Field ecology of sylvatic Rhodnius populations (Heteroptera, Triatominae): risk factors for palm tree infestation in western Ecuador.

Most Rhodnius species (Triatominae) are primarily associated with palm trees. They maintain enzootic Trypanosoma cruzi transmission and are responsible for human infection (causing Chagas disease) through the Neotropics. Assessing whether individual palm traits (ecological and/or botanical) may increase the risk of palm infestation by triatomines is relevant in areas where bugs invade houses flying from peridomestic palms. We developed a novel fieldwork approach with that objective, and applied it to study infestation by sylvatic Rhodnius ecuadoriensis in 110 tagua palms (Phytelephas aequatorialis). Palm infestation (23% overall) was non-randomly distributed in our sample. Palms located in anthropic landscapes were frequently infested (>27%, n=92), whereas no bugs were collected from palms surveyed within forest remnants (n=18; P=0.01). The presence of abundant decaying vegetable matter (P=0.001) and (to a lesser extent) epiphytic plants (P=0.049) on palm crowns and stems increased the probability of infestation and was positively correlated with the apparent density of bug colonies (R2=0.68). A trend towards higher infestation rates in male palms (34% vs. 18%) could relate to female palm management (removal of infrutescences and vegetable debris) in areas where palm seeds are harvested. An outline of 'risk palm ecotopes' and environmental management-based strategies for the control of peridomestic, palm tree-living vector populations are proposed.