Faunistic analysis of pest insects and their natural enemies associated with hairy fleabane in soybean crop1

Abstract

In addition to competing with crops, weeds can provide shelter for arthropods in cropping fields and adjacent areas. This study aimed to investigate the occurrence and population fluctuation of insect pests and their natural enemies associated with hairy fleabane (Conyza spp.), in soybean farming areas. The predominant species were Schizaphis graminum, Taylorilygus apicalis, Empoasca spp. and Nysius simulans. Species that comprise important pest complexes, including stink bugs and caterpillars, can develop on fleabane plants. Among them, the stink bugs Edessa meditabunda, Dichelops spp., Piezodorus guildinii, Nezara viridula and Euschistus heros, as well as the caterpillars Anticarsia gemmatalis, Spodoptera frugiperda, Spodoptera eridania, Chrysodeixis includens and Helicoverpa spp. have prevailed. The most common natural enemies were Orius spp., Eriopis connexa, Cycloneda sanuiinea and Chrysoperla spp. The population fluctuation analysis indicated that hairy fleabane mainly hosted stink bugs at the beginning of the crop cycle and after soybean maturation. The caterpillars, however, use this weed as an alternative host throughout the crop cycle, continuing after soybean maturation and harvesting. For natural enemies species, the population fluctuation depends on the occurrence of insects that serve as a food source for them. Thus, it is possible to conclude that hairy fleabane is an important alternative host for pest insects and their natural enemies in soybean crops.

Occurrence of pests in weeds with different crop managements

“…It can be observed in Figure 3 that the pests that differed in only this area were D. melacanthus, D. speciosa, and T. urticae. In the evaluation of soybean/Crotalaria, only H. armigera, P. sennae and A. rumicis differed from the others.In a study byDalazen et al (2017) in 2010 in the cities of São Vicente do Sul and Boa Vista do Incra (both in the state of Rio Grande do Sul), they carried out a faunal and pest analysis in soybean where they verified some pests found in this work such as: Dichelops spp., E. heros, A. gemmatalis, S. frugiperda, C. includens and Helicoverpa spp., and also observed the same result found in the population fluctuation analysis which indicated the occurrence of pests on weeds more frequently, especially in the initial cultivation period (October and November).…”

“…Some authors argue that non-weed control affects the population dynamics of arthropod pests, which persist throughout the year in economic crop environments in the absence of major crops (Sá et al, 2009). This is due to the availability of weeds as a green bridge for the next crops when an economically viable crop sowing stabilizes, and as a consequence the severe attack of pests (Dalazen et al, 2017).…”

“…Crop rotation and soil cover in the off-season provides diversification in the environment, reducing the selection and occurrence of weed species (Silva et al, 2018) that interferes in the maintenance or proliferation of crop pest insects (Dalazen et al ., 2016;2017;Fontanetti, Salgado & Galvão, 2018). Crop rotation can define the evolutionary behavior of fauna and flora ecophysiology, which takes into account plant ecology and integration with the living environment (Erasmo, Pinheiro & Costa, 2004),…”

“…Nevertheless, the interaction and behavior in these two situations must be taken into account and studied together, considering the population dynamics, migration and use of hosts, as research by Dalazan et al (2016;2017) indicates. Therefore, this research aimed to evaluate the occurrence of pests in weeds with different crop managements.…”

Seleção de espécies bioindicadoras do herbicida ethoxysulfuron

“…Um dos fatores que limitam o crescimento, o desenvolvimento e a produtividade de culturas agrícolas é a interferência provocada por plantas daninhas, pois além de competir por fatores essenciais como luz, água e nutrientes (Ferreira et al, 2015;Medeiros et al, 2016), depreciam a qualidade da produção e podem ser hospedeiras de pragas, patógenos e nematoides (Sales Junior et al, 2012;Bellé et al, 2017;Dalazen et al, 2017).…”