Does semi-natural habitat amplify spider populations in a California organic vineyard?

Phelps, Cord; Norgrove, Lindsey (1 July 2019). Does semi-natural habitat amplify spider populations in a California organic vineyard? In: 10th IALE World Congress. Milano, Italy. 1-5 July 2019.

Semi-natural habitats (SNH), areas characterized by reduced management activity and the presence of native vegetation, are thought to represent a persistent reservoir of beneficial insect populations. Faced with an array pest management challenges, the organic wine grape industry and research institutions have studied the potential contribution of SNH to biological control strategies. However, conclusions are often contradictory and qualitative. Here, we track the spatial occurrence of spiders over the course of the growing season, comparing a transect supported by a native oak grove and a transect bordered by an empty field. To evaluate the density of insect populations, we collect samples from non-lethal vane traps suspended in the canopy. We find that species abundance is higher by 30% in the SNH transect early in the growing season, while species diversity is always comparable for the two transects. Three distinct population clusters persist throughout the season in both transects. Contrary to our initial assumptions, we conclude that, for a California Central Coast organic vineyard, SNH dominated by mature oak trees promotes populations of the generalist spiders Thomisidae beyond the first 15 meters of the transect. This result suggests that producers could consider reinforcing SNH effects by emphasizing under-trellis cover crop strategies for the initial 15 meters of the rows.

Item Type:

Conference or Workshop Item (Speech)


School of Agricultural, Forest and Food Sciences HAFL > Resource-efficient agricultural production systems


Phelps, Cord and
Norgrove, Lindsey


Q Science > QH Natural history > QH301 Biology
S Agriculture > S Agriculture (General)




Lindsey Norgrove

Date Deposited:

10 Jan 2020 09:50

Last Modified:

10 Jan 2020 09:50


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