Study

Actions

This study is summarised as evidence for the following.

Action Category

Grow cover crops beneath the main crop (living mulches) or between crop rows

Action Link
Soil Fertility

Use pesticides only when pests or crop damage reach threshold levels

Action Link
Natural Pest Control
  1. Grow cover crops beneath the main crop (living mulches) or between crop rows

    A randomized, replicated, controlled study in 1988-1989 in Oklahoma, USA (Roberts & Cartwright 1991) found that cabbage Brassica oleracea plots with rye Secale cereal cover crops retained more soil (25% drop in bed height over nine months) than bare ground controls (35% drop). Beds with hairy vetch Vicia villosa cover crops dropped in height by 29% over nine months but mean bed height was similar to beds in rye cover-cropped plots and bare controls. Above ground, rye produced more dry vegetation (4,754 kg/ha after six months) than hairy vetch (1,213 kg/ha). Raised cabbage beds (90 cm wide, 20 cm tall) were planted with cover crops (rye, hairy vetch or left bare) in mid-October 1988. Plots were sprayed with glyphosate on 5 April 1989 and cabbages were planted into cover crops on 17 April. Cover crop treatments were replicated three times in plots of 1.8 x 6.1 m. Bed height was measured on 3 November 1988, 27 March and 12 July 1989.

     

  2. Use pesticides only when pests or crop damage reach threshold levels

    A randomised, replicated, controlled study in 1988-1989 in Oklahoma, USA (Roberts & Cartwright 1991) found similar numbers of cabbage loopers Trichoplusia ni, thrips Frankliniella spp. and aphids (Aphidoidea) in plots with a threshold-based spraying regime and plots with a conventional, weekly spraying regime, when averaged across the season. Damage to cabbages Brassica oleracea and cabbage yield were also similar in plots with threshold-based and conventional spraying regimes. Cabbages in the threshold-based regime were sprayed with Dipel 2X biological insecticide when moths and butterflies (Lepidoptera) averaged 0.5 larvae/plant in early to mid-growth stages and 0.3 larvae/plant in late growth stages. In the conventional regime plots received weekly sprays of Bacillus thuringiensis biological insecticide. Plots sprayed when pest thresholds were exceeded received 7-8 sprays compared to 11 sprays in the plots treated weekly. Each spraying regime was replicated 18 times. Insect pests were sampled on 5-10 plants/plot and one or two times/week. Figures and effects on natural enemies were not presented.

Output references
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