Data/hora: 14/06/2024 19:23:09

Biblioteca(s): | Embrapa Soja.
Data corrente: | 30/06/2005
Data da última atualização: | 22/05/2006
Autoria: | BROWN, G. G.; OLIVEIRA, L. J.
Título: | White grubs as agricultural pests and as ecosystem engineers.
Ano de publicação: | 2004
Fonte/Imprenta: | In: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY AND ECOLOGY, 14., 2004. Mont Saint Aignan. Abstracts. Mont Saint Aignan: Université de Rouen, 2004. p. 112.
Idioma: | Inglês
Conteúdo: | The family Melolonthidae (Scarabaeoidae) can be divided into six subfamilies, and in Brazil, the most common larvae living in soils in agroecosystems are of the Rutelinae (e. g., Anomala spp.) and Dynastinae (e. g., Cyclocephala and Bothynus spp.) subfamilies, that feed on OM and rarely on roots and of the Melolonthinae subfamily (e. g., Phyllophaga, Diloboderus spp.), that feed mostly on roots and less on OM. The objective of this study  was evaluate the role of Melolonthidae in agroecosystems, where the density of melolonthid larvae in soils can range from a few to >100 individuals m -2. Larvae can vary from less than 1cm, at first instars up to 7cm at the final (3rd) instar. Melolonthid larvae consume from 45 to 80 times their own weight during their development (Móron 1987). Phyllophaga cuyabana in the 3 rd instar, feeding on soybean roots, weigh on average 0.8 to 1g and can consume >30 times their biomass, returning about 16 to 20% to the soil as faeces. In soybean production systems in Brazil, rhizophagous larvae generally tend to become pests in situations where soil biodiversity is reduced, favoring the predominance and population increase of rhizophages, and when the larger individuals (3rd instar) occur in synchrony with the most susceptible plant stages. Furthermore, environmental conditions can also reduce plant tolerance to rhizophagy, or cause the facultativly phytophagous larvae to move from saprophagy to rhizophagy. Obbligatory (e. g., Bothynus spp.) and facultatively (e. g., Diloboderus spp.) saprophagous species are typically more abundant in no-tillage agroecosystems, where the larvae construct vertical tunnels in the soil (galleries up to 3cm wide), connected to the soil surface when they are actively feeding. In samples taken in soybean in Londrina, PR we observed that the total volume of the holes opened by the beetles and/or larvae per surface area (m²), was almost 10 times greater in no-tillage than conventional tillage. On the other hand, population fluctuation of the rhizophagous P. cuyabana was similar in both no- and conventionall-tillage, although rhizophagous larvae also open tunnels (temporary) in the soil, generally for locomotion (searching for food) and pupation. Tunnels of saprophagous species can be abundant (>70m-2) and >1 m deep. Some species bury large amounts of plant litter, contributing to its decomposition and mineralization, significantly increasing P, K and OM content of the galleries compared with adjacent soil (Gassen 1993). These bopores also increase soil porosity and aeration, improve drainage, serve as pathways for root growth and as refuge for many other invertebrates. However, in cases where large saprophagous larvae populations are present, most of the surface litter is rapidly incorported, reducing available resources for other saprophagous organisms (e.g., millipedes, earthworms), possibly reducing their abundance by competition. In sum, due to their physical effects on soils and the induced changes to resource availability in the soil ecosystem, white grubs should be considered as ecosystem engineers.
Palavras-Chave: | Ecologia do solo; Fertilidade so solo.
Thesagro: | Ecologia Vegetal.
Categoria do assunto: | --
Registro original: | Embrapa Soja (CNPSO)
Exemplares: | CNPSO - (25238-1) - UPC - SP - -- - 9937 -  - 9937 - DIS