Agricultural practices for food safety threaten pest control services for fresh produce

Published source details Karp D. S., Moses R., Gennet S., Jones M., Joseph S., M'Gonigle L. K., Ponisio L. C., Snyder W. E. & Kremen C. (2016) Agricultural practices for food safety threaten pest control services for fresh produce. Journal of Applied Ecology, 53, 1402-1412.
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This study is summarised as evidence for the following.

	Action	Category
	Pest regulation: Add compost to the soil Action Link
	Other biodiversity: Add compost to the soil Action Link
	Crop production: Add compost to the soil Action Link
	Soil: Add compost to the soil Action Link

Pest regulation: Add compost to the soil

A replicated, controlled study in 2014 in 29 organic vegetable fields on the Central Coast, California, USA, found similar numbers of pests, pathogens, and natural enemies, and similar levels of pest regulation, in plots with or without added compost. Pest regulation: Similar percentages of pests (Helicoverpa zea corn earworm eggs, Spodoptera exigua beet armyworm larvae, and Macrosiphum euphorbiae potato aphids) were consumed by natural enemies in plots with or without added compost (data reported as model coefficients). Ratio of natural enemies to pests: Similar ratios of natural enemies to pests (mostly aphids) were found in plots with or without added compost (data reported as model coefficients). Pest numbers: Similar numbers of pests (mostly aphids) and pathogens (Escherichia coli bacteria) were found in plots with or without added compost (one sample from each had E. coli, but neither had shiga toxins; data on pests reported as model coefficients). Methods: In each of 29 vegetable fields, compost was added to one plot, but not to one adjacent plot (5 x 5 m plots), 1–2 months before lettuces were planted (25 t compost/ha, made from cow, chicken, and green manures). Lettuces were planted in spring (5–28 March) and summer (30 May–5 July). Pests and natural enemies were collected in pitfall traps (three/plot, 7.5 cm diameter) and pan traps (two/plot, blue and yellow, 15 cm diameter) after 48 hours of trapping (one sample when lettuces were seedlings and one when mature). Pests were also collected from three mature lettuces/plot. Five S. exidua larvae (second or third instar) and 25–70 H. zea eggs, glued to paper cards, were used to monitor pest regulation (48 hours/plot when lettuces were seedlings and when lettuces were mature). Regulation of aphids was measured by comparing mature lettuces in field cages (40 x 40 x 40 cm cages, 0.4 x 6 mm mesh, three caged lettuces/plot, two open cages and one closed to excluded natural enemies; all insects were removed and 50 aphids were added to one closed and one open cage/plot; aphids were collected from all three lettuces after two weeks). E. coli bacteria were measured in soil samples in spring (1.25 cm diameter, 0–10 cm depth).
Other biodiversity: Add compost to the soil

A replicated, controlled study in 2014 in 29 organic vegetable fields on the Central Coast, California, USA, found no differences in invertebrate biodiversity between plots with or without added compost. Invertebrates: Similar numbers of invertebrates and invertebrate families were found in plots with or without added compost (data reported as model coefficients). Methods: In each of 29 vegetable fields, compost was added to one plot, but not to one adjacent plot (5 x 5 m plots), 1–2 months before lettuces were planted (25 t compost/ha, made from cow, chicken, and green manures). Lettuces were planted in spring (5–28 March) and summer (30 May–5 July). Invertebrates (insects, springtails, and spiders) were collected in pitfall traps (three/plot, 7.5 cm diameter) and pan traps (two/plot, blue and yellow, 15 cm diameter) after 48 hours of trapping (one sample when lettuces were seedlings and one when mature).
Crop production: Add compost to the soil

A replicated, controlled study in 2014 in 29 organic vegetable fields on the Central Coast, California, USA, found higher lettuce yields in plots with added compost, compared to plots without added compost. Crop yield: Larger lettuces were found in plots with added compost, compared to plots without added compost (65 g larger, fresh weight). Methods: In each of 29 vegetable fields, compost was added to one plot, but not to one adjacent plot (5 x 5 m plots), 1–2 months before lettuces were planted (25 t compost/ha, made from cow, chicken, and green manures). Lettuces were planted in spring (5–28 March) and summer (30 May–5 July). Lettuce weights were measured at maturity in one 1 x 1 m quadrat/plot.
Soil: Add compost to the soil

A replicated, controlled study in 2014 in 29 organic vegetable fields on the Central Coast, California, USA, found more organic matter, phosphorus, and potassium in soils with added compost, compared to soils without added compost. Organic matter: More organic matter was found in soils with added compost, compared to soils without added compost (data reported as model coefficients). Nutrients: More phosphorus and potassium, but similar amounts of nitrate and similar pH levels, were found in soils with added compost, compared to soils without added compost (data reported as model coefficients). Methods: In each of 29 vegetable fields, compost was added to one plot, but not to one adjacent plot (5 x 5 m plots), 1–2 months before lettuces were planted (25 t compost/ha, made from cow, chicken, and green manures). Lettuces were planted in spring (5–28 March) and summer (30 May–5 July). Lettuce weights were measured at maturity in one 1 x 1 m quadrat/plot. Soil samples were collected in spring (1.25 cm diameter, 0–10 cm depth).