Parthenium hysterophorus, a native of Central America, is a problem weed of Australian rangeland, particularly in Queensland. Following field surveys in Mexico, the rust fungus Puccinia abrupta var. partheniicola was selected as a potential biological control agent. One isolate was chosen for further investigation after infection studies with one Kenyan and five Mexican isolates. Assessment of inoculation conditions showed that temperatures of less than 20° C and dew periods of more than 6 hours were required for abundant pustule production. Infection with the rust hastened leaf senescence, significantly decreased the life span and dry weight of Parthenium plants, and reduced flower production 10‐fold. Subsequent host‐range studies against 120 species and varieties, with further screening against a limited number of species conducted under a range of environmental regimes, indicated the rust to be sufficiently host‐specific to be considered for introduction. Additional host‐range tests against sunflowers demonstrated that resistance to P. abrupta var. partheniicola was not modified by prior inoculation with P. helianthi.

Abstract:Triterpenoid profiles from latex of 56 accessions of European leafy spurges (Euphorbia spp.) were analyzed by gas-liquid chromatography. Qualitative and quantitative differences for components of the profiles were employed to distinguish between accessions. Triterpenoid profiles were diagnostic for the species, E. amygdaloides, E. agraria, E. cyparissias, E. lucida, and E. seguierana and were similar for each of these species in accessions collected from distant areas of Europe. By contrast, the 37 accessions of the E. esula complex were separated into 15 groups on qualitative and quantitative differences for components in the profiles. Identical profiles were detected among neighboring accessions as well as those in collections from widely distant sites; conversely, different profiles also were identified for such collections. Profiles among these groups were compared with profiles of 39 United States (U.S.) accessions of leafy spurge from Montana, Nebraska, North Dakota, and South Dakota. Profiles of U.S. accessions, which were less variable than those from Europe, grouped into only 3 of the 15 European groups, whereas one U.S. group could not be placed directly into a European group. This study demonstrates that latex analyses of European leafy spurges can distinguish between spurge populations and will identify potential plant sources of biocontrol agents for application against their leafy spurge counterparts in North America.

No abstract

In August 2002, a sample of Ceanothus was submitted to the Central Science Laboratory by the Plant Health and Seeds Inspectorate with symptoms of wilt and shoot blight. The disease was affecting 10% of 200 containergrown plants at a nursery in East Anglia, eastern England; no recent import connection was found. There were numerous dark brown-to-black diffuse lesions on the stems, with profuse white sporulation on the surface. No sporulation was observed on the leaves, and roots were unaffected.Microscopic examination of the fungus revealed characters typical of the genus Cylindrocladium , primarily due to the presence of a sterile appendage on the conidiophore. Examination of the culture on carnation leaf agar, after 7 days at 25 ° C and 12 h near ultraviolet light, revealed that vesicles were clavate to obpyriform (5-12 m diameter; mean 6·85 µ m) with the widest part below the middle on the majority of occasions (77%). Conidia were hyaline, cylindrical, rounded at both ends, one septate with a range of 44 -58 × 3·5 -4·5 µ m (mean 49·0 × 4·0 µ m). The fungus was identified as Cylindrocladium pauciramosum as described by Schoch et al . (1999). The 5 ′ end of the β -tubulin gene was amplified using primers T1 and Bt2b as described previously (Henricot & Culham, 2002). Comparison of the sequence of the β -tubulin region (accession no. AY880064) with other sequences available in the GenBank database showed it was identical to C. pauciramosum (teleomorph Calonectria pauciramosa ). Koch's postulates were fulfilled by inoculating young plants with a spore suspension (1 × 10 5 conidia mL − 1 ) of the fungus, which was successfully reisolated from the leading edge of infected stems. Control plants did not develop any symptoms. This is the first record of C. pauciramosum in the UK and the first record on Ceanothus . The pathogen has a cosmopolitan distribution and is recorded as affecting other ornamental hosts, but on several occasions has been misidentified as C. scoparium (Schoch et al ., 1999; Henricot & Culham, 2002, Henricot & Beales, 2003 et al ., 1996). In order to analyse the Spanish DED fungal population, 108 isolates were collected from 1992 to 2002 from twigs of DED-affected Ulmus minor trees and stored as described by Brasier (1981). Determination of growth rates at 20 and 33 ° C on malt extract agar, colony morphology, mating type and subspecies were performed as described by Brasier (1981). Reference strains H172, H363 ( O. novo-ulmi ssp. americana ), were used for comparison. Sixteen strains from markedly different isolation origins (La Coruña, Murcia, Navarra or Cáceres) were identified as O. novo-ulmi ssp. novo-ulmi , with a mean in vitro growth rate ( ± SD) of 3·3 ± 1·1 (20 ° C) and 0·0 ± 0·0 mm day − 1 (30 ° C). All the colonies were morphologically typical for O. novo-ulmi ssp. novo-ulmi (powdery and uneven fibrous-striate), and were mating type B. The oldest O. novo-ulmi ssp. novo-ulmi strain was collected in Villadiego, Burgos, in 1994. The identification was checked using RAPD markers (Hoegger ...

Chromolaena odorata (L.) King & Robinson originates from tropical America and is a serious introduced weed in Africa and Asia. A survey for pathogens was conducted in Trinidad and Tobago over a 24-month period. The rust Cionothrix praelonga (Wint.) Arthur is reported in Trinidad for the first time, where it was found at two sites in Temple Village, Armina (altitude 200-300 ft) and on the Macqueripe Road, Chaguaramas. No seasonal fluctuation in the incidence of the disease was observed in the field during the 2-year study. The optimum conditions for infection were established and infection was achieved with laboratory-inoculated plants. Young leaves appeared to be more susceptible to infection than older tissues.