Influence of Canopy Cover and Meteorological Factors on the Abundance of Bark and Ambrosia Beetles (Coleoptera: Curculionidae) in Avocado Orchards Affected by Laurel Wilt

Octavio Menocal,Edvan A. Chagas,Armando Padilla,Paul E. Kendra,Jonathan H. Crane,Pollyana C. Chagas,Daniel Carrillo

doi:10.3390/agronomy12030547

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 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 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). Canopy management alters the microclimatic conditions in avocado orchards, affecting ambrosia beetle abundance and flight activity.

Highlights

Avocado (Persea americana Mill.) is the most important commodity from the Lauraceae family
Species previously reported in association with the laurel wilt (LW) pathogen (i.e., X. crassiusculus, X. affinis, X. volvulus, X. bispinatus, and X. saxesenii) were more abundant in orchards 2 and 3 (Table 1)
Species not known to interact with the LW pathogen in avocado (i.e., A. lecontei, A. minor, E. perbrevis, P. cavipennis, T. ricini, X. andrewesi, X. gracilis, Hypothenemus spp., and E. parallelus) were more abundant in orchard 1

Summary

Introduction

Avocado (Persea americana Mill.) is the most important commodity from the Lauraceae family. Avocado production in the Americas has increased significantly in the past two decades. In the United States, avocado production in Florida has been impacted by a new lethal disease known as laurel wilt (LW). This is a fungal disease transmitted by ambrosia beetles (Coleoptera: Curculionidae: Scolytinae: Xyleborini) that represents a potential threat to avocado industries in California, Mexico, and the rest of Latin America. Xyleborus glabratus Eichhoff, is rarely detected in avocado systems [2,3,4,5,6,7,8], other ambrosia beetle species have acquired this symbiont and function as alternative vectors [9,10,11]

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