Joe: What is a California "creosote dump?" Where I come from it just means "ash heap" or "land fill." From the song wiki:

"In addition to being a lament for the braceros killed in the crash, the opening lines of "Deportee (Plane Wreck at Los Gatos)":

    "The crops are all in and the peaches are rott'ning,
    The oranges piled in their creosote dumps."[6]

are another protest by Guthrie. At the time, government policies paid farmers to destroy their crops in order to keep farm production and prices high.[7] Guthrie felt that it was wrong to render food inedible by poisoning it in a world where hungry people lived."

[7] "Before I start, you should know that even back in the 40's the government paid farmers to destroy their crops in order to keep supply short and prices high. The song refers to oranges in creosote dumps, a method of rendering the fruit inedible. Meanwhile people then, as they do today, go hungry. And even though crop prices are kept artificially high, the workers who harvest the food are denied a living wage."
Chapel Talk (PDF), Mark Hammond, January 7, 2004.

What is the primary source here? Did Woody Guthrie ever actually say this about the California fruit grower co-ops? If not, where did Hammond get it from?

I've lived and worked in and around citrus groves for six decades and have never even heard of the practice. Have you? Everything I find online takes me in a big circle starting and ending with Mark Hammond, c.2004.