of the palm just below the infested area
Telescopic Chain saw
Mechanical Mechanical removal of Stage 1,2 : healthy terminal Telescopic sanitation infested parts above the bud. For stage 3: the success Chain saw
terminal bud allows palm to recover its foliage in a few weeks
Fig.1: Geographic position the three study areas: Carthage, Sidi Bou Said and Marsa in northern Tunisia
Results
70
and Fungicide Spray
of sanitation is low
64
60
Number of palms
50 41 40 32
Sanitation Pollarding Cutting down
30 20
16
15
26%
10
19 Marsa
50%
13
Sidi Bou Said
10
9 Carthage
5 0
0
0 Carthage
Marsa
24% Sidi bou Said
Study area
Fig. 2: Geographic distribution of palm trees attacked by the red palm weevil in the three studied areas
Fig. 3: Type of interventions and number of palm trees treated by area 45
Fig. 6: Re-infestation rates of regenerated palm trees in the three study sites
43
40
Number of palms
35 30 25
5%
27
26
Sidi Bou Said
5 21
20
regenerated unregenerated
15
15
Marsa
49%
54
50
46%
10
Carthage
5
5 0 Carthage
Marsa
Sidi bou said
Study area
Fig. 4: Localization of palms mechanically sanitized in the study areas from 15/01 to 15/05/2014
Fig. 5:Number of regenerated and unregenerate palms in each study area
Fig. 7: Proportions of infested and untreated palm trees in the three study sites
Discussion
The cutting down and the pollarding of palms that could regenerate after mechanical sanitation are extreme solutions that mean the loss of landscape patrimony without any supplementary benefit for the RPW control. The use of these operations should be performed only when mechanical sanitation could not be followed by regular preventive treatment to avoid re-infestation. On the other hand, the cutting down operation requires a lot of time, heavy means and manpower. The mechanical sanitation is a curative treatment that must be considered as a control method as it allows the complete elimination of the RPW from infested palms. The highest regeneration rate was found in the area of Marsa followed by the city of Carthage because of an easier access to the palm trees and a larger number of palm trees that were at a low or middle stage of infestation (terminal bud intact) making low the failure rate of sanitation operation. However, in Sidi Bou Said the percentage of recorded success was probably lower because of the rugged ground and slopes and inaccessibility of palm trees located in residences and presidential dwellings (Palace of Sidi Dhrif) making the achievement of the sanitation difficult or even impossible. The great profitability of mechanical sanitation has been limited. The failure of regeneration is due to several factors. Degree of infestation and season of treatment are key factors. If the palm is deeply infested, sanitation will oblige to come too close to the terminal bud. Too deeply infested palms should be pollarded or cut down. Climatic conditions have a major influence on the palms status: the ability of the cut central leaves to grow quickly and of a new foliage to develop is fundamental to protect the fragile tissues that have be exposed by the sanitation operation. This ability depends of the season. Mechanical sanitation must be avoided from the end of autumn to the end of winter; Skillfulness of the operators is also an important factor. Furthermore, the risk of re-infestation of the sanitized palms will be very high if they are not treated. Unfortunately, the regenerated palms were later neglected and have not undergone a continuous monitoring and a regular treatment
Conclusion and Prospects The monitoring of the palms status that have undergone mechanical operations ( mechanical sanitation , pollarding and cutting down) shows that most of the infested palm trees were treated except a few that have been abandoned and can constitute a source of dissemination of the pest. In fact, the temperature is a factor to take into consideration when planning the recommended sanitation rather in springtime for more success. Regeneration of remediated palms showed a great efficiency in the three study areas reaching a success rate of 70%. However, the regenerated palm trees have to undergo a continuous monitoring and a regular chemical treatment in order to avoid the re-infestation of these palms
