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Invasive Weevil Scare

Posted by socal23 USDA10/Sunset23 (My Page) on
Fri, Jun 21, 13 at 13:56

A few days ago I collected this in my driveway:

Curious, because I had never seen a weevil like it before, I forwarded a picture to an entomologist at UCR for ID. He originally misidentified it as Diaprepes abbreviatus.

(note, there is considerable variability in coloration, since this is at least partly a PSA, I selected a picture of a typical individual instead of one that looked the most like my specimen)

The Diaprepes root weevil is an invasive generalist herbivore that is destructive of numerous economically important plants, both ornamental and edible. Of particular concern is its role in increasing susceptibility of citrus and avocado to Phytophthera root rot. It has been found in Los Angeles, Orange and San Diego Counties and a quarantine has been enacted to confine it.

It has not (yet) been found in Ventura County so as you can imagine, this caused quite a stir.

It has now been identified as: Sphenophorus pertinax a native weevil of the type commonly known as billbugs:

Of course, if history is any guide, all we can hope to do is to slow the rate of spread until Diaprepes abbreviatus is stopped by some biogeographic barrier while we learn how to mitigate its impact, but for now, it appears to remain contained in the quarantine zone.

edited to repair broken link

This post was edited by socal23 on Fri, Jun 21, 13 at 18:00


Follow-Up Postings:

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RE: Invasive Weevil Scare

Gosh, they look almost identical. So yours was the native and the invader is still confined to the quarantine area? That's good. I'll be on the lookout for any similar bugs and save them in my bug jar, just in case.
Renee


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RE: Invasive Weevil Scare

The thorax on the bugs in the first two photos are different and so they are different species. Which is the invader?


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RE: Invasive Weevil Scare

  • Posted by socal23 USDA10/Sunset23 (My Page) on
    Sat, Jun 22, 13 at 11:33

Westelle, the middle image is the invader and it is highly polymorphic, the distinguishing feature in this case is the position of the antenna on the rostrum.

Bear in mind that UCR (California's most important agricultural entomological research center), the UCCE, and the county Ag. Commissioner are are already pretty keyed up because the pace of pest introductions has increased dramatically over the last ten years or so.

Usually by the time they are called out, there's a severe infestation, not merely an isolated sighting. While this is perhaps understandable in the case of the Glassy Winged Sharpshooter or the Asian Citrus Psyllid (neither one is particularly remarkable in appearance), that isn't always the case. The only reason I inquired about the Billbug was because it was about 3/4" long (which happens to match the typical size of the Diaprepes - a fact I became aware of only after the fact) instead of the more usual 1/4" to 3/8" in length. A lot of people, especially those who aren't gardeners, wouldn't have taken the time to do more than perhaps squash the bug.

Ryan


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