Phytophthora cactorum, Crown rot, Neck rot, Basal rot (PHYTCC)
Estrategias Efectivas para el Control de Phytophthora spp. en el Cultivo de la Fresa
Strawberry is one of the most dynamic and profitable crops in world horticulture, with great economic relevance in producing regions such as Spain, the United States and Mexico. However, its profitability is threatened by various soil diseases, among which the most important is root rot caused by root rot caused by Phytophthora spp. Phytophthora spp.
This pathogen, known as a “plant destroyer”, causes significant losses in both nurseries and commercial plots. Its ability to persist in the soil for years and spread rapidly in wet conditions makes it a constant challenge for growers and technical advisors.
In this article we analyze the biology of the pathogen, its infection cycle, characteristic symptoms, monitoring methods and integrated management strategies. . In addition, we will explore the role of biocontrol and introduce T34 Biocontrol® as a sustainable and effective alternative against Phytophthora spp. in strawberry cultivation.
Economic Importance of Strawberry Cultivation
Strategic relevance in the global agricultural economy
According to data from FAOSTAT (2023)world strawberry production exceeds 9 million tons per year. In the European Unionthe harvest is around 1 million tonsof which Spain contributes about 30% (eurostat, 2023). (EUROSTAT, 2023).
In Spain, production is mainly concentrated in Andalusia (93% of the cultivated area). Andalusia (93% of the cultivated surface area)reaching up to 97% of the 97% of the national totalthanks to the high yields obtained in tunnel cultivation.. The country is positioned, together with the Netherlands, as one of the main soft fruit exporters in the EU. the EU as one of the main red fruit exporters, with preferentialwith preferential destination in the EU market and the United Kingdom. United Kingdom..
Source: https://efeagro.com/temporada-fresa-2023-produccion/
A product with a high commercial value
Strawberry has established itself as one of the world’s leading red berries most appreciated by consumersthanks to its flavor, culinary versatility and nutritional properties. This combination has driven a sustained worldwide consumptionwith a constant demand throughout the yearespecially in countries with temperate climates that allow its continuous production or importation.
Source of income for producers
Strawberry cultivation represents an important important source of income for farmers. Your short cycle several harvests per year, which translates into rapid economic returns and high profitability. These characteristics make it a strategic choice for small and medium-sized producers that seek to optimize resources and benefits.
Impact on regional economies
In highly specialized regions such as Huelva (Spain), California (United States) or Michoacán (Mexico).the strawberry acts as a key economic driver. Its production generates a direct impact on farmers, but it also stimulates a extensive network of ancillary industries.. In this way, strawberry cultivation makes a decisive contribution to the economic and social development of the producing areas.
Relevance to foreign trade and the trade balance
The role of strawberries in international markets
Strawberries occupy a position in the international fruit and vegetable trade.. Countries such as Spain, Mexico, the United States, Morocco and Egypt are among the main are among the world’s leading exporters.
However, the intensification crop intensification challenges related to the use of pesticides pesticide use and its consequences on the health of workers, consumers and the environment. This scenario has prompted a transition to sustainable agricultural practices, including the rise ofincluding the rise of organic farming and organic certification. organic certification.
The incorporation of biocontrol agents incorporation of biocontrol agents, not only innot only in organic farms, but also in conventional systems. These tools have proven to offer results equal or superior results to chemical treatments, with the addedwith the added value of being safer and more environmentally friendly.
Currently, there are registered biological crop protection for crops such as blueberry, raspberry or currant, and soon also for strawberry.and soon also for strawberry. Among them, the following stand out T34 Biocontrol®which has demonstrated statistically comparable efficacy to chemical products, offering a sustainable and cost-effective solution already available to growers.offering a sustainable and cost-effective solution already available to growers.
What is Phytophthora spp.
A pathogen known as the "plant destroyer".
The genus Phytophthora spp. groups numerous organisms that affect a wide variety of crops: horticultural, fruit, forest and ornamental. Its impact is especially relevant in nurseries (horticultural, fruit and ornamental crops), where growing conditions favor the spread of the disease.
The term Phytophthora comes from Greek and literally means “plant destroyer“reflecting the severity of the damage damage it has caused since it was first described.
Although they resemble fungi, oomycetes, which are oomycetes such as Phytophthora are classified within a different group of eukaryotic organisms. They are commonly known as “water fungi” o “false fungi“due to their preference for moist environments and their ability to generate motile zoospores in water. mobile zoospores in waterThis explains their ease of dispersal in conditions of excess humidity.
Taxonomic classification:
edge:
class:
order:
family:
gender:
EPPO CODE:
SAR (Stramenopiles - Alveolata - Rhizaria)
Oomycetes
Peronosporales
Peronosporaceae
Phytophthora spp.
PHYTSP
Disease cycle
How Phytophthora spp. develops and spreads on strawberries
Species of the genus Phytophthora spp. are highly destructive highly destructive pathogens belonging to the class Oomycetes. Although they exhibit characteristics similar to true fungi, are not considered to be strict fungi..
Its development is favored by soil temperatures between 15 and 23 °C and by high humidity levelshigher than those optimal for strawberry cultivation.
A. Survival structures
Phytophthora can overwinter in the soil or in infected plant material (roots, tubers, bulbs), adopting different forms of resistance:
Oospores
Sexual spores in a state of prolonged dormancy.
Sporangios
Structures capable of germinating or releasing motile zoospores.
Chlamydospores
Thickened mycelium cells, resistant to adverse conditions.
Mycelium
Vegetative network of the fungus that ensures its development.
These structures allow the organism to survive for to survive for long periods of time in the absence of a host.
B. Onset of infection
The zoospores released from sporangia or oospores, are motile thanks to their two two The zoospores, released from the sporangia or oospores, are mobile thanks to their two spores, which allow them to move in the water until they reach the roots of the host plant.
The infection process usually begins in the roots of the roots then progressing to the base of the the base of the stem (foot of the plant). although in some cases it may start directly in this area.
The root exudates -substances rich in organic compounds released by root apices – stimulate the germination of zoospores. germination of zoospores and attract them to the plant tissues. Once established, the pathogen may colonize the stem and, under favorable conditions, reach aerial surfaces such as leaves and petioles.
Source: https://doi.org/10.3390/microorganisms8071012
C. Reproduction and propagation
In the infected tissue, the pathogen forms sporangiophores in sporangiophores structures that emerge from the stomata and produce new sporangia. These can germinate directly, infectingdirectly, infecting nearby tissues, oriberate zoosporesgenerating new secondary infections.
For aerial infection to occur (leaves, stems), it is necessary that the surfaces remain moist. surfaces must remain moist indispensable condition for the germination of spores.
Font: https://rmf.smf.org.mx/RevistaMexicana/articulo-hdoi.php?clave=RMF2007-5
D. Dispersal of the pathogen
The spread of Phytophthora occurs mainly through water and wind. water and wind :
Rain
Rain washes spores from infected
tissues to the ground.
SOIL
In the soil, water from irrigation or waterlogging facilitates movement to healthy plants.
WIND
Wind contributes to the transport of sporangia
in humid conditions.
This explains the rapid spread of the disease in situations of excess moisture. excess humidity even if these are not optimal for the crop.
Symptoms and damage of Phytophthora cactorum in strawberry crop.
How to identify and recognize the impact of Phytophthora cactorum
Symptoms caused by Phytophthora cactorum in strawberry can easily be easily confused with other pathologies such as frost damage, anthracnose or problems resulting from poor plant problems caused by poor preservation of the plants in cold storage..
Infection can occur both in the field as well as in nurseryaffecting young and adult plants.
lateral wilting
Sexual spores in a state of prolonged dormancy.
Fruits
affected
Structures capable of germinating or releasing motile zoospores.
Invasion From the base of the crown
Thickened mycelium cells, resistant to adverse conditions.
Invasion from the side of the crown
Vegetative network of the fungus that ensures its development.
A. Wilt and plant weakening
Infected plants show a general wilting generalized or unilateral wilting or unilateral wilting, accompanied by stunted growth.
The first symptoms are usually observed on young leaves young leaveswhich take on a bluish-green bluish-greenwhile adult leaves remain apparently normal.
As the disease progresses, the plant undergoes a rapid collapse rapid collapse and dies within a few days.
B. Crown necrosis
By making a longitudinal longitudinal cut on the rhizome or crown an internal necrosis internal necrosis brown or reddish-brown brown or reddish-brown .
- In some cases, infection starts at the top of the crown and progresses downward.
When the pathogen invades from the upper zone, the first tissues to be affected are the conducting vessels closest to the leaves and petioles. - In others, it starts in the lower or middle part, progressively advancing.
When the infection originates in the base or middle part of the crown, the damage is usually associated with excess soil moisture or already weakened roots.
This damage to the crown is one of the most most characteristic diagnostic symptoms. .
C. Affection in fruits
The strawberry fruits can be attacked at any stage of development:
- Unripe fruit : they present brown or dark brown spots in infected areas.
- Ripe fruit : show a dull dull coloration with soft and watery areas that affect their commercial quality.
Other species of interest
In addition to P. cactorum other species of Phytophthora species can also affect the strawberry crop:
- P. cambivora y P. cinnamomi frequent in heavy soils, attack roots.
- P. citricola y P. cryptogea cause root rots in nurseries.
- P. rubi associated with raspberry, can infect strawberry in North America.
- P. drechsleri , P erythroseptica y P. megasperma occasional on strawberry, generally in poorly drained soils or humid climates.
The coexistence of these species with P. fragariae o P. cactorum aggravates the severity of the disease especially in conditions of excessive humidity.
Infection by Phytophthora cactorum
The incidence of Phytophthora cactorum and the factors favoring its development.
Infection by Phytophthora cactorum develops in a temperature range between 15 and 25 ºC, as long as there is free water in the environment.
Water stress plays a determining role in the manifestation of the disease. The times of greatest risk occur when the plant’s water demand is high, for example:
After the transplant when the root system is still underdeveloped and not very efficient.
During flowering and flowering and harvesting where transpiration transpiration increases significantly.
A. Susceptibility in nurseries
The nursery plantsplants, especially the frigoare particularly susceptible to susceptible to attack by P. cactorum . The nursery plantsplants, especially the frigoare particularly susceptible to susceptible to attack by P. cactorum .
When these plants arrive to the field already infected, they can introduce introduce the pathogen the plot, favoring its establishment and dispersal.
B. Fruit infection
< Infection of strawberry fruit only occurs in the presence of free water on the surface, either by rainfall, sprinkler irrigation or condensation inside the greenhouse. This direct contact facilitates spore germination and penetration of the pathogen into the fruit tissues.
The duration of ambient humidity is a critical factor in disease development. The longer the period of humidity, the greater the likelihood of infection and establishment of the pathogen.
- At temperatures between 17 to 25 ºC are sufficient 2 hours of continuous humidity is enough for up to 80% of the fruits infected.
Important:
It is not necessary for the fruits to come into direct contact with the soil to be damaged.
Integrated control of Phytophthora spp. in strawberry:
Agronomic, cultural, chemical and biological strategies.
Effective control of Phytophthora spp. in strawberry cultivation requires a integrated approachcombining agronomic, cultural, chemical and biological measures. No single strategy is sufficient; the key is in implement a set of coordinated practices that reduce the risk of infection and keep the disease under control.
A. Agronomic measures
The implementation of appropriate agronomic measures is the first line of defense against Phytophthora cactorum in strawberry. These practices not only help to reduce the incidence of the disease, but also contribute to create a less favorable environment for the development of the pathogen.
1
Crop rotation:
Avoid planting strawberries continuously in the same plot. We recommend a rotation of 2 to 3 years with non-host crops such as corn, wheat or legumes is recommended. This is especially useful against Phytophthora fragariae which has a very narrow host range.
2
Soil drainage
Select plots with adequate natural drainage and form raised beds of 30-35 cm This reduces waterlogging and the accumulation of free water.
3
Choice of cultivation site
Avoid heavy soils, depressed areas or areas prone to flooding, as these conditions favor waterlogging and the accumulation of free water. This excess moisture increases the survival and spread of Phytophthora cactorum.
4
Subsoiling and solarization:
A deep tillage breaks up compacted layers, favoring water infiltration. In hot climates, soil solarization of the soil with transparent plastic for 4-6 weeks in summer significantly reduces the population of oospores.
5
Biofumigation
Incorporate fresh organic matter which, upon decomposition, releases volatile compounds with a natural fungicidal effect (Bello et al.).
6
Tolerant varieties
Although no variety is totally immune, there are materials with partial tolerance ( Frontiers, Merced, Albion, San Andreas, Portolas ).
Recent breeding programs in California and Florida have developed varieties with advanced genetics, such as UC Monarch , UC Surfline Florida Ember y Encore which show remarkable resistance to the disease.
B. Cultural measures
Weed control and ground cover:
Eliminate weeds that compete for water or act as alternate hosts. Use organic mulch or plastic to reduce splashing of infected particles to crowns and fruit.
Cleaning of flowerbeds and plant debris:
The material resulting from pruning or defoliation must be completely removed from the field to avoid reinfection.
Hygiene of tools and machinery:
Regularly disinfect agricultural equipment and machinery, especially after working in wet soils. Avoid introducing machinery in infected fields without previous cleaning.
Crop monitoring:
Periodically inspect the plants, observing suspicious crowns and roots by means of longitudinal or transversal cuts. This constant control allows to detect early symptoms and to take quick measures.
Irrigation management:
Prioritize drip irrigation over sprinkler irrigation, avoid standing water and, when possible, filter irrigation water. Alternate flows to minimize saturated zones.
Integration of practices:
Efficacy increases when strategies are combined in a programmed manner. For example, high ridges + solarization + field hygiene + constant monitoring → significant reduction of initial inoculum.
C. Management with conventional phytosanitary products (chemicals)
Chemical control should be considered as a complementary complementary tool applicable only with products authorized authorized for strawberry in the MAGRAMA against Phytophthora spp.
It is advisable to always consult the current official register It is advisable to always consult the current official registry, since the available active ingredients may vary with time and regulations.
Repeated use of the same active ingredients without fungicide rotation accelerates the emergence of resistant strains and reduces the effectiveness of chemical control.
D. Management with Biological Inputs
The biocontrol has established itself as one of the most effective and sustainable tools for the management of soil diseases in strawberry cultivation. Compared to chemical treatments, biofungicides offer decisive advantages:
1
Proven efficacy
authorized phytosanitary inputs such as T34 Biocontrol® have demonstrated an efficacy for their authorization, comparable and even superior to conventional phytosanitary products. comparable and even superior to conventional phytosanitary products.
2
Absence of resistance
Microorganisms classified as BM02 (FRAC Code List) act with multiple mechanisms of action, making the appearance of resistance very difficult. This allows its continuous application season after season.
3
Resistance Induction
Symbiotic microorganisms such as Trichoderma spp. or Bacillus spp. activate the natural defense mechanisms of the plant (induced systemic response). of the plant (induced systemic response). The plants act faster and with greater strength their own defense mechanisms.
4
Improved Root System
They stimulate the formation of secondary roots by increasing the exploration capacity of the soil. This favors greater water and nutrient absorption, improves tolerance to abiotic stress situations (drought, salinity) and contributes to the overall vigor of the plant.
These properties have transformed biocontrol agents from being considered as a simple complement to become true first-line solutions. to become true first-line solutions in integrated pest in integrated management programs of Phytophthora spp. Phytophthora spp.
T34 Biocontrol®: sustainable and effective solution against Phytophthora spp. on strawberries
T34 Biocontrol® is a biofungicide registered formulated with Trichoderma asperellum strain T34 a beneficial fungus with high root colonization capacity and direct action against the main soil pathogens including Phytophthora spp.
Main benefits of using T34 Biocontrol®:
The use of T34 Biocontrol® offers multiple benefits for the crop, especially its effective control of Phytophthora spp. and other root pathogens. In the rhizosphere, it occupies the ecological niche and displaces the pathogen, in addition to producing antifungal metabolites that inhibit its development. It also stimulates the root system, favoring the formation of denser, more vigorous and efficient roots in the absorption of nutrients. In addition, it activates the plant’s natural defenses, which strengthen its resistance to secondary infections. Finally, it contributes to environmental sustainability and safety by reducing dependence on chemical fungicides and minimizing risks for the farmer, the consumer and the ecosystem.
Conclusions: Towards a sustainable and effective management of Phytophthora spp. in strawberry.
Root rot caused by Phytophthora spp. is one of the most serious the most serious threats to strawberry, with direct with direct impact on nurseries and commercial farms.
The integrated management is the most effective strategy for dealing with this disease, combining preventive, cultural, chemical and biological measures. Within this scheme, biocontrol biocontrol has become an essential part of this Biocontrol has become an essential part of this scheme, providing efficacy, sustainability and additional benefits for the crop.
In this context, T34 Biocontrol® represents a reference solution, combining which combines:
DISEASE-FREE
Proven control against Phytophthora spp.
HEALTHY ROOTS
Strengthening the health of the root system.
SYSTEMIC RESISTANCE
Activation of the plant's natural defenses.
SAFE and SUSTAINABLE
Safety and respect for the environment.
In short, the protection of strawberry crops against Phytophthora spp. involves integrating innovation, sustainability and biocontrol. Among the tools available, T34 Biocontrol® has established itself as an effective and reliable alternative for growers and growers and advisors aligned with the current demands of the sector and international markets.
Bibliography
- Bascón, J. (2005).Main diseases and physiopathologies of strawberry crop in the province of Huelva. Agrícola Vergel , (277), 36-40.
- Duhart, M. E., Montes, F., Páez, J. I., & Vega, J. M. (2000). Main diseases of strawberry in Huelva. Agrícola Vergel , (218), 117-128.
- Ellis, M. A., & Madden, L. V. (1998). Leather Rot. In J. L. Maas (Ed.), Compendium of Strawberry Diseases (2nd ed., pp. 33-35). APS Press.
- Medina, J. J., Domínguez, P., Miranda, L., Soria, C., Chamorro, M., De los Santos, B., Talavera, M., Sánchez, R., & López, J. M. (2013). Technical workshop “Soil disinfection in protected horticultural crops-Fresas”. Conclusions (pp. 1-39). Consejería de Agricultura, Pesca y Desarrollo Rural, Instituto de Investigación y Formación Agraria y Pesquera.
- Páez, J. I., & Vega, J. M. (1996). Phytophthora cactorum (Lebert and Cohn) Schröter. . Fichas de diagnóstico en laboratorio de organismos nocivos de los vegetales ( Vol. I, No. 56). Ministry of Agriculture, Fisheries and Food.
- Seemüller, E. (1998). Crown Rot. In J. L. Maas (Ed.), Compendium of Strawberry Diseases (2nd ed., pp. 50-51). APS Press.
- Tello, J., Páez, J. I., Vega, J., Duhart, M., & González, L. (1996). Diseases of strawberry. Hortoinformación magazine April supplement, 30 pp.
- Bello, A., López-Pérez, J. A., & Díaz, L. (n.d.). Biofumigation and solarization as alternatives to methyl bromide. . CSIC.
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