Spiders on Grapes

 

Spiders are found in and around grape vineyards. They prey on insect pests that are found associated with grapes. However there is an increased frequency of finding spiders in containers of exported table grapes. When the grapes are harvested some spiders are able to escape detection during the packing process. The spiders hide in silk retreats made in the stems of the grapes. The grapes are chilled prior to transporting causing the spiders to become dormant and immobile. However, spiders are able to lower their metabolism enabling them to survive long periods of low temperatures. When the exported containers are opened at the retailers or consumers the spiders become active after this period of inactivity. They are then observe seen when they try to escape. The first author receives annually several queries from grape exporters regarding spiders exported on grapes.

Spiders are common predators find in agro-ecosystems worldwide and they are known to play an important role in controlling pest species . They are present in high number in most crop systems as also found in Southern Africa. Nothing is known from vineyards in Africa and our present knowledge is from research undertaken in southern Germany and central California.

During a recent survey undertaken on the border of Namibia and South Africa a total of 106 spiders represented by eight species from six families were collected from grapes. Two species Cheiracanthium furculatum (Miturgidae) and a unidentified Theridion sp. (Theridiidae) constituted 86% of all the spiders collected. Two of the species collected C. furculatum (sac spider) and Latrodectus geometricus (brown button spider) are listed as of medically importance in Southern Africa.

Dippenaar-Schoeman, A.S. & Mansell, M. (in preparation).
First records on spiders from grapes in Southern Africa (Arachnida: Araneae).

Miturgidae: Cheiracanthium sp.

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