The dry shoot disease of peach

Savvas Pastopoulos, Agronomist MSc, Pastopoulos Agronomics, Neos Mylotopos, Pella, Greece

Since 2021 the plain of Giannitsa, the most important clingstone peach producing district in the world, has been living through an epidemic that growers named themselves: the dry shoot. Dead annual shoots with the leaves hanging on them, buds that fail to break, and in heavy attacks cultivars that lose the entire crop. The cause is a fungus, Diaporthe amygdali. This article is the detailed picture of the disease, and it starts from the distinction that has cost the greatest number of wrong sprays in recent years: the dry shoot is not the blind shoot.

1. Why «dry shoot», and why the name matters

The disease has at least five names in circulation: dry shoot in the orchard, Phomopsis in the Greek technical literature, constriction canker in the North American usage, twig canker and shoot dieback in the most recent Greek review [2], and TCSB, twig canker and shoot blight, internationally [4]. They are all the same disease.

The title of this article keeps the name growers use, because that is the name with which the problem will be described to the agronomist. The reason the names matter in practice is simple: a literature search under the wrong name returns nothing, and a conversation under the wrong name ends in the wrong product.

2. Dry shoot and blind shoot, the field distinction

The two problems appeared in Pella and Imathia almost simultaneously, are discussed together at every meeting, and the confusion has reached the point where acaricides are sprayed against a fungus and fungicides against a mite. The distinction takes a knife and ten seconds.

3. The pathogen and its three names

The cause was identified in France in 1905 as Fusicoccum amygdali and kept that name for several decades, until it was renamed Phomopsis amygdali. In 2010, phylogenetic analyses of isolates led to its placement in the genus Diaporthe [2]. The current name is Diaporthe amygdali (Ascomycota, Sordariomycetes, Diaporthales, Diaporthaceae), with the two older names as synonyms.

That taxonomic history is why the literature looks thin when searched under a single name. In practice a complete search requires all three.

The host range is wide. Beyond peach, nectarine and almond, where it causes the most severe damage, the pathogen attacks plum, apricot and pear, and also avocado, walnut, grapevine and various ornamental species [2]. Its global distribution includes the United States, China, Japan and Uruguay, with the most severe attacks recorded in the Mediterranean basin, meaning Spain, France, Italy and Greece [2]. In Greece its presence on peach has been formally recorded since 2006, in a report concerning fruit rot [7].

For the plain of Giannitsa the question of aetiology is now closed. In a thesis from the same laboratory, isolates collected in spring 2021 from more than ten commercial orchards in Imathia and Pella, mainly peach but also almond and apricot, were identified molecularly by sequencing two genes, β-tubulin and calmodulin. All one hundred isolates matched Diaporthe amygdali at 98 to 100% [14]. It is the first nationwide molecular identification of the pathogen in Greece. It does not rule out other canker fungi coexisting in the field, but it does show that in the samples from this district D. amygdali was the only species found.

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4. The symptoms, in the order they appear

Stage 1. The bud that did not open

The first symptoms are small, oval necroses around the buds on annual shoots. The bud fails to break and the shoot shows reduced flowering and reduced growth [2]. This is the stage that passes unnoticed, because one dead bud among dozens of healthy ones does not stand out from a distance.

Stage 2. The canker that girdles

In spring the necroses enlarge and extend laterally into elongated cankers 1 to 5 cm long [2]. They are brown or reddish-brown at first, then become sunken and take on a silvery colour. The international description is more precise about the shape: oval, reddish-brown cankers centred on a bud or a leaf scar, with a necrotic centre and a purple halo [5].

The canker enlarges until it girdles the shoot. From the moment the ring closes, everything above the canker is lost, and that is where the name comes from, constriction canker.

Stage 3. The dead shoot with the leaves on it

The annual shoot dies entirely above the canker, and the leaves or fruit it was carrying stay attached to the dead shoot [2]. This is the symptom the grower sees from the road, and it is almost diagnostic on its own: on a tree that is otherwise growing normally, a brown shoot with its leaves hanging on it does not have many explanations.

The character that separates Phomopsis from the other diebacks

More rarely, on the fruit

On fruit the attack appears as brown cankers [1]. It is the rarest expression, but the first official record of the pathogen in Greece concerned precisely a rot of peach fruit [7]. In very severe attacks, researchers in China have reported the dieback of whole trees [1].

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5. Fusicoccin and why the shoot collapses so fast

Here lies the answer to a question every grower has: how a canker a few centimetres long kills an entire shoot within days. The mechanical explanation, that the canker girdles and cuts the flow, is correct but partial.

The complete genome of D. amygdali, published in 2025, showed that the fungus carries the entire biosynthetic gene cluster for fusicoccin [4]. Fusicoccin is a diterpenoid phytotoxin with a very specific action: it irreversibly activates the plasma-membrane proton pumps of the guard cells of the stomata. The result is that the stomata open and do not close again, the shoot loses water uncontrollably and the tissues collapse [4].

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6. The disease cycle and its numbers

The fungus overwinters as mycelium inside the cankers on the twigs and as pycnidia on those cankers and on the dead shoots [1] [2]. The pycnidiospores are the inoculum that causes infection.

The temperature ranges

The Greek data for peach give the following [2]:

The range in the last two rows explains why this disease has no dead season. Both cirrhus release and conidium production continue from 0 to 37 °C, and the fungus sporulates even under cool conditions, between 0 and 20 °C [14]. A mild, rainy winter is not a respite.

The numbers from almond

The most complete quantitative study of the pathogen's biology was published in 2025 and concerns almond [3]. It is given here as an order of magnitude, with the host stated explicitly:

• Mycelial growth: from 5 to 35 °C, with an optimum of 26.7 °C and a maximum rate of 13.89 mm per day.
• Germination of α-conidia: from 5 to 35 °C. Above 15 °C and after 20 to 50 hours of incubation, germination reaches 100%. At 15 °C or below, with fewer than 20 hours, it stays at 0 to 20%.
• Conidial production: from 11 to 33 °C, with an optimum of 21.6 °C and a maximum of 608,688 α-conidia per pycnidium.
• Formation of mature pycnidia: from 11 to 28 °C, with an optimum of 16.5 °C. The fungus is therefore adapted to mature its fruiting bodies under cool conditions, in late winter and early spring.
• Leaf infection: a maximum of 62% at about 33 °C with 72 hours of wetness; a minimum of 12% at 28 °C with only 6 hours. Prolonged wetness is the decisive factor.
• Lesion development on detached twigs: a maximum rate of 7.7 mm per day at 30 °C.

The inoculum curve through the year

The only study that followed inoculum month by month for two years was carried out in New Jersey, sampling thirty cankers per cultivar every month from January 1997 to December 1998 [13]. Its findings:

• Canker size follows a sinusoidal pattern: smallest in late winter and early spring, largest in late summer and early autumn.
• Pycnidia per canker: from a mean of 94 in one year to 205 to 221 in the next, more than twice as many, depending on the season.
• Proportion of pycnidia exuding cirrhi: from about 10% in winter to 70 to 80% in summer and autumn.
• Conidia per canker: peaking between day 170 and day 210 of the year, that is, 19 June to 29 July, with 7.4 to 10.8 million conidia per canker. The lowest levels, 1.0 to 3.9 million, in December and January.

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7. The entry points and why autumn decides the season

The pathogen is a weak one. It does not penetrate healthy, intact bark: it needs a wound or a natural opening in order to infect [2]. That weakness is also the grower's greatest opportunity, because it means managing the openings is managing the disease.

The entry points, in order of importance [2]:

1. The petiole scars at leaf fall. The most important by a wide margin. Every falling leaf leaves a fresh scar, and on an annual shoot the scars number in the dozens. They all open within a few weeks, exactly when temperature and rainfall are ideal.
2. The bud scars and their scales.
3. The scars left by flowers that were not fertilised.
4. The scars left by the drop of aborted fruitlets.
5. Micro-cracks in the bark caused by late or early frost.
6. Fruit scars in summer. June drop, thinning and harvest itself all leave scars. On a highly susceptible cultivar, 6% of the nodes examined after such events had become infected [6]. It is a small proportion, but it explains why the orchard is never entirely out of danger.

The size of what is at stake is clear from how far these infections can go: in a heavy attack up to 50% of a tree's shoots are affected [9]. These are not isolated shoots. This is half of next season's bearing surface.

A second, equally overlooked entry point is fresh pruning cuts. The removal of infected shoots must not be carried out before expected rainfall, precisely because fresh cuts are an entry point for the pathogen [2]. The right action at the wrong moment becomes the wrong action.

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8. What the Greek data have shown since 2021

The disease has been present in Greece for a long time and probably predates its recognition. For decades it was controlled without anyone knowing it: the preventive sprays aimed at other diseases, leaf curl first among them, kept it at low levels [1].

The three explanations that have been proposed

Why did a disease that was manageable for decades become an epidemic? Three factors are cited [2]:

• The withdrawal of thiophanate-methyl. This benzimidazole fungicide, applied for other targets, as a rule kept the intensity of the disease low without causing any particular concern about it. Its approval was not renewed in the European Union, with authorisations withdrawn by April 2021 [11], that is, exactly the year of the first outbreak.
• The susceptibility of the cultivars grown, especially the older clingstone ones.
• The role of the deforming mite: heavy infestation by Eriophyes spp. weakens or kills buds, and dead buds serve as an entry point.

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9. Cultivar susceptibility

This is where the Greek research produced the most directly usable result, and since 2024 a complete list exists. In the experimental orchards of the Institute of Plant Breeding and Genetic Resources of ELGO DIMITRA, in May 2023, twenty-three peach and nectarine cultivars were inoculated artificially. For each cultivar three trees were chosen and five annual shoots per tree, the mycelial plug was placed in a superficial wound of 15 by 2 mm and covered with parafilm, and fifteen days later the length of the necrosis under the bark was measured. The study was repeated twice [14].

The ranking was defined in advance: a necrosis below 3.5 cm means a tolerant cultivar, 3.51 to 5.49 cm moderately tolerant, above 5.5 cm susceptible [14].

Recent experience from Greek orchards shows that the disease is particularly severe in clingstone peach orchards and specifically in orchards of older cultivars such as Andross and Katerina [2], and these are precisely the cultivars in which the greatest destruction is recorded on the plain of Giannitsa, together with A37 [1].

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10. Control, the cultural measures

Control rests entirely on prevention. There is no curative intervention for a shoot that has already been girdled by a canker: the part above the canker is dead and does not recover. Whatever is done, is done for the next shoots [1].

A. Removal and destruction of the inoculum

This is the most important measure, and it is the precondition for all the others. No chemical intervention can succeed unless the inoculum has been cleared first [1].

• All year round, not only at winter pruning. The pathogen is maintained and dispersed from the pycnidia on the infected shoots; removal must continue throughout the year [2].
• The cut is made 15 to 20 centimetres below the lesion, in healthy tissue [15]. The canker extends invisibly within the tissues before it shows on the surface. An earlier bulletin gave ten centimetres [8]; the greater distance prevails.
• Destruction by burning. Prunings are not left stacked at the edge of the orchard, because there the pycnidia go on maturing and releasing spores.
• Disinfected tools, with frequent disinfection during the work [2] [8].
• Never before rain. Removal must not be carried out before expected rainfall, because fresh cuts are an entry point [2].

B. Pruning as a humidity measure

Beyond removal, pruning helps to reduce humidity levels around the tree, creating an environment less favourable to the fungus [2]. Proper aeration of the canopy through summer pruning is a basic control technique [1].

C. Fertilisation in both directions

D. Irrigation, the trunk and the canopy stay dry

Avoiding wetting the tree during irrigation limits the spread of the fungus, while drip irrigation, which keeps the potential infection sites dry, makes infection harder [2]. Any overhead irrigation in a risk period is the equivalent of artificial rain on the pycnidia.

E. Confirming the diagnosis

Twig cankers are not a pathognomonic symptom: several fungi and bacteria produce a similar picture, such as Cytospora spp., Monilinia spp., Botryosphaeria spp., Leucostoma spp., Valsalia spp., and other species of the genus Diaporthe [1] [2] [10]. Where there is doubt, samples are sent to the Benaki Phytopathological Institute for identification of the pathogen and for guidance [1].

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11. Control, chemical

Chemical control is, and remains, the most effective way of managing the disease [2]. There are two conditions, however, and both concern timing.

How much each season counts, the figures

The three-year field trial in two commercial New Jersey orchards, with repeated applications in autumn during leaf fall and in spring from bud break to full bloom, at intervals of about ten days, gave the clearest answer available in the literature [6]:

The number of applications is not given here as a recommendation. It is set case by case by the agronomist, according to disease pressure, the weather of the season, the duration of leaf fall and the constraints on each product label.

What the trials of the active substances show

The withdrawal of thiophanate-methyl raised the question of how effective the remaining approved fungicides are. A recent study by the Plant Pathology Laboratory of the Aristotle University of Thessaloniki, using protective applications followed by artificial inoculation of annual shoots, showed that among the active substances assessed dithianon gave the highest efficacy, followed by triazole fungicides such as difenoconazole and tebuconazole [2].

The full picture of that trial is published in the accompanying thesis. In September 2023, 360 GF 677 rootstocks were used, split into twenty-four groups of fifteen plants. Each product was applied at the maximum rate on its label, artificial inoculation followed twenty-four hours later with a mycelial plug placed on a leaf scar, and fifteen days afterwards the length of the necrosis was measured. The study was repeated twice. Twenty active substances and one biological control agent were assessed [14].

The Greek practical recommendation to growers turns the above into a programme: alternating applications from 10% leaf fall up to the copper spray [8].

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12. Diseases that can be confused with dry shoot

The pairs most often confused in the field, and the one character that separates them.

13. The year's programme at a glance

14. Sources

The numbers in the text refer to the list below.

• [1] Pastopoulos, S. (2023). Phomopsis in peach. Georgia - Ktinotrofia 5/2023 (in Greek). The basis of this article; full text. Source for the outbreak from 2021 on the plain of Giannitsa and in the cultivars Katerina, Andros and A37, for the observation that gum exudation is rarer in Phomopsis than in Monilinia, Botryosphaeria and Cytospora, for the observation that the outbreak correlates with cultivar susceptibility rather than directly with the weather, for the limited intensity in hot dry situations in autumn, for the link between excessive fertilisation and infection, for the priority of clearing the inoculum over any chemical intervention, and for sending samples to the Benaki Phytopathological Institute.
• [2] Karaoglanidis, G. (2026). Twig cankers and shoot dieback of stone fruit, an emerging threat to peach and almond growing in Greece. Georgia - Ktinotrofia 4/2026, pp. 52-55 (in Greek). Professor of Plant Pathology, School of Agriculture, Aristotle University of Thessaloniki. Full text. Source for the taxonomic history of the pathogen and its placement in the genus Diaporthe in 2010, for the 2021 sampling by the Plant Pathology Laboratory of the Aristotle University in Pella and Imathia with D. amygdali identified in every case, for the host range, for the temperature ranges of 5-37 °C with an optimum around 20 °C for germination and infection and 0-37 °C with an optimum of 22 °C for sporulation, for the 19-20 °C release of cirrhi, for cankers 1-5 cm long and the one-month incubation, for the entry points and the role of leaf fall, for the assessment of ten clingstone cultivars with Fortuna and VLG as the most susceptible and Ferlot as resistant, for the highest efficacy of dithianon followed by difenoconazole and tebuconazole, for the link between the outbreak and the withdrawal of thiophanate-methyl and the attacks by Eriophyes spp., and for the cultural measures.
• [3] Francia, C., Lázaro, E., Novellón, M., Ramón-Albalat, A., Beluzán, F., Vicent, A., Berbegal, M. & Armengol, J. (2025). Biology and epidemiology of Diaporthe amygdali: understanding how environmental factors influence fungal growth, sporulation, infection and lesion development on almond. Frontiers in Plant Science 16:1717223. Full text, open access, peer reviewed. Source for every quantitative figure in section 6: mycelial growth 5-35 °C with an optimum of 26.7 °C and 13.89 mm/day, germination of α-conidia up to 100% above 15 °C after 20-50 hours, production of up to 608,688 α-conidia per pycnidium with an optimum of 21.6 °C, formation of mature pycnidia 11-28 °C with an optimum of 16.5 °C, leaf infection of 62% at 33 °C with 72 hours of wetness, and a lesion growth rate of 7.7 mm/day at 30 °C. The data concern ALMOND and are given as an order of magnitude.
• [4] Turco, S., Brugneti, F., Cardacino, A. & Mazzaglia, A. (2025). Harnessing genomics of Diaporthe amygdali for improved control of peach twig canker and shoot blight (TCSB). Plants 14(19):2960. Full text, open access, peer reviewed. Source for the complete fusicoccin biosynthetic gene cluster in the pathogen's genome, for the mode of action of the toxin, meaning irreversible activation of the plasma-membrane proton pumps of the guard cells, permanent stomatal opening, uncontrolled water loss and tissue collapse, and for the proposed direction of double-stranded RNA gene silencing.
• [5] Michigan State University, Integrated Pest Management, Fusicoccum canker (constriction canker). Full text of the page. Source for the morphology of the cankers: oval, reddish-brown cankers centred on a bud or a leaf scar, a necrotic centre with a purple halo, girdling and dieback of the shoot above the canker, and black pycnidia on the lesion.
• [6] Lalancette, N. & Robison, D.M. (2002). Effect of fungicides, application timing, and canker removal on incidence and severity of constriction canker of peach. Plant Disease 86(7):721-728. Full text. A three-year field trial in two commercial New Jersey orchards. Source for 45 to 63% control from autumn sprays against 10 to 28% from spring sprays, for the 71% achieved by chlorothalonil and 69% by captan applied in autumn and spring, for the 41% of azoxystrobin and 28 to 44% of myclobutanil, for the improvement of only 0 to 8% from adding spring applications to the autumn programme, for the 42% reduction from canker removal in one year only, for yield losses of 28.5% and 21.0% and 500 to 800 cankers per tree, for the 6% of nodes infected through fruit scars in summer, and, through the review it contains, for the detached-shoot assay in which benomyl and thiophanate-methyl, together with sulphur, lime sulphur and iprodione, gave no control, while chlorothalonil protected 78% and bitertanol 89% of the shoots. Also the source for the economic valuation of US$4,009 and US$2,803 per hectare, for the 78% of the best season of chlorothalonil applied in autumn and spring, for the 90% bar the authors set and did not reach, for the three explanations of that shortfall, namely the low to moderate activity of the fungicides, the single test trees inside an unsprayed environment and the infections occurring outside the treated windows, and for the at least three years needed to rehabilitate severely infected orchards.
• [7] First report of Phomopsis amygdali causing fruit rot on peaches in Greece. Plant Disease 90(12):1551. Abstract used. Documentation that the pathogen is recorded in Greece on peach, the first official report concerning fruit rot. The taxonomy has since been revised to Diaporthe amygdali.
• [8] Greek Interbranch Organisation of Peach (2026). Clarifications on dry and «blind» shoots in peach, control guidance for growers (in Greek). Full text of the bulletin. Source for the official distinction between dry and blind shoots, with the first caused by the fungus with infection at leaf fall and the second by eriophyid mites associated with the viroid PLMVd and expressed in spring, for the burning of prunings, for tool disinfection, and for alternating applications from 10% leaf fall up to the copper spray. The guidance and the approvals behind it are valid in Greece only.
• [9] Luo, C.-X., Schnabel, G., Hu, M. & De Cal, A. (2022). Global distribution and management of peach diseases. Phytopathology Research 4:30. Full text, open access, peer reviewed. Source for the ranking of the disease among the most important peach diseases worldwide and for infection of up to 50% of a tree's shoots in a heavy attack.
• [10] Adaskaveg, J.E., Schnabel, G., Ritchie, D.F. & Förster, H. Common preharvest diseases of peach and nectarine caused by fungi and bacteria: biology, epidemiology and management, chapter 12, CABI. Full text of the chapter. Source for the general epidemiology of stone fruit cankers and for the differential diagnosis from Cytospora, Monilinia and Botryosphaeria.
• [11] Commission Implementing Regulation (EU) 2020/1498 on the non-renewal of approval of the active substance thiophanate-methyl. Source for the date by which authorisations were withdrawn, 19 April 2021.
• [12] Database of approved plant protection products (in Greek), from the register of the Greek Ministry of Rural Development and Food. The only authoritative source for what is permitted in peach in Greece today, at what rate, with what maximum number of applications and with what pre-harvest interval. Valid in Greece only.
• [13] Lalancette, N. & Robison, D.M. (2001). Seasonal availability of inoculum for constriction canker of peach in New Jersey. Phytopathology 91(11):1109-1115. Full text. Two years of monthly sampling of thirty cankers per cultivar, 1997 and 1998. Source for the sinusoidal pattern of canker size, for 94 against 205 to 221 pycnidia per canker between the two years, for the proportion of pycnidia exuding cirrhi rising from 10% in winter to 70 to 80% in summer and autumn, for the peak in conidia between day 170 and day 210 of the year at 7.4 to 10.8 million per canker and the minimum of 1.0 to 3.9 million in December and January, and for the conclusion that the pathogen behaves as an r strategist and that inoculum availability is not the limiting factor of the epidemic.
• [14] Papadimitriou, D.V. (2024). Study of the aetiology, cultivar susceptibility and chemical control of shoot cankers of peach. MSc thesis, Plant Pathology Laboratory, School of Agriculture, Aristotle University of Thessaloniki. Supervisor: G. Karaoglanidis. Defended 15 October 2024 (in Greek; Greek title: «Μελέτη της αιτιολογίας, ευπάθειας ποικιλιών και χημικής αντιμετώπισης σε έλκη βλαστών της ροδακινιάς»). Full text. An MSc thesis, not a peer-reviewed paper, which is why every quantitative figure taken from it is given together with source [2], which covers the same material. Source for the molecular identification of 100 isolates from more than ten commercial orchards in Imathia and Pella, for the field assessment of 23 cultivars by artificial inoculation and the thresholds used to rank them, for the in planta assessment of twenty active substances and one biological control agent on GF 677 rootstocks, and for the confusion of the disease with brown rot in the orchards of the district.
• [15] Directorate of Rural Economy and Veterinary Services, Regional Unit of Pella (2026). Guidance on the control of Phomopsis, or twig canker, in peach, nectarine and other stone fruit crops (in Greek). Announcement of 29 September 2026, as republished in the local press, with laboratory confirmation by the Benaki Phytopathological Institute in samples from Gypsochori, Arnissa, Stavrodromi and Plagiari. Full text of the announcement. Source for the removal of infected branches with the cut 15 to 20 centimetres into healthy tissue, below the symptom. The guidance is valid in Greece only.