Emergent and potentially invasive weevils are a permanent threat to the survival of palm plantations. Hence, understanding the role of emergent pests may be key for preventing future phytosanitary emergencies. In the present study, the role of Rhynchophorus palmarum L. and Dynamis borassi F. (both Coleoptera: Curculionidae) as main causative agents of the peach palm (Bactris gasipaes Kunth; Arecaceae) crown toppling problem were investigated, and the damage was described in 36 farms in the principal production areas of Colombia. A management strategy with the use of 2 pheromones (Rhynchophorol and Ferrolure) in 2 production areas also was evaluated. In total, 4,098 palms were examined from Nov 2017 to Feb 2019. Visible damage oscillated between 0 to 70% of palms affected and was highest on the Pacific coast. Larvae of D. borassi were found exclusively in the inflorescences suggesting that it initiates the damage. Meanwhile, adults of D. borassi and all stages of R. palmarum were recovered from stem damages. Also, new reports of damage were confirmed at the southern Pacific coast, the Andes, and the Amazon region. A total of 8,239 D. borassi and 2,886 R. palmarum were captured in pheromone traps for 14 mo on the Pacific coast. The traps baited with Ferrolure + Rhynchophorol captured a greater number of D. borassi specimens. The data strongly confirm the central role of D. borassi in peach palm damage. Therefore, it is recommended strongly that pheromones be used to prevent further spread of this pest in other countries of this region and to protect palm industries.

The morphology of the larvae of Dynamis borassi (Fabricius) and Rhynchophorus palmarum (Linnaeus) was compared, described and illustrated. A complete definition of subtribe Rhynchophorina at the larval stage was elaborated, based on mature and submature larvae, and characters of the first instar larvae are provided for the first time. Diagnostic characters to distinguish the larvae of D. borassi and R. palmarum are mainly from the epipharynx and maxillae, but the abdominal terminal plate also provides differential features that can aid in the identification. The characterization of both species at the larval stage is expected to be useful in the implementation of new control strategies in palm plantations in South America. For practical reasons, a comparative table is appended in Spanish to serve as a quick diagnostic guide for species identification.

During studies to adapt pheromone trapping of Rhynchophorus palmarum to the special coconut growing conditions at the Colombian Pacific coast, 152 atypically-colored specimens were captured in a total collection of 53,802 of the normally completely black weevil. Five specimens had the typical coloration of Rhynchophorus ferrugineus, an invasive species recently introduced to Aruba and Curação. A regional expansion of this invasion to the South American continent was feared and all atypical specimens were submitted to taxonomic analysis. Both conventional and molecular methods were employed. Conventional taxonomics confirmed the samples as belonging to R. palmarum but registered undescribed and species-atypical morphological variability in the subgular suture (wide vs. narrow), the ratio between intraocular distance and width of antennal scrobes (>0.35 vs. < 0.29) and the indentation of the mandibles (up to three mandibular teeth vs. bilobed). Molecular analysis placed all samples inspected, black and reddish alike, firmly within the R. palmarum group and the hypothesis of having inter-specific hybrids was rejected using co-dominant single sequence repeat markers with allelic specificity for both species.

Deforestation produces homogeneous agricultural environments creating an imbalance between herbivores and their hosts. Since 2010, there has been a phytosanitary crisis in the peach palm (or chontaduro), Bactris gasipaes in the Colombian Pacific Region which can be attributed to two species of palm weevils: Rhynchophorus palmarum and Dynamis borassi. It has been proposed that deforestation of native palms, used by these weevils, induces these to find new resources in the peach palm. This study examined the association of these two weevils with native palms near chontaduro crops and how this occurs in two types of habitats. Six secondary forests and six anthropogenically disturbed areas were visited in third administrative division: “corregimientos” 1 and 2 (Zone A) and 7 and 8 (Zone B) in the municipality of Buenaventura. Three 50 x 100 m plots were designated in each zone, all palms with damage being recorded; the sampling was also complemented with a free sample. Twelve palm species distributed into one subfamily and nine generawere identified. A total of 271 unopened inflorescences were examined in Zone A and 501 in Zone B. Only evidence of damage was found in individuals of the “milpesos” palm (Oenocarpus bataua), an economically exploitable species. The proportion of palms affected in terms of habitat was significantly higher in the disturbed habitat. This is the first record that quantifies a high percentage of association between D. borassi and the “milpesos” palm in the Colombian Pacific Region, a phenomenon that could be explained by agroecological hypotheses.

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