Relationships between Tetranychus urticae Koch and some plant viruses.

Abstract

Abstract None of 9 plant viruses tested were transmitted by Tetranychus urticae Koch following short or long acquisition feeding periods. However, the presence in mites of tobacco mosaic virus (TMV), potato virus X (PVX), onion yellow dwarf virus, and tomato bushy stunt virus could be demonstrated by means of bioassay, serology, and/or electron microscopy. Mites acquired TMV in 10 seconds, and percentage of mites acquiring the virus during a 16-hour acquisition feed was nearly 100%. It was estimated that single mites contained about 1.7 μg/ml of TMV of which 0.02 μg/ml was infectious. Retention of TMV in mites depended on the rate of feeding; mites lost infectious virus after 9 days on a host plant but retained a high virus titer for at least 9 days on a nonhost. Mite excretions were infectious, but no infection resulted from this source in the presence of feeding and moving mites. Mites were able to inoculate TMV and PVX deposited on the leaf surface, and number of TMV lesions increased with increasing feeding time and in proportion to the virus concentration put on the leaf. Feeding punctures created by mites could serve as infectible sites for TMV and TMV-ribonucleic acid. No evidence for a release of virus during feeding of TMV-carrying mites was obtained. TMV applied to the mouthparts of mites could be carried to healthy leaves but was not released into the tissue.