Integrated pest management in sugarcane

At fight against sugarcane borer, root leafhoppers and Sphenophorus levis, main pests in sugar cane, the The best path lies in the adoption of integrated management, with the use of techniques cultural, varietal, biological and chemical. Among the control strategies biological the use of entomatogenic fungi has an important role in combating these insects.

Integrated Pest Management (IPM) has as its main objective the use of several cultural, varietal, biological and chemical techniques to control pests in crops of economic interest, with the principle of using the most sustainable ones, such as resistant varieties, cultural techniques, pest monitoring, biological control agents and finally chemical insecticides (preferably the least toxic ones), which should be applied when the level of pest control reaches a dangerous level for the crop.

However, this management methodology is not always taken into consideration due to lack of knowledge of the levels of control and economic damage to most crops. When this occurs, the tendency is to apply chemical insecticides indiscriminately.

Entomopathogenic fungi are important biological control agents for integrated pest management in sugarcane, as this crop is known as the one that has most successfully supported the use of biological pest control, especially in Brazil.

The state of São Paulo produces half of Brazil's sugarcane (the remainder is located around 30% in the Northeast, and 20% in the Central West and Paraná). At least 5% of the cost of producing sugar and alcohol is affected by pests, among which the sugarcane borer, root leafhoppers and Sphenophorus levis.

The sugarcane borer Diatraea saccharalis is considered the main pest of this crop, occurring in all areas where sugarcane is planted in the world. The caterpillars cause direct damage to the stalk, opening galleries that cause weight loss of the cane and also death of the buds, which lead to germination failures. Indirect damage is caused by infection of fungi that penetrate the gallery and cause red rot, such as Colletotrichum falcatum e Fusarium moniliforme, which invert sucrose, reducing the purity of the juice and giving a lower yield of sugar and alcohol. According to research results on the damage caused by the borer, only 1% of pest infestation is capable of generating losses of 0,25% of sugar, 0,20% of alcohol and 0,77% of weight.

The main control method is biological, through wasps. cotesia flavipes, introduced in Brazil since 1974. In recent years, this parasitoid has reduced losses of up to 100 million dollars per year, 20 million of which in São Paulo, reducing the pest infestation from 10% to 2%. The egg parasitoid Trichogramma galloi has also been used to control the borer, and can reach 60% control when associated with C. flavipes.

In areas of sugarcane crop expansion, the fungus Beauveria bassiana can be used to control first-instar sugarcane borer caterpillars, and should be sprayed at a dosage of at least 6x1012 conidia/hectare.

Root sharpshooters

The root hoppers, Mahanarva fimbriolata, M. spectabilis, Mahanarva sp. are considered the most important pests of sugarcane. When feeding, the nymphs cause "physiological disorder" due to their bites, which, when reaching the woody vessels of the root, deteriorate them, preventing or hindering the flow of water and nutrients. The death of roots causes imbalances in the physiology of the plant, characterized by the dehydration of the phloem and xylem, which will give the stalk hollow characteristics, thinning and subsequent appearance of wrinkles on the external surface.

When adults inject toxins, they produce small yellow spots on the leaves that become reddish and eventually opaque over time, significantly reducing the photosynthetic capacity of the leaves and the sucrose content of the stalk. The perforations of the tissues by the infected stylets cause contamination by microorganisms in the nutrient liquid, causing deterioration of tissues at the growth points of the stalk and, gradually, from the lower internodes to the underground roots. The aqueous deterioration presents dark colors starting at the tip of the cane and can cause the death of the stalk.

The nymphs are specifically radicicolous and develop on the superficial roots or lower adventitious roots of the host grasses. They suck sap according to their age, enveloping themselves in a thick, white foam that serves as protection from natural enemies. The adults have crepuscular-nocturnal habits, hiding within the eyes or on the edges of the leaves during the day. The most important damage that leafhoppers cause is the “burning of the sugarcane”, which is a direct consequence of the attack on the leaves, due to the injection of toxic substances from the leafhopper’s saliva, in addition to reducing the sucrose content. They also cause a reduction in the size and thickness of the inter-noses of large sugarcane and the death of young shoots.

Biological control with entomopathogenic fungus Metarhikum anisopliae It is one of the main components of integrated leafhopper management. It is non-polluting, does not cause biological imbalances, is long-lasting and takes advantage of the biotic potential of the agroecosystem. It is non-toxic to humans and animals and can be applied with conventional machines, with minor adaptations.

In the period 2015/2016, the area applied with the fungus was approximately 350 thousand hectares, with another biofactory starting production. The cost of application and the value of the bioinsecticide sold did not vary in relation to the previous period.

Sphenophorus levis

The beetle from the Curculionidae family is another pest that has caused great damage to sugarcane cultivation, mainly in the Piracicaba and Jaú region, São Paulo, destroying the ratoons and causing them to die. The larvae pierce the sugarcane rhizome throughout its biological cycle, causing a decrease in sugarcane production.

The application of the insecticide fipronil over the entire area, with a cutting disc on the ratoon, is a strategy that has provided some control, forming a chemical barrier. However, it is still a technique that has been used in a unique way, which can lead to resistant pest populations and environmental contamination.

Chemical control is the most widely used, applied in baits of cut sugarcane stalks previously treated with insecticides such as carbaryl 850 PM, applying 200 baits/hectare. Currently, research is being carried out into the use of entomopathogenic fungi, beauveria bassiana selected for this pest in baits and entomopathogenic nematodes such as Steinernema spp.

The lack of knowledge on the use of entomopathogenic fungi for the biological control of sugarcane pests is still an important factor in explaining the low application of these biological control agents, and it is important to disseminate techniques for applying these fungi in the total area or through baits. or advanced systems, in order to target sugarcane pests, as the fungi act through contact with the insect's body.

The use of biological control agents depends on products available on the market capable of meeting this demand. There are currently 55 companies that produce entomopathogenic fungi and approximately 20 companies that produce parasitoids for sugarcane.

The state of São Paulo has provided support in this area of ​​knowledge, supporting the development of new productions or an increase in the quantity of entomopathogenic fungi. The Biological Institute (SAA-SP/APTA) has a technical advisory program for the production of bioinsecticides based on entomopathogenic fungi, with the supply of selected strains for these main sugarcane pests. The Institute has already advised 54 of these companies. In addition, it develops research into production methods using liquid fermentation and formulations, essential for the development of biological control. However, it is necessary for companies and the government to encourage innovations in this area, both for research, commercialization and application.

Research is needed to develop new isolates, formulations, traps, baits or other suitable strategies for controlling the main sugarcane pests, but without a doubt, entomopathogenic fungi are already an important tool for Integrated Pest Management in sugarcane. -sugar.

* By Jose Eduardo M. de Almeida, Biological Institute

Article published in issue 217 of Cultivar Grandes Culturas, June 2017.