Types of frass produced by the ambrosia beetlePlatypus quercivorusduring gallery construction, and host suitability of five tree species for the beetle

Abstract

We studied the biology of the ambrosia beetle Platypus quercivorus in the logs of five tree species to determine: (1) the relationship between the amount of frass produced by beetles and tunnel length, (2) the relationship between frass shape and the morphological characteristics of P. quercivorus mouthparts, and (3) the suitability of five tree species for P. quercivorus reproduction. Five logs each from healthy Quercus crispula, Q. serrata, Castanea crenata, Sorbus japonica, and Cryptomeria japonica trees were used in this experiment. The results showed that there was a linear relationship between the amount of frass and tunnel length. Whenever powdery frass was produced, larvae were found in the gallery in the log, while fibrous frass was present only in galleries that contained just adults. The mouthparts of adults were completely sclerotized, which likely accounts for the fibrous frass production. Host preference of P. quercivorus was examined at two stages using five tree species. The first stage is digging initiation, which concerns male preference for digging a tunnel. More holes were made by males on S. japonica and Q. serrata logs, while fewer holes were made on C. japonica logs. The second stage is characterized by female orientation, mating, and progeny development. Platypus quercivorus could complete its lifecycle only in the two Quercus spp.

TWO ACTIVE STAGES OF THE AMBROSIA BEETLE, Platypus quercivorus MURAYAMA ESTIMATED FROM FRASS PRODUCTION

“…Tarno et al (2011) reported that fibrous frass indicated both male and female activity in the boring tunnel for reproduction. First a male makes a simple tunnel.…”

“…Adult males start the formation of galleries in June and females begin to deposit eggs at the terminal parts of tunnels two to three weeks after the commencement of gallery formation (Sone et al, 1998). More eggs are laid in healthy logs than infected logs by Raffaelea quercivora of Q. crispula, or in logs of any other tree species (Tarno et al, 2011).…”

“…Like other ambrosia beetles, Platypus quercivorus Murayama also produces gallery excrement/frass when attacking fagaceous trees and logs such as Quercus crispula and Q. serrata (Ueda and Kobayashi, 2001;Tarno et al, 2011). Adult males start the formation of galleries in June and females begin to deposit eggs at the terminal parts of tunnels two to three weeks after the commencement of gallery formation (Sone et al, 1998).…”

“…The presence of adult or larval stages of ambrosia beetles such as M. mutatus and P. quercivorus was evaluated by the presence of the different types of frass in the holes or on the base of the trunks (Girardi et al, 2006 andTarno et al 2011). There were two types of frass produced by P. quercivorus beetle: fibrous and powdery frass.…”

“…Whenever powdery frass was produced, larvae were found in the galleries, while fibrous frass was present only in galleries with just adults. The mouthparts of adults are completely sclerotized, which likely accounts for the fibrous frass production (Tarno et al, 2011). Because detailed observations of the life cycle are difficult, as sampling is necessarily destructive (Kent and Simpson, 1992), we proposed to monitor the frass production both in the field and under laboratory conditions to study the long-term changes in P. quercivorus activity carried out deep inside the wood.…”