**1. Introduction**

Bt corn is a type of transgenic corn that produces a protein of bacterial origin. The Cry protein, naturally produced by *Bacillus thuringiensis*, is toxic to defoliating caterpillars or stem borers, but not toxic to stink bugs. Maize is cultivated practically throughout the Paraguayan territory with different production systems and

technological levels used. Some changes in the corn production system have contributed to the increase in productivity: the direct sowing system, the use of hybrids with high productive potential, the increase in cultivated areas in the second harvest, after the soybean harvest, and the use of genetically modified hybrids such as Bt maize [1].

In recent years, the main problem faced by maize producers is the difficulty of protecting the maize crop from leaf damage caused by *Dichelops melacanthus* (Hemiptera: Pentatomidae) during the first weeks after maize emergence. At this stage, the seedling is quite susceptible to leaf punctures caused by Hemipteran stylets during feeding.

Studies to estimate the economic threshold level for *D. melacanthus* in maize were carried out by Bianco [2] who estimated two insects per five plants of corn, which is equivalent to 2 stinkbugs/1.25 lineal m under field conditions. In addition, Gassen [3, 4] and Cruz et al. [5] recommend control measures for stinkbugs in the corn crop when two insects/m<sup>2</sup> are found, which is equivalent to one bug/lineal m. Both levels are higher than that found by Duarte [6] with 0.8 stinkbugs/m<sup>2</sup> equivalent to 0.4 insects/linear m under controlled population conditions.

What is worrying is that both Bt technology and seed treatment with neurotoxic insecticides fail to provide protection to the maize plant in the initial vegetative phase, this forces producers to be vigilant and take early control actions so that economic damages do not render production unfeasible due to foliar damage and the increase in production costs. The question that arises is: What percentage of attack can a commercial corn crop suffer and how much can it reduce the production of corn grains in weight and economic income?

However, these changes can trigger new problems and require constant studies for proper management. The occurrence of new pests or the increase of others that attack the crop can be seen as a direct reflection of alterations in the productive systems. The appearance of *Dichelops melacanthus* (Hemiptera: Pentatomidae), commonly known as green-bellied bug, is currently found in Brazil, Argentina, Paraguay, Uruguay, Bolivia, Colombia, Peru and Venezuela [7]. Infestation and damage occur at the seedling stage as a result of adult migration from surrounding crop debris or other plants within the field [8–10].

A transformation of great magnitude, such as the one experienced in our agriculture, should respond to a reasoned process, supported by knowledge and adequate technological management of each component of the production system. One of the fundamental pillars on which the cultivation of corn rests and that, therefore, directly influences the yields achieved, is pest control.

Knowledge of the population dynamics of these pests is important in the management of these organisms since through it the incidence is estimated and the management of the insect can be planned, which is essential when determining a control strategy that avoids the increase in the existing gap between potential returns and real returns [11]. Damage to maize from seedlings causes brown spots, leaf discolouration and twisting, reduced yield [12] or plant death [10, 13].

The realization of this work is based on the current concern about the high incidence of *D. melacanthus* in the corn crop, even with seed treatment and a series of insecticide applications during the crop cycle. This research tries to obtain real data from the field that can contribute to verify the level of damage caused by the attack of bugs in corn production and how this can affect the producer economically.

In this research, the objectives have been to evaluate the foliar damage caused by the attack of the green-bellied bug *D. melacanthus* on transgenic Bt maize, grain production, to identify the number of attacked and non-attacked plants. Quantify the number of punctures per plant, verify the height of the plant in the phenological state V6 of maize and determine the weight of grains of the attacked and unattacked plants to compare the yield.
