Impacts of tillage practices on hoppers and predatory wolf spiders (Araneae: Lycosidae) in rice paddies

Abstract

We investigated the effects of tillage practices on the densities of wolf spiders and planthoppers and leafhoppers in rice paddy fields. Paddies were subjected to one of two different treatments (no tillage and conventional tillage), and seasonal changes in the densities of wolf spiders and hoppers were investigated over two growing seasons (1999 and 2000). In both years, the density of wolf spiders was significantly higher and the density of hoppers tended to be lower in no-tilled paddies than in conventionally tilled paddies, although the latter difference was not statistically significant. The Iwao's omega values, which represent the degree of correlation between the spatial distributions of wolf spiders and hoppers, were higher in no-tilled than in tilled paddies during August when the hopper density decreased in notilled paddies.

The effects of soil tillage on beneficial invertebrates within the vineyard

“…Adequate ground cover may be needed in agricultural ecosystems for the conservation of spider populations and enhanced predatory control of prey species ( Riechert, 1999 ). For example, the number of wolf spiders (Lycosidae) was reduced by tillage in rice paddies and this was associated with an increase in numbers of pest leaf hoppers ( Ishijima et al , 2004 ).…”

Effects of tillage practices on spider assemblage in rice paddy fields

“…However, studies of habitat manipulation, including no-tillage practices, for the promotion of spider activity, are limited in rice paddy systems (Settle et al, 1996). Hidaka (1993Hidaka ( , 1997 and Ishijima et al (2004) found that lycosid spiders were more abundant in untilled than in conventionally tilled paddy fields. However, whole spider assemblages in untilled paddy fields have not been examined.…”

Effect of spiders on inoculated populations of the migrant skipper Parnara guttata guttata Bremer et Grey (Lepidoptera: Hesperiidae) in untilled and tilled paddy fields

“…Mortality caused by unknown factors was also important at late larval stages, and was significantly higher in untilled than in tilled paddies. Previous studies have indicated that spider abundance and biomass was significantly greater in untilled than in tilled paddies in late August to early September (Ishijima et al, 2004;Motobayashi et al, 2006). Polistes wasps (Nakasuji, 1982) and birds (Matsumura, 1992) were reported as predators of late larval-stage migrant skippers; however, these and other predators were not observed in the experimental fields.…”

“…Hidaka (1993Hidaka ( , 1997 showed that Lycosidae (wolf spiders) were more abundant in winter mulch and untilled paddy fields than in conventionally tilled paddy fields. Previous studies have also shown that the spider assemblage, including wolf spiders, was enhanced by no-tillage management in paddy fields (Ishijima et al, 2004;Motobayashi et al, 2006). Spiders have been characterized as the most important biological control agent of rice insect pests (Itô et al, 1962;Kiritani et al, 1972;Kiritani and Kakiya, 1975;Oraze and Grigarick, 1989).…”

“…Spiders have been characterized as the most important biological control agent of rice insect pests (Itô et al, 1962;Kiritani et al, 1972;Kiritani and Kakiya, 1975;Oraze and Grigarick, 1989). Planthopper density tended to be lower in untilled than in tilled paddies, and the spatial distribution of wolf spiders overlapped that of planthoppers (Ishijima et al, 2004). Enhancement of the spider assemblage by no-tillage management practices may reduce other rice insect pests.…”