Correct management of lepidoptera

Pests like Helicoverpa, Heliothis, Chrysodeixis, Anticarsia, Elasmopalpus, Spodoptera, Alabama, Mocis, Pectinophora, Elaphria, Striacosta and Agrotis are among those that require serious care in agricultural systems. Managing these insects correctly involves understanding their dynamics, adopting a systemic view of the entire production process and rescuing established practices that have been abandoned over the years.

Agricultural production systems are increasingly in evidence, demonstrating that specific attitudes are not capable of efficiently affecting the final result and guaranteeing the desired profitability in agriculture. In the management of agricultural pests, thinking about the agricultural production system is no different and among pests, lepidoptera (butterflies and moths), characterized by the presence of scales (“lepido”) that cover the body and wings (“ptero”) of insects, deserve special attention due to the number of pests in this group.

In their life cycle, the young phase (when they are called caterpillars and taturanas) are major leaf devourers and constitute important agricultural pests, and can also attack grains and flour. As a curiosity, it is worth remembering that butterflies, due to the beauty of their wings, are highly appreciated by artists and collectors.

Insects have been on Earth for more than 350 million years. They went through all types of environmental hardships, including an asteroid collision that probably killed all the dinosaurs and created the Ice Age. In this context, it would be very naive that human interference would be able to eliminate these pests in crops. It remains, then, to learn to live with or apply the concepts of Integrated Pest Management (IPM).

The topic of interest for Lepidoptera in agricultural production systems includes pests such as Helicoverpa, Heliothis, Chrysodeixis, Anticarsia, Elasmopalpus, Spodoptera, Alabama, Mocis, Pectinophora, Elaphria, Striacosta, Agrotis and others more.

It is necessary to understand the agricultural production system as one made up of several crops, where there are several common management practices associated with a plant species such as soybeans, corn or cotton, for example. All this in a region where there is an interconnection between these agricultural crops or crops. This is why gates do not solve the problems of pests such as Lepidoptera, which fly hundreds of kilometers.

The interconnection between agricultural crops in a region or even a continent guarantees the flow of Lepidoptera from one region to another, from one crop to another and from one crop to another. The procedures adopted by a farmer directly reflect the dynamics of these pest populations, therefore strategies must be joint and coordinated to produce more positive results, which reinforces the systemic perspective of the agricultural process.

Damage caused by lepidoptera

Before making a decision to control Lepidoptera, it is essential to know the damage and its potential on crops, as they are not always the same for each agricultural crop. In a given crop, the damage may be greater or lesser.

The study of damage can be in-depth when it is recognized that in the same crop this may be different depending on the plant's development phase. Normally in the vegetative phase, plants have a greater capacity to overcome injuries caused by caterpillars, except in the emergency phase where the damage can result in the death of the plant.

Lepidoptera can attack vegetative structures such as plant leaves and stems, as well as floral buds, flowers, fruits and dry grains. The type of damage must be characterized individually and this information will establish the rigor of control at each phase of the culture. They will determine the severity, urgency and tendency of the caterpillar attack in order to guide the priority in making management decisions.

The tendency of a pest, when observed that there are no natural elements capable of establishing the balance of lepidoptera, can cause damage to other crops. For example, millet, a crop very widespread among cotton farmers in Mato Grosso for establishing vegetation cover and which is affected by spodoptera. In this culture, care focuses on defoliation and control levels are higher than those adopted when the focus of spodoptera becomes the establishment of the cotton seedling. In this case, control must be carried out in millet, when cotton sowing approaches.

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Among the management strategies there are transgenic plants capable of offering good controls, although the risks of resistance are worrying and there are already demonstrations of failures in the control of this relatively recent technology, as well as the resistance of insects to the action of synthetic insecticides.

An intelligent way to avoid increases in Lepidoptera populations in agricultural production systems is to favor the natural control present in all crops without the need to spend any financial resources, among the natural controls there is the control offered by climatic conditions such as sun, rain and wind. There are also natural biological control agents in any crop such as parasites, fungi, viruses and bacteria, but to benefit from this you need to know your crop in depth. At this point the need for crop monitoring arises.

A good monitor, knowledgeable in all the concepts of Integrated Pest Management (IPM) must have the ability to look in depth at every detail of your crop. In addition to the almost “microscopic” view, a holistic view of the entire region is necessary, including the interconnections between one crop and another, inside and outside the property limits.

To manage Lepidoptera in agricultural production systems, characteristics of the insect biology of this group must be known. It is very common to focus on morphological aspects for identification, but details related to environmental habits and preferences can be more useful for management, since the agroecosystem is significantly altered by man.

Man has a certain dominance over the agricultural environment and the agroecosystem. Of course, it is not possible to interfere with the climatic elements, but in all other aspects there is the possibility of human action. From the choice of plant species to be cultivated, proportion of crops, distribution in areas, spacing, population, sowing time and cultural treatments affect lepidoptera populations, in addition to chemical interventions as pest control measures.

This series of combinations directly reflects the results on your own and your neighbors' farms. The main objective of lepidopteran management is to maintain populations of these insects below damage rates, since the presence of the insect is essential for the balance of the system.

As the biblical character Noah preserved a couple of each species in the face of the flood, modern farmers must, before learning how to control pests, know how to keep them at non-harmful levels in the field. This is the basis of increasingly widespread biological control, but preaching the use of exotic products applied like any chemical pesticide.

If crop conditions are not favorable to the establishment of a biological insecticide, applications will be in vain. Another cost with low benefit. Biological control is a powerful tool in combating pests, but not when used inappropriately.

When all non-chemical lepidopteran controls have been exhausted, chemical control may be the solution, subject to all necessary precautions. Chemical interventions require knowledge in several areas, ranging from the chemical attributes of these compounds to the metabolic processes that affect insects and their forms of degradation in the plant and in the environment. It is also essential to pay attention to the application technology and the appropriate weather conditions for the use of this resource in order to benefit from the effectiveness and efficiency of these compounds.

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Miraculous ways of managing lepidopterans will not appear, either in the medium or long term. The solutions are very obvious and there is no secret for anyone. Anyone can adopt them without side effects, but this requires awareness that concrete measures can be taken individually and others need to be collective.

Given the evolution and dimensions of Brazilian agricultural areas, the presence of professionals capable of developing rational lepidopteran management strategies is essential. The mere fact that a professional is able to recommend an insecticide does not qualify him or her for IPM. It is important to reflect on the direction in which agriculture is headed.

The big problem at the moment is the abandonment of established good agricultural practices. Restoring these measures will have a direct impact not only on the occurrence of lepidoptera but on all issues linked to plant health and nutrition. A systemic view of the agricultural production process is fundamental for understanding and applying IPM.

Evaldo Kazushi Takizawa, Ceres Consultoria 

Article published in issue 213 of Cultivar Grandes Culturas.