Oviposition by the leafhopperAmrasca devastans (Distant) on its susceptible host plant, cotton (Gossypium hirsutum var. PS-10), was inhibited by the volatiles of certain plants and by the vapors of some chemicals occurring in various plants when these were presented at a distance from the ovipositional substrate. The effectiveness of the volatiles of the plants for inhibiting the oviposition decreased in the order: eucalyptus > coriander=castor=tomato > lime,Ocimum being without effect. Among the volatile plant chemicals tested, the inhibitory effects decreased in the order: citral=carvacrol > citronellol=farnesol = geraniol=eucalyptus oil > neem oil=Cymbopogan oil. These chemicals served as volatile antiovipositants and did not reduce the arrival/stay of the insects on the host plants. Carvacrol had a slight toxic effect on the nymphs, but none of the volatiles was toxic to the adults.

SummaryIsolates of rose mosaic virus (RMV) from South Australia were purified by differential centrifugation of cucumber extracts clarified by emulsification with ether, followed by sucrose density-gradient centrifugation. The virus was shown to be serologically similar to and to have many physical properties in common with RMV from North America. However, the Australian isolates studied appear to hlwe narrower host ranges.It has been confirmed that RMV is serologically related to apple mosaic virus, Prunu8 necrotic ringspot virus, and Danish plum line-pattern virus, and a serological relationship between RMV and cherry rugose mosaic virus has been established. Although RMV has certain physical properties in common with cucumber mosaic virus and alfalfa mosaic virus, no serological relationships were demonstrated. The inclusion of RMV in the Prunus necrotic ringspot virus group is discussed and it is suggested that the name RMV be confined at present to virus isolates inducing line-pattern symptoms in rose plants.

Fulton (1952) reported the transmission of rose mosaic virus (RMV) by mechanical inoculation from Rosa setigera Michx. to cucumber and thereafter to other herbaceous plants. This made possible the characterization of the virus, and later, its purification (Fulton 1967). In South Australia we have been unable to transmit viruses from rose leaves, flowers, or roots by mechanical inoculation directly to herbaceous plants. However, we have transmitted several virus isolates by patchbark grafting rose material to young peach seedlings and then mechanically transmitting virus from young peach leaves to cucumber seedlings (Basit and Francki, unpublished data). From at least one rose plant we have consistently isolated two pathogens via peach seedlings to cucumber seedlings, both of which were at first thought to be viruses but later one of the pathogens was identified as a species of Pseudomonas. Experimental and ResultsYoung leaves of peach seedlings [Prunus persica (L.) Batsch cv. Elberta], patch-bark grafted with diseased material of garden rose cv. Peace, at least 1 month previously, were ground with water in a pestle and mortar. The extract was mechanically inoculated to carborundum-dusted cotyledons of young cucumber (Cucumis sativus L. cv. Polaris) seedlings which developed chlorotic and necrotic lesions 3-4 days later and subsequently the plants often collapsed from wilting. No symptoms were produced by inocula prepared from ungrafted control peach seedlings. On mechanical inoculation of Chenopodium quinoa L. and Momordica balsamina L. with extracts of diseased cucumber cotyledons, young C. quinoa leaves developed mosaic symptoms (Fig. 1) whereas M. balsamina developed necrotic lesions only on the inoculated leaves (Fig. 2). When the pathogens were reinoculated to cucumber seedlings from each of these plants, the symptoms produced by inocula from the two species were quite distinct (Figs. 3 and 4) and the pathogen recovered from C. quinoa was serologically identified as a strain of RMV. The pathogen recovered from M. balsamina produced small necrotic lesions with yellow margins * Manuscript