On our highways fossil energy propels nearly incessant rivers of iron and plastic machines at velocities approaching one hundred feet per second. These machines produce billowing vortices of dust, microbes, micronutrients, and exhaust chemicals in the surrounding atmosphere as they pass. These billowing vortices are nearly invisible on paved roads but are readily apparent from the higher dust content on dirt roads in the vineyards.
It has been well-known for a long time that dust in orchards and vineyards fosters mites and dust suppression has been long advised. This year has been a bad mite year and anyone paying attention can see mite damage beginning at vineyard row ends near highways and progressing in. If you practice a bit, you can begin to distinguish mite damage from other red symptoms because it typically produces a more bronze than red coloration that reads duller from a distance.
The bronze patch in this roadside vineyard is mite damage.
Working in the Northern California wine country, business and habits carry me widely and last year it seemed red vines were cropping up on highway row ends. Whether because these high profile red plants were deemed unsightly, or because the owners were wise, many of these plants were removed and replaced. No farmer would replace a vine for mite damage.
RGBaV typically produces a brighter and more translucent red coloration that progresses from the veins of the leaf like these wild grape leaves photographed on the St. Helena road.
To the best of my knowledge RGBaV has not yet been identified in Vitis californica and I had been watching for symptoms for a couple of years. This was the first red coloration of any kind I had seen in wild grape and I took samples to the UCD Oakville field station where it will be assayed for the presence of the virus.
If this test proves positive, it will be interesting because there are no neighboring vineyards and this plant and another on the St. Helena side are right on the road.
The natural world we live in is far more complex than we care to believe, and we must avoid jumping to hasty conclusions. We offer here only a hypothesis based on a few observations that will need far more testing, but it is possible this circular virus is taking a ride down the turbulent rivers of air pumped along by our cars.