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Faced with a devastating plague of pests in their vineyards, California’s
grape-growers are teaming up with NASA to see if remote sensing can help
them to spot infestations earlier.

The aphid-like phylloxera louse infests the roots of grapevines, sucking
out their juices until they sicken and die (see ‘California’s lousy vintage’,
New Å®ÉúСÊÓƵ, 17 April). There is no effective pesticide to treat the blight,
and so the usual strategy is to graft high – quality vines onto resistant
rootstocks. Unfortunately, 65 per cent of California’s rootstocks are susceptible
to a new strain of phylloxera, and vineyards must replant all these.

There is no getting away from the arduous task of replanting but the
Grapevine Remote Sensing Analysis of Phylloxera Early Stress project – better
known as GRAPES – could buy much-needed time.

The first signs of phylloxera generally appears years after the infestation
began. ‘All of a sudden the vine starts showing stress, and then, fairly
rapidly, it dies,’ says Harvey Posert, of the Robert Mondavi winery in Napa
Valley, the heartland of California’s $10 billion-a-year wine industry.

A few years’ warning would give wine growers time to plan their replantings
and nurse sick fields to squeeze the last drop of grape juice out of vines
before they are uprooted. ‘When you replant, you don’t get grapes out of
the vineyard for another four to five years,’ says Posert. ‘So planning
is crucial.’ Starting this May, scientists will walk through the Mondavi
vineyards with hand-held sensors, scanning vine leaves for changes in the
amount of heat and light they reflect – both measures are invisible indicators
of stress.

In July and August, aircraft and satellites will scan the Napa Valley,
taking similar measurements on a larger scale. These readings might even
provide clues about which areas – which soil types, for instance – are
most susceptible to the root louse.

GRAPES is a joint effort between NASA’s Ames Research Center, the Mondavi
winery and scientists at several Californian universities, and its findings
will be freely shared with all other vineyards in the region.

From NASA’s point of view, the project is part of its continuing effort
to apply remote sensing technology to industry. ‘Obviously this tool is
no good sitting on the shelf,’ says Joan Salute, project manager for GRAPES.
‘To help US competitiveness, NASA wants to teach as many people as possible
what remote sensing can do for their problems.’