Semipersistency of <Emphasis Type="Italic">Myzus persicae</Emphasis> Transmission of Cucumoviruses Systemically Infecting Leguminous Plants

Sequential transmission tests of Peanut stunt virus (PSV) and Cucumber mosaic virus (CMV) systemically infecting common bean, Phaseolus vulgaris, were conducted using Myzus persicae allowed to fast for 2 hr and then to acquisition feed on infected common bean plants or purified virus for 10 min. In the sequential transmission tests using either one or 10 aphids per assay plant, three isolates of PSV (J,S,Y5) and one of CMV (V) were transmitted from and to common bean up to a third or fourth inoculation access. Many aphids transmitted these viruses to two or three plants. Purified viruses of PSV-S and CMV-V were also transmitted up to a third or second inoculation access at low percentage. On tobacco, Nicotiana tabacum, aphids transmitted PSV-S and CMV-V only in the first inoculation access, although PSV-S was transmitted to only one plant in the fourth and fifth inoculation access. These viruses may be transmitted in two phases by aphids, depending on the plant species. Received 16 April 1999/ Accepted in revised form 1 September 1999     

Survival and Fluctuation in Density of Myrothecium roridum in Mulberry Field Soil

The density of Myrothecium roridum increased in field soil from June to October and decreased from February to April in 1996–1998. The fluctuation in density of M. roridum in the surface soil was affected by the average temperature. In the greenhouse, mulberry leaves were infected by conidia that splashed from soil artificially infested with conidia of M. roridum at 10³ or more conidia/g soil. Disease incidence on mulberry increased when soil was amended with the fallen leaves and when mulberries were planted densely in soil artificially infested with a high conidial density of M. roridum. Received 9 December 1999/ Accepted in revised form 21 July 2000