Apricot; Peach, Nectarine

Psyllid vector: Cacopsylla pruni

Sensitive stone fruit species (apricot and Japanese plum) can indicate the presence of ESFY in a given area; thus particular attention should be paid to these hosts.

Follow instructions in Phytoplasma Sample Screening and Confirmation

If you have taken the hands-on phytoplasma specific training at S&T Beltsville lab, you can screen your own phytoplasma samples. Note: You will still have to follow the protocol in the linked document for confirmations.

No specific signs are present.

Ca. Phytoplasma prunorum is associated with ESFY disease, which primarily includes diseases of apricot, Japanese plum, and peach.

Symptoms of ESFY are influenced by species, cultivar, root stock, and environmental factors. There are many tolerant hosts that do not show any symptoms of disease but can harbor infections.

Apricot and Japanese plum trees in general show typical "yellows" symptoms accompanied by leaf roll, followed by leaf reddening, reduction or suppression of dormancy with the consequent risk of frost damage, severe and progressive necrosis, decline, and eventual death of the tree. Peaches exhibit early leaf reddening, severe upward longitudinal rolling of leaves, abnormal thickening and suberization of the midribs and primary veins, autumnal growth of latent buds which produce tiny chlorotic leaves and sometimes flowers, and early leaf fall. The leaves also tend to be "more brittle" than normal.

ESFY affects tree flowers and shoots in winter, which leads to lack of fruit production and chlorosis of the leaves later in the growing season. The early break in dormancy increases the susceptibility of affected trees to frost, which can cause damage to the phloem. Disease often starts with only a few branches affected but the whole tree may become affected as the disease progresses. Infected shoots are typically shorter and bear smaller, deformed leaves. Leaves can drop prematurely. Shoots may die back. Yield is reduced. Fruit on affected branches develops poorly and may fall prematurely.

Follow instructions in Phytoplasma Sample Screening and Confirmation

If you have taken the hands-on phytoplasma specific training at S&T Beltsville lab, you can screen your own phytoplasma samples. Note: You will still have to follow the protocol in the linked document for confirmations.

Phylogenetically closely related to the apple proliferation and pear decline phytoplasmas.

Molecular: A "universal" PCR assay has been developed that enables amplification of the 16S rRNA genes of phytoplasmas. Digestion of these PCR products with selected restriction enzymes provides a DNA fingerprint in the form of 16S rDNA fragment patterns that can be used to determine phytoplasma identity (Ahrens and Seemuller, 1992; Deng and Hiruki, 1991; Lee et al., 1993; Lee et al., 1995; Schneider et al., 1995; Gundersen and Lee, 1996; Smart et al., 1996; Gibb et al., 1999; Jarausch et al., 2000; Heinrich et al., 2001).

Seemuller and Schneider (2004) offer a summary of the molecular studies conducted on on the apple proliferation, European stone fruit yellows, and pear decline phytoplasmas.

Nested and Species-specific PCR: Torres et al. (2004) used nested PCR with 16SrX group specific primers and were able to detect the ESFY phytoplasma in asymptomatic trees.

A primer pair (ECA1/ ECA 2), designed from conserved chromosomal sequences, showed no cross reaction in PCR amplification with other phytoplasmas of the apple proliferation group and proved to be highly specific for ESFY phytoplasma (Jarausch et al., 1998).

Rubio-Cabetas and Sancho (2009) evaluated nested PCR with group-specific primers followed by RFLP and direct PCR with specific primers for Ca. Phytoplasma prunorum from Jarausch et al. (1998). Rubio-Cabetas and Sancho (2009) recommended the nested PCR followed by RFLP analysis for routine diagnosis rather than the direct PCR.

PCR-ELISA: Poggi Pollini et al. (1997) used immunoenzymatic detection of PCR products to detect phytoplasmas, including ESFY.

Co-operational PCR: Bertolini et al. (2007) developed a co-operational PCR coupled with dot blot hybridization for detection of Ca. Phytoplasma mali, Ca. Phytoplasma prunorum, and Ca. Phytoplasma pyri. The sensitivity of this method was at least one hundred times greater than conventional PCR and similar to that achieved by nested PCR and real-time PCR.

Real-time PCR: Torres et al. (2005) developed a real-time PCR that detects Ca. Phytoplasma mali, Ca. Phytoplasma prunorum, and Ca.Phytoplasma pyri (three pytoplasmas in apple proliferation group of quarantine importance). Martini et al. (2007) and Yvon et al. (2009) developed a specific PCR and real-time PCR assay for Ca. Phytoplasma prunorum in plants and insect vectors. Pignatta et al. (2008) developed a specific multiplex real-time PCR procedure that allows the simultaneous detection of ESFY phytoplasma and host DNA, in order to avoid false negatives due to PCR inhibition.