Dichelops melacanthus and Euschistus heros injury on maize: Basis for re-evaluating stink bug thresholds for IPM decisions

This study compared injuries caused by different densities of adults and nymphs of Dichelops melacanthus and Euschistus heros to better assess the stink bug economic threshold (ET) for maize in integrated pest management. Thus, four different trials were conducted in Londrina, Brazil from 2017 to 2018 in the greenhouse and under field conditions. The first and second trial compared the degree of injuries caused by different adult densities of D. melacanthus and E. heros on maize, using artificial infestation. The third trial compared the capacity of adults and nymphs of both species to injury maize. The fourth trial evaluated different ETs under field conditions. The study demonstrated that the ET for stink bugs in maize should be three adults of D. melacanthus m(-1) of row. A lower ET triggered a higher number of insecticide applications, but did not improve either yield or net income, as shown by economic analysis. Moreover, the potential of E. heros for damaging maize was shown to be low. The results show the control is not justified for densities up to 6 stink bugs m(-1) of row, since yield was not reduced at these densities. Also, stink bug nymphs and adults might not produce the same injuries. Not only were adults of D. melacanthus more harmful to maize than nymphs of the same species but also than adults or nymphs of E. heros. Further research comparing the insect damage caused by different developmental stages is still needed in order to refine current ETs for future application.