**2. Integrated Pest Management (IPM)**

The failure to reduce the population of a phytophagous species recognized as a key pest in a given situation usually occurs by not using the principles of integrated pest management (IPM). By its name, it is already implied that the solution of phytosanitary issues should not be thought of in a single tactic, even though apparently it may be "very practical" and convenient for the farmer. Because of lack of implementation of IPM, it is easy to understand statements and questions, such as the following: there are cases of pest resistance to insecti‐ cides; it is necessary to increase the dose of products; there are chemical residues in the soil, water, and harvested products; there are pesticides effects on flora and fauna; cost of control is prohibitive.

Brazil is already becoming a major agrochemical consumer in the world. Information of this nature in the media needs to be changed. What is expected is to reach the point of having an IPM program where there is satisfaction of both the farmer and the consumer, including the protection of the environment as a whole [5].

#### **2.1. Fall armyworm (***Spodoptera frugiperda***) and** *Helicoverpa armigera*

knowledge, the IPM aims at integrating various management tactics instead of relying on the control by the exclusive use of insecticides [3]. Its concept essentially consists of a decisionmaking process involving the coordinated use of multiple tactics to optimize the control of all classes of pests in a sustainable and economically compatible way [4]. This philosophy of management has spread worldwide and arrived in Brazil, being rapidly incorporated into the

Brazilian agriculture has evolved in recent years, with significant yield gains in many eco‐ nomically important crops, including maize. Besides the use of agricultural inputs with quality and cutting-edge technologies, the climate in general has contributed to the increase in production. Despite these favorable factors, phytophagous insects also continue to be a cause for concern in agribusiness because of its great ability to adapt to changes seen in production systems. The solution adopted to reduce the losses arising from the injury caused by pests has been, in most cases, the application of chemical insecticides. It is relatively easy to understand the reasons that have led the farmer to choose chemical control as a control tactic of "recog‐

The general understanding is that chemical insecticides have indisputable advantages: low cost, acts quickly, little demand in knowledge, and can be used to control various pest species. Other causes for probably using chemical control almost in a predominant way is the lack of knowledge about other control tactics or even the lack of conviction about the effectiveness of

The efficiency of chemical control is often not the expected by the simple fact that it depends on several technical factors, which most often are not considered when applying the product. Sprayer type, application type, nozzles for spraying, droplet size needed for good plant cover, solution volume, application speed, climatic factors (such as wind speed, rainfall, temperature, and humidity), phenological stage of the plant and of the pest target, attack site and economic level damage of the pest, and even the applicator qualification are some factors that can compromise the action of the applied product. Therefore, when these factors are not consid‐

As soon as frustrations to control a certain pest begin to occur, the farmer must analyze, along with an expert, the causes of failure of the means adopted so far. When this analysis is not done, in general, there is always a risk of a mistaken decision making and probably leading to a situation worse than already detected. For example, making new applications or mixing or changing active ingredients (without considering that perhaps the causes are not related to the product used). Applications in excess also entail higher cost, with no evidence that they would

The failure to reduce the population of a phytophagous species recognized as a key pest in a given situation usually occurs by not using the principles of integrated pest management

control of pests, especially for maize crop.

56 Insecticides Resistance

nized" insects to cause economic losses.

be effective to control the pest satisfactorily.

**2. Integrated Pest Management (IPM)**

these alternative methods such as integrated pest management.

ered, the probability of not achieving the expected results is high.

In maize (*Zea mays* L.), historically, fall armyworm has been the main pest. However, it is interesting to note that even with the advance in science in providing new technologies for their control, the pest is still present in the agroecosystem causing losses to agribusiness, even with use of means for their control. The lack of IPM should again be highlighted. As a main feature, the pest has as hosts several cultivated plant species or native species, available yearround in Brazil. Furthermore, general climatic conditions in the country are not limiting for their development.

As a result of this, the moth can be detected all year round in traps containing pheromone as attractive. That is, there is the real possibility of having the presence of caterpillars in their hosts just after the emergence of the plant and also throughout the plant cycle.

The moth of *S. frugiperda* lays its eggs in clusters, and each cluster contains up to 300 eggs. At hatch, the aggregate larvae begin to feed, in a short period of time, in the plant where the eggs were placed, by ragged feeding the leaf, leaving a characteristic symptom. Subsequently, they migrate into adjacent plants. In the migration process, the caterpillar produces a thread that is adhered to the leaf and is projected into the air by the wind and is easily carried to other plants. Often, in the new plant, the caterpillar goes toward the interior of the leaves still rolled ("whorl") without causing the symptom of "ragged feeding."

This symptom has been used as an indicator to control the pest. However, for the reasons mentioned, it may underestimate the level of infestation. The caterpillar phase lasts around 21 days, influenced mainly by temperature. When the initial infestation coincides with the "whorl" phase, the caterpillar remains housed in this location. When fully developed, by reaching the size between 4 and 5 cm, it leaves the whorl and heads to the ground, where it becomes known as the pupa stage. Eleven days after this stage, the adult emerges, which will restart another cycle. The period of time between laying the eggs and the appearance of a young adult insect varies between 35 and 45 days. Therefore, from the same oviposition, there could be at least three discrete generations during a maize cycle. However, because the flow of moths is constant, it normally occurs in overlapping generations, and therefore caterpillars and postures of different ages can be found in the same plant at the same time. This fact is usually a complicating factor for applying insecticides via spraying. Caterpillars of different ages require different doses of the applied insecticide, either chemical or biological. Therefore, the management of the pest is essential to know not only the pest population density but also the distribution by age-group of insects. It is not an easy task when making the decision on the need for control after sampling only based on symptoms of damage such as the scraping of leaves. A decision on the need to control based on captured moths in pheromone trap, when placed in the area soon after planting, is a more efficient procedure than those based on the injury symptom of the pest.

Because the continuous flow of *S. frugiperda* moths is not uncommon, the presence of postures and caterpillars in more developed maize plants.

However, such insect stages are not easily observed in the plant when there is no more whorl. Often the insect can be found feeding in the tassel or ear, in silks or directly in the grains, causing direct damage to yield, because any method of control via spraying is difficult to apply in these places. In addition to machines handling difficulties in the target area, there is also the difficulty of reaching the pest, protected by the leaves or the ear husks. The presence of larvae of *S. frugiperda* in the ear can be as common as corn earworm itself, the *Helicoverpa zea*. Insect infestations in the ear can cause severe damage to the farmer, as it jeopardizes the expected yield. Therefore, alternative methods should be prioritized to such pests in maize. Obviously, to reduce the population density of fall armyworm in the ear, there must be a proper pest management in the previous stages of insect development.

Morphologically, the new species is very similar to Brazilian corn earworm (*H. zea*) and also presents a very similar life cycle. However, its potential for destruction to the preferred hosts is undeniable. Due to these similarities, the problem that initially occurred in Bahia was ascribed to *H. zea*.

The oviposition is usually performed on the style stigma of maize. At hatch, the larvae consume grains in development. Secondary bacterial infections are common in the ear. The larvae can also feed on the new leaves of the whorl, from the most developed leaves and from the tassel of the plant. Mobility, polyphagia, and high reproductive rate are attributes that differentiate *H. armigera* from *H. zea*. The caterpillars are quite aggressive, occasionally carnivorous, and can be cannibals when the opportunity arises. If disturbed, they drop from the plant and wound up on the ground. Caterpillars turn into pupae within a cocoon silk, some centimeters below the soil surface. Under favorable conditions, the development cycle can be completed in just over a month. Therefore, several generations per season are possible, especially in warmer areas.

In the tropics, reproduction continues throughout the year. *H. armigera*, also called the "old world caterpillar," is usually found in parts of Europe, Asia, Africa, and Australia, while *H. zea*, the caterpillar of the "new world," is common in the Americas. The pest is more abundant in maize during the phase of "silking," when the adult female lays the egg individually on the style stigma. Adults feed on nectar or on other exudates from different plant species. The young larvae tend to feed initially on the style stigma but soon start to feed on the grain in formation. There are six larval stages, and the fully developed larva measures about 40 mm long. Third,

instar caterpillars (8–13 mm long) and so on account for 90% of all food consumed (and thus its damage). Large caterpillars (above 24 mm) are the most harmful ones once they consume approximately 50% of their diet, when they are between the fifth and sixth instars. Therefore, control measures should be directed when the caterpillars are still small (less than 10 mm).

The pupa is dark brown, measuring between 14 mm and 18 mm in length, with a smooth surface, rounded, with two parallel spines on the posterior end. The moth has a wingspan between 30 and 45 mm. Females lay over a thousand eggs in her lifetime. The ease with which the pest acquires resistance to insecticides has been considered a hallmark of the species in areas where the pest usually occurs. At these locations, the development of resistance has been most extensively documented for synthetic pyrethroids, but already there is record of resist‐ ance to other groups of insecticides as carbamates and organophosphates.

The migration movements of the species could explain the resistance propagation. In regions of origin, research has shown that maize is among the preferred hosts of the pest, followed by soybeans and cotton. In Brazil, the simultaneous presence of these three crops in the same region is common, as occurred in western Bahia, the starting point of an outbreak of the pest. However, *H. armigera* can survive in more than 300 taxa of plants.

#### *2.1.1. Control strategies*

a complicating factor for applying insecticides via spraying. Caterpillars of different ages require different doses of the applied insecticide, either chemical or biological. Therefore, the management of the pest is essential to know not only the pest population density but also the distribution by age-group of insects. It is not an easy task when making the decision on the need for control after sampling only based on symptoms of damage such as the scraping of leaves. A decision on the need to control based on captured moths in pheromone trap, when placed in the area soon after planting, is a more efficient procedure than those based on the

Because the continuous flow of *S. frugiperda* moths is not uncommon, the presence of postures

However, such insect stages are not easily observed in the plant when there is no more whorl. Often the insect can be found feeding in the tassel or ear, in silks or directly in the grains, causing direct damage to yield, because any method of control via spraying is difficult to apply in these places. In addition to machines handling difficulties in the target area, there is also the difficulty of reaching the pest, protected by the leaves or the ear husks. The presence of larvae of *S. frugiperda* in the ear can be as common as corn earworm itself, the *Helicoverpa zea*. Insect infestations in the ear can cause severe damage to the farmer, as it jeopardizes the expected yield. Therefore, alternative methods should be prioritized to such pests in maize. Obviously, to reduce the population density of fall armyworm in the ear, there must be a proper pest

Morphologically, the new species is very similar to Brazilian corn earworm (*H. zea*) and also presents a very similar life cycle. However, its potential for destruction to the preferred hosts is undeniable. Due to these similarities, the problem that initially occurred in Bahia was

The oviposition is usually performed on the style stigma of maize. At hatch, the larvae consume grains in development. Secondary bacterial infections are common in the ear. The larvae can also feed on the new leaves of the whorl, from the most developed leaves and from the tassel of the plant. Mobility, polyphagia, and high reproductive rate are attributes that differentiate *H. armigera* from *H. zea*. The caterpillars are quite aggressive, occasionally carnivorous, and can be cannibals when the opportunity arises. If disturbed, they drop from the plant and wound up on the ground. Caterpillars turn into pupae within a cocoon silk, some centimeters below the soil surface. Under favorable conditions, the development cycle can be completed in just over a month. Therefore, several generations per season are possible, especially in

In the tropics, reproduction continues throughout the year. *H. armigera*, also called the "old world caterpillar," is usually found in parts of Europe, Asia, Africa, and Australia, while *H. zea*, the caterpillar of the "new world," is common in the Americas. The pest is more abundant in maize during the phase of "silking," when the adult female lays the egg individually on the style stigma. Adults feed on nectar or on other exudates from different plant species. The young larvae tend to feed initially on the style stigma but soon start to feed on the grain in formation. There are six larval stages, and the fully developed larva measures about 40 mm long. Third,

injury symptom of the pest.

58 Insecticides Resistance

ascribed to *H. zea*.

warmer areas.

and caterpillars in more developed maize plants.

management in the previous stages of insect development.

The occurrence of insects in the ear, in general, makes the management more complex. Besides the difficulty of monitoring, there is also the difficulty of reaching the pest, protected by the leaves or the ear husks. Therefore, alternative methods should be prioritized for such pests. In the specific case of the fall armyworm, one should make a proper management also during the vegetative stage of corn.

#### *2.1.2. Biological control*

The production system for maize is the pest combat, including species that attacks the ear. A first reason is the less frequent use of chemical insecticides. This fact can be explained by the use of *Bacillus thuringiensis* Berliner (*Bt*) plants, whose consequence was a significant reduction in foliar sprayers to control fall armyworm during the growing phase of the plant. Addition‐ ally, in the case of pests that attack the ears, because the caterpillars stay housed under the straw, which reduces its exposition to chemical spraying, there is greater difficulty in control‐ ling by other methods.

The egg phase has been considered critical in the life cycle of many species of insects belonging to the order Lepidoptera. For example, to *H. armigera* always occurs a high rate and natural mortality, reaching values above 88%, mainly in the first 3 days of oviposition. Such index can reach 95%, considering the mortality of eggs and the first larval stages. Significant indexes have also been verified for *H. zea*.

Species of *Trichogramma* mainly (Hymenoptera: Trichogrammatidae) and, in a lower degree, *Telenomus* (Hymenoptera: Scelionidae) are common egg parasitoids. Among larvae parasi‐ toids, the most common include *Cotesia* spp. and *Microplitis croceipes* (Cresson) (Hymenoptera: Braconidae); *Campoletis* spp. (Hymenoptera: Ichneumonidae); and *Eucelatoria* spp. and *Archytas marmoratus* (Townsend) (Diptera: Tachinidae).

Considering the commercial existence and experience in releasing *Trichogramma* in Brazil and in other countries, this biological control agent is recommended for both conventional and *Bt* maize planting. The inundative release of parasitoid should be associated with the monitoring of moths in the target area.

This monitoring is carried out with traps containing synthetic sexual pheromone, specific to each type of target pest. The release of the parasitoid can be made by the distribution of card plants containing parasitized eggs near the emergence of the adult parasitoid or the direct adult release. As the parasitoid has an objective to target the pest, it can also be used in soybeans, cotton, and other crops where pests cause economic damage, regardless of the size of the cultivated area.

Obviously, one should consider that chemical insecticides required for other targets must not be applied at the same time of the release of the biological control agent.

Reduced use of chemical insecticides, through the use of applied biological control, leads to the gradual return of other biological control agents. In maize, over 100 insect species have already been described as predators of phytophagous species that feeds on both eggs to larvae. Some species prey in both the immature stage, as in the adult stage. Among the most common predators are lady beetle *Hippodamia convergens* Guerin-Meneville and *Coleomegilla maculata* DeGeer (Coleoptera: Coccinellidae), lacewings such as *Chrysoperla* spp. (Neuroptera: Chryso‐ pidae), minute pirate bugs such as *Orius* spp. (Hemiptera: Anthocoridae) and *Geocoris* spp. (Hemiptera: Lygaeidae), and earwigs such as *Doru luteipes* (Dermaptera: Forficulidae) and *Euborelia* spp. (Dermaptera: Carcinophoridae).
