Study validates fall armyworm control strategies in integrated systems

Research by Embrapa Milho e Sorgo (MG) highlights corn fall armyworm management practices (Spodoptera frugiperda) adapted to Crop-Livestock-Forest Integration (ILPF) systems. These are guidelines constructed based on the new scenario of agricultural exploitation of corn, which involves intercropping with brachiaria. The techniques are recommended for the formation of pasture and straw in the direct planting system and integrate the prerogatives of these models, which combine productivity and sustainability.

The fall armyworm is one of the most worrying pests in integrated production systems, and its management must take into account effective control practices, since the insect feeds on several plant species. Another problem is that the S. frugiperda presents rapid adaptation to the main current management strategies, which are the use of Bt plants (which contain genes from the bacterium Bacillus thuringiensis) and chemical control.

“The management of fall armyworm in the field is complex and must take into account the entire production system involved. Therefore, it is necessary to better understand its occurrence and permanence in systems such as ILPF and Crop-Livestock Integration (ILP), which are increasingly adopted in different regions of Brazil”, comments researcher Ivênio Oliveira.

The research alerts producers to the fact that they need to be more careful when planting brachiaria with corn, since this grass is one of the main hosts of the fall armyworm. The objective is to help them understand the behavior of the S. frugiperda and offer options to manage it within integrated production systems. “Understanding the monitoring stages and observing the decision-making moments for control, or not, is the basis for Integrated Pest Management (IPM)”, points out Oliveira.

It was found that there is interference from brachiaria in the system, favoring the increase in the caterpillar population, but that there are also adaptations in management strategies that can minimize this problem. “The key is to understand the positioning of these strategies and the levels of decision-making”, adds the researcher.

MIP is the most appropriate control option in integrated systems

In the study conducted at Embrapa Milho e Sorgo, IPM was adopted as a sustainable alternative for controlling corn fall armyworm.

“Control strategies were tested, involving different products, in compliance with the validation of decision-making indices for controlling this pest. The difference is that there was still no recommendation for control in integrated cultivation systems, and this study draws attention to this”, observes Oliveira.

In the work, insecticide applications to control fall armyworm were conducted observing the decision-making indices: level of economic damage (NDE) and level of control (NC). The research points out that population monitoring of the pest is essential so that applications are only carried out when the NC is reached, which is before the NDE. The value of the control cost cannot be greater than the damage caused by the pest attack.

In general, chemical control with the use of insecticides for management is recommended when a NC of around 20% of scraped or punctured plants is reached. “This value is detected from samples taken with pheromone traps or, visually, from scales of damage caused by caterpillars”, describes the researcher.

The experiments were carried out in environments adapted to reproduce the conditions of commercial crops, with the adoption of large plots to better express the effect of different conditions and treatments.

“It was evident that, under the conditions under which this work was carried out, the parameters for decision-making on control of S. frugiperda in corn cultivation in ILP and ILPF systems have different characteristics from monoculture, as the injuries caused to the aerial parts of corn plants have been shown to be influenced by the presence of brachiaria”, highlights Oliveira.

According to him, in the initial cultivation period, up to approximately the V5 vegetative stage, in which only corn plants are present in the planting area, the same conventional sampling parameters with traps or visual scales can be used. Therefore, decision-making for control is based on the average capture of three moths. S. frugiperda adults per trap or 20% of attacked plants with damage scores greater than 3.

“The IPM strategy proved to be more appropriate than the scheduled use of chemical insecticides. For the Bt bioinsecticide, spraying must be carried out after the occurrence of damage grade up to 2, through visual sampling, which means the presence of caterpillars smaller than 1 centimeter. From the point at which brachiaria plants develop and have cartridges, they become a component of the production area and must also be considered in the sampling units, because there is the possibility of migration of brachiaria caterpillars to corn and vice versa. -versa”, explains the researcher.

The experiments showed a possible increase in caterpillars per unit area and greater pest pressure on corn plants, including the occurrence of damage score 1, typical of smaller caterpillars.

Decision-making for control becomes more assertive with continuous sampling and the use of pheromone-based traps, due to the difficulty of visual sampling in brachiaria plants. “The use of the IPM strategy to control the caterpillar in integrated systems reduces the need for chemical insecticide applications from four to three, per corn agricultural harvest”, concludes Oliveira.