Studies on aphid vectors of Plum pox potyvirus in North America
In North America, Plum pox potyvirus (PPV - EPPO A2 list) was first found in peach and plum orchards in 1999 in Adams County in Pennsylvania (US) and in 2000 in Ontario (CA). So far, in North America, only PPV-D strains have been found. PPV is transmitted in a non-persistent manner by aphids. Studies were done to identify aphid species occurring commonly in Pennsylvania stone fruit orchards, and which could transmit PPV. During these experiments, 3 different PPV isolates were used. Results showed that the 4 following species consistently transmitted PPV in preliminary transmission tests: Aphis fabae, A. spiraecola, Brachycaudus persicae and Myzus persicae. In further transmission tests, Myzus persicae was found the most efficient vector followed by A. spiraecola, A. fabae and B. persicae. These species were able to transmit PPV from infected peach seedlings to the following percentages of healthy peach seedlings: 63, 31, 38 and 32 %. Toxoptera citricida (EPPO A1 list) was found to be an efficient vector, but this species only occurs in Florida and is not present in areas affected by PPV. Metopolophium dirhodum and Rhopalosiphum padi were considered as occasional and relatively inefficient vectors. During these studies no transmission was obtained with: Acyrthosiphon pisum, Aphis glycines, Aulacorthum solani, Macrosiphum euphorbiae, Rhopalosiphum maidis and Sitobion avenae. Preliminary surveys done in peach orchards in Pennsylvania indicated that A. spiraecola and M. persicae were the 2nd and 3rd most numerous species (the most abundant species was R. maidis, which is not a vector). Both A. spiraecola and M. persicae have been observed colonizing peach trees in spring on expanding leaves (later they migrate to herbaceous plants). It is therefore considered that the most efficient vector of PPV is probably M. persicae and then A. spiraecola. It is recalled that in Western Europe (e.g. in France and Spain), Myzus persicae is also considered as the most efficient vector, and that in Eastern Europe, Brachycaudus helichrysi, Hyalopterus pruni and Phorodon humuli are important PPV vectors. Similar transmission studies were also done in the possible transmission of PPV by aphids from infected fruits to healthy plants. It was found that Myzus persicae, Aphis spiraecola, A. fabae and B. persicae could transmit PPV from infested fruits to 50, 35, 0, 0 % of seedlings, respectively.
Sources
Gildow F, Damsteegt, V, Stone A, Schneider W, Luster D, Levy L (2004) Plum pox in North America: identification of aphid vectors and a potential role for fruit in virus spread.
Phytopathology, 94(8), 868-874.