Saturday, June 2, 2018

Bad Bug: Black Vine Weevil (Otiorhyncus sulcatus)

Early on in our career as farmers, we saw a kind of damage to our grapevines that we thought was due to deer. The tops of the young, growing vines would be cleanly chomped off. Deer! We engaged our hunter to see if he could rid the vineyard of this nuisance. As time went on, we learned that the type of damage that we were seeing was not due to deer, but due to a much, much smaller offender, the Black Vine Weevil (Otiorhyncus sulcatus). This bug is so tiny, not much larger than 1/2-inch but it can do serious damage to buds, flowers, foliage and cluster rachis.
I consulted University of California IPM Site, to learn more about this little pest.
The adults emerge from the soil in early April through May. About 2 to 3 weeks after they emerge, females begin laying eggs and continue for 6 to 8 weeks. Eggs hatch into white grubs (larvae) that feed on roots. Larvae feed for about 10 months before pupating in the soil during late winter.
This weevil has a long and broad snout, that projects from the front of the head. The snout is the offending appendage since this is what the weevil uses to pierce vine parts when it is feeding. The telltale sign that the damage is done by beetles (and not deer) is the presence of small holes in the growing shoot. The small holes become the weak point and snap off. It is really unfortunate if this damage appears on what should be next year's cane!

No comments:

Post a Comment