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Agricultural pests: a quick guide to identify and control

Agricultural pests: know what they are, their impact on your crop, the best management tactics, and more!

Agricultural pests are organisms that feed on agricultural crops, reducing their quality and productivity. In Brazil, the extensive geographical area facilitates the development of many species of these organisms.

Do you know how to identify the main agricultural pests and control them in farming? Being aware of this information helps you in your decision-making in the field.

In this article, see which are the main most dangerous pests and all possible forms of management. Enjoy your reading!

What are agricultural pests?

There are many insects that damage plants. However, to be considered a pest, these insects must cause great damage to the planted area.

Agricultural pests are capable of reducing the productivity and/or quality of agricultural crops by feeding on them. They can also be transmitters of disease.

Living organisms are present in all cropping systems. When these systems have biological diversity, the organisms are kept in a certain balance.

In large areas with the same crop, the diversity of organisms present in this environment is reduced. Because of this, some organisms lose their predators or natural enemies, thus increasing their population.

As the population increases, the organisms take on the role of pests and cause damage to agricultural crops.

When is an insect considered an agricultural pest?

An insect can be considered an agricultural pest when it reaches a level of economic damage to the crop.

Generally speaking, an organism becomes a pest due to a lack of biodiversity in large areas with a single crop.

In most agricultural regions, one crop is grown in summer and another in winter in the same agricultural year. The plant remains of the main crops, such as soybeans, do not have time to be broken down by the soil organisms.

This is how the pests stay in the growing area. When host crops are introduced, in the absence of natural enemies, these organisms increase their population. From there, they cause damage to the crop.

Temperature and humidity can also make an organism become a pest. This is the case of mites and aphids, which are very much favored by dry periods.

Very humid and hot periods can favor the reproduction of insects, accelerating their life cycle. In addition, they can be favorable to certain plant diseases.

Main agricultural pests and how to fight them

The impact of agricultural pests depends on the host crop. Nevertheless, many of them cause damage to a range of crop species. Here are some of the main pests insects and how to control them:

  • Caterpillar
  • Brown bug
  • Helicoverpa armigera
  • Cory’s bug
  • Whitefly
  • Aphids
  • Gypsy Moth
  • Spotted Mite

Below you can see in detail each of them, the damage they cause, and the most recommended forms of control.

Caterpillar (Spodoptera frugiperda)

If you work with corn, you know very well the corn borer caterpillar, considered one of the most relevant in this crop. This caterpillar has other crops as hosts, including:

  • soybean;
  • cotton
  • rice
  • sorghum;
  • wheat;
  • oats;
  • sugar cane;
  • beans;
  • barley
  • rye.

Damage

Caterpillar can greatly reduce crop production. This pest can attack any part of the plant, but the most affected part is usually the central part of the corn.

The caterpillar larvae attack plants at any stage of development. In addition, the excretions that the adult caterpillar leaves on the plant open doors for the presence of pathogens.

Plants with between 8 and 10 leaves can have their bases cut off by the caterpillar. The consequence of this is the tillering of the crop, and in more severe cases, the death of the plants.

S. frugiperda has a “Y” mark on its head

Cartridge caterpillar control

For the management of the caterpillar, IPM (Integrated Pest Management) is strongly recommended. It works by using several control methods together.

The main control methods are:

  • Crop rotation: one should thoroughly analyze which crops reduce the survival of the pest. After all, the caterpillar is able to feed on many of the crops normally used in the rotation;
  • Use of resistant or more tolerant varieties to the insect (always adopting a refuge area);
  • Biological control and insecticides: It is important to emphasize that Bt-based insecticides in cultivars (such as corn, which has Bt technology) should not be used to control the caterpillar.

However, the use of insecticides must be done with a rotation of action mechanisms. This will prevent the emergence of resistant populations.

Brown Stink Bug (Euschistus heros)

The brown bug is one of the main pests of soybeans, being present in several regions of the country.

There are phenotypes of this pest resistant to products that contain organophosphates or cyclodienes (endosulfan) as active ingredients.

Cases of resistance are located in areas with a history of continuous applications of these products. Brown bug host crops include cotton, pastures, and soybeans.

Damage

The presence of brown bugs causes shriveled beans. This is because these pests attack the soy pods. Brown Bugs can also be vectors for diseases caused by fungi.

Ways to control the Brown bug

In applications for the control of caterpillars, use products that have a different mode of action from insecticides used in bed bug control. For the control of both, the same active ingredients can be used.

Therefore, it is important not to use the same active ingredients. This way, you avoid problems with pest resistance to insecticides.

Make applications only in areas that present population density that corresponds to the level of action. To do this, monitor the infestation.

Monitoring with damage maps can be done digitally and directly in the area by farm employees. In addition, it is important to analyze which plants can be used in crop rotation. After all, they cannot be hosts for the bed bug.

Cotton Bollworm

Helicoverpa armigera is a pest that feeds on various crops. Beans, soybeans, corn, cotton, coffee, and citrus are some examples.

Damage

The presence of the caterpillar significantly reduces yields and can wipe out the crop from the earliest stages.

It feeds on all parts of the plant. This can cause the structures of your crop to rot and fall off.

Ways to control

Some cases of resistance of the pest to pyrethroid insecticides have been found. For this reason, the most indicated management for the caterpillar are:

  • Use of Bt resistant plants (always using refuge area);
  • Crop rotation;
  • Sanitary vacuum;
  • Management of the pest’s natural enemies;
  • Integrated Pest Management.

Chemical control should also be used. However, don’t forget to rotate the action mechanisms. Avoid using phosphorus and pyrethroid insecticides at the beginning of the crop, as they are considered toxic to natural enemies.

New World Scarab Beetles

Bettles are larvae that are considered important soil pests. Both in the larval and adult stages, they can cause damage to crops.

In the US, Phyllophaga, Dilobodereus and Liogenys are the most common types.

  • Phyllophaga causes damage mainly in the culture of safrinha corn and soybeans in the Midwest region of the country.
  • Diloboderus is more common in the South of the country, causing damage mainly in winter cereals.
  • Liogenys occur mainly in the Midwest regions, causing damage to soybeans and corn.
Male of Dilobodereus abdereus figures A and B, and female in figure C. In the last image, it is possible to observe the larval stage of the cereal and soybean hornworm D. abdereus

Crop damage

Bettles feed on plant roots, causing crop yield reduction damage. This can affect the initial plant stand, and in some cases replanting is necessary.

As adults, the beetles feed mainly on leaves and plant parts at different stages of development.

Ways of controlling bettles

Not disturbing the soil, as is characteristic of the no-till farming system, favors the development and survival of the beetles.

Crop rotation with non-host plants can also help in the control. Some species of crotalaria, for example, are toxic to hornworms and can be used.

Seed treatment with insecticides is a complementary measure. However, it is not effective when the larvae are bigger. The population of hornworms that justifies control is different depending on the species in which it occurs.

The hornworms are not uniformly distributed in the area. Therefore, you can apply chemical control only where they occur.

Some of the insecticides recommended for the control of different species of the hornworm, chemical groups, and active ingredients, and crops where their application is recommended

To mitigate the problem, it is recommended that areas with a history of hornworms be sown first. This way, the plants will have contact with the hornworms at a milder stage and will be able to develop their root system.

Measures that favor the rapid development of the plants are also allies in the control of hornworms. For example, balanced fertilization, inoculation with bacteria, and soil correction, among others.

Whitefly (Aleyrodidae)

The whitefly is an insect that sucks the sap from the plant and causes damage to its development. This reduces the yield and also the quality of the produce.

It’s relatively easy to spot in the field. After all, the insect has a pale yellow body and white wings.

Whitefly on the reverse side of leaves of (figure A), adult stage (B and C), and yellowish translucent (slightly transparent) nymphs (figure D)

The life cycle lasts from 38 to 74 days, and females can lay between 100 and 300 eggs in their lifetime. The main host crops are:

  • Large crops such as beans, soybeans, and cotton;
  • Host weeds that survive in the off-season, making it difficult to break the pest cycle.

Crop damage

The observed damage can be direct when they present discoloration or direct leaf spots on the crop.

This damage can also be indirect when they act as vectors of diseases in crops of agricultural interest. In such cases, insect control is required for disease control. Other damages include:

  • Developmental changes;
  • Silvering of the leaves;
  • Whitening of the stem;
  • Bleaching of the veins in the foliage
  • Early leaf fall and fiber spots on cotton;

Ways to control the whitefly

IPM is also recommended for control. You can use cultural control, with the cultivation of non-host species.

Whitefly monitoring is also necessary and can be done with the use of yellow traps that attract the adults. Insecticides of the tetranortripenoid chemical group are recommended for control in all crops.

The entomopathogenic fungi Beauveria bassiana and Isaria fumosorosea are also recommended for control.

Resistant cultivars are also an efficient control alternative.

In case of observation and inefficient control with insecticides, it is necessary to investigate which race or biotype is occurring in the area. Some races or biotypes of the whitefly are resistant to several products.

Aphids

Aphids can cause damage to a variety of plant species, including major crops such as soybeans and winter cereals.

There are more than 1,500 reported species. The coloration of aphids as adults and nymphs (before adulthood) can vary from yellowish, white, black, red, and green. However, their appearance is similar.

Aphis gossypii aphid

Aphids are favored and cause greater problems in years of dry and hot weather, especially in the southern regions. In these regions, they cause serious problems in the culture of wheat, such as the dissemination of viruses.

They are found mainly on the underside of the leaf and in young tissues.

Crop damage

Aphids can cause damage to various parts of plants, including roots, stems, leaves, and even ears.

Due to their feeding habit of sucking, aphids cause the yellowing of leaves and curling (twisted and folded leaves that serve as a shelter).

Another damage is the spread of viruses. In addition, due to feeding, they release sugary substances that favor the development of the fumaginous fungus.

Ants can be observed when large aphid populations are present.

Ways to control aphids

Several control measures can and should be taken for the efficient control of aphids, among them:

  • Elimination of cultural remains with which aphids are associated;
  • Rotation of non-host crops;
  • Elimination of host weeds in the cultivation area;
  • Nitrogen fertilization;
  • Installation of yellow adhesive traps;
  • Chemical control with recommended products, such as systemic products. Good regulation of the sprayer is also essential because aphids stay on the inner side of the leaves;
  • Biological control: depending on the aphid species, there are different natural enemies that can be used in the control;
  • Genetic control through the use of resistant cultivars. However, it is necessary to correctly identify which aphid species occurs and causes damage in the cultivation area.
  • It is worth pointing out that the recommendation for chemical control is the use of selective products to the natural enemies. Aphids were not considered pests of importance but became so due to the incorrect use of non-selective products.

The leafminer larva (Liriomyza huidobrensis)

The leafminer larva is a species of fly of the genus Liriomyza spp. It is small and has a yellow and black coloration. Its characteristic is that it lays eggs inside the leaves, where they hatch.

Adult female of the leaf miner larva, showing characteristic yellow and black coloration.

With the hatching of the eggs, the larvae form mines. After the larval stage, the pupal stage occurs. This phase occurs on the ground or on the leaves, making its control difficult. The life cycle of this insect is short, approximately 17 days.

Crop damage

Crop damage includes the construction of galleries or mines. This affects photosynthesis by reducing leaf area.

However, leaf necrosis and the feeding of the females themselves by “biting” can facilitate the entry of pathogens into the plants.

Forms of Control

As with numerous pest species, maggot has become a problem due to the excessive use of non-selective products.

For monitoring the fly population in the production area, yellow adhesive traps or plastic panels can be used. According to Agrofit, there are no commercial products for biological control.

Generally speaking, in balanced environments, the populations of the leafminer larvae remain balanced because of the natural enemies.

The main form of control is the chemical one. It has action, especially on the larvae that are inside the epidermis of the leaves. It is essential that the products used are able to penetrate the leaf, reaching its interior.

Among the translaminar, according to Agrofit, are used mainly with abamectin and cyromazine in their composition.

Other strategies can be used for more efficient chemical control, such as

  • the elimination of cultural remains;
  • elimination of alternative host plants (including weeds);
  • crop rotation with non-host plants.

Two-spotted Spider Mite

The spider mite is considered to be one of the most important pest species. It can attack numerous agricultural species.

The spider mite has dark spots on the sides of its body.

Crop damage

The damage is observed on the underside of the leaves. They are caused by the pest feeding on chlorophyll and plant sap. The damage is characterized by the presence of whitish spots on the leaves.

It is possible to observe the presence of webs in a disorderly shape and small granules, also on the lower back of the leaves.

The feeding of the mites causes the yellowing of the leaves. Over time the leaves fall, reducing production.

Forms of Control

The control of mites is carried out mainly through the use of acaricides. It is important to emphasize that only products registered for the crop of interest should be used.

For the cotton crop, for example, there are 89 products registered in Agrofit.

For soybeans, the available options are 39. These products include abamectin, flupyradifurone, vegetable oil, pyridabem, propargite, diafentiurom, fluazinam and bifenthrin + methomyl.

Management of the main agricultural pests

IPM and IMD (Integrated Pest and Disease Management) are used to optimize pest control. They are characterized by different control methods in combination.

The control of pests and diseases in crops starts even before sowing.

The basis of successful control is the monitoring of the areas, with a survey of the incidents and their population. Thus, control will be done at the correct time, before economic damage occurs.

Legislative Controle

Through normative instructions and laws, the introduction of pests into cultivated areas is prevented.

In addition, inspection and monitoring of plant materials is carried out. For example, when plants move between countries, quarantine measures are taken.

This keeps the plant materials under observation for a given period of time in order to identify the presence of any pests that could be introduced into the country.

In addition, due to the favorable climate conditions for the plague in other states, the transportation of contaminated materials is avoided. This is because the pest could easily cause damage to crops.

When contaminated materials are detected, they are destroyed.

Genetic control

It consists of using cultivars that are resistant or tolerant to a particular pest. Genetic control is the cheapest and most effective method of control. It can be applied to large areas of cultivation.

However, it is necessary that other methods are used in combination. This prevents the material from becoming pest resistant (resistance breakdown).

A classic case is the Bt technology, applied to corn to control the caterpillar. The refuge areas in the plantation are essential for resistant caterpillar populations not to be selected.

In addition, it is essential to know which pests occur in the field and which are the most limiting. This ensures that the most suitable cultivars are implemented in the area.

In the case of some fungi and nematodes, it is necessary to know which race is occurring in the area. The genetic resistance of the cultivars, in many cases, is directed at a specific race of the pathogen.

Cultural control

It consists of using different cultural treatments to help reduce the pathogen population in the growing area.

Cultivation practices such as the use of healthy propagation material (whether seedlings or seeds), certified and of good origin, are fundamental.

In addition, the growing season can be changed (respecting the agricultural zoning), and the location. For example, sowing at the beginning of the zoning is an alternative. In this period, the pressure of pests is lower.

It is also possible to punctuate the more humid areas of the plantation, using more adapted cultivars. This, of course, provided they have a cycle close to the cultivar used in the rest of the area.

Balanced nutrition is also fundamental. Very high concentrations of some nutrients, such as nitrogen, make the plants more susceptible to pest attacks. The same happens with potassium deficiency.

Crop rotation is also a very effective method when it is done correctly. However, it is worth remembering that rotation can reduce the pest population, but not control it.

The elimination of host plants means that in the off-season, the pests do not survive.

Physical/mechanical control

This method mainly changes the temperature, humidity, and radiation conditions in the field. You can employ, for example, heat treatment of seedlings and seeds.

The same method is used for vegetable seeds. Using hot water or steam for a certain period of time helps to eliminate fungi associated with the seeds.

Biological control

Biological control consists of the mass insertion of organisms beneficial to plants and natural enemies of pests. These organisms are already found naturally in cultivation sites, but in lower density.

Biological control is often used in conjunction with chemical control.

However, it’s important to note that biological control products require that the manufacturer’s recommendations be followed.

Before purchasing a microorganism, it is necessary to check the manufacturer’s recommendations. After all, the same microorganism can be recommended for the control of different diseases.

Another important point is to consult the compatibility of the biological control products with other products that will be used in the field.

Control through modification of insect behavior

This method consists of using attractive traps and repellents. Hormones and sterilization of insects alter their behavior and reproduction.

Chemical control

It is employed through the use of phytosanitary products, which should always follow good agronomic practices.

In addition, always use products registered with the Map (Ministry of Agriculture, Livestock, and Supply) for the crop in question.

Do the chemical control with care in relation to the active ingredients. Don’t forget to rotate to prevent pests from becoming resistant.

Conclusion

The classification of an organism as a pest depends on several factors, including the set of management carried out in the field.

IPM is essential for an increasingly expressive agricultural production, combined with the optimization of the use of control resources.

To produce more and more, the monitoring of agricultural areas and good agronomic practices are fundamental.

Be sure to use all available technologies to map the area and obtain pest occurrence histories. This will certainly help you in your decision-making.