*2.1.4. Chemical control*

Braconidae); *Campoletis* spp. (Hymenoptera: Ichneumonidae); and *Eucelatoria* spp. and

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

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

Obviously, one should consider that chemical insecticides required for other targets must not

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

Viruses, bacteria, and fungi have also been used against pests of maize. Especially for *H. armigera* control, in the literature, although they mention the use of baculovirus, they highlight the increase use of *Bt.* The control efficiency with microorganism depends largely on the period

In Brazil, there is a great experience in using baculovirus to control fall armyworm. In other countries, a commercial product based in nuclear polyhedrosis virus (NPV) already exists, such as, for example, in the USA, to control *H. zea* and *H. armigera*. To achieve success in the control ear pests with virus, the product must be applied in order to hit the target, both for the attack location as compared to the caterpillar development stage, which cannot be greater than

Similarly to the virus, maize ear pests can be controlled by the *Bt*-based products. However, the efficiency of the products depends essentially on adjustment of the solution volume (liters of spray solution/ unit area) that can be evaluated by the use of sensitive papers which should

and the application technique because caterpillars cannot be protected within the ear.

be applied at the same time of the release of the biological control agent.

*Euborelia* spp. (Dermaptera: Carcinophoridae).

obtain a minimum number of 30 drops cm-2.

*Archytas marmoratus* (Townsend) (Diptera: Tachinidae).

of moths in the target area.

60 Insecticides Resistance

of the cultivated area.

*2.1.3. Microbial control*

10 mm in length.

The same cares from microorganism applications are valid for the use of chemical insecticides. In addition to the restrictions, the possibility of a negative action of product on populations of natural enemies is considered. This fact is critical when it comes to reaching a target pest that is generally protected against the action of the applied products.

On the other hand, the exposure period of the pest to the action of the chemical is very small, and therefore, the application of pesticides must follow a strict pest monitoring system and thus avoid adverse effects on nontarget insects.

Eggs and larvae are often not sampled in corn because eggs are difficult to detect among the silks and caterpillars are generally being within the ear, making it a costly and low-precision process.

The moths, however, can be monitored by light traps and pheromone traps. Both genders are caught in light traps and only males are attracted by the pheromone. Both types of traps give an estimate of when the moths invade or emerge in a given area. However, pheromone traps are easier to use because they are selective. The pheromone is usually used in conjunction with a suitable trap, the inverted cone type, or the Delta type. Moreover, the presence of three to five moths per night is sufficient to indicate that pest control measures must be taken.

Therefore, improvements in cultural practices to maintain and enhance the impact of natural enemies represent an excellent strategy to improve the perspective for the natural biological control. Growing plants around the main crop and that attract natural enemies, such as sunflower, should be encouraged. The "trap crop" is often suggested for several species of pest, including the ear pest complex. It should, however, consider the high degree of preference of moths to lay eggs on maize in early stage of development of silks. Planting small plots of maize before the main crop can be interesting because the farmer can thus eliminate the initial infestation of the pest before their population grows enough to cause damage to the main crop.

In areas where pest populations initially develop into weeds and then disperse for major crops, the elimination of these plants by mowing or using herbicides or even applying insecticides can significantly reduce damage to neighboring crops.

#### **2.2. Sugarcane borer (***Diatraea saccharalis***)**

Indirect losses caused by this pest are more important economically because of the galleries built inside the stalk, thus the plants become more susceptible to tipping, tassel infertility, and reduced productivity and still favor the entry of opportunistic pathogens. According to EMBRAPA [6], by attacking the interior of the stalk of the plant, the larvae cause damage that can result in losses between 10% and 50% on yield. The highest losses are results from attacks in the internodes that are closer to the ear because it results in interference in the movement of nutrients produced by the plant, which are carried to a higher production of leaves instead of grain production.

The adult, with nocturnal habits, has the aspect of moth, with the forewings of a straw-yellow color, some brownish drawings, and whitish hind wings and a 25-mm wingspan. The caterpillars measure approximately 22–25 mm long, with brown head and whitish/yellowish body with numerous dark spots.

Regarding the cycle, oviposition is made in maize leaf after mating, generally on the dorsal side. The number of eggs in each oviposition is from 5 to 50, with an imbricated posture, resembling snake leather or fish scale. Immediately after hatching, and upon reaching the second instar, they enter the stem. Its attack can be identified by the inlet and outlet holes, as well as the longitudinal opening of the maize stalk, where the presence of the caterpillar or the passageway left by it is observed.

In high infestations, the attack of this insect can cause losses up to 21% in production. It can attack 65 plant species such as sugarcane, maize, millet, sweet sorghum, wheat, grain sorghum, and rice, besides many other grasses (Poaceae) and spontaneous weeds such as *Sorghum halepense*, *Paspalum* sp., *Panicum* spp., and *Holcu* ssp. Moreover, *Andropogon* ssp. The larvae damage maize in various ways: in small plants, by attacking the whorl, causing holes in the leaf blade to the death of the meristem. In more developed plants, they open galleries, feeding on the stem. These galleries are usually longitudinal but may present circular aspect, making the plant very susceptible to falling. Damages can also occur in the ear, allowing the cross infestation with weevils *Sitophilus* spp.

#### *2.2.1. Methods of control*

## *2.2.1.1. Chemical control*

Depending on the behavior of this pest, chemical control usually does not present satisfactory result, unless the attack begins very early. In this case, seed treatment with systemic insecticides or pyrethroid sprays directed toward the base of the plant gives good results.

#### *2.2.1.2. Biological control:*

In the past 60 years, the biological control of this pest in sugarcane crop has been successful with the caterpillar parasitoid *Cotesia flavipes* and, more recently, with the egg parasitoid *Trichogramma galloi* and may be extended to the control methodology for the maize crop.

#### *2.2.1.3. Mechanical control*

Elimination of crop residues and host plants, especially grasses (Poaceae), help reduce the infestation for the next crop season.

#### **2.3. Black cutworm (***Agrotis ipsilon***)**

Black cutworm, from the genus *Agrotis*, constitute an important group of insect pests, mainly due to damages to the large number of cultivated plants and their wide geographic distribu‐ tion. *Agrotis ipsilon* is the main species of black cutworm referred to in Brazil and is a poly‐ phagous insect, which attacks mainly horticultural crops [7]. It can also attack other species of different plant families, in crops such as maize, soybeans, beans, and cotton [8].

The adults of this pest are moths with a 35-mm wingspan, whose anterior wings are brown with some black spots, and posterior are hyaline white, with a gray lateral edge [9]. Eggs are deposited on the shoot of the plant, stalks, stems, or on the ground near host plants; they are whitish and may be found individually or in groups. Each female can lay over a thousand eggs in a lifetime [8].

After the first instar, the caterpillars are directed to the ground, where they remain protected during the day. They measure up to 5 cm in length, are robust, smooth, and in a variable coloration, with a predominance of dark gray and brown with black spots. They have nocturnal habits and are housed in the soil under debris during the day [11].

Regarding the cycle, after 4 days of the oviposture on the leaves, the caterpillars emerge. After approximately 30 days, they become pupae and remain in the soil for a period of 10 to 20 days until they become adults. The process varies 34–64 days (egg: 4; caterpillar: 20–40; pupae: 10– 20). A female can lay up to 1,260 eggs, with a preoviposition period of 3 days [8].

The caterpillars attack at night, and to find them during the day, you need to revolve the soil at the base of the host plant. The main damage occurs on the establishment period of the crop when the caterpillars cut the young plants—seedlings of up to 20 cm—tumbling them and may cause high reduction of the stand. However, attacks in older plants can occur, which in this case will demonstrate the presence of cut leaves or galleries open at the stem base (they can cause the symptom of "dead heart") or more shallow roots.

When the death of plant is not observed, the attack causes tillering. It is not common to see small caterpillars exerting plant cutting activity; they often destroy the leaf blade and the petiole [8, 9].
