IB develops research for biological control of insects that transmit greening

Research by the Institute of the Secretariat of Agriculture and Supply seeks more sustainable strategies for managing the most destructive citrus disease in the world

12.08.2020 | 20:59 (UTC -3)
Biological Institute

Research carried out by the Department of Agriculture and Supply of the State of São Paulo, through the Biological Institute (IB-APTA), seeks new ways to control the psyllid, the insect that transmits greening (huanglongbing/HLB), the most destructive citrus disease worldwide. IB's strategy is to use natural enemies of the psyllid for its control, providing more options for management actions by Brazilian citrus growers.

Data from Fundecitrus show that 20,87% of orange trees in the citrus belt of São Paulo and the Triângulo/Southwest of Minas Gerais have symptoms of greening, which corresponds to around 41 million contaminated trees. This index, according to the Foundation, is 9,7% higher than that of 2019, estimated at 19,02%.

According to José Eduardo de Almeida, a researcher at IB, the Institute is carrying out research with a private company to develop an innovative product for the biological control of the psyllid. "We have already isolated three strains of fungi that have proven effective in controlling the insect. A biofactory has already started producing the product, which should be on the market in three years", says the researcher.

According to Almeida, greening is a difficult disease to control. There are no orange cultivars in the world that are resistant to the disease, also known as yellow dragon. Control strategies are the eradication of contaminated orange trees and the use of agricultural pesticides to eliminate the psyllid, which, as it is a flying insect, requires many applications of chemical products, increasing production costs and causing impacts on the environment.

Ashy Gray Lady Beetle

Another important result of IB in the area of ​​biological control in citrus was the selection of predatory ladybird beetles that feed on eggs and young forms of the psyllid. According to a study coordinated by IB researcher Terezinha Monteiro dos Santos Cividanes, from the Ribeirão Preto Plant Parasitology Laboratory, ladybug populations in organic orchards were higher and the species diversity found was double that observed in conventionally managed orchards.

"In the laboratory, it was recorded that the coccinellids Cycloneda sanguinea, Cycloneda conjugata, Harmonia axyridis and Hippodamia convergens fed on the psyllid. The results of this study proved the relevance of ladybugs as controlling agents of the insect pest", says Terezinha. The study was funded by the São Paulo Research Foundation (FAPESP).

According to Terezinha, a recommended tactic for farmers is to recognize ladybugs to keep them in the orchard and also use practices to attract these natural enemies, such as maintaining flowering plants. "The selective management of insecticides in citrus crops is relevant for the survival of ladybugs in the orchard", she highlights.

Predatory mites for psyllid and leprosy mite control

Researchers at the Biological Institute are working on yet another strategy for biological control of the psyllid: the use of a predatory mite, called Amblydromalus limonicus, which is its natural enemy. According to Mario Eidi Sato, a researcher at IB, this predatory mite feeds on the eggs of the psyllid Diaphorina citri, which is the vector of greening.

"These mites are small organisms, approximately 0,5 mm in size, that live on a large number of host plants, including citrus. In addition to attacking psyllid eggs, they can also control mites and phytophagous insects of different species, including the purple mite (Panonychus citri), whiteflies and thrips", explains Sato.

The research carried out by the IB also aims to use predatory mites to control the leprosy mite (Brevipalpus yothersi), a vector of citrus leprosis (CiLV-C), one of the main diseases of citrus and which mainly affects orange trees. candy. The disease causes production losses and reduces the useful life of the weakened tree.

The recent studies were carried out by a master's student from the Postgraduate Course in Health, Food and Environmental Safety in Agribusiness at IB. The research was carried out in a citrus area being converted to organic production. Predatory mites of the species Neoseiulus calfornicus were released in this orchard. In addition to controlling the leprosy mite and other pest mites, the organism is resistant to the main chemical acaricides and insecticides registered for citrus, which makes its use interesting in areas with frequent applications of pesticides for pest control.

The research showed that despite being efficient predators, N. californicus do not establish themselves permanently in the area, acting more or less like a chemical product: "they are introduced, kill the target and after a short time they leave".

The studies also seek to identify new species or lineages of predatory mites (e.g. Euseius, Amblyseius) with a high predation capacity for mites and insect pests, and which are able to establish themselves for a long period of time in orchards after their release.

According to Sato, the use of mites for citrus farming is best suited for small and peripheral areas of the property, in addition to those with an imbalanced insect and mite population. "Another interesting use is for abandoned orchards or citrus cultivation in the city, which if not well cared for, could be the focus of the greening vector, for example, and impact commercial areas," she says.

Biological control

Biological control consists of using natural enemies to reduce the population of a pest. Briefly, it can be defined as nature controlling nature. Biological control agents act on a specific target, do not leave residues in food, are safe for rural workers, protect biodiversity and preserve pollinators.

IB is a reference in Brazil and the world in biological control and has a strong presence in the production sector, having guided the creation and maintenance of biofactories, which develop these biological products to be applied to crops. In total, more than 80 biofactories across Brazil receive guidance from IB researchers. In 2019, the Institute signed 23 contracts for technology transfer to these companies, located in São Paulo, Minas Gerais, Mato Grosso and Paraná.

The Institute maintains the Innovation and Technology Transfer Program in Biological Control (Probio), which brings together the technologies and services provided at the Institute, mainly for the crops of sugar cane, soybeans, bananas, rubber trees, flowers, strawberries, beans and vegetables.

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