Effects of tillage practices on spider assemblage in rice paddy fields

Abstract

To examine the effects of tillage practices on spider assemblages in rice paddy fields, we investigated the abundance and biomass of spiders in untilled and tilled paddy fields over three cropping seasons (from 1999 to 2001). In total, we collected 6,829 spiders, consisting of 13 species in seven families. The family Lycosidae was the most abundant, followed by Tetragnathidae, Linyphiidae, and Salticidae. Spider abundance and biomass were greater in untilled than in tilled paddies during each cropping season. Although we detected no significant effect of tillage on spider abundance, we did observe a significant effect of tillage on spider biomass in 2000 and 2001. No differences were found in the abundance and biomass of tetragnathid and linyphiid spiders during the cropping season. In contrast, the abundance and biomass of lycosid or salticid spiders tended to be larger in untilled paddies than in tilled paddies, especially later in the cropping season.

Observational evidence that the diet of wolf spiders (Araneae: Lycosidae) in paddies temporarily depends on dipterous insects

“…The two species commonly inhabit the basements of the rice plant tillers. Lycosid spiders constituted about 60% in number and 80% in biomass of all spiders collected at the study site (Motobayashi et al, 2006).…”

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.…”

“…During late August to early September, the abundance of lycosid and salticid spiders in untilled plots was 2-2.5-fold and 4-10-fold larger than tilled plots, respectively (Motobayashi et al, 2006). These spiders may mainly cause a reduction in the late-stage larval skipper population; however, we could not clarify the contribution of each spider species to the predation of migrant skipper larvae.…”

“…No insecticides or fungicides were applied during the experimental period. The cultivation procedure is described in Motobayashi et al (2006) in detail.…”

“…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).…”