Bacterial blight, caused by Xylophilus ampelinus (PANAGOPOULUS) WILLEMS et al. is a destructive disease of grapevine (Vitis vinifera). Incubation of cuttings at 15 degrees C for three days under moist conditions significantly increased the number of isolated X. ampelinus colonies. This treatment facilitates the isolation of the pathogen from infected material from which it could previously not be isolated.

Litchi die-back is becoming a serious problem in litchi orchards in South Africa where adult trees become sick and eventually die. Together with a survey conducted in all litchi producing areas in South Africa to determine the main agents causing the disease, trials in Tzaneen, Limpopo Province, and Nelspruit, Mpumalanga Province, with both nematicides (including cadusaphos and fenamiphos) and fungicides (chlorothalonil/metalaxyl, carbendazim and captan) were conducted to determine the efficacy of the products over a period of 3 years. Results showed that the disease should be controlled in the early stages of development. A fungicide able to kill soil pathogens like Phytophthora and Pythium will be able to control litchi die-back if applied early enough. If nematodes are a problem they should be controlled with a nematicide as nematodes enhance stress of the root system and therefore making the tree more susceptible to litchi die-back. Other management practices such as irrigation, fertilization and soil preparation should be optimal as this will reduce stress to the tree.

A sensitive and specific assay was developed to detect bacterial blight of grapevine caused by Xylophilus ampelinus (Panagopoulos, 1969) comb. nov. in grapevine cuttings. The 16S−23S rDNA intergenic spacer region of X. ampelinus was sequenced and pathogen‐specific primers were designed from a region in the spacer between the tRNA (Ala) and the 23S genes. A nested PCR (n‐PCR) reaction was applied with a first‐stage PCR using universal primers within the ends of the 16S and 23S genes, followed by a second‐stage PCR with nested primers specific to the X. ampelinus spacer region. A 277‐bp fragment was amplified from 38 Xylophilus strains tested, but not from saprophytes associated with grapevine or phylogenetically related phytobacteria. The 277‐bp product was shown to be derived from the X. ampelinus spacer region by restriction with Dra I, Sau 3AI, Taq I and Msp I, Southern hybridization and genomic DNA dot blots. When the (n‐PCR) procedure was applied in the absence of nontarget DNA, the limit of detection was less than 10 colony‐forming units (CFU) per µL. The same number of X. ampelinus CFU could be detected in the presence of 1·5 × 105 CFU µL−1 of Erwinia herbicola cells using the n‐PCR procedure.

Crown gall of hop caused by Agrobacterium tumefaciens biovar 1 is reported for the first time from South Africa. The causal organism was inhibited in vitro by the agrocin of A. radiobacter strain D286 but not by that of the control strain K84. Nevertheless, control was achieved on hop stems in glasshouse inoculations by both biological control strains.