The pests and diseases that affect plantations in the Amazon should not be underestimated. Losses of 70% of açaí seedlings cultivated in nurseries due to anthracnose have already been identified. In the municipality of Tomé-Açu, in the northeast of the State of Pará, there is an example of the so-called “progressive death”, which affected 50% of the cupuaçu clones in the field. 

These numbers are closely observed by researchers who study the subject and produce a warning signal for more investments in research that promote solutions to combat pests and diseases in the Amazon rainforest.

In respect to anthracnose disease, Professor Allan Lobato, from the Federal Rural University of the Amazon (Ufra), points out that the causative fungi have been observed both in açaí trees managed on dry land and in floodplains. 

"As commercial açaí plantations expand, anthracnose may become a major phytosanitary problem limiting production", he says.

Lobato leads a study that seeks to increase the resistance of açaí trees to pests, diseases in general and fungi. 

The research is dedicated to brassinosteroids, plant steroids that act in the regulation of the development and growth of plants, with a similar function to that of  steroids used in humans and animals.

"These molecules are produced in plants in low concentrations and recent research has revealed that external application, by spraying, can bring several benefits to plants. Although there is limited literature available on the action mechanisms of these molecules, in plants, the brassinosteroids stimulate the metabolism of the plant, bringing benefits including in photosynthesis dynamics, improving growth, flowering and production”, he says.

Lobato points out that any case of diseases or pests affecting açaí trees is worrying, as they assure food security for a significant portion of the Amazonian population, in addition to being responsible for an economic chain that generates more than 25,000 jobs. 

The reduction in the rate of photosynthesis caused by anthracnose delays seedling development causing severe damage. 

The possibilities envisaged by the researcher from the use of these plant steroids involve thicker and stronger cell walls and epidermis, which is expected to make penetration of fungi more difficult.

Cycle

Research has been carried out for almost ten years with positive results besides the defense against pests and diseases, with tests already carried out on soybeans, rice, tomatoes, cowpeas and eucalyptus. 

The use of brassinosteroids can accelerate the cycle of the plant, allowing the farmer to plant and harvest in a shorter period of time, since the plants can produce more flowers and, therefore, more fruits or grains, in addition to improving the anatomical structures of the plant, leaf and root, resulting in higher rates of photosynthesis.

"During cultivation, subject to field conditions, the plants are exposed to climatic variations and to imbalances generated by global warming. So, the more prepared the plant is for these bad weather conditions, the smaller the production loss. We are very hopeful that the use of these steroids will reduce the damage to the açaí trees. We expect that it is possible to apply the technology directly with the producer", comments the researcher, who hopes that the scientific study receives more resources and encouragement to generate consistent results.

Amazon rainforest is a conducive environment for epidemics

There are three necessary main factors for the occurrence of a disease in a vegetable. At one end of the triangle, is the host – a susceptible plant. In the other, a virulent pathogen that causes the disease. Finally, a favorable environment is also necessary. 

"In the Amazon, we experience the equatorial climate, with high temperatures and humidity throughout the year, that means, a highly favorable environment for the development of fungi, with possible diseases evolving throughout the twelve months of the year. The impact of the disease will depend on how the handling is processed", points out researcher from the Brazilian Agricultural Research Corporation (Embrapa), Ruth Linda Benchimol.

Ruth – PhD in phytosanitary – emphasizes the importance of producers who are consistent with the instructions of the Agricultural Climate Risk Zoning Program from Ministry of Agriculture and Livestock, with studies that mapped the best points for each crop. 

"The challenge to control plant diseases is enormous in the Amazon. It is always essential to use crops and seeds certified by people and companies accredited by the MDA. In the region, we still have people reporting many disease problems as a result of buying abandoned pepper cuttings, from not certified origin. It is a very high risk of spreading diseases", she points out. 

Moniliasis cases in cupuaçu trees is increasing

Moniliasis, a disease caused by the fungus Moniliaphthora roreri, has gained prominence in the last decade due to the increasing incidence of the disease in cupuaçu trees. 

There are already occurrences of the disease in the states of Acre and Amazonas.

The fungus causes lesions inside the fruit - cupuacu - and evolves to the external part, resulting in spots, necrosis, and the formation of a white powder. 

The pest can cause up to 100% loss in the production of the fruit and, although it has a high proliferation potential in the environment, it does not affect humans. The disease has also affected cocoa trees.

Another disease that severely affects cupuaçu is “witch's broom”, caused by Moniliophthora perniciosa, a fungus that infects plant tissues, leading to the proliferation of lateral buds in infected branches, which gradually take on a broom-like shape, a peculiar symptom that named the disease.

Ruth Linda Benchimol emphasizes that it is an endemic pathogen in the Amazon rainforest, present in cultivation areas throughout the year, with higher visibility between May and August. 

The researcher highlights that currently, the management of witch's broom in cupuaçu trees is mainly achieved through cultural and genetic control measures – able to reduce the severity of the disease to levels that do not compromise the economic viability of the business.

“There is also the possibility of planting species known as “improved varieties”: genetic studies aim to find productive and disease-resistant plants. In the case of a short-cycle crop, the problem is easier to solve, as genetic improvement is faster and can determine more suitable crops according to the needs and the surrounding environment. In long-cycle crops, however, studies take longer. In the case of cupuaçu trees, we have been following the trajectory of witch's broom, the worst disease to cupuaçu cultivation. Approximately every ten years, we witness the release of a new technology. The dream of plant pathologists is to have a resistant plant species, of course, but it is challenging. In the case of cupuaçu trees, we have already made significant progress. Last year, the so-called Kit 5.0 was released, consisting of five improved cupuaçu varieties with low incidence of witch's broom. One can cut the tree canopies and replace them. When you cut a canopy up to one and a half meters, new buds will appear at the treetop as a mechanism to survive, then clones are inserted onto it, resulting in a plant with the root of a tree and the canopy of another one. Rubber tree problem was solved this way. These control techniques are environmentally friendly because we won't need to use fungicides. That's why it is important to have increasing investments in these solutions," she states. 

Black pepper cultivation is affected by fungus.

The Amazon region has experienced difficult moments of disease outbreaks in crops causing a strong socioeconomical impact. 

Introduced in the 1930s in Pará, black pepper quickly became synonymous with prosperity in the northeastern part of the state, especially due to the efforts of the Japanese community in Tomé-Açu.

However, a total collapse in the mid-1960s was provoked by the fusariosis, a disease caused by the fungus Fusarium solani. 

Ruth Linda Benchimol emphasizes that black pepper is a perennial crop, guaranteeing an average of 20 to 30 years of production when properly managed.

 "When this fungus started to spread, there was a complete devastation, and no one knew what to do. Some areas were completely abandoned, and the lifetime of the plants reduced to around five to six years. At that time, it became a migratory agriculture, because there was no knowledge on how to combat the disease," says Ruth Benchimol.

Fordlândia

Another classic case was the “leaf blight” [microcyclus ulei] that affected rubber trees, just when the automobile company Ford arrived in the Amazon in 1920 to establish rubber plantations on four thousand hectares in the city of Fordlândia, in the state of Pará. 

Despite promises of employment and development, the American multinational company faced a disease called “leaf blight”, which quickly spread throughout the company's plantations and made rubber production unviable, resulting in Ford to abandon the rubber plantations in 1934. 

There was a second attempt in the city of Belterra, also in western Pará, with new techniques, new genotypes, and canopy grafting. 

The effort managed to delay the leaf blight epidemic in the plantation, but it was not efficient enough to control and eradicate the disease once and for all. 

With the crops infested over again, the Americans had to abandon the rubber plantations in 1945.

"Despite the significant technological advancements since then, every cultivation needs to be monitored and supervised to identify potential problems and ensure efficient interventions. The goal is to increasingly work towards innovative and economically viable solutions, particularly cultural techniques that can replace the use of pesticides. In addition to canopy replacements, fungi and biological agents can be utilized. There is a vast scope of alternatives to face this challenge. Human action is crucial, as it can either help or hinder. Among the beneficial actions are: reforestation which restores soils, prevents issues, industrial filters that treat wastewater before it reaches rivers, and the essential promotion of environmental education. On the other hand, negative human impact includes deforestation, river pollution, and increased greenhouse gas emissions... All these factors affect plantations because nature is a complex system with many interconnected actors," highlights Ruth Benchimol.