Although several biological control agents (especially Fungi & Nematodes) have been reported against red palm weevil, unfortunately these are not effective in the field, due to constraints associated with delivery and sustenance.
As regards detection of infested palms, currently regular (1-2 month interval) periodic visual inspection of palms is the only reliable method of detecting infested palms. Acoustic detectors are promising but are not yet field worthy. Besides Acoustic detection, research to develop user friendly detectors based on detection of chemical signatures, thermal imaging,X-ray, high frequency radar technology etc are in progress.In large corporate date plantations sniffer dogs could be trained to detect infested palms but this technique also has its own limitations.
Trap and bait free 'Attract &Kill' technology can be introduced where additional food baited pheromone traps need to be deployed.
its interesting point that you highlight on, now I work on a new project to isolate entomophagous fungi from soil and I will be tested on some key pests. please if you have some adult of red palm weevil so we can maybe work together to evaluate these fungi on it.