Study validates fall armyworm control strategies in integrated systems

Date:08-08-2024

Research by Embrapa Milho e Sorgo (MG) indicates management practices for the fall armyworm (Spodoptera frugiperda) adapted to Integrated Crop-Livestock-Forestry (ICLF) systems. 

These guidelines are based on the new scenario for corn farming, which involves intercropping with Brachiaria. The techniques are recommended for the formation of pasture and straw in the no- till system, and the prerogatives of these models, which combine productivity and sustainability, are integrated. 

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

″Managing fall armyworm in the field is complex and must consider the 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,″ commented researcher Ivênio Oliveira.

The research alerts producers 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 goal is to help them understand the behavior of  S. frugiperda  and offer options for managing it within integrated production systems. ″Understanding the monitoring steps and observing the decision-making moments for control or not is the basis for Integrated Pest Management (IPM),″ Oliveira said.

It was found that there is interference from Brachiaria in the system, favoring the increase in the caterpillar population. However, 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,″ the researcher added.

MIP most suitable control option in integrated systems

In the Embrapa Milho e Sorgo study, IPM was adopted as a sustainable alternative for controlling the 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,″ Oliveira noted.

In this study, insecticide applications to control fall armyworm were conducted based on decision-making indices: economic damage level (EDL) and control level (CL). The study indicates that monitoring the pest population is essential to ensure that applications are only conducted when the CL is reached before the ELD. The control cost cannot be greater than the loss caused by the pest attack. 

Generally, chemical control using insecticides for management is recommended when an NC of around 20% of scraped or perforated plants is reached. ″This value is detected from sampling done with pheromone traps or, visually, from scales of damage caused by caterpillars,″ the researcher described.

The experiments were conducted 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 in which this work was carried out, the parameters for decision-making on the 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 were shown to be influenced by the presence of Brachiaria,″ Oliveira highlighted.

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. Thus, the decision-making for control is based on the average capture of three adult S. frugiperda moths per trap or 20% of attacked plants with damage scores greater than 3.

″The IPM strategy proved more appropriate than the scheduled use of chemical insecticides. For the Bt bioinsecticide, spraying should be conducted as soon as the damage of up to grade 2 occurs through visual sampling, which means the presence of caterpillars smaller than 1 centimeter. From the point at which the Brachiaria plants develop and have cartridges, they become a component of the production area and should also be considered in the sampling units because there is a possibility of caterpillars migrating from Brachiaria to corn and vice versa,″ the researcher explained. 

The experiments showed a possible increase in caterpillars per unit area and more significant pest pressure on corn plants, including damage grade 1, typical of smaller caterpillars. 

Decision-making for control becomes more assertive with continuous sampling and using pheromone-based traps due to the difficulty of visual sampling in Brachiaria plants. ″The use of the IPM strategy for caterpillar control in integrated systems reduces the need for chemical insecticide applications from four to three per corn crop,″ Oliveira said in conclusion.

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