Peach fruit deformation disease: the Greek chronicle and the Chinese evidence

Savvas Pastopoulos, Agronomist, Pastopoulos Agronomics

Five years after the first scattered symptoms at Ampelies, Giannitsa, deformation of peach fruit has become the most serious open question in the area. This article brings together the whole chronicle with dates and file numbers, and exactly what the virological analyses showed and what they ruled out.

It also includes something that has not circulated in Greek. After an exhaustive search of Chinese scientific papers, I found that the same phenomenon has been recorded in China since 1972 and has been studied in depth, with field studies, re-inoculations and histology. That material is published exclusively in Chinese and remains effectively unknown here. The Chinese experience does not prove identity with the Greek problem, but it does give a map that is available from nowhere else.

1. The Greek chronicle, step by step

What the press release of 5 September 2024 actually said

Because it is the fullest public document of the case and is rarely read in full, its substantive points are set out here [1].

A. The six virological analyses of the Institute's Virology laboratory

B. The two acarological examinations of the Entomology-Acarology laboratory

C. What the Institute recommended

• For the mites: a spray the following year early in spring, at bud break and the formation of new growth. Products are always used according to the approvals in force from the Ministry.
• A hygiene measure: after pruning, the cut wood should not remain in the block or in adjacent peach blocks and should, if possible, be destroyed, so that the mite is not carried and spread through it.
• For the viruses: it is noted that in agricultural practice there is no curative measure. Management is exclusively preventive, certified propagation material, resistant cultivars and rootstocks, mineral oil treatments in the first three years, disinfection of pruning tools (indicatively with a 0.5% NaOCl bleach solution for one minute), destruction of the water shoots that aphids prefer, and avoidance of budwood from untested trees.

2. What the virological analyses showed and ruled out

The analyses did find viruses, they are simply not the ones responsible for the picture on the fruit.

The Institute's results of 17/5/2023 (report 626) and 30/5/2023 (report 640) showed the presence of two agents:

The results were forwarded to the Quality and Phytosanitary Control Department of the Regional Unit of Pella, which in consultation with the Institute proceeded to further genetic testing to search for unknown viral pathogens. In the autumn 2023 briefing, the answer was that no clear conclusion on the aetiology could be reached.

3. The mite, the main cause of the problem, the official positions

From September 2024 onwards the official line changes direction. The sequence of wordings also shows the degree of certainty at each moment:

Something that confuses many people has to be stated here, because the two problems appeared in the area at about the same time and are discussed together: dead shoots are an entirely different problem from blind shoots and deformed fruit.

Dead shoots are a fungal disease. They are caused by the fungus the literature calls Fusicoccum amygdali / Phomopsis amygdali, and under current nomenclature Diaporthe amygdali. Its picture is characteristic and recognisable: oval reddish-brown cankers centred on a bud or a leaf scar, which enlarge, acquire a necrotic centre with a purple halo, girdle the shoot and kill everything above the canker. On the lesion, black pycnidia, the fungus's fruiting bodies, are visible with a hand lens [7]. The fungus is recorded in Greece on peach [9].

The difference of practical importance is the timing of infection. The fungus enters through petiole scars during leaf fall in autumn and through bud scale scars and flowers in spring. That is why autumn sprays during leaf fall reduced cankers by 45 to 63% in field trials in the United States [8]. The mite, by contrast, attacks the buds in spring at bud break. Two different enemies, two different intervention windows, two different categories of product.

4. The Aristotle University study: the mite in the buds of all 18 affected orchards

The most complete Greek evidence to date comes from a joint study by the Plant Pathology and Applied Zoology and Parasitology (Entomology) Laboratories of the School of Agriculture, Aristotle University of Thessaloniki, published in the Greek journal Georgia - Ktinotrofia in October 2024 [17]. It examined the two candidate causes in turn, viruses and the mite, on separate samples.

First part: the viruses, once again

In early June 2024 the Plant Pathology Laboratory collected more than 230 samples of fruit and leaves from 27 orchards in Pella and Imathia, from symptomatic and apparently healthy trees aged 2 to 26 years. They were tested by RT-PCR, real-time RT-PCR and high-throughput sequencing (HTS), which detects every virus in a sample, even unknown ones [17].

The Aristotle University plant pathologists reach the same conclusion as the Benaki Institute (section 2): none of the viruses found appears to be directly linked to the deformation [17].

Second part: the mite inside the bud

In September 2024, peach shoots from orchards with deformed fruit in the Neos Mylotopos area near Giannitsa were sent to the Entomology Laboratory. Individuals of the family Eriophyidae were found under the scales of the buds, shoots and flowers [17]. A systematic comparison followed:

The shoot percentages are read from the paper's charts and are approximate; the mean mite numbers are as stated in the text [17].

Shoots from orchards in Imathia with no deformation yet were also examined: no Eriophyidae were found in any bud. Earlier research in Imathia had recorded another species of the family, Aculus fockeui, in buds and leaves, but without causing fruit deformation [17]. So «an eriophyid» on peach is not enough; the link concerns this particular bud mite.

What kind of mite, and how it causes the damage

• Size. 150 to 250 micrometres, invisible to the naked eye [17].
• Genus. According to the team's data it is a species of the genus Eriophyes; confirmation of the species is pending [17].
• Where it lives. Exclusively or mainly inside the buds, like E. insidiosus. Active all year, with limited activity in winter. The bud protects it from desiccation and sunlight and gives it undifferentiated tissue to feed on [17].
• How it spreads. Mainly by wind: when a bud dries out, the individuals move to the surface and disperse to new buds [17]. This fits the spread from the contact line into the field (section 2).
• How it causes the damage. It feeds with two stylets and salivary secretions that can kill cells and deform plant parts. The damage probably happens inside the bud and shows the following year, when the bud opens and fruit sets [17].
• Short internodes. On many shoots of affected trees the internodes were shorter, i.e. the buds closer together. The same symptom, together with fruit deformation, is described for E. insidiosus in Mexico [17]. It is an additional sign that can be recognised at pruning.

What the team proposes

Control trials to confirm the mite's role: pilot applications at different timings, with substances of specialised acaricidal action, aimed at the mites inside the buds before new growth breaks, evaluated by sampling buds before and after treatment [17]. Any product is used only on the basis of the Greek Ministry's approvals, which are valid in Greece only.

Sources: 17

5. China: fifty years with the same phenomenon

The Chinese record is the fullest available, because there the phenomenon is not new, it has been studied for decades, with field studies, re-inoculations and histology.

The common names of the disease in Chinese are 猴头果 (houtouguo), «monkey-head fruit», and 疙瘩桃 (gedatao), «lumpy peach», names that describe exactly what is seen here as well.

6. The mite and what exactly it does

In the Chinese literature the causal agent is identified as Eriophyes catacardiae Keifer, in Chinese 下心瘿螨. It is an eriophyid mite, that is, from the same family as those found in the Greek samples.

Sources: 13 14

On the fruit

• After petal fall, irregular dark green spots appear on the small fruit.
• As the fruit grows, the down at the affected points turns brown, and the area shows delayed growth with a sunken, concave form.
• At the final stage the fruit is misshapen, unevenly coloured, in a «monkey-head» form. The affected flesh remains deep green.
• Under severe infestation the flesh becomes woody and the fruit inedible.
• Where infestation occurs during swelling: cracks on the surface, some deep and long.

In the buds, this is where the next year is decided

This is the part that connects directly with the bud abscission and blind shoots described in the Greek orchards:

• Affected buds become dry, shrivelled, thin, and cling tightly to the shoot.
• The scales increase by one or two layers and gradually lignify, so the bud is tightly wrapped and struggles to open.
• In histological section, the leaf primordia are damaged; in severe cases they are entirely absent and the bud permanently loses the ability to break.
• Within the scales and between the young leaves, large numbers of feeding mites are found.
• Vegetative buds are attacked more than flower buds.
• Affected flower buds bloom with a delay of about 10 days; some petals wither and drop before they even open.
• A characteristic picture under heavy infestation: trees «with fruit but no leaves», or trees that flower and never come into leaf.

Sources: 13 14

7. The annual cycle, the key to timing

If there is one thing to take from this whole article, it is this. The cycle explains why the damage seen in May was decided the previous summer.

Sources: 10 13

8. The numbers from the Chinese studies

How large the damage becomes

That is, the mean nearly doubled within one year. The authors note the reason explicitly: the disease had first been detected in Lanzhou five years earlier, but because the cause was unknown and no timely control was applied, in the last two years the incidence sharpened [10].

What proportion of the buds is affected, according to the Chinese data

Sources: 13

What happens to the fruit at cell level

Measurements on three cultivars showed that the infestation is not simple surface deformation, the metabolism of the fruit changes:

Sources: 10 13

The numbers in the table say four things, and each is worth reading on its own.

First, the fruit is under stress. The rise in free proline of 111.57% and in catalase activity of about 53% is the classic biochemical signature of stress. Proline accumulates when the cell is struggling to hold its water, and catalase rises when there is an oxidative load to neutralise. The affected fruit is therefore not merely deformed at the surface, it reacts like tissue under strain.

Second, the direction of metabolism changes. Soluble sugars fall, by up to 76.96% in one cultivar, while soluble proteins rise by 66.16% and free amino acids by 64.95%. The fruit stops acting as a sink for carbohydrate and fills with nitrogen compounds instead. The flavour is not lost because the fruit is deformed, it is lost because the sugar is missing.

Third, the flesh cells never reach full size. Their diameter stays at 58 μm against 102 μm in healthy fruit, that is about 57% of the diameter. Since volume varies with the cube of the diameter, the cell holds roughly one fifth of the volume it would otherwise have: 0.57 cubed gives 0.18. The flesh is built from far less mass, and that is why the fruit stays small, ripens late and tastes poor however good it looks.

Fourth, the surface changes too. Trichome density rises from 3.5 to 4.5 thousand hairs per square centimetre and trichome length from 110 to 170 μm. It is a detail that does not show in a photograph but does show to the touch, and it is useful on the grading line: affected fruit is noticeably hairier and rougher than the fruit next to it.

9. How it is managed in China

The Chinese sources converge on four lines of action, with timing the critical element:

Preventive

• Avoid taking budwood and rootstocks from affected trees.
• Disinfect pruning tools.

Cultural

• An open canopy form for better light inside the tree.
• Immediate removal of affected fruit.
• Removal of thin, dry branches at winter pruning.

Biological

• Release of predatory mites during bloom.

Chemical, the timing, not the product

The Chinese sources name specific products, which there is no point in reproducing here: the approval regime in China bears no relation to the Greek one, and an active substance used there may not be permitted at all on peach here. Product choice is made solely on the basis of the approvals of the Greek Ministry for the particular crop and the particular pest, and, outside Greece, of the corresponding national register.

What does transfer, and has real value, is the matching of treatments to phenological stages, because the order of the stages follows from the biology of the mite. The dates do not transfer: Lanzhou lies in a continental climate at high altitude, and the time of emergence from overwintering has not been measured in the Greek production areas. The stages are:

• Autumn, after leaf fall, or at the pink bud tip stage.
• Immediately after petal fall, with one or two treatments.

10. Similarities, differences, and what is not known

The comparison is only useful if it is made honestly. Both sides follow.

The similarities are striking

• Fruit deformation with sunken, dark green areas that do not colour.
• Bud abscission and blind shoots, buds that do not break.
• Irregular, delayed flowering.
• Gradual spread from one orchard to the neighbouring one.
• In both cases, eriophyid mites in the samples.
• In both cases, years of confusion before identification, with the search running in the wrong direction.

The differences and the gaps, which have to be stated

11. What remains unanswered

It would be dishonest to close the article as if the matter were settled. It is not.

• Which species exactly? The Aristotle University team places it in the genus Eriophyes and awaits confirmation of the species [17]. Without taxonomic identification to species level, it is not known whether this is a species described in the literature or something new for the area.
• Is it the mite alone, or together with PLMVd? The answer changes the strategy: if there is synergy, clean propagation material takes on double importance.
• How effective are the approved acaricides against this species, under these conditions? There are no published Greek efficacy trials.
• What is the exact date of emergence from overwintering here? The Chinese measurements give late March for Lanzhou and Xinjiang. In this region it has not been measured, and spray timing depends precisely on it.
• Which cultivars are less susceptible? Symptoms are recorded on Andros, A37, Katerina, Everts and on table cultivars, but without comparative evaluation. So far, the cultivars A37 and Andros appear to be the most susceptible. In addition, several apricot cultivars may be affected, reinforced by the fact that the July 2026 advice from the Pella directorate extends the recommendation to apricot blocks with deformation not attributable to plum pox virus [5]. A comparative record by cultivar is needed, because future plantings depend on it.

12. Sources

The numbers in the text refer to the list below. Greek-language official announcements are marked as such.

• [1] Regional Unit of Pella (5/9/2024). Press release, Actions to resolve the problem of the unknown disease in peach and nectarine crops. In Greek. The most detailed public source. It reproduces verbatim the six virological analysis reports and the two entomological-acarological reports of the Benaki Institute, with file numbers, sampling areas, findings, conclusions and recommendations.
• [2] Regional Unit of Pella (18/9/2024). Guidance on the control of mites of the genus Eriophyes sp. in stone fruit crops, following Ministry document ref. 10086/278395 of 17-09-2024 and the press release of 5/9/2024. In Greek. Source for the finding of Eriophyes sp. mites by the Institute in samples from Larissa, Imathia and Pella, and for the full seasonal package of measures.
• [3] Region of Central Macedonia, agricultural directorate of the Regional Unit of Imathia (11/8/2025). Announcement on the phenomenon of deformed peach fruit. In Greek. The most categorical official statement: this is not a virus but in all probability an infestation by a mite of the genus Eriophyes attacking the buds of the new growth. Also the source for the recommendation of wettable sulphur and other acaricides.
• [4] Pella agricultural directorate (14/5/2026). May advisory on the control of Eriophyes mites in the peaches and nectarines of the Regional Unit of Pella. In Greek. Source for the recommendation of wettable sulphur or an approved acaricide and for the point about neighbouring abandoned orchards.
• [5] Pella agricultural directorate (31/7/2026). July 2026 advisory. In Greek. Source for the sampling of 1 July 2026 that found an Eriophyes population on the fruit, for the recommendation of a post-harvest treatment, for the extension of the recommendation to apricot, and for the service's contact numbers.
• [6] National Interbranch Organisation for Peach (2026). Briefing on dead and «blind» shoots, protection guidance. In Greek. Source for the distinction between dead and blind shoots, for the link between Eriophyidae mites and transmission of PLMVd, and for the programme with abamectin, beneficial predators, restraint with pyrethroids, sulphur products and lime sulphur.
• [7] Michigan State University, Integrated Pest Management, Fusicoccum canker (constriction canker). Source for the symptomatology of the dead-shoot disease: oval reddish-brown cankers centred on a bud or leaf scar, a necrotic centre with a purple halo, girdling and death of the shoot above the canker, and black pycnidia on the lesion.
• [8] Seasonal Availability of Inoculum for Constriction Canker of Peach. Phytopathology 91(11): 1109-1115, and Effect of Fungicides, Application Timing, and Canker Removal on Incidence and Severity of Constriction Canker of Peach, Plant Disease 86(7): 721. Source for the finding that infections occur through petiole scars in autumn during leaf fall and through bud scale scars and flowers in spring, and that autumn sprays during leaf fall reduced cankers by 45 to 63%. That is, a timing entirely different from that of the mites.
• [9] First Report of Phomopsis amygdali Causing Fruit Rot on Peaches in Greece. Plant Disease 90(12): 1551. Documentation that the fungus is present and recorded in Greece on peach. Note that the taxonomy of the pathogen has been revised: the same pathogen appears in the literature as Fusicoccum amygdali, Phomopsis amygdali and, under current nomenclature, Diaporthe amygdali.
• [10] Li Shijuan, Xu Bingliang, Liang Qiaolan, Zhang Wenli, Wu Bumei (2011). Occurrence of deformed peach and its effects on peach physiol-biochemical indexes (桃畸果病的发生及对桃果实生理生化指标的影响). Plant Protection (植物保护) 37(5): 139-143. DOI: 10.3969/j.issn.0529-1542.2011.05.026. In Chinese. Source for infestation rates of 40.30% in 2009 and 73.65% in 2010 with a maximum of 86%, for the timing of emergence from overwintering in late March with a peak on 25 March, and for all the changes in the physiological and biochemical indices.
• [11] History of spread in China: first appearance in 1972 in Qian'an county, Hebei; ~400 hectares by 1988; extension into Xinjiang in 1988-1991; new foci in Lanzhou, Gansu in the 2000s. As summarised in the introduction of the 2014 study [13] and in the Chinese agricultural sources [14].
• [12] Zheng Youxian, Liu Chunde, Shi Zhanshan et al. (1988). The causal agent of peach deformed fruit disease and its control. China Fruits (4): 17-19. In Chinese. The first identification of the cause.
• [13] Zhang Mingzhen, Xu Bingliang, Li Shijuan (2014). Pathogen determination and microscopic tissue observation in affected peach buds and fruit in the Anning district of Lanzhou. Gansu Agricultural University. In Chinese. The fullest study. Source for bud infestation rates of 52.9% in 2010 and 61.9% in 2011 with a maximum of 76%, for the morphometry of the mite, for the histology of the buds with destruction of the leaf primordia, for the cell diameter of 58 against 102 μm, for the trichome data, and for the re-inoculation trial that produced symptoms at 9 days.
• [14] Chinese agricultural and encyclopaedic sources on the disease 桃瘿螨畸果病, among them Baidu Baike. In Chinese. Source for the detailed annual cycle, the symptomatology on shoots and leaves, the «fruit but no leaves» phenomenon, and the timing of the recommended interventions. Note that these are secondary sources. The products they name relate to the Chinese approval regime and are not reproduced.
• [15] Biology of the Transmission of Peach Mosaic Virus by Eriophyes insidiosus (Acari: Eriophyidae). Plant Disease 82(12): 1371. Source for the documented precedent of a peach virus transmitted by an eriophyid mite.
• [16] Navia, D., Ochoa, R., Welbourn, C. and Ferragut, F. (2010). Adventive eriophyoid mites: a global review of their impact, pathways, prevention and challenges. Experimental and Applied Acarology 51: 225-255. DOI: 10.1007/s10493-009-9327-2. Source for the high potential of eriophyids as invasive species, because their small size makes them hard to detect and easy to move through global trade.
• [17] Maliogka, V.I., Orfanidou, C., Vasileiou, N., Georgousi, M., Lotos, L., Katis, N.I. (Plant Pathology team), Kovaios, D., Floros, G., Kokkari, A., Kopriti, E. and Koulousis, N. (Entomology team) (2024). Peach fruit deformation: a close association with the presence of Eriophyidae mites in buds (in Greek). Georgia - Ktinotrofia, issue 10/2024, pp. 22-26. School of Agriculture, Aristotle University of Thessaloniki. Full text. Source for the virological tests on more than 230 samples from 27 orchards (PPV, PNRSV, PLMVd, CGRMV, ACLSV, HTS, absence of phytoplasma and PcMV), the comparison of 18 orchards with and 18 without deformation at Plagiari, Lakka and Drosero near Giannitsa (1,440 shoots, 5,760 buds), the presence of mites in all affected orchards and the means of 10.3-53.0 mites per shoot, the absence of mites from leaves and from buds in Imathia, Aculus fockeui, the mite's biology, the short internodes, and the proposal for acaricide trials before bud break.