Genetic control of Red Palm Weevil

Red palm weevil is difficult to control by current methods, in part because of the inaccessible and potentially cryptic presence of its larvae in infested trees.  This has led to interest in the use of genetic control approaches, both classical methods such as the Sterile Insect Technique, and modern derivatives such as RIDL, in which genetics is used both to separate males from females and to circumvent the need for radiation-sterilisation. In a RIDL control programme ‘sterile’ male insects of the pest species are periodically released to mate with the target pest population; death of progeny due to inheritance of the RIDL transgene leads to population reduction.  Such methods use the mate-seeking behaviour of the modified males to find the females, even if hidden or present only at low density.  The mating-based action also makes such methods extremely species-specific, with minimal off-target effects on other organisms.  The RIDL method is ‘self-limiting’; making it controllable and reversible, in contrast to ‘self-sustaining’ methods where the genetic change needs to persist in the wild population. RIDL strains have been developed for several pest species, with successful field trials for the mosquito Aedes aegypti, but there are as yet no such strains for a palm weevil.  The potential strengths and limitations of such an approach for red palm weevil will be discussed.