Plant diseases

Helicoverpa armigera

Today we are going to talk about a new species of insect that is considered a pest that threatens agricultural crops. It is about the Helicoverpa armígera. It is a new species that threatens crops and, therefore, has worried institutions, researchers, companies and producers in the agricultural field. It is known by the common name of the old world cocoon caterpillar. This name is due to the various damages it causes in Europe, Asia, Africa and Oceania.

In this article we are going to tell you about all the characteristics, life cycle and control of the Helicoverpa armígera pest.

Main features

It is a type of insect that attacks agricultural crops and was first identified in Brazil in 2013. The concern comes from the fact that its populations have increased considerably in recent years. Not only this specific species, but all the species that belong to the genus Helicoverpa. The cause of the increase in these populations is mainly due to a series of modifications that have taken place in agricultural systems. One of these modifications is the successive planting of various host plant species.

These are species where these insects can develop and expand. They are crops like leaves, corn and cotton. All these crops are spread over very large areas and help to provide food and habitat so that Helicoverpa armígera can spread for much of the year.

It is a species of quite polyphagous insect which causes its larvae to cause damage both in the vegetative cap and in the reproductive stage of the plants. It basically feeds on the leaves, buds, stems, flowers, flower buds and even the fruits that are larger. It is mainly found in crops such as sorghum, tomato, chickpea, sunflower, cotton, corn and soybeans, among others.

Because agriculture currently has large fields with a wide range of host species and we add weeds, they contribute to good survival and seasonal dynamics of the pest. This weed plays a fundamental role in the survival and development of the Helicoverpa armigera.

Biological aspects of the Helicoverpa armígera

It is a species that has a high reproductive potential. Only one female is capable of laying between 1000-1500 eggs, reaching a quantity of 150 eggs per day. These eggs are placed in isolation or in small groups that makes their identification difficult. It is usually placed on the flowers, stems, fruits and leaves and the most normal is that they are located on the upper side.

The duration of the biological cycle of these insects is 4-6 weeks, although depending on the environmental conditions it can have between 2-11 generations per year. In order to identify these eggs, which is where you have to attack at the root, you have to look at the yellowish-white color that sometimes turns darker as it approaches hatching. The incubation period of the eggs is only 3 days. This makes action to stop the development and growth of the pest vital to slow its spread.

Biological cycle of Helicoverpa armígera

The larval period consists of 6 instars. In the first part, they feed on the most tender parts of the crops and it is the right time for the chemical control of the pest. Its control becomes easier thanks to the larvae being more exposed and more susceptible to external chemical agents. As they grow, they acquire different colors that vary depending on the type of food they consume. In this way, its detection is more difficult since it can be camouflaged between the weed and the rest of the crops.

The prepupal phase is that which comprises the period from when the larva stops its continuous feeding until the pupal phase. It is here when the pupa of the Helicoverpa armígera has a brown color and its development occurs on the ground. Depending on the prevailing weather conditions at that time, it can go into diapause. This means that it stops growing for a time until the environmental conditions are favorable.

Once it reaches the adult stage , the butterflies have a yellowish coloration in the females and a greenish gray in the males. The easy way to distinguish them is by analyzing the darker band in the distal third and a darker spot in the center of the front wings. The hind wings are somewhat lighter and have a dark apical border.

L to Helicoverpa armigera has a great capacity for dispersion and adults can be moved over distances up to 1000 kilometers per campaign. Associated with this, there is also a high capacity for survival even when environmental conditions are adverse. These conditions can be excessive heat, period, or a prolonged drought. Another characteristic for which this pest stands out is its high potential to develop resistance to different insecticides. Among the insecticides to which they are most resistant are pyrethroids, carbamates and organophosphates, and transgenic crops.

Damages and treatment

Among the damages caused by this plague, we find annual losses that reach 5 billion dollars worldwide. And it can cause damage to the reproductive structures of crops and cause them to not be able to develop. In order to have an effective treatment against these pests, it is necessary to know the biology and dynamics of the populations of this insect. Monitoring is the most important thing in order to analyze the part of their life cycle where they are most vulnerable.

Light traps and pheromones can be used for this monitoring. Chemical control is mainly based on the use of insecticides, although great resistance to different types of them has been seen. About coal that you produce to take into account the following aspects:

  • Selectivity of the insecticide to preserve natural enemies. In this way we will ensure that the predators of the Helicoverpa armígera can continue hunting.
  • Know the mechanisms of action of insecticides to carry out a rotation, avoiding the development of resistance.
  • Use the dose to be used well.

I hope that with this information you can learn more about Helicoverpa armígera and its characteristics.

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