Every time the next slide was changed, it was observed how numerous attendees raised their cell phones to take a photo of the symptoms of the different foliar diseases presented by the expert researcher and plant pathologist, Andrés France, during the last seminar organized by Blueberries Consulting in Trujillo.

With a presentation loaded with photographs, the agronomist presented the topic "Foliar diseases of blueberries: a growing challenge", a title that expressed the concern and interest expressed by many of the Peruvian producers present.

In Peru, many of the productive departments have humidity and temperature characteristics that facilitate the spread of pathogens that cause foliar diseases. This type of pathology affects the leaves, buds and new stems of plants with symptoms such as pustules or foliar lesions, which reduce the surface available for photosynthesis. By ceasing to accumulate energy reserves, the total production of blueberries and their quality are diminished.

Although it is easy to identify that there is a problem, given the similarity of the lesions, there can be confusion when trying to identify if it is a pathogen and which one is causing the symptoms.

Of all the pathogens presented by the phytopathologist, there were two that stole the attention. "The main foliar diseases in Peru are rust and powdery mildew, because they cause economic loss, weaken the plant and affect production," said the expert.

the rust (Pucciniastrum vaccinii) It is present in two types: Eastern Rust and Western Rust, due to the location where they were found in the US. Although they differ in the color of their lesions, both follow the same treatment. 

The disease is aggressive; It is easy to spread since it produces numerous necrotic foliar pustules with a large number of spores, which can be spread throughout the different sectors of the crop. When plants are affected by rust, they suffer from defoliation, and the energy diverted from trying to replace this loss of leaves affects blueberry production, fruit quality and longevity. 

The other big problem is the presence of powdery mildew (Microsphaera vaccinii) on Peruvian farms. Also known as Dust or Gravilla, it is usually found in blueberry plantations, however, the severity of its consequences depends on how early it is identified on the farm. If Powdery Mildew reaches crops during its sexual phase, it becomes a problem due to its resistance to fungicides, it causes an earlier onset of the disease and there is a greater chance of generating new races. 

Powdery mildew is identified by looking at the underside of the leaves and finding irregular, watery, oily lesions and/or with a white powdery deposit depending on the progress of the condition. 

On the management and prevention of rust and powdery mildew in crops, France is blunt: “Unfortunately, diseases are here to stay. In this particular case, what can be done is to prevent their entry, because despite the fact that we have already had several seasons with these two pathologies in Peru, there are places where they have not yet arrived and orchards that are still free of rust or powdery mildew. It is important to maintain that condition because we would have a serious forward handling problem.”

In his presentation, the plant pathologist recommends quarantine as the best control measure, avoiding the movement of people from contaminated areas to other sectors of the crop, recommending the use of fungicides and attention to details such as cleaning the leaves for the appropriate absorption of the products to combat the condition and the direction from which the chemical or biological controllers are sprayed; especially with Powdery Mildew, whose lesions are on the underside of the leaf and therefore you need to spray with the controllers from the bottom up.

For this last condition, the use of water, aggressive pruning of the roots is recommended to improve ventilation and radiation that reaches the affected areas of the plant, in addition to facilitating the removal of fallen leaves by the action of Powdery Mildew. 

Andrés France encourages prevention and constant monitoring, and warns: “They can end up killing the plant, weakening it to such an extent that it is easy to be affected by a second or third pathogen. Direct losses will also be seen, first in the quality of the fruit, because as there is less photosynthesis, then the fruit is less sweet, and there are cases where total losses have been reached as a result of the damage caused by these pathologies”