Influence of canopy cover and meteorological factors on the abundance of bark and ambrosia beetles (coleoptera: curculionidae) in avocado orchards affected by laurel wilt

Authors: MENOCAL, OCTAVIO - University Of Florida; Kendra, Paul; PADILLA, ARMANDO - University Of Florida; CHAGAS, POLLYANA - University Of Florida; CHAGAS, EDVAN - University Of Florida; CRANE, JONATHAN - University Of Florida; CARRILLO, DANIEL - University Of Florida

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2022
Publication Date: 2/22/2022
Citation: Menocal, O., Kendra, P.E., Padilla, A., Chagas, P.C., Chagas, E.A., Crane, J.H., Carrillo, D. 2022. Influence of canopy cover and meteorological factors on the abundance of bark and ambrosia beetles (coleoptera: curculionidae) in avocado orchards affected by laurel wilt. Agronomy. 12(3):547. https://doi.org/10.3390/agronomy12030547.
DOI: https://doi.org/10.3390/agronomy12030547

Interpretive Summary: In the last decade, approximately 200,000 avocado trees in Florida have succumbed to laurel wilt (LW), a fungal disease vectored by ambrosia beetles. Sanitation (e.g., pruning, stumping, and removal of LW-affected trees) and replanting with young trees are cultural practices currently used by growers to reduce the incidence of LW. Surveillance in these managed orchards suggests a decline in ambrosia beetle abundance. In addition, previous research determined that beetle flight activity is influenced by light intensity. Therefore, scientists from the University of Florida (Homestead) in collaboration with USDA-ARS (Miami, FL) investigated the effect of three canopy covers (i.e., full canopy, topworked, and new planting) on ambrosia beetle abundance. A total of 28,184 beetles, representing 15 species, were captured in three replicate avocado orchards over a one-year period. Full canopy cover exhibited the highest number of beetles and the lowest light intensity. The opposite was found for topworked and new planting covers. Additionally, the effect of weather factors on female flight dispersal was documented for five species known to carry the LW-pathogen. Flight activity of Xylosandrus crassiusculus and Xyleborinus saxesenii was highly influenced by abiotic factors, especially solar radiation, whereas the flight of Xyleborus affinis, Xyleborus volvulus, and Xyleborus bispinatus was only partially explained by climatic variables. The results indicate that thinning canopy cover, which increases light intensity, suppresses ambrosia beetle abundance, especially for species associated with the LW-pathogen. Abiotic factors play a critical role in the dispersal of invasive species (X. crassiusculus and X. saxesenii), but their effect is less pronounced on native species (X. affinis, X. volvulus, and X. bispinatus). These findings will benefit avocado growers by identifying cultural practices that can reduce the number of ambrosia beetles in commercial groves, thereby reducing the spread of laurel wilt.

Technical Abstract: In the last decade in South Florida, approximately 200,000 avocado trees have succumbed to laurel wilt (LW), a fungal disease vectored by ambrosia beetles. Sanitation (e.g., pruning, stumping, and removal of LW-affected trees) and replanting with young trees are cultural practices currently used by avocado growers to reduce the incidence of LW. Surveillance in these managed orchards with missing mature trees suggests a decline in ambrosia beetle abundance and previous research determined that female flight activity is influenced by light intensity. Therefore, we investigated the effect of three canopy covers (i.e., full canopy, topworked, and new planting) on ambrosia beetle abundance. A total of 28,184 individuals, representing 15 species within the Scolytinae and Platypodinae, were captured passively in three LW-affected avocado orchards over a one-year period. Full canopy cover exhibited the highest number of beetles and the lowest light intensity. The opposite was found for topworked and new planting covers. Additionally, we documented the effect of meteorological factors on the flight dispersal of five species known to vector the LW-pathogen. The flight activity of Xylosandrus crassiusculus and Xyleborinus saxesenii was highly influenced by abiotic factors (R2 > 0.50), especially solar radiation, whereas the flight of Xyleborus affinis, Xyleborus volvulus, and Xyleborus bispinatus was only partially explained by climatic variables (0.20 < R2 < 0.30). Our results indicate that reducing canopy cover, thereby increasing light intensity, suppresses ambrosia beetle abundance, especially for species associated with the LW-pathogen. Abiotic factors play a critical role in the dispersal of invasive species (X. crassiusculus and X. saxesenii), but their effect is less pronounced on native species (X. affinis, X. volvulus, and X. bispinatus).