Abstract
Understanding the ecological and toxicological relationship between genetically modified cultivars (GM) and biological control agents is of great importance for discussions related to the compatability of GM cultivars and integrated management strategies for pest resistance. The present study evaluated the search behavior and predatory capacity of Orius insidiosus (Say) (Hemiptera: Anthocoridae) and Doru luteipes (Scudder) (Dermaptera: Forficulidae) on eggs and caterpillars of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) resistant or not to the protein Cry1F expressed in Bt corn. To determine the search time, a stopwatch was run until the capture of the first prey, predation capacity was evaluated by counting the prey remaining after 24 hours of infestation. The injuries of S. frugiperda in genetically modified and conventional corn in the presence and absence of predators was also evaluated. The predators were not able to distinguish between resistant and susceptible prey (eggs or caterpillars), given the predatory behaviour observed. There was no difference in searching time or predatory capacity between the predators for eggs and caterpillars of either resistant or susceptible S. frugiperda. In the presence of predators, the injury scores for resistant S. frugiperda on the Bt corn plants were lower. It was concluded that O. insidiosus and D. luteipes did not notice the presence of the protein Cry1F in the prey S. frugiperda, which may facilitate the combined use of GM corn and biological control in integrated management programs and for management of pest resistance.
Highlights
In agricultural cultivation, tropical systems favor the presence of host plants for profligate pests during the greater part of the year during either successive or simultaneous cultivation of diverse cultivars
There was no significant difference for the searching time of O. insidiosus for eggs of susceptible or resistant S. frugiperda (F = 0.34; df = 2.12; P = 0.5628) or between the different instars of the predator, while the instar x prey interaction did not show significance (F = 0.524; df = 2.12; P = 0.5931)
There was a difference between the instars (F = 19.18; df = 2.12; P = 0.0000); 1st instar O. insidiosus nymphs preyed on the least number of eggs in 24h in comparison with the 3rd and 5th instar nymphs, while the prey x instar interaction was not significant (F = 1.97; df = 2.12; P = 0.1426) (Table 1)
Summary
Tropical systems favor the presence of host plants for profligate pests during the greater part of the year during either successive or simultaneous cultivation of diverse cultivars. This availability of host cultivars for pests is known as a green point, and has made the control of insect pests increasingly difficult (Bernardi et al, 2015). The use of integrated pest management (IPM), which optimizes the use of different management methods and strategies, has been increasingly recommended in the search for greater sustainability in cultivation systems (Van Lenteren et al, 2018). One of the most widespread pests in tropical cultivation systems and of great importance in the Americas is the fall armyworm Spodoptera frugiperda The fall armyworm is considered the principal pest for corn, reducing the production of grains by up to 34% (Cruz, 1995; Figueiredo et al, 2006)
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