Lasiodiplodia thebromae or regressive death (LSDPPS)
Control of Lasiodiplodia theobromae in the avocado crop.
Lasiodiplodia: A Necrotrophic Pathogen Causing Downward Death in Avocado Crops.
Avocado crops have increased significantly due to the current high demand, up to 70% more, becoming one of the most preferred alternative crops in Peru (1).
One of the limiting factors in production are the diseases that appear both pre- and post-harvest. For example, the most representative pathologies in the Piura area on avocado crops are:
Anthracnose
Produced by Colletotrichum gloeosporioides.
Anthracnose on fruit and microscopy image
Root rot
Produced by Phytophthora sp.
Root rot death caused by Phytophthora in avocado seedlings.
Wilting.
Produced by Verticillium spp.
Verticillium in microscopy image and avocado tree with evident signs of wilt.
1) Source (Data from Rodríguez-Gálvez, unpublished data)
In recent years, a high incidence of lesions or cankers on avocado branches with the presence of whitish exudations and dieback has been observed, causing alarm among growers. In Peru, this type of symptomatology was believed to be related to Dothiorella spp. since it was also responsible for cankers and dieback (downward death, from the apex to the base of the branch) in this crop (2).
A recent study showed that depending on agro-climatic conditions, and specifically in northern Peru, avocado dieback and canker is mainly affected by Lasiodiplodia theobromae (2).
In this blog we present a summary of the most relevant information to understand the role of Lasiodiplodia theobromae and its relationship with avocado crops. To make it easier to read and understand, we will divide this blog into three sections:
Table of Contents
1. Summary of Lasiodiplodia theobromae.
It is a necrotrophic pathogenic fungus, whose sexed form is called: Botryodiplodia theobromae Pat (1).
Kingdom: Fungi (fungi).
Division: Ascomycota.
Class: Dothideomycetes.
Order: Botryosphaeriales.
Family: Botryosphaeriaceae.
Genus: Lasiodiplodia .
Epecies: Lasiodiplodia theobromae.
Geographic distribution: Worldwide dispersal, concentrated in the tropics and subtropics. L. theobromae can establish on more than 500 host species, which increases its distribution (1).
Crops susceptible to attack by the pathogen Lasiodiplodia theobromae.
It is a pathogen that affects a wide range of crops, the ones shown here are the most representative, although scientific studies indicate that there are many more.
Morphology.
It is a fungus that presents a mycelial development of white color, later turning dark ash-colored until it becomes blackish. The hyphae are septate, forming short and simple conidiophores that later form conidia. (1).
Caracterización morfológica de Lasiodiplodia theobromae. (A) Crecimiento en placa de Petri, (B) Paráfisis (estructuras de protección de gametangios), (C) Conodias maduras e inmmaduras, (D)= Conidias maduras separadas.
2. Disease cycle.
To understand how to treat this type of fungi, it is essential to know their life cycle.
In this section we share with you some significant details of the disease cycle, specifically we will talk about the cocoa crop, but the data are representative for other crops (1) L. theobromae is a phytopathogen that survives in soil and crop debris (source of inoculum, Figure 1), mainly in the form of pycnidiasclerotia (4,5) and/or chlamydospores which act as resistance structures in infected tissue debris and/or soil (6).
Infection cycle of Lasiodiplodia theobromae in cocoa plants and pods.
The microorganism in the soil could remain as a saprophyte on leaves, infected fruits and fragments of fallen branches and also as chlamydospores.. The spores contained in the pycnidia are released into the environment under optimal conditions (minimum 15ºC and optimum 28ºC, maximum at 40ºC), being disseminated by wind, rain (7) or transported by tools and insects of the Miridae family (Helopeltis thetvora,H. ammonliyH. theobromae)(8, 9, Figure 1).
Once the fungus reaches the plant, lesions can be observed on fruits ( Kranz et al . , 1977 ), shoots and young twigs (10), causing serious damage to pod yields, especially in susceptible cocoa varieties (11, Figure 1).
3. Study of the disease in avocado crop: Symptoms in the field.
We will now develop the information published in the first scientific report in Peru on the causal agent of the disease, Lasiodiplodia theobromae, and how it affects the avocado crop.
The incidence of chancrosis in the study was over 80%, demonstrating the dangerousness of the pathogen. Downward dieback symptoms were observed in only 10% of the affected plants (2).
Symptoms of the disease in the field:
The data presented in this section come from the study carried out at the Phytopathology laboratory of the National University of Piura (Peru), where fungal isolates were obtained from affected tissue.
All caused the formation of chancres with whitish secretions, as well as regressive death (2).
(14) Al cortar el fruto afectado se observa la pudrición del mesocarpo que se inicia en la zona de inserción y avanza a todo el fruto.
2: Canker with whitish exudations located along a branch.
3: Canker disseminated on the main branches of the tree, note the whitish secretions.
4: Canker located on the apparently healthy branch.
6: Cankers and exudations on the stem of a young plant.
7: Cankers with exudations on three branches of the same plant.
8a: Cankers on a branch, the whitish secretions have been removed.
8b: Necrotized tissue located below the canker, after a longitudinal cut.
Symptoms of the disease in the field
More symptoms of the disease in the field.
4. Integrated Control of Lasiodiplodia with T34 Biocontrol®.
1
Use of resistant varieties, be well informed of possible new varieties resistant to the disease.
2
Fertilization: avoid excessive doses of nitrogen fertilizer.
3
Pruning :
– Be careful not to make wounds to avoid being a point of entry for the pathogen..
– Early pruning, taking advantage that spore/inoculum production will be low..
– Avoid pruning at times of high humidity (due to high spore release)..
– Sanitary pruning, watch out for branches with cankers and prune “generously”in these areas..
– Vacuuming of fallen/infected leaves. .
– Remove pruning debris from the farm and take care not to spread contamination: pruning tools, hands, shoes (movement from infected areas to healthy areas)..
5. Glossary.
Necrotroph: An organism that feeds on dead tissues or organisms. The pathogen produces metabolites and toxins that produce cell death, feeding on these dead cells (12).
Pycnidium: Fruiting bodies that have an opening through which they release the conidia produced inside (13).
Chlamydospore: Thick-walled thallic conidium that acts as a resistance spore (14).
Canker: Necrotic or dead tissue is a symptom of plant disease caused by pathogenic fungi.
6. Bibliography.
1. Source: Moreira-Morrillo, Anthony A., Cedeño-Moreira, Ángel V., Canchignia-Martínez, Fabricio, & Garcés-Fiallos, Felipe R.. (2021). Lasiodiplodia theobromae (Pat.) Griffon & Maul [(syn.) Botryodiplodia theobromae Pat] in cocoa crop: symptoms, life cycle and management strategies. Scientia Agropecuaria , 12 (4), 653-662. Epub 00 Oct 2021. https://dx.doi.org/10.17268/sci.agropecu.2021.068
3. https://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-33092015000100054 Michereff, S. J., Andrade, D.E.G.T. & Menezes, M. (2005). Integrated management of root diseases. In Michereff, S. J., Andrade, D.E.G.T. & Menezes, M. (Eds.), Ecologia e Manejo de Patógenos Radiculares em Solos Tropicais, (367-388). [Links]
4. Kuswinanti, T., Junaid, M., Surapati, U., & Ratnawaty, R. (2019). A promising microbial use on cocoa: decomposing cocoa waste and controlling. Lasiodiplodia theobromae in-vitro. IOP Conference Series: Earth and Environmental Science , 343 , 012256.
5. Ogundana, S. K. (1983). Life cycle of Botryodiplodia theobromae a soft rot pathogen of yam. Journal of Phytopathology , 106 (3), 204-213.
6. Vásquez-López, A., Mora-Aguilera, J. A., Cárdenas-Soriano, E., & Téliz-Ortiz, D. (2009). Etiology and histopathology of downward death of mamey trees [ Pouteria sapota (Jacq.) H. E. E. Moore and Stearn] in the state of Guerrero, Mexico. Agrociencia , 43 , 717-728
7. Kranz, J., Schmutterer, H., & Koch, W. (1978). Diseases, Pests, and Weeds in Tropical Crops. Soil Science , 125 (4), 272.
8. Ploetz, R. C. (2003). Diseases of Tropical Fruit Crops. CABI Publishing. Wallingford, UK. pp 76-77.
9. Martoredjo, T., Ardy, D., Hermansyah, H., & Sunardi, T. (1995). Peran infeksi jamur dalam memperparah kerusakan buah kakao akibat serangan. Helopeltis sp. Jurnal Perlindungan Tanaman Indonesia. , 1(1), 28-32.
10. Adu-Acheampong, R., Archer, S., & Leather, S. (2012). Resistance to dieback disease caused by FusariumandLasiodiplodiaspecies in cacao (Theobroma cacaoL.) Genotypes.Experimental agriculture,48(1), 85-98.
11. https://dicciomed.usal.es/palabra/necrotrofo-fa#:~:text=adj.,de%20tejidos%20u%20organismos%20muertos .
These are necrotrophic necrotrophic fungi which affect a wide variety of crops including the lettuce, cabbage, tobacco, sunflower, potato, alfalfa, carrot, celery, cucumber, eggplant, legumes, tomatoes and melons, among others..
Within the species of the genus Sclerotinia the causal agents of some plant diseases, such as the White moldthe so-called damping-off (fungal wilt) or the disease known as “fungal wilt” (fungal wilt) or the disease known as “fungal wilt” (fungal wilt).Dollar Spot” (Sclerotinia homeocarpa).
It should also be clarified that fungal wilt fungal wilt is not only caused by this fungus, but also by species of the genus Phytophthora, Rhizoctonia, Botrytis y Pythium are also related to this disease.
Did you know that...?
… Necrotrophic necrotrophic are those that secrete compounds that kill plant cells in order to subsequently absorb their nutrients.
