Xylosandrus crassiusculus (Motschulsky) (Coleoptera: Curculionidae) and Its Fungal Symbiont Ambrosiella roeperi Associated with Arecanut Kernel Decay in Karnataka, India

SIMPLE SUMMARY: The Asian ambrosia beetle Xylosandrus crassiusculus is a polyphagous pest that causes extensive damage to several tree crops. The present research reports the incidence of X. crassiusculus infestations on areca nuts (betel nuts) in India. Beside the new host plant record, the data provided here represent the first documented case of spermatophagy for this beetle and Xileborini in general. Further, investigations confirmed the association of fungal symbiont Ambrosiella roeperi with adult beetles of X. crassiusculus. This fungal symbiont was also recovered from the infested galleries present in the arecanut kernel. A preliminary survey showed that the infestation is so far restricted to a limited number of plantations in the Coastal part of Karnataka, India. Incidence of this symbiotic insect-fungus complex in the economic part of arecanut i.e., kernel is of serious concern. In a climate change scenario, this beetle with fungal symbionts may pose a serious threat to arecanut production in India and elsewhere. ABSTRACT: Xylosandrus crassiusculus (Coleoptera: Curculionidae: Scolytinae) is reported causing damage to areca palm plantations (Areca catechu L.—Arecaceae) in Karnataka (India). In particular, X. crassiusculus has been observed attacking and successfully reproducing on areca nuts; besides the new host plant record, the data provided here represent the first documented case of spermatophagy for this xyleborine beetle. All infestation symptoms of this polyphagous pest were documented and illustrated. The identity of the scolytid, besides morphologically, was confirmed by its DNA barcoding. Eggs, larvae and pupae were found within the galleries of infested kernels. All galleries of the infested kernels were characterized by the presence of whitish to greyish fungal growth. The fungus was identified as Ambrosiella roeperi, a known symbiont of Xylosandrus crassiusculus. Incidence of this symbiotic insect-fungus complex in the economic part of arecanut, i.e., the kernel, is of serious concern. In a climate change scenario, this beetle with fungal symbionts may pose a serious threat to arecanut production in India and elsewhere.