Alternaria solani (early blight of potato and tomato)
This page contains a subset of the full datasheet, which can be found on the CABI Compendium. Some datasheets within the Compendium are access-restricted and require either an institutional login or a direct purchase. For more information on accessing the full datasheet, please see the access options help page on the CABI Digital Library.
Identity
- Preferred Scientific Name
- Alternaria solani Sorauer
- Preferred Common Name
- early blight of potato and tomato
- Other Scientific Names
- Alternaria dauci f.sp. solani
- Alternaria porri f.sp. solani
- Macrosporium solani Ell. & G.Martin
- International Common Names
- Englishalternaria blightdry blight of potato and tomatoearly blight of eggplantearly blight of potatoearly blight of tomatotarget spot of tomato
- Spanishalternariosis de la papa y tomatetizon tempranotizon temprano de las papas
- Frenchalternaria des solanaceesalternariose de la chicoreealternariose de la pomme de terre et de la tomatebrulure alternarienne de la pomme de terrebrulure alternarienne de la tomatetaches foliaires larges
- Local Common Names
- GermanyBlattfleckenkrankheit: EierfruchtBlattfleckenkrankheit: TomateDuerrfleckenkrankheit: KartoffelHartfaeule: Kartoffel
- EPPO code
- ALTESO (Alternaria solani)
Pictures
Field symptoms
Symptoms on tomato leaves.
M. Rutherford/CABI BioScience
Field symptoms
Symptoms on okra leaf.
M. Rutherford/CABI BioScience
Symptoms
Advanced symptoms on potato leaf.
©CSL/Crown Copyright
Alternaria solani target spot on potato leaves
CABI
"Alternaria solani, target spot on potato leaves"
CABI
Alternaria solani
Early blight of tomato
James Muema, MOALFD, Kenya
Alternaria solani
Early blight of tomato
James Muema, MOALFD, Kenya
Early Blight in Tomato
Alternaria solani
TA Zitter
Distribution
Host Plants and Other Plants Affected
| Host | Family | Host status | References |
|---|---|---|---|
| Brassica oleracea (cabbages, cauliflowers) | Brassicaceae | Unknown | Muradov et al. (2019) |
| Capsicum (peppers) | Solanaceae | Main | |
| Capsicum annuum (bell pepper) | Solanaceae | Main | |
| Convolvulus arvensis (bindweed) | Convolvulaceae | Wild host | |
| Lactuca sativa (lettuce) | Asteraceae | Other | |
| Moringa oleifera (horse radish tree) | Moringaceae | Other | |
| Nicotiana rustica (wild tobacco) | Solanaceae | Wild host | |
| Solanum lycopersicum (tomato) | Solanaceae | Main | Kondaiah and Sreeramulu (2014) Munde et al. (2013) Muradov et al. (2019) Hussain et al. (2019) |
| Solanum melongena (aubergine) | Solanaceae | Main | Kondaiah and Sreeramulu (2014) Muradov et al. (2019) |
| Solanum nigrum (black nightshade) | Solanaceae | Wild host | |
| Solanum sarrachoides (green nightshade) | Wild host | ||
| Solanum tuberosum (potato) | Solanaceae | Main | Zheng and Wu (2013) Miles et al. (2013) Bagherabadi et al. (2015) Blixt and Andersson (2010) Rashtra (2017) Muradov et al. (2019) Baideng et al. (2019) Naim (2007) |
| Triticum aestivum (wheat) | Poaceae | Unknown |
Symptoms
The symptoms of early blight vary depending on the host and plant tissue.
Foliar symptoms are dark brown to black necrosis. The first symptoms usually appear on the older leaves as small, dark, necrotic lesions, a few millimetres in diameter, which increase in size. Sometimes the lesions are restricted by leaf veins and take on an angular shape. The size of the necrosis can vary in width, from a few millimetres to 2 cm. Within larger lesions, concentric rings (so call target spot or bullseye) are visible, often surrounded by a chlorotic, yellowing zone. The chlorosis can extend to the whole infected leaf. The infected lesions enlarge and the whole leaf becomes necrotic which results in premature defoliation. In tomato production, the premature defoliation can cause injury to the fruits due to sunscald.
On tomato, A. solani can cause symptoms on the stem. Dark and sunken lesions can appear on the stems of seedlings, so called collar rot. The infected seedling shows reduced plant vigour or can die when the stem is completely girdled by the lesion. The main stem of adult tomato plants can also be infected, showing small, slightly sunken lesions (stem lesion). As on the leaves, typical concentric rings are visible on the infected stem.
On green or ripe tomato fruits, dark lesions can occur at the end of the stem. Ripe fruits are less susceptible than semi-ripe ones (Mehta et al., 1975). Heavily infected fruits drop prematurely. On less resistant cultivars, the calyx and blossom also can be infected (Pandey et al., 2003) and show comparable symptoms.
The symptoms on potato tubers are dark, slightly sunken lesions (dry rot). The dry or hard rot of tubers causes storage losses, reduces the quality of table potatoes, and reduces germination capacity of seed potatoes.
List of Symptoms/Signs
| Symptom or sign | Life stages | Sign or diagnosis | Disease stage |
|---|---|---|---|
| Plants/Fruit/lesions: black or brown | |||
| Plants/Leaves/abnormal leaf fall | |||
| Plants/Leaves/necrotic areas | |||
| Plants/Stems/discoloration of bark |
Prevention and Control
The control of early blight requires the implementation of several approaches. Integrated pest management is based on good agricultural practices, cultivation of a less susceptible cultivar and the use of biological and synthetic components.
Reduction in the amount of initial inoculum
The fungus survives on plant debris and in the soil for several years. Crop rotation therefore reduces the initial soilborne inoculum. The control of host plants such as black nightshade, volunteer potatoes and tomatoes, and cull piles in the non-host crops is also important to reduce the inoculum. Clearing the infected debris from the field results in inoculum reduction.
Biofumigation is also a possibility to reduce soilborne inoculum. Isothiocyanates (ITC) produced by the hydrolization of glucosinolates by myrosinase in disrupted plant cells suppress the soilborne inoculum. Biofumigative active plants include white mustard and leaf radish (Volz et al., 2014).
Tillage practices such as autumn ploughing that bury plant refuse can be used (see: https://www.canr.msu.edu/resources/potato_diseases_early_blight_e2991)
Harvest and storage
The potato tuber gets infected during harvest, but the fungus cannot infect through the intact periderm of the tuber. Killing off the foliage before harvesting and allowing tubers to fully mature can therefore prevent tuber infection.
Avoiding wounding of the tubers at harvest, transport and storage and promoting wound healing in storage reduces tuber infection.
Fertilization
Plant nutrition should be based on balanced fertilization. Low nitrogen results in a significantly higher early blightdisease.
The kind of N-fertilizer also influences the disease progression of A. solani. In potatoes, calcium cyanamide results in a delay of early blight disease. The degradation products of calcium cyanamide have a side-effect on the fungus and therefore reduce the initial inoculum in the soil (Volz et al., 2014).
Biotic and abiotic stress
Biotic or abiotic stress results in plants becoming more susceptible to the fungus Alternaria solani. Promotion of plant health therefore results in lower disease progression. Abiotic stress is driven by drought, high temperature and overhead irrigation. Additionally, overhead irrigation, especially at night, can prolong the leaf wetness period and therefore increase the risk of a fungal infection. The use of drip irrigation instead of overhead irrigation reduces this risk.
There are different biotic stress factors for plants during the growing season, mainly associated with attack by insects (aphids, Colorado beetle, Aleyrodoidea species).
Certified seed and seed tuber
The use of virus- and disease-free seeds and seed tubers is important for healthy plant growth. Plant tissues of Potato virus Y-infected tubers are more susceptible to A. solani and PVY-infected plants showed an increased sensitivity for the pathogen (Metz, 2016).
Others
In tomato and aubergine production, the application of plastic or an organic mulch provides a barrier between contaminated soil and leaves.
For greenhouse production, early blight has been reduced by covering houses with UV-absorbing vinyl film.
Chemical Control
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
•
EU pesticides database (https://food.ec.europa.eu/plants/pesticides/eu-pesticides-database_en)
•
PAN pesticide database (www.pesticideinfo.org)
•
Your national pesticide guide
Host-Plant Resistance
Potato and tomato cultivars with reduced susceptibility to early blight are available. Complete resistance to early blight has not been found. The field resistance of potato varieties to early blight is associated with plant maturity. Early maturing cultivars are in general more susceptible, and late maturing cultivars are more resistant to A. solani (Johanson and Thurston, 1990; Abuley et al., 2017). There is a strong correlation between maturity group and disease progression, with the epidemic in early-maturing potato cultivars starting earlier. Interestingly, there are varieties within a maturity group which are more resistant to early blight (Johanson and Thurston, 1990; Leiminger and Hausladen, 2014). Also, immature potato and tomato plants are relatively resistant to early blight. After tuberisation (potato) or fruit initiation (tomato, aubergine) the plant tissue becomes more susceptible.
IPM - Decision Support Systems
Different decision support systems (DSS) for the control of early blight in potato or tomato are available. The models can be divided into three different sub-categories: plant-based, pathogen-based or plant-pathogen-based.
P-day model and GDD: The P-day model developed by Sands et al. (1979) predicts the growth and development of potatoes based on daily temperature values. On the basis of interaction of plant maturity and susceptibility (see Host-Plant Resistance) the model calculates a daily P-value. Finally, the P-day model uses different thresholds (cumulative P-value) to optimize the fungicide application. The growing degree-day (GDD) model published by Franc et al. (1988) is similar to the P-day model.
EPIDEM, FAST, IWP: EPIDEM is a pathogen-based model developed by Waggoner and Horsfall (1969). This model simulates the different stages of the life-cycle of A. solani based on weather data.
FAST, a forecasting system for A. solani in tomato has been developed to identify periods when environmental conditions are favorable for the fungi (Madden et al., 1978).
Van der Waals et al. (2003) published a model called interrupted wet periods (IWP), also based on weather data.
The FAST model was modified by Pscheidt and Stevenson (1986) and Christ and Maczuga (1989) to control early blight on potato. This modified model combines the FAST and the P-day model.
Threshold value model: Leiminger and Hausladen (2012) have also published a threshold value model for control of early blight in potatoes, based on disease progress.
Information & Authors
Information
Published In
Copyright
Copyright © CABI. CABI is a registered EU trademark. This article is published under a Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
History
Published online: 6 May 2019
Language
English
Authors
Metrics & Citations
Metrics
SCITE_
Citations
Export citation
Select the format you want to export the citations of this publication.
EXPORT CITATIONS