Thursday, May 28, 2020

Grape Cane Girdler Active in Vineyards

Fig. 1.  Grape shoot with girdling caused by grape cane girdler - two rings of punctures, 2-3 inches apart.

Fig. 2. Grape cane girdler in process of creating a shoot puncture.

Hello, everyone,

At this time of spring, a little weevil is active that creates an injury that most grape growers have seen - girdling caused by grape cane girdler, Ampeloglypter sesostrisThis is a small, black weevil about 3 mm long. Its damage may look alarming but is usually not too important.
   
Adults overwinter in debris on the ground. In late May, usually before bloom, the female encircles a shoot with a series of punctures made with her mouthparts. Eggs are deposited in these holes. She then makes a similar girdle a few inches higher on the shoot but without eggs. The grubs feed in the cane pith and both injured portions may break off (usually at the outer girdle first).  Larval development takes about a month. 
Larvae pupate in July and adults appear in late July and August. Development also occurs on Virginia creeper.

The damage may be seen frequently but is minor on established vines because the girdles are usually beyond the clusters. However this injury is of greater importance in new blocks because it may make training of the young vine difficult.  Growers may wish to spray fo grape cane girdler when greater than 10% of the shoots are injured.  Several insecticides are included in our vineyard pest management guide, under New Shoot Spray (https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-017/ENTO-337C.pdf).

If injured portions are to be pruned as a means of control, this should be done below the lower girdle before adults emerge.

More later,
Doug 

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