CURRENT AND UNEFFICIENT MEANS OF FIGHT
Currently, the main means of control against these two main species are of four types: mechanical, chemical, biological and repellent.
For mechanical means, three techniques are used. The first is the use of nets: infested or susceptible trees are covered with a wintering veil or hail net. In the long term, they must be systematically torn off, crushed and then burned.
The second is the application of a glue on the terminal bud that will prevent females from laying their eggs on the palm.
Finally olfactory traps can be used to attract adults away from the palm trees and capture them.
For biological means, they consist of the use of predators or parasites of the insect to be targeted. As entomopathogenic agents, mention may be made of Beauvaria bassiana, Steinernema carpocapsae and Steinernema feltiae.
For the repellent means, it is used of garlic manure, Neem oil and Fenugreek extract (Stifénia).
As regards the chemical means, multiple treatments are used among which we may mention the use of organophosphorus compounds which inhibit cholinesterase, such as chlorpyrifos (Suxon vert®, Nufarm), acephate, dimethoate (Dimezyl 40 EC®, Agriphyt), and phosalone (Zolone®, Fertiligenic) or the neonicotinoid family (Confidor vert®, Kiros®, Bayer Cropscience).
To overcome these difficulties, these insecticides should be used repeatedly, at a frequency chosen according to the importance of the infestation: for example, when the infestation is weak, two single treatments may be sufficient, one in June. and the other in August; when the infestation is important, the treatment should be monthly during the entire flight period of the parasites.
Moreover, these chemicals prove to be extremely harmful for man, the environment as well as for the production from the treated plant. Once chemically treated, it is no longer possible to sell the production for two years
The latest means of control, endotherapy is the injection of Emamectin Benzoate (Syngenta) directly into the palm of the trunk. 3 to 4 holes are made at the base of the stipe, cannulae are placed and the chemical sucked and conveyed by the sap.
This treatment is effective in killing parasites, it also offers some persistence, but also has significant defects: impossible to reseal the holes in the stipe that weaken the plant and are as many gateways for other parasites. As a result, the treatments can not be performed more than twice.
As with other chemical treatments, this treatment does not prevent the development of pink rot following the decomposition of the bodies of larvae and excrements inside the palm tree. A large number of palms die after treatment.
The fruit production of remaining ones can not be sold for two years after treatment.
In Europe and in all the countries affected by these parasites, the current control methods against P. archon and R. ferrugineus have the major disadvantage of not producing satisfactory results.
None of these means of control has made it possible to stem or eradicate the proliferation of these pests. The direct and indirect losses due to these pests represent several billion euros a year on a worldwide scale.
The situation is critical and palms are threatened with short-term extinction in many areas. There is therefore an urgent need to improve the fight against them.