An iridescent virus fromPopillia japonica (Col.: Scarabaeidae)

Abstract

A very low incidence (< 0.01%) of a blue iridovirus (IV) was found in larvae of the Japanese beetle, Popillia japonica Newman, that were sampled over a two year period on Terceira Island (Azores, Portugal). In the most heavily infected larvae, a deep blue iridescence was observed, particularly in the fat body. Transmission electron microscopy revealed the characteristic crystalline arrays of the hexagonal virus particles in the cytoplasm of fat body cells, tracheal matrix, muscle, hypodermis and blood cells. Crystals of the virus particles were also observed freely circulating in the hemolymph. The average diameter of negatively stained purified virus particles was 157 nm. Similarities and differences with other IVs found in the Scarabaeidae are discussed. Considering the broad host range of some of the iridescent viruses, the relatively recent invasion of Terceira by P. japonica, and the rarity of the virus in the beetle, it is probable that the infection was the result of transmission from another species of soil-inhabiting arthropod. Its value as a potential biological control agent of P. japonica is negligible.

Biology and Management of the Japanese Beetle

“…Bacteria in the genus Serratia colonize the gut, causing depletion of fat body, starvation, and development of an amber color (44). Low incidence of infection by a blue iridovirus was found in the Azores (94). Trophozoites and gamonts of a cephaline eugregarine were associated with JB larvae in North Carolina (154).…”

The Insect Viruses

“…Measurements of dehydrated particles in ultrathin sections are most common and range from about 120 to 130 nm for the small IVs and 180 to 200 nm for large IVs, although several isolates have been reported with intermediate sizes (Stoltz et a1., 1968;Popel-kova, 1982), indicating that size alone is not an infallible criterion by which isolates can be assigned to genera. Measurements from negatively stained material give particle diameters some 20% larger than dehydrated sections (Wagner et a1., 1973;Fukaya and Nasu, 1966;Cole and Morris, 1980;Poprawski and Yule, 1990;Lacey and Adams, 1994). A smaller variant of IV3 showing turquoise iridescence has been detected in laboratory cultures (Wagner et a1., 1973) and was termed "turquoise mosquito iridescent virus./I However, all the studies described in this chapter refer to the original "regular" strain, unless otherwise stated.…”

“…Alternative hosts have also been suspected as providing a source of infection in Japanese beetle, Popillia japonica, populations. About 1 in 10,000 beetle larvae were patently infected, an incidence at which, the authors argued, the disease could not persist unless it originated from another soil arthropod (Lacey and Adams, 1994).…”

Transcriptomics Reveal Several Novel Viruses from Canegrubs (Coleoptera: Scarabaeidae) in Central Queensland, Australia

“…Several viral pathogens have been reported from scarab beetles across the world ( Table 1 ), and some of these can induce significant mortality in pest populations [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. The effective control of the coconut rhinoceros beetle, Oryctes rhinoceros (Coleoptera: Scarabaeidae), in southeast Asia and the South Pacific islands by a double stranded DNA virus (OrNV: Oryctes rhinoceros nudivirus) [ 25 ] is widely considered to be a landmark example of classical biological control, and it represents one of the few examples of successful classical biological control involving an entomopathogen [ 33 ].…”