Aspectos de la dinámica poblacional de las chinches Nezara viridula y Piezodorus guildinii e implicancias con relación a su manejo en el cultivo de soja

• Autores: Liljeström, Gerardo; Coviella, Carlos E.
• Año de publicación: 1999
• Idioma: español castellano
• Tipo de recurso: artículo
• Materia: Nezara viridula; Piezodorus guildinii; Soja; Control
• Institución: Universidad Nacional de Luján

Fil: Liljeström, Gerardo. Universidad Nacional de Luján; Argentina
Population dynamics of the stink bugs Nezara viridula and Piezodorus guildinii and control strategies in soybean cultures. Nezara viri-dula (L.) and Piezodorus guildinii (West.) are considered soybean pests. The activity period lasts from mid September up to mid April, approximately, and successive generations exhibit a progressive colonisation of areas with difie¬re nt vegetation. To study the space and temporal variations, the study area (2.7 ha placed in La Plata and Berisso counties) was divided into 4 plots: a) a 450 m2 weed plot dominated by Ricinus communis, Brasssica spp., and Raphanus sp.; b) a 2.0 hectares plot dominated by Stipa spp., Cynodon spp., and Bro¬mos spp, and Eucalyptus trees; c) a 0.5 ha plot cultivated with soybean; d) a vegetable garden 0.5 ha plot with patches of clover (Trifolium spp.). Both N. viridula and P. guildinii populations were simultaneously sampled in all plots at peak density, and older nymphs and adults, as well as N. viridula adult pa- rasitism by the tachinid Trichopoda giacomellii (Blanchard) and egg parasi- tism by oophagous parasitoids, were measured. Nezara viridula developed four generations in the activity period and P. guildinii five. At the beginning of the period post-invernating adults concentrated on some plots, where feeding, mating and oviposition took place. Nezara viridula concentrated mainly on the weed and vegetable garden plots, while P. guildinii concentrated on the vegetable garden plot, in patches of clover and other leguminous species. Both species showed a negative preference by the 2.0 ha plot. Successive ge¬nerations of N. viridula (3rd and partial ly the 4th) and P. guildinii (3rd, 4th and partially the 5th), showed a progressive colonisation of the soybean plot from the R3 phenological stage. However, the highest densities were found during the R4 phenological stage (mid February) when both species showed a positi- ve preference. Both populations showed a relative high stability in the study area during the 24 N. viridula and the 15 P. guildinii generations studied. The persistent parasitism was always higher than 10%, and in the case of N. viri¬dula, previous results identified parasitism by T. giacomellii (Blanchard) as density dependent and capable of regúlate the host-parasitoid system. These results were comparable with those obtained in soybean fields in Alberti, Chivilcoy, and Luján counties (with no pesticide applications, except in only one occasion in Luján): a progressive colonisation of soybean by N. viridula and P. guildinii, and populations of both species (as well as other soybean pests) fluctuating usually under the economic level, and the persistence of different predators and parasitoids species. These results suggest that the phytophagous insect community on soybean could be characterised as the theoretical type II community: predictable populations maintained in rather less density by density dependent mortality factors. In this case, different control measures must be scheduled in a way that natural enemies would not be affected.