Individual study: Crops with reduced pesticide applications had greater spider abundance than conventional spraying in Finland
Huusela-Veistola E. (1998) Effects of perennial grass strips on spiders (Araneae) in cereal fields and impact on pesticide side-effects. Journal of Applied Entomology, 122, 575-583
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Use pesticides only when pests or crop damage reach threshold levels
A randomised, replicated, controlled study in cereal fields in 1992-1994 in Finland (Huusela-Veistola 1998) found more spiders (Araneae) in plots using a threshold-based spraying regime (peaking at 17-31 spiders/3 traps) compared to conventional plots sprayed annually (12-23 spiders) in 1992 and 1994. The effect lasted for three weeks in 1992 and at least six weeks in 1994, but overall spider numbers were similar between treatments in 1993. More money spiders (Linyphiidae) were found in plots in the threshold-based spraying regime (peaking at 10-20 spiders/3 traps) than conventional plots (9-12 spiders) in all years. Wolf spider (Lycosidae) numbers were only greater in the threshold-based than conventional plots in 1994. At the species level, only one of three species tested (the money spider Erigone atra) was affected by pesticide regime type. In the threshold-based regime, sprays were made when control thresholds were exceeded, resulting in one insecticide (pirimicarb) spray in 1992 and one herbicide spray in 1994. Insecticides (dimethoate and deltamethrin), fungicides (carboxin, imazalil and propiconazole), herbicides and growth regulators were applied annually in conventional plots. Barley Hordeum vulgare was grown in 1992-1993 and wheat Triticum aestivum in 1994. Spiders were captured using pitfall traps monitored weekly (8-10 times between sowing and harvest).
Undersow spring cereals, with clover for example
A replicated, controlled, randomized study of spiders (Araneae) in arable fields in Finland (Huusela-Veistola 1998) (same study as (Huusela-Veistola 1996)), found no significant difference in spider abundance between conventional and integrated farming practices (including undersowing with grass/clover Trifolium spp.). Abundance was higher with reduced pesticide applications. There were six replicate blocks and the treatments (in 0.7 ha plots) were fully randomized within blocks (one treatment combination/plot). Treatments were conventional pesticide applications or reduced pesticides and customary or integrated (including undersowing) cultivation. Spiders were sampled with pitfall traps at 12, 66 and 120 m into each crop 8-10 times (one week/sample) between sowing and harvest.
Plant grass buffer strips/margins around arable or pasture fields
A replicated, controlled, randomized study in Finland (Huusela-Veistola 1998) found that spider (Araneae) abundance was higher in perennial grass/clover Trifolium spp. strips than in the crop (approximately 1,200-3,000 vs 400-900 spiders respectively). Wolf spiders (Lycosidae) dominated in grass strips (57-77% of total catches). Money spiders (Linyphiidae) were also more common in grass strips than in the crop. Total spider catches including wolf spiders decreased with distance into the crop. Perennial grass/clover strips 12 m wide were sown with a mixture of timothy Phleum pratense, meadow fescue Festuca pratensis, red clover T. pratense, and white clover T. repens at the ends of 24 plots in 1991. Spiders were sampled with a pitfall trap in the centre of the grass strip and at 12, 66 and 120 m into each plot from the grass strip 8-10 times (each trapping period lasting one week) between sowing and harvest (1992-1994).
Reduce fertilizer, pesticide or herbicide use generally
A replicated, controlled, randomized study in arable fields in Finland (Huusela-Veistola 1998) (same study as (Huusela-Veistola 1996)), found that spider (Araneae) abundance was greater in reduced pesticide compared to conventional plots. This was the case in 1992 and 1994 (reduced fertilizer: peak 17-31/three traps/week, conventional: 12-23), there was no significant difference in 1993. Conventional pesticide use decreased money spider (Linyphiidae) numbers in all years (peak: 9-12 vs 10-20/three traps/week), but wolf spider (Lycosidae) catches only in 1994. Only one of the species tested (Erigone atra, money spider family) differed significantly between pesticide regimes. There was no significant difference in spider abundance between cultivation treatments: customary (deep ploughing, conventional fertilizer use, no undergrowth) vs integrated (soil treatment with cultivator only, reduced fertilizer use, undersowing with grass/clover Trifolium spp.). There were six replicate blocks and the treatments (in 0.7 ha plots) were fully randomized within blocks (one treatment combination/plot). Treatments were conventional pesticide applications or reduced pesticides and customary or integrated cultivation. Spiders were sampled with pitfall traps at 12, 66 and 120 m into each crop 8-10 times (one week/sample) between sowing and harvest.