Data were collected to estimate transmission efficiency, infectivity and net transmission rates, latent and retention periods, and retention and efficiency indexes of the strawberry crinkle virus (SCV) transmitted by apterae of Chaetosiphon fragaefolii (Cockerell) and C. jacobi (Hille Ris Lambers) infected by injection. The infectious extracts of (SCV) were prepared from virus-infected donor aphids. Data also were collected on the longevity and larviposition of SCV-infected as well as comparable apterae that were injected with similar extracts prepared from SCV-free aphids. Additional trials were done to assess the probability of transovarial passage (TOP). The effect of infection was monitored by serially transferring individual aphids to healthy Alpine strawberry test seedlings at 24-hr intervals at constant temperature (25°C) and continuous light until all aphids had died.

The data on the comparative biology supported the following conclusions: 1.

Injection with SCV resulted in reduced longevity of both vectors, with no significant evidence that the effect was different between the species.

Infection tended to reduce the number of larvae produced by C. fragaefolii, but not by C. jacobi.

The net reproductive rate of both infected and healthy C. jacobi tended to be lower than that of healthy C. fragaefolii.

Infection tended to reduce the generation time and to increase the intrinsic rate of population increase more for C. fragaefolii than for C. jacobi, but neither parameter appeared to be significantly affected by SCV infection.

Evidence of TOP included electron microscopic confirmation of SCV-like particles in two C. jacobi “aborted” embryos and by transmission by one larval cohort from an infected C. fragaefolii aptera.

The transmission data from the five comparative trials supported the following conclusions: 1.

Sixty-eight to 100 percent of the individuals of both species transmitted virus following injection.

SCV had a similar median latent period in both aphid species, but C. fragaefolii tended to have a somewhat higher net transmission rate of the virus than did C. jacobi.

The retention period of SCV and the virus retention and transmission efficiency indexes for the two vector species were similar.

The current information available on the biology of C. fragaefolii and C. jacobi and on the aphid transmission of SCV is reviewed and discussed. This information indicates that C. fragaefolii is the only known vector of SCV in commercial strawberries in California. C. jacobi does not infest commercial cultivars, and C. thomasi (Hille Ris Lambers) is believed to be confined to species of wild and cultivated roses.