Abstract
This is the first report of a pathogenic virus in citrus aphids, and its subsequent transovarial transmission. Aphids are important horticultural pests which have few biological control agents available for use in their management. A known entomopathogenic virus, insect iridescent virus 6 (IIV6), was evaluated for pathogenicity to the brown citrus aphid, Toxoptera citricida (Kirkaldy). The virus, an Iridovirus, is a dsDNA virus, with an icosahedral symmetry and is ~120 nm in diameter. Although invertebrate iridescent iridoviruses are known to infect insects, this is the first report of an iridovirus infection in citrus aphids that is pathogenic. Modes of transmission for iridoviruses in other insect systems have been shown to be through oral ingestion and cuticular wounding. We demonstrated virus acquisition by aphids through oral ingestion via artificial membrane feeding experiments, and show the first evidence of vertical, transovarial transmission of an iridovirus, as confirmed by PCR analysis of virus-infected nymphs. Virusfed aphids had a decrease in longevity and reduced fecundity over control aphids. At 19 d post-treatment, the control aphid population had a 30% mortality rate, while the virus-fed aphid adults had a 68.3% mortality rate. Virus-fed aphids had a lower fecundity rate, producing on average 1.6 nymphs per day, while control aphids produced an average of 3 nymphs per day. Entomopathogenic viruses in aphids need to be re-examined for use in developing molecular tools and for their potential as biological control agents.
