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Fabricio Fagundes Pereira

Professor of Entomology at UF-Grande Dourados-MS


Biological control of defoliating caterpillars

The forest sector has contributed significantly to the economic and social development of Mato Grosso do Sul. The expansion of planted forest areas, with around 1,124,637 hectares, and the arrival of industries in the area generated thousands of jobs and definitively transformed the east coast of the state. Among the obstacles that can compromise the productivity of forest essences, insect pests, diseases and weeds stand out.

Defoliator caterpillars, mainly Iridopsis panopla and thyrinteira arnobia are pests that, in recent years, have reached high population levels, especially in the eucalyptus crop, in producing areas located in the eastern mesoregion of Mato Grosso do Sul. The associated occurrence of these defoliating Lepidoptera and their damage, in the year 2021, according to monitoring carried out by foresters, was recorded in about 681,886 hectares cultivated with eucalyptus, occurring throughout the year, with greater prevalence between January and July, due to several factors, among them, the favorable climatic conditions that are different every year.

In 2022, the occurrence of defoliating Lepidoptera in eucalyptus plantations was reported in 233,816 hectares. Each year, there is a variation in the population fluctuation of defoliating lepidopterans and, therefore, the implementation of the monitoring plan and the adoption of emergency control measures are essential to avoid the negative effects resulting from the damage caused by the mentioned pests, which can surprise foresters, with population surges and immeasurable economic and environmental damage throughout the year.

It is noticed that the increase in the population of lepidopterans can occur from January, with population peaks in May, in Mato Grosso do Sul. There are biological products based on Bacillus thuringiensis and chemicals registered with the Ministry of Agriculture, Livestock and Supply for Thyrinteira arnobia, but, in recent years, population outbreaks of Iridopsis panopla and its damage has foresters worried. It is a new pest, with high biotic potential, great defoliation capacity and, in addition, there is no basic information or registered products for its control.

Palmistichus elaesis, Trichospilus diatraeae, Tetrastichus howardi are parasitoids, mainly of lepidopteran pupae that occur in agricultural and forestry crops. We have been working with these biological control agents for over 20 years. Over the past 5 years, the Biological Insect Control research group at the Federal University of Grande Dourados, in partnership with Reflore in Mato Grosso do Sul, the Association of Producers and Consumers of Planted Forests, the Ministry of Agriculture, Livestock and Supply and Startup Systemic Kovê, a biological control company founded by students and incubated at the Federal University Grande Dourados, with support from the National Council for Scientific and Technological Development, Foundation for Supporting the Development of Teaching, Science and Technology of the State of Mato Grosso do Sul and the Coordination for the Improvement of Higher Education Personnel, through research actions, generated results for the specifications of references to be published.

This implied new bioinputs, Palmistichus elaeisis, Trichospilus diatraeae, Tetrastichus howardi, to control defoliating Lepidoptera in eucalyptus. In parallel, we discovered that, naturally, the microwasp Trichogramma pretiosum parasite eggs of Iridopsis panopla. Since then, we have been working to validate the efficiency of this natural enemy so that it can be used as a new bioinput in the biological control of this caterpillar.

It is important to point out that monthly meetings between associates and technicians from companies in the forestry sector have been held to update the monitored, infested and controlled areas, including with other producers in the region, in order to adopt uniform and joint actions based on the principles of integrated forest management. pests and good agronomic practices. Companies associated with Reflore in Mato Grosso do Sul invest in a robust team of monitors for the early identification of pests and diseases in their forest base. Efforts to contain the advance of defoliating lepidopterans range from the release of parasitoid insects and predators with production on the farm to the use of microbiological agents, such as fungi and entomopathogenic bacteria.

But, in addition to the costs with controls, there are production losses caused by defoliation, which range from 10 to 40% reduction in the volume of eucalyptus wood at the cutting age (between 6 and 7 years). Professor Carlos Frederico Wilcken from Universidade Estadual Paulista, a professional with knowledge in the area, emphasizes that this variation depends on the intensity of defoliation (partial to total), number of defoliations and genetic material (clones or species) of eucalyptus planted. Due to the outbreak in 2021, it is estimated that the eucalyptus sector in Mato Grosso do Sul failed to harvest 35,225,475 cubic meters of wood. And that represented a loss of 1,761,273,78.00 reais.

In this context, government agencies, foresters, technicians and researchers in the forest sector reached a consensus that there is a need to develop a state forest health program, and call attention to several guidelines, among which the following can be highlighted: the establishment of an information network for the unification of decision-making in the control of pests, diseases and plants, especially defoliating coleopterans, soil termites, leaf-cutting ants, crickets, lepidopterans (defoliating caterpillars), tan bug, shell psyllid and gall wasps, which are among the groups of insects that can be harmful to forest plantations, especially eucalyptus in Mato Grosso do Sul; the creation of a phytosanitary alert system for the “defoliator caterpillars” (Iridopsis panopla and Thyrinteina arnobia) in Mato Grosso do Sul, as an auxiliary tool for foresters, for monitoring and disclosing favorable conditions for the incidence of eucalyptus defoliator caterpillars, aiming at decision-making on the implementation of management procedures, mitigating local damage and losses and promoting, regionally, keeping the pest population level under control; the establishment of management criteria for caterpillar populations in eucalyptus areas 250 meters from water sources; the determination and selection of clone species more resistant to Iridopsis panopla ; control of small outbreaks (up to 100 hectares) to prevent the spread of pests to larger and neighboring areas; the importance of correlating occurrence, damage, control measures and costs throughout the entire crop cycle, considering plots and the total area of the farm, as well as its net income; priority given to research and registration of biological and synthetic products selective for natural enemies to control pests, diseases and nesting plants; support for setting up biofactories for the local production of biological pest control agents; and, finally, the promotion of public-private partnerships (municipal governments, teaching and research institutions, associations of producers and companies in the sector), aimed at generating and disseminating information and alternatives for the monitoring and sustainable management of eucalyptus defoliator caterpillars.