About 2 weeks ago, Roger Duncan (Pomology Advisor, UCCE-Stanislaus) and I had a field visit based on a farm call about mealybug infestation in one of almond orchards. Upon looking the mealybug externally, we agreed that it is not Gill's mealy bug which is common in almond and pistachio plants. I collected samples and sent it to the CDFA for identification. Based on the report, it is 'obscure mealybug, Pseudococcus viburni (Signoret).
This mealybug is commonly found in grapes, in fact it is very closely related to grape mealybug, Pseudococcus maritimus (Ehrhorn). But, it is probably the first report of finding this bug in almond. A good way to differentiate these two species in the field is to prod the female mealybug with a sharp object, and look for the color of the exuded fluid (ostiolar fluid) which is red for grape mealybug while white to opaque for obscure mealybug (Daane et al. 2012; Biology and Management of Mealybugs in Vineyards).
This mealybug was found just in one orchard north-east side of Modesto, and we dont know whether this species in out there in other orchards as well. We also have no clue about potential of this species causing problem in almond. When I have looked the specimen under microscope, there was high rate of parasitization. So, may be it is well controlled under natural condition. This article published in EntomologyToday.