This site has highlighted a long series of articles revolving around the topic of "crops rotting in the fields unless we get more cheap labor." Most of those articles - even one appearing in al Guardian - are simply propaganda, with the "reporters" simply transcribing the hyperbolic remarks of farmers and growers.

Now, however, Jim Downing of the SacBee offers "Farmers scurry to recruit workers/Growers blame immigration-law impasse and tight border controls, but other factors may play role". While it doesn't address the issue of whether those other reports are propaganda, it at least tries to determine whether those growers are telling the truth:

All year, California farm groups have complained that congressional inaction on overhauling immigration laws, coupled with tightening border controls, would lead to a critical shortage of labor.

With harvest time having arrived, state agricultural leaders are preparing to join their counterparts from around the country this week for a major lobbying push in Washington, D.C. They have been gathering anecdotes describing what they say is a damaging labor crisis in the state...

...So far, however, state surveys show no discernible drop in total farm employment for May, June and July, though an uptick in farm wages suggests a tighter labor supply...

Some of the other factors include weather shifting harvest times and growers keeping more people on year round.

The article quotes Philip L. Martin of UC Davis, and contains this bit of deja vu:

Hand-picking of grapes is declining statewide because of the widespread adoption of grape-harvesting machines. Even taking into account the capital cost of $250,000, a mechanized harvester can pick grapes for about $270 an acre, just over half the price of manual laborers, [Supervisor Matt Manna of Manna Ranch in Acampo] said.

In the Lodi area, about 80 percent of wine grapes are now harvested by machine. Raisin growers in the San Joaquin Valley are following a similar trend. As a result, the number of grape-harvesting jobs in the state has been dropping steadily -- from 56,700 workers in 1995 to 41,700 last year, even as the harvest tonnage has remained relatively stable.

Compare that with this quote from Martin's "The Mirage of Mexican Guest Workers":

Reality, however, never confirmed these dire predictions. In 1960 some 45,000 farm workers (mostly braceros) had harvested 2.2 million tons of processing tomatoes. By 1999, it took only 5,000 workers to operate machinery that harvested some 12 million tons. Thanks to these efficiency gains from mechanization, the real price of processing tomatoes declined 54 percent while per capita consumption rose 23 percent...

The article also says that some growers are threatening to move to Mexico. Of course, if they did that they'd probably start trying to import labor from Guatemala.