Integrated management and monitoring to combat the Helicoverpa caterpillar

Caused by a cumulative process of inadequate cultivation practices, the population explosion of helicoverpa and the economic damage resulting from this pest in soybean crops points to the need to reestablish the balance of agricultural production systems before the situation worsens even further. Within integrated management, efficient insect monitoring plays an important role in preventing and minimizing losses.

From the 2012/13 harvest, mainly in soybean, cotton and corn crops in the Cerrado region, the occurrence of caterpillars of the genus helicoverpa was observed at population levels never before recorded, responsible for serious economic losses. The gender helicoverpa It has biological characteristics, such as polyphagy, high fecundity, high mobility of caterpillars on the plant and migration of moths that allows it to feed on various host plants, survive in unstable environments and adapt to seasonal climate changes. The life cycle of helicoverpa spp. It lasts from 42 to 58 days. Of these, 14 to 21 days the species remains in the caterpillar phase, which comprises the period of attack on host plants (Figure 1).

In soybean cultivation, helicoverpa attacks from the initial stages until the pod maturation phase. Under field conditions it is practically impossible to identify and separate Helicoverpa armigera de helicoverpa zea or even Heliothis virescens, which are also insect pests that occur in this crop. Only laboratory identification can prove these differences.

The occurrence and population increase of helicoverpa spp. in production areas, in addition to the biological characteristics that favor the presence and survival of the pest, factors of climatic imbalance in the cultivation areas can be attributed; the succession of crops that favor the pest; the withdrawal of the insecticide endosulfan from the market (possibly favoring the lack of control of the pest in cotton crops); the reduction in the efficiency of insecticides for medium and large caterpillars (which made good plant protection unfeasible); and also, in some cases, the absence of quality agronomic assistance at the beginning of pest infestations. helicoverpa spp.

The population growth of caterpillars of the genus helicoverpa and consequently the damage caused by the insect to production systems was caused by a cumulative process of inadequate cultivation practices, making the agroecosystem susceptible to diseases and insect pests due to the abundant supply of food, breeding sites and shelter during almost the entire year, in addition to the elimination of its natural agents of mortality.

Considering the significant economic losses caused by helicoverpa in soybean cultivation in the Cerrado region, it is necessary to reestablish the balance of agricultural production systems, before other insects, in addition to the genus helicoverpa, adapt in due time, increasing losses in the agricultural harvests that follow. In addition to emergency measures to be adopted to reestablish this balance, it is essential to adopt actions on planning cultivation areas based on the concepts and practices of Integrated Pest Management (IPM).

Monitoring is extremely important for the success of integrated pest management in soybeans. It is through this that the necessary knowledge will be obtained to proceed, or not, with control tactics. As a benefit, the producer, when choosing to adhere to IPM, carrying out correct monitoring, will not need to carry out preventive applications of insecticides. In this way, costs will be reduced and populations of beneficial insects that help control pests will be reduced. helicoverpa will not be harmed.

Monitoring procedures

Pre-sowing

Monitoring must begin even before sowing. If there is a history of occurrence of helicoverpa In the designated area, direct planting should be avoided. When choosing conventional planting in areas with reports of caterpillar attacks, proceed with desiccation of weeds before cultivation. The joint application of insecticides at this stage is not recommended, as it drastically reduces natural enemy populations. If resistant weeds are observed in the area, such as horseweed (conyza bonariensis), which can be host to helicoverpa, apply only selective insecticides that do not harm the future action of natural enemies, such as diamides, spinosins and growth regulating insecticides. The use of insecticide seed treatments is an excellent option that protects the crop for approximately 25 to 35 days after emergence.

Seeding

The use of transgenic varieties (Intact RR2 PRO ^TM: BRS 245RR, BRS 334RR, BRS 359 RR) has been widely used by producers, however, for the success of the technology in the field it is necessary to observe the creation of the refuge, which consists of 20% of the cultivated area with the absence of transgenic plants to reduce the risk of resistant populations of the pest. It is worth noting that the refuge cannot exceed 800 meters from crops with transgenic plants.

After sowing

To carry out sampling after soybean emergence, the area must be divided into homogeneous plots, which correspond to the same sowing time, variety, soil conditions, etc. This area should not exceed 400 ha, preferably 100 ha when possible.

Vegetative phase     

Sampling in the vegetative phase must occur weekly and evaluate one point every 10 ha throughout the vegetative stage. At this stage, it will be essential to observe the percentage of defoliation and number of caterpillars/sampling point. It is extremely important to direct observation to the pointers, as this is where oviposition of birds preferentially occurs. helicoverpa.

reproductive phase

In the reproductive phase, sampling must occur at least twice a week and one point every 10 ha. At this stage, the floral buds must be carefully observed, as they are targets for oviposition and attacks by caterpillars. During the pod filling phase, monitoring is also essential.

Sampling techniques for monitoring

Cloth

The beating cloth is 1mx1m with the help of wood at the ends (Figure 2A). Its color is neutral, generally white to facilitate pest identification. To proceed with the technique, the steps described in Table 1 must be followed.

Table 1 - How to use the beating cloth

Plastic tray

Very similar to the beating cloth technique, the tray is a very practical and simple device (Figure 2B). The white plastic tray is generally 50x30 cm and to perform the technique simply follow the steps described in table 2.

Table 2 - How to use the plastic tray

Pheromone trap

In pheromone traps, only male moths are captured. The intensity of capture of adults of helicoverpa in a given area provides prediction of the potential occurrence of eggs and caterpillars. Among the traps, the most common is the Delta type, which has an adhesive floor and a pheromone capsule (Figure 2C). The male, when attracted, enters the trap and becomes trapped in the adhesive floor. For monitoring, at least one pheromone trap/ha must be installed.

light trap

The light trap attracts adult females and males, being very efficient in quantitatively surveying the nocturnal migratory habit of helicoverpa. The operation of the trap is very simple. The equipment has ultraviolet light to attract insects, using batteries as a power source. Below the light there are funnels that direct the insects to a container with water and oil to prevent the moths from moving (Figure 2D). The trap must be set up after 18 pm and the following day it is possible to count the moths trapped in the container. One light trap/ha is recommended. 

Flávio Lemes Fernandes, Entomologist, Prof. UFV-CRP; Nayara Cecília Rodrigues Costa, Eng^a Agronomist, Master’s Student UFV-CRP; Jéssica Emiliane Rodrigues Gorri, Eng^a Agronomist; Maria Elisa de Sena Fernandes, Breeder, prof. UFV-CRP

Article published in issue 201 of Cultivar Grandes Culturas.