Real-time alerts
You receive a notification when the risk of Alternaria increases according to weather conditions.
Alternaria alerts when the weather raises the risk
Alternaria in citrus appears with rain, humidity and mild temperatures. Agrimaps alerts you in real time when the risk increases according to weather conditions and shows you how it evolves alongside the treatments you have already applied.
The disease
What Alternaria in citrus is
Alternaria (Alternaria alternata pv. citri), also known as Alternaria brown spot of mandarins, is a fungal disease that attacks young leaves, shoots and fruit.
According to the Red de Alerta e Información Fitosanitaria de la Junta de Andalucía (the Andalusian plant health alert network, 29/12/2025), it mainly affects varieties such as Fortune, Nova/Clemenvilla, Tangelo Minneola and Murcott, and infection can begin when the temperature is between 20 and 25 °C and there are more than 8 hours of free water on young leaves, fruit or shoots. Symptoms may appear 24 to 72 hours later.
- On the leaves: dark spots with a yellow halo that grow to around one centimetre; in some lesions the necrosis follows the veins and the tree can end up defoliated.
- On the fruit: sunken, irregular lesions, with a yellow halo if the fruit has not yet reached colour break, and fruit drop, especially in young fruit.
Alternaria alerts
What Agrimaps does with Alternaria risk
Risk chart
The risk level of each record by date, with horizontal lines marking the different levels.
Your treatments overlaid
Applied treatments that affect Alternaria appear as vertical lines; click one to see the full treatment.
All in the logbook
These are the same treatments used to generate the field logbook at the click of a button.
Prevention
Why it pays to know in time when the risk rises
The most common infection periods are spring and late summer and autumn, and the free water on the plant can come from dew, fog or rain (Vicent et al., ‘Daños producidos por Alternaria alternata en mandarina Fortune’, Vida Rural, 01/05/2003).
That is why the Andalusian alert network (Red de Alerta de Andalucía) recommends taking the weather forecast into account when applying preventive measures, keeping trees pruned so the canopy is well aired, keeping the rows clear of debris, avoiding out-of-season flushes, and using only products registered and authorised for that purpose by Spain’s Ministerio de Agricultura, Pesca y Alimentación. The decision lies with the technician: Agrimaps gives them the alert and the risk and treatment history of each plot.
The alert is complemented by pest sampling, fruit assessment in citrus and geolocated notes to mark where you have seen symptoms. What to record at each inspection is covered on our blog: Alternaria in citrus: when to monitor it and how to record it (in Spanish).
What is Alternaria in citrus?
It is Alternaria brown spot of mandarins, a disease caused by the fungus Alternaria alternata pv. citri on young leaves, shoots and fruit of susceptible varieties such as Fortune, Nova/Clemenvilla, Tangelo Minneola and Murcott (Red de Alerta e Información Fitosanitaria de Andalucía, the Andalusian plant health alert network, 29/12/2025).
What conditions favour Alternaria?
Rain or high relative humidity with mild or warm temperatures. Infection can begin at 20 to 25 °C with more than 8 hours of free water on young leaves, fruit or shoots, according to the Andalusian alert network (Red de Alerta de Andalucía).
How does Agrimaps alert me?
With real-time notifications when the risk of Alternaria increases according to weather conditions. On the web you can also see the chart of the risk level by date.
Can I see the treatments I have applied on the chart?
Yes. Applied treatments that affect Alternaria appear as vertical lines on the risk chart, and clicking one shows you all the treatment details.
Does Agrimaps decide the treatment?
No. Agrimaps alerts and records: the technician decides what measures to take based on the alert, the weather forecast and the history of the plot.
Can I try Agrimaps?
Yes. Fill in the contact form and we will show you with a demo.
Agrimaps
More from Agrimaps
Field logbook with SIGPAC
Your field logbook at the click of a button, with SIGPAC plots imported from the online register.
Pest sampling and monitoring
The status of pests in each plot, phenological stages and Alternaria alerts.
Geolocated notes
Every incident with a photo, at the exact spot on the farm, with directions to get there.
Citrus
Clareta, Delottococcus and calyx assessments, plus a final assessment of the fruit.
Citrus mealybug guide
The South African citrus mealybug (Delottococcus aberiae): its damage, where to look for it and how to assess the lesions it leaves.
SIGPAC map guide
What SIGPAC is, what plots and enclosures are and where to view its map.
Agrimaps
Try it on your farm
Ask for a no-obligation demo and we will show you Agrimaps with your own farms.